Marshall 2203 Keeps Blowing Expensive 6550 Tubes!
ฝัง
- เผยแพร่เมื่อ 1 ต.ค. 2024
- I really hate to say it, but maybe some tube amps aren't practical or economical to keep repairing. Is this vintage 1980s Marshall JMP 2203 Lead Master Volume head one of them? I installed Sovtek 6550 tubes from CE Distribution, the wholesale arm of Antique Electronic Supply, aka TubesandMore.com, but they keep blowing up prematurely, despite biasing to 70% of max plate dissipation at idle. Then to top it off, they refused to replace the burnt out tube! The only solution is to bias much colder and rant to TH-cam.
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Hi Brad, Alan Here. I have a repair business in New Zealand (Anvil Amplifiers). CEdist have done the same to me with a quad of 6550EH. Because the Tubes were in my stock for more than 90 days until used and I only then discovered that one of the tubes had an open circuit heater they told me I could not get a replacement. Am I supposed to test all tubes on delivery? BTW I now buy most of my tubes bulk from JJ direct or other brands from UK distributors. Just bought another 3000 Euro worth.
It’s bullshit, ain’t it!
I'm in the US and have had the same proble with CE and their 90 day policy. I have tried to tell then as a repair center that I stock up on tubes and then sell them as needed. Some times the tubes set on the self more than 90 days before they are needed. CE told me 90 days was thier policy. I told them it was a unreasonable policy for a dealer/ repair center.
UK has just done a free trade deal with NZ, so that should make you happy in the future - be good !
I like ya Brad, but throwing your channel around like that is an ugly look. We all have problems bro, but come on.
Agreed
That was a real Karen move. 2 in a row from the same amp, 2 years later. They are a business, not a charity. That was a real tantrum and he needs to grow up.
TH-camrs primarily post videos to make money on views… Think about it.
@@j_freed This one seems genuine though. It's really not that deep.
Ya know, I have always pretty much considered myself a Guitologist fan and have always enjoyed the videos but this one disappointed me. Why would you expect a company to replace something that far beyond their return policy. There has to be a limit. Just because there has been a pandemic and the customer hasn't played any shows doesn't mean he hasn't used the amp. I haven't played any shows either but I still crank up at home. I could understand if it was a only couple months over the return period but how long was this... well over a year? The part that really disappointed me was that after you belittle and berate this employ on the phone and claim that the amp is not at fault, you proceed to test the amp again and discover that the amp probably was at fault. To me, it was you that missed the heat issue on the previous repair and had already been comped one tube. It seems that this company had already gone above and beyond their responsibility to you as a customer and I applaud them for standing up to you when you tried to bully them with threats of using your subscriber base against them. Just my opinion...
Well said sir!
Yes, given the global crisis (which nobody in the situation caused) Guitologist is placing the entire locus of control for the warranty runout problem entirely on the tube reseller. This would in principle also make the company liable for countless thousands of other products that have all been sold since December of 2019, regardless how the items were used or handled or stored for all that time.
I think one assessment is to say: as with other crises like terrible wars, everyone owns some material loss from the pandemic, and we can’t all shift it onto someone else. It really sucks but in the balance we still have a really great life here to be grateful for.
In fact, Guitologist might have done better in the long run sticking by this company… I don’t know. They did try to offer him the item at cost before he shut them down with the ‘long term customer’ refrain. That would be effectively one tube at a full loss, and one tube for zero gain, all assuming he’s 100% correct and above board. You can’t buy that good faith and respect. I guess businesses sometimes have to let customers go.
@@j_freed lol except for the rich who have all gained wealth
Even in amp and guitar land the talk of “sheep and goats” comes out. This is amp and guitar land. Rock and Roll.
100% agree ...this is disgusting.
If there is high frequency oscillation in the amp going on as seen in the flashback and while you were testing it on the bench there is something wrong! If the customer doesn't use the FX-Loop disconnect it and put the amp back to original. If he want to keep it test it as well and ask how he is using it. Depending on what is connected there it also could lead to oscillation. High frequency oscillation can kill the amp without you even noticing it. Replace those sockets! And CHECK the coupling capacitors!!! If they are leaky the Bias will run away. Replace them with good 630V types as 400 are not enough! Yeah modern foil caps blablabla, i've had exactly that in a Laney. The cap was damaged internally and when it got hot it leaked and the tubes blew. Also by changing the grid resistors you have now changed the bass response of the amp. If the customer doesn't notice it okay otherwise enlarge the coupling caps. Keep an eye on crossover distortion when running it with less bias. Finally get rid of those 6550 and put EL34s in. Those are what the amp was made for. You are putting a V8 in a Mini and wonder why the brakes are failing.
There were a lot of things you could have done before berating CE Distributions customer service like that; they run a good business and probably won't feel your absence at all. See Pentode3000's comment below - he covers most of what you should have checked.
You know, I read the title of this and thought "NICE, Brad probably dealt with a really perplexing issue - I bet I'm going to learn a lot from this"... and then you started making phone calls... Please just post a 30 minute video of you fixing an amp next time and keep the yelp reviews off camera. It's unbecoming.
"I'vE GoT 125k SubZ on Yew TewB!" - Yeah, and we're all going to watch you totally play yourself.
To be fair, it’s not that clear the tubes were entirely at fault, especially since the grid resistors were out of spec, which you replaced. As such, you should pass the cost on to the client and explain the tube failed and too much time has passed to qualify for a warranty claim. I can see their perspective as well, where do they draw the line?
Wait a minute. The customer is responsible for his own equipment and the costs therein. Brad you are totally wrong to say that you have to eat the cost of the tube. That's you customer's responsilbity just as it would be if he had purchased a quad on his own and installed them. You need to get your business acumen in order. The supplier already did what they agreed to with the initial replacement. Plus, you have NOT proven that the amp itself is blowing up tubes nor did you explain that the bad tube was in the same socket as the other that faile! Cmon, get real,
@@stephc4427 It's not the customer's fault. The expert who repairs the amp has possession and agreed to repair it. Good business practice means taking responsibility. You wont last long in business if everytime you misdiagnose you throw it back into the customer's lap.
@@tombryan1 That might be true in the world of guitar amps, but not in the world of cars. Plenty of mechanics will replace a part because 90% of the time that's the part that needs to be replaced when symptoms X, Y, and Z occur on a particular model of vehicle, and then when it turns out this particular case is one of the other 10% they have to replace something else to actually fix the problem, and the customer gets charged for the part and labor of both parts. Have you never heard of someone having to take their car back to the same shop 2 or 3 times before it actually gets fixed? It's pretty much standard practice to fleece customers whenever possible, and these shops don't go out of business.
You also don’t vacuum the dust off. Isn’t that proper amp hygiene?
Gosh, how can you possibly think you’re anything close to rational by claiming that a purchase with a 90 day warranty should still be honored three years out of warranty because the customer didn’t play, whether or not due to pandemic. That’s ridiculous! And certainly not relevant to the vendor’s warranty. Your reasoning is pathetic and an embarrassment to the customer. Sad🙈
"Kan I speak to your manager?" - Karen The Guitologist :D
I bet it's got something to do with electricity.
XD
🤣
lol
Nailed it
It could also be thirsty. Pour some water in it.
"I'm a Yelp reviewer and I'm very important...."
All joking aside, I see both sides, but its just a shitty situation all around. Let's just blame the Russians.
Anyone who See's both sides of an issue, See's nothing at all !!!!!
@@RaulHernandez-lg5nw ummm... thats a pretty moronic saying
@@RaulHernandez-lg5nw that is tied for first place of the all time stupidest thing that I've ever heard!
But I can see why you would say it.
@@RaulHernandez-lg5nw I was just lying! I have no idea why you would say such a moronic thing! ...and on a public forum no less.
The amp isn't built for that kind of power consumption. I think these tubes need to be biased to draw no more current at max volume than the original EL34s would. Anything higher would reduce the life of the output and power sections.
Another thing I don't hear about much is octal socket contacts. I have encountered so many amps with socket problems that I check all the octal contacts of every amp with output tube issues. I use an old screw driver (with the tip rounded off) with a shaft that is only a hair's breadth smaller than a tube pin. Any contact that doesn't have a fairly firm grip is gently bent to make better contact. If the contacts are charred, the socket is replaced. Better safe than sorry.
Good Analysis.
Not gonna lie I'm not trying to stick anything metal into a tube pin socket, drained or not I would be shitting myself one way or another!
Agreed!!! I've seen so many of those cheap china sockets fail, or cheap wire that breaks down with use, or thin conductive boards.
I watched this all the way through and at the end the conclusion is that it's most likely that the amp is blowing the tubes, so there was probably nothing wrong with those Sovteks that failed? This makes a bit of a mockery of the first part of the video where you are ranting at the company that supplied the tubes. I agree a 90 days wholesale warranty is a bit farcical, but you really need to provide some balance here. Maybe you should have checked the readings on the tubes before you called the supplier?
Check the coupling cap from the previous stage feeding the grid. If leaky it will put a positive voltage on the grid. This will kill the tube.
Kind of full' yourself ain't ya' ? where are you measuring tube current anywhere ? Eat the 35 bucks and move on ! How do you know the client didn't swap that from another batch of tubes he had ? You don't ........Thousands of dollars ? If you spent hundreds of thousands they might care
let's go Brandon,,,,let's go Brandon,,,,
Who is this Brandon of who you speak, Rusty? 🍻 😎
@@RHR-221b Thanks for asking and best wishes from Columbus Ohio USA let's go Brandon,,,,let's go Brandon,,,, is code for Fu@k Joe Biden
@Rusty Robinson get the fuck out of here with your polotics.. this is a channel about amps and shit not politics.
@@YeeThirty Thanks Yee for taking the time to respond to my comment and best wishes from Columbus Ohio USA
Man, I don't want to see you pissed! I want everybody to be happy all the time! You know, kum ba ya, Don't Worry Be Happy, & sh!t like that..
Hi Brad, great video. Old school 6550 amps used to be driven regularly well beyond their rated max screen voltage. New production 6550s are not at all happy with high screen voltages. I have a stereo amp that drove 6550s at 550v on the screen. Used to work fine with nos 6550s. Eats new production 6550s like candy. I switched over to kt88s and tube failure ceased. KT88s are rated for over 600v on the screens. 6550s are only rated for 425. Check the screen voltage. What are the screen resistors? You may want to increase these. I use 1.5k - 2.5k for Amps like this. Adds a hit of compression but most often the effect is a desirable one. Or increase the dropping resistor for the screen supply to lower it. Although you would then probably need to decrease the droppers for the preamp supplies to bring them back up a bit. New production 6550s are just not as rugged as the old school ones. Their design maximums can't be exceeded like the NOS tubes.
1K screens
@@TheGuitologist Under the circumstances you encountered, I would bump those up. 2k probably won't hurt anything but might help the 6550's last longer
Seems like something preceding the tubes is an issue, you gotta be missing something.. MrCarlsonslab channel might have some suggestions- dudes amazing with stuff like this.
Hey Brad keep an eye on Brimar, there are a group of people over here in England trying to bring back British valve production in case you hadn't already heard. They'll always be a market for valve amps, theres just no soul in a fucking kemper 😆
That's right James. I use a Kemper but you can't beat a valve amp the Kemper for me is convenience. My AC30, JTM45 and other amps that are valve state along with my Guitars are my pride and joy. I agree there's no soul in a Kemper it's an amazing piece of tech but there's something not included with modeling gear. I like yourself am in the UK and I've been using a load of nos Mallards and Sovteks that I got from an Auction, massive job lot all sizes, I proper dropped on they came out of an old Radio Rentals store in Mold, Wales from what I can gather. Anyway sorry for the waffling but I agree and the Brimar's are decent valves.
Really? Brimar is coming back? Nice.
@@nickdevriese hopefully so mate, they have started producing ecc81s in the britian I think, so hopefully they'll expand the range to include so more common models
@@fongy200 that's it man nothing can replace the experience and inspiration attributed to playing a big bold valve amp, the spirit is what makes the music, musical
Hi, maybe its all clear by now but your problem is high frequency oscillation because of the more than 50K return path to ground from the tube control grid. You can get away with more than 50K but with a very careful choosen maximun screen voltage and a super well designed output transformer and power supply. HF oscillation in 6550 occurs at high power usually and its very destructive for the internals of the tube. Marshalls are prone to it because of the long cabling in the power supply, in my opinion, and because OT are never well balanced, besides the obvious errors in the design. Thanks for the video.
I thought that was what those grid stopper resistors were for.
They usually eliminate any of those problems you described.
@@Dennis-mq6or Indeed but the total value to ground, thats the stopper resistor plus the one that goes to the bias supply (ac ground), has a limit.
You are right. I smell oscillation or alot of ripple.
Problem is Brad, if you bought 10,000 tubes, they would be talking to you. You only bought 4, so there isn't enough wiggle room to replace the tube. They replaced one, and you're asking for another. I side with your prospective, but I think you may have some success getting in touch with New Sensor.
I think he's bought a lot more than 4. If you listen he has been a customer since 1994 and spent thousands of dollars.
Brad buys lots of tubes
If that is an added effects loop then the return jack is the best spot to inject your generator as you'd be passing all the preamps and tone stages and end up with a much more linear sine wave for analysis aft the output. There would be no guessing where any issues with linearity are coming from.
I had to watch this video again and I just realized that this amp has a circuit board and not a turret board. Marshall had a passel of trouble in the late 90's with conductive circuit boards used in the DSL and TSL models that would exhibit this type of failure as evidenced by slowly rising bias all the way positive many times. This is not saying that the board is the culprit but I had to have another look. I still don't know, it's a tricky diagnosis.
Yep, I have taken a Dremel and cut the PCB around the grid pin and ran a wire to the grid stopper resistor. This takes out the chance of a conductive PCB bleeding positive voltage from the screen pin next to it changing the bias voltage. I’ve done 12-15 TSL, and DSL amps with runaway bias. Seems his bias was changing as it warmed up. Marshall has been using these PCB’s since the late 70’s but whatever substrate they used in the 90’s was conductive with heat. You could take a heat gun with a meter clipped to the grid and see the resistance change as the heat increased on the PCB.
Hey, how can i contact you? Do you have an IG account?
@@omarcusihuaman4261 Yeah, I do, it's bustedjunkstudio but I don't use it much.
Maybe you jumped the gun on blaming the tubes…. Awkward
So it was not bad tubes? Do you need to make an amends to your dealer? CALL Marshall and go off on them.
unfortunatley brad at this time sellers like apex ( for the record i stopped using apex prior to pandemic for constantly getting infant death tubes) are using the pandemic to their advantage and are also using shipping delays as excuses to, i ordered over $200 in total for multiple parts from multiple sellers and out of all of it one item still hasnt arrived and tracking has shown it sitting in nj for 10 days even everythign else is showing up on time including some items coming from canada and the uk. as far as price increases, yeah that is complete bs, a 40 uf 450v cap that use to cost me liek $2.50 is now setting me back $16 ( mouser), to $29.99 ( ebay) so ive basically been telling my customers that im out of business and am only honoring the warranty i offer them i will not be accepting any other jobs because with everythign going on it is no longer cost effective to stay in business for me.
I've also had problems with Sovteks. I recently returned a 5AR4 that arced over with very low hours on it. Also I've had problems with 6l6s. One low hour tube developed grid emission and the other one became noisy.
Have not watched your videos for over a year because of your constant drama. I really find your videos INTERESTING. It looks like it's the same old thing.
I always cringe when people start dropping the Fbomb with customer service reps. They are trying to do there job. It’s yelling at a the guy who is just doing his job.
There was no yelling. Standing up for oneself isn’t yelling. I’m not sure where this idea comes from that one isn’t allowed to express frustration in stark terms. It needs to change.
31:20 are you going to cry, man? You bullied the poor customer rep and then threaten them but sometimes you DO have to eat some cost on a job for one reason or another. You can ASK, but you don't always get what you ask for. Buy another tube, add half of it to the cost of the repair and move on with your life.
I moved on with my life by stopping buying from them.
@@TheGuitologist That's fine. If you were a 5 year customer and bought a lot from them and they wouldn't comp you one defective tube or two per year, then I get your point. It's business. They have to decide if it's worth ignoring their hard/fast 3 month warranty rule and lose $20 OR tell you sorry man, we got rules and lose hundreds of dollars in the coming months or years. Really been enjoying your vids though even though I don't do amp repair or mods. Just play guitar really. thx!
It's blowing 6550s because it wasn't designed to use 6550s and definitely not KT88s!!
2203s and the transformers were designed for EL34s. It was only when the quality of EL34s and high fallout, that Marshall had to scramble to get product continuing to flow out the door, so just dropped in 6550s. However the transformers can't handle the current draw, so if you use them, you have to bias them cold! Likewise, lay people that are naive and don't understand the engineering behind it, don't realize the output transformer is designed to match the vacuum tubes for ideal loads. However, the ideal load for 6550/KT88 is double what an EL34 is (5k v. 2.5k), so when using an 8 ohm cabinet, you can't or shouldn't have the impedance on 8 ohm, and it should be (i forget which way to go with it) 4 ohm or 16 ohm setting, but NOT 8 ohm!!
Use the proper tubes (EL34s) and bias them correctly and you won't be stressing your amp and transformers and blowing shit up, it's THAT simple!!
After CE hung up the phone, I'm sure they will have agreed that the win for them is, that they no longer have to deal with you.
What a dick move. There is NO reason why they should replace the tube for you. I just bought a set of matched gold lion KT88's from AES in support of them.
I was so embarrassed about your behavior in this video that I called the supplier to apologize on behalf of those TH-cam viewers who don't like bullying and threatening of people who are only doing their job and following their company's policies. You really need to practice some more self-control.
Why don'y you change those resistors???? That is the first thing I would of done go back to oem Resistors daaaaa that would of solved all the over the amp problem!!!! And hats off to the co to stand by there warnity!!!!!!! 90 days you were wrong to try to get the co to replace. I will order all my parts from them from now on!!! I am a tech also.
Check negative bias before you put any tube in amp . Don't be amateur.
You should have shit canned all that stupid mod stuff and put it all back to stock and then perform any mod that the customer might want. These volume pots where they are installed don't make any sense for a Marshall. Fun vid, but I think you should have just taken it back to a known robust design and call it a day.
Yeah...dunno if I would have tried to throw the # of subscribers out to try and influence the outcome. I agree with the fellow who pointed out that modern 6550 are not as robust as vintage Era stuff..primarily because they are now boutique specialty items and not in the mainstream. ...I would recommend converting to Kt-88's...that will be expensive but will probably solve the issue.
It’s probably kind of dishonest, but I’d wait a week and return the bad one on the order number for the new tube for a refund lol it would serve them right for screwing over a customer. What your saying is 100% correct. When I worked on the road as a guitar tech I kept a set of 6l6’s and 6550’s for the guitarist Marshall and the bassists Ampeg as spares. So if 3 months into a tour I had to change tubes and the new ones were bad, that’s now on me? Total BS man.
Just curious. Wouldn’t you break in a set of spare tubes so you know exactly the performance and reliability rather than trust brand new ones not to fail on the gig?
I hear of players and studio amp techs doing this partly from a sonic perspective. Always keep on hand a newish set that is working and sounding just right.
@@j_freed I’ve heard of people doing that too, but no, I personally never did. The guitarist I teched for used a Marshall 9200 dual monoblock, which is basically two separate 100w amplifiers, so if one went down I could switch from one half to the other until I could fix the main side he always used. That amp never had any kind of problems or failures. The bassist used an Ampeg SVT II Pro, and also had a mesa boogie (I don’t remember the model) as a backup. The SVT is the only amp that ever suffered a power tube failure on me while on the road. He also ran a DI box straight to the FOH board, and that’s mainly what the audience was always hearing. He ran a Proco Rat pedal to the amp for distorted parts and the sound man would blend the two, amp/DI, in the PA mix. Just the amp is what was heard on stage and in the monitors of coarse. The amp went south a little ways into the last song of their set, and with him DI to the PA I never even swapped to the Mesa. They were filming a music video for that song too, and his amp rack was in the back line, so I didn’t think it was a good idea to rush on stage and start repatching cords 😂 The next day they had more film shooting to do so it was no problem to pull the amp and service it. The bass player got on the phone with his Ampeg rep and he sent us another replacement set of tubes since I just replaced those. I swapped tubes, let it warm up for about 30 minutes and that was it. I never even had to readjust the bias if I remember correctly, the LED’s showed it was fine.
Your at fault here,...you missed the obvious problem from the start,...you need to apologize and own this one,...period.
I can't help to wonder why ypu didn't test your work. I never threaten people because it becomes a D measurement....js
I've had problems with Sovtek 6550's and excessive screen voltage. I've had better results using JJ KT88's in place of the Sovtek's.
That's the part of the RISK, getting tubes? Brad should tell the dude that IF you want this amp, you're gonna pay like 200$ / tube, that's the esy it is, and why a good working amp like this can sell over 1k$. IT'S A BIG GAMBLE, this is why the tubes only have 90 days warranty. No more Radio Shack ""LIFETIME"" tubes, lol. Ted Nugent can afford new tubes for every concert.
So it wasn't the tubes and the whole seller CE, wasn't at fault? It's very confusing now!
The fuzzy sinewave is a high frequency oscilation impossed over the signal. You cant hear it but it burns stuff. Uncle Doug once had that issue on video. I once had a damn relay with no visible carbon tracking, I did scrape it alot and still had the coil leaking current to the switch side. Could your socket become conductive internaly also? Thanks for the video Brad
I think that issue was the output tube already being intermittent, or lead dress related.
Sure looks like parasitic oscillation to me. The only way you're going to get that smear is if there's some high frequency stuff mixed in. (Or very low frequency) Since that looked like a preamp stage, I'm not sure as you can blame the output tube. Fixing it by moving a wire would be consistent with a parasitic problem.
@Orandy oh, you are one of THOSE guys 🤣🤷♀️🥂
@@russellhltn1396 I agree with your comment on possible hf oscillation. If he'd changed the scope triggering and expanded the time base that may well have indicated that. Definately hf oscillation can cause problems. I've experienced similar problems in hifi amps and they become high power oscillators drawing excessive current.
Those bias resisters were probably replaced by the importer when they changed the EL34's out for the 6550's
6550s were meant for the USA market as the EL34s didn't like the boat ride across the pond.
@@alwaysopen7970 During that time period they were having major quality control problems with the EL34's even before they came across the pond. After the importer started having to replace tubes all the time they decided to go with the 6550's which required a bias resister change. So they came over initially as EL34's and before they were sold they changed the bias resisters and the tubes.
MIght have been worth checking the amp out with EL34's (which is what it was built for) to see if they too ran too hot at high volume.
I understand your frustration. The thing about making threats is that, it's warring words, ya know? When you're making a threat of ruining a Distributers reputation under the weight of your Subscribers. Well, it gets them thinking as to how they can make you look like a Dick.
Believe me, I understand, I have made the same sort of video. It's a fine line we have to walk in Business.
You are THEIR customer. If you have been doing business with them since 2014 without much complaint. You would think they would take you on your word. In warranty or not. Customer Service SUCKS.
And it sucks even worse when you are trying to provide excellent Service to your own Customer's.
I'm glad you changed those bias resistors. Note that the spec sheet at 59:23 shows the maximum grid resistance is supposed to be 0.050 Mohm. 68K is still too high, but 150K would be 3x the spec. It's unclear what happens if you exceed that spec. Some say you can have runaway bias - especially when the tube gets hot or gassy.
That's what we have in politics right now, "runaway bias".
Exactly this. I've had these amps back in the day where they still had 220k bias splitters with 6550s installed and the bias had run away and burnt up the valves (even with the bias supply adjusted to be biased correctly at idle). We get away with things in valve amps as they're very robust, but sometimes you get caught out. I too spotted the 50k max spec at grid 1 of 6550s. Some Marshalls in the mid 70s (with KT88s / 6550s) used 68k resistors for this application, so Marshall obviously were aware of this (despite still being over spec). I say that the bias will run away, but exceeding grid 1 spec might just (in some cases) cause the valve to become unstable and/or fail.
The way I understand it is the grid stopper resistors work with the tubes interelectrode capacitance to prevent oscillations in the tube. If the tubes were to go into oscillation for any reason they would inaudibly be drawing high current trying to amplify that ultrasonic frequency and all you might hear is a slight hissing. If the player were at a gig, he'd for sure never hear this or probably think it was just noise.
I've see this type of oscillation in many older amps were it is merely lead dress causing the oscillation and sometimes a decoupling filter. The power tubes do their level best to honoraby amplify to the max whatever frequency it happens to be oscillation at.
You are right Russell. Additionally, that spec is for a single tube. The leakage current from two tubes will generate 2x the voltage across it so 150k is 6x too high. As HTH AMPS says below, we do get away with a lot fo stuff in tube amps!
@@glenwhatley8034 A valid issue, but I don't think that's what's happening here. A higher resistance value would lower the frequency of the resulting low-pass filter - reducing the problem, not creating one.
I'm a little confused Brad, ain't the 2204 a 50 watt head and the 2203 a 100 watt head (2 power tubes vs 4)? Just wondering because I have a 2203 story coming up. I know Marshall has a lot of models, maybe they changed things up?
Yes
You're right, I screwed up the title. I'll fix.
@@TheGuitologist Appreciated, B. 🍻 😎
Did you check BIAS stability ?
Spring retainers are ground electrodes on top of the tube all around the anode, it can be dangerous. A current from plate can hit the glass over small spots , It depends on tube geometry. Usually no problems with el34, but other tubes may need different retainers..
Intermittent open in the output transformer possibly… she’s going high impeadance and that “smear” is oscillation, you’ve got bad capacitance and inductance in the circuit that shouldn’t be there or something isn’t being loaded properly… I seriously doubt that it’s defective a tube problem… you’re gonna put a new tube in and it’s definitely gonna happen again…. Would be good to study the Barkhausen criterion for this condition to understand why this is the case…
The second bad tube failure was intermittent and would have affected one half of the waveform. Maybe my speculation was correct that the tube was already failing in the flashback clip.
Brad lets make it clear there is nothing wrong in your position on telling us how shit this company is online.your actually right and helping others not fall into this trap .90 days for new tubes is not great..dont feel bad you did the right thing.i have calls like this all the time..the customer used to be always right. but not in 2023
I hope CE Distribution discovers the error of their ways. Good luck brother, we support you.
shitty old vintage carbon resistors have been the bane of my life on many occasions always get rid of em not worth the hassle.
Heck yea! What's better than a long form Guitologist amp repair mystery video on a lazy Saturday late afternoon? Thanks Brad!
Viva Barnes on a Sunday evening?
So did changing the resistors to 82 lower the output wattage. Your tech said those amps are not happy with anything other than 82. If that thing was making too much power because of the 150's that could melt a good tube, right? And running them at higher than they are rated could find different weakest spots in the tube causing failures in more than just one way? I have a feeling it will be fine now.
This guy's ego got in the way of good judgement.
Sorry, but if I were CE Dist, I wouldn't have replaced the tubes either esp after that period of time regardless of what's up with the amp. Business is business. I've dealt with CE Dist for years when i had my full time business and even presently and never had any issues with them when I had a request like this in a reasonable time period. Hey, sometimes ya just gotta eat the tubes & chalk it up to life in the tube amp world.
I believe there is something going on with the amp that is being missed. Something along the lines of parasitic oscillation esp given the scope waveform you showed from the previous repair. I Seem to have some recollection of lead dress from the output xfrm underneath the board causing some weirdness at some point.
I'm curious what the pots on the rear of the chassis near V-1 are. Is that an add on presence control or perhaps an effects loop?
That might be an area to pay attention to.
In hindsight, I think the smear on the waveform in that clip was either a lead dress issue I solved by moving a wire, or it was that tube issue already becoming an intermittent problem and it just didn't do it again while on my bench. One of the initial issues with this one was it had a bit of the coating on one of the power caps worn through and there was arching from the negative shield to chassis. Those needed to be isolated completely due to being in series.
I second the possibility of self oscillation - the first scope trace def. looks like it. The nasty thing about it is it may come and go semi-randomly depending on a number of factors, one for example being the actual load impedance. You load the amp with a matching purely resistive load and you don’t observe it anymore, but what about your customer? Does he always plug his cabinet in to the correct impedance output? Does he use an attenuator, esp. one of those “reactive” types? Does he ever forget to plug the cabinet in altogether, even w/out passing any signal through the amp? You might want to carefully try these scenarios and see if oscillation raises its ugly head again. That little mod in the back corner and the routing of the wires connected to it might also contribute to such an issue. My $0.02 anyway. Been enjoying your videos for quite a long time. All the best!
After looking at your scope waveforms, I am concerned that one half of the push pull stage is going into clipping before the other one is...so you may have one tube doing all the work on 1/2 of the push pull output, or possibly an output transformer problem.
The best thing to do to troubleshoot the problem is to look at the AC voltages across each one of those 4 cathode resistors to see if one or more are way different than the others.
That could end up being something like a screen resistor that overheated and changed value, or it could be unequal outputs from your phase inverter stage that drives the grids of the output tubes.
In any case, you will have to drive the amp into non-symmetrical clipping, (not square wave), and look at some waveforms to troubleshoot and repair..
And pray that it is not a shorted turn output transformer problem causing unequal loading of the power tubes.
In any case......
It looks like you may get to produce at least one more episode regarding this amp repair on your TH-cam channel..., and I will be looking forward to watching it...
Exactly! Just had that happen on an Orange Dual Terror. Easy test proved my theory. Unhooked all output transformer leads from amp, injected into the secondary a 5Vac swept sine wave from 30Hz-4Khz, used two channels of my scope with each lead on the two primary leads with ground on the center tap. Right away you could see one side was way uneven in amplitude from the other with notch distortion on the low amplitude side. Amp has shorted a tube, replaced tubes and would only push 6-7 watts maxed out when it is rated for 30. After checking all the obvious I tested the output transformer and bingo. What a time to find some of the right impedance, physical size for a lunch box amp that would put out 30 watts. Mojotone had a Trainwreck style output transformer that I made barely fin for $95. Either that or order from Orange and have it shipped from England. I bet it would have been $300 with shipping and duty tax……….. works great now. I bypassed that 2/4 tube switch too. Flicking a switch with 330v is just asking for trouble. Should never be switched only while off or in standby. Most players don’t know better and just do it anyway. Switch was jumping all around on resistance with meter in one position. I bet it arced internally. Has a half power switch for the output anyway, how many attenuation does one lunch box amp need. Hitting 32 watts with this new transformer. Personally with all the new tubes, caps and transformer you could have bought a used one. Terrible build quality, more Chinese junk. Just need to up the cathode bias resistance a bit. New transformer upped the B+ a bit. It was on the edge before with 120 ohm resistor for each pair of EL 84’s. RCA manual calls for 150 ohm minimum. I think I will try 180 ohm. Right now it is at 15 watts max dissipation. Need to get it under 12. Guy had a half dozen used tubes in amp soft case. Obviously been eating tubes. Orange didn’t design this amp well at all. Hopefully I took out some of the questionable design choices to make it more reliable.
Yep not a problem you want to see, burning 200 usd of tubes all the time, good job they weren't winged Cs ! Brad, I was curious, how's the reaction in general when the guys have to bring back their amps multiple times, are they mostly pissed off or just cool about it ? And what's the average threshold from going from cool to pissed off, 1st return, 2nd ?...
And in this case how do you know it's not user error ?... moving a hot amp ? I mean you have to believe the person who says "oh yeah it failed mid gig by itself"... Not a nice position for a repair dude.
On a side note i'm only 14min in so maybe that question was answered, but it's also a general question, how would you know if someone is BSing you or not ? Coz one has to admit the most common reason for premature tube failure is hurrying up moving your gear after a gig (not having the luxury of waiting for shit to cool down while you drink a vodka or 10), it's happened to me, not just once, and they don't always fail the same way, microphonic, shorting or air, but 99% of the time I know why something has failed
Lol ok, got to the phone call, they're idiots, independent of what actually happened, it's retarded from them to not want to lose 50 usd on an order when you're dealing with a long term client... I'm in the import export business (and on way higher invoices), I deal with things like that I never let my clients hanging, sometimes you don't know if it's a user problem or a manufacturer problem, but when you sell things you put in a provision on your price for things like that, and if it's a problem that happens out of warranty that shouldn't happen (out of the normal standards) I fix the problem I go to my supplier to say ok you're giving me a discount on my next order
i've had problems that happen out of warranty that should not happen, I don't put it on my client
That being said, tubes are a more delicate matter...
EDIT : Oh shit that's the only 2 returns you would have done since 2014 ! And so actually only one comped tube since 2014, they're fucking crazy ! For all managers out there, this is a great example of what not to do if your're managing a company
Hate to say, but this was a really bad move. You are ultimately in the wrong, and CE is actually a great company for shops to deal with. I have been dealing with them for 5+ years and have honestly received nothing short of steller customer service when issues do arise, but the statue of limitations ran out here. I cringed on how this poor customer service guy was treated for this. I am actually grateful for CE right now. They still have _most_ of our parts needed in stock. We need them, and if they blacklist you, well......
In other words, don't bite the hand that feeds you is my moto.
They don’t feed me. I feed them. They forgot who the customer is. They’re selling products wholesale and offering bullshit retail limits on returns. That is NOT the way wholesale business is run. You think that rep was treated poorly? That’s some thin-skin you e got there. I was being nice.
A Tip for you….Don’t buy Sovteks!! They are garbage, every one of them! BTW, I’ve dealt with CE since they started. They’re great folks, but they are bound by Mike Matthews rules on tubes. They don’t realize that guys like you & me buy stuff and it sits for awhile until we have a repair where we can use it.
When it comes to 6550’s in the JCM800’s you need to get the Best 6550’s you can buy!
I had a similar beef with a drum pad from Alesis. The pad broke within warranty, not because of miss use, the store sent it to the distributor, yes the distributor; the response from both was that they couldn’t replace the pad and it had to be repaired, and I would pay for the repair. I reluctantly agreed. The thing went to the distributor to be repaired and came back with a awful job with freackin cement glue showing. A BS repair job, that I simply could not accept, so I did not payed for it and they kept it. This is the best part; I contacted Alesis through their forum, explained them the situation and they promptly offered to send a new pad.
How's that similar? This was way out off warranty, they already replaced it once and it was probably the amp's fault...
@@TheEchelon look up "similar" in the dictionary.
With reactive load things are just worse...
I'm not big on strong-arm tactics but corporations have been taking advantage of the little guy for too long now that they have become arrogant about trade laws in their favor it's about time we hold their feet to the fire they want to sit there and survive. Tired of paying full price for half-ass products
🙄 if only he knew how to speak to people. No wonder he's always getting into trouble. There's no proof of how long the tube has been used or even proof that this tube came from them. A label is easily replaced.
Brilliant I wish I could be like Brad on the Phone!! Love you Brad! x
My current tech refuses to use Sovtek tubes. Thinks they're junk OEM stuff that Marshall puts in their factory amps to save a buck. Sure enough, after a similar problem blowing one tube after another in my JTM, I went to a different tech and this guy switched to Tung Sols; it has been rock steady ever since.
Dude kept his cool though... I would've given you a refund and closed the account.
Replace the tubes and watch power output on a Variac at 60% to 70% power and see what it does.
Might have an issue with the tube sockets too. Looks like you have spent a lot of time on it. 1800 on the screens
on those new Sovteks probably may help. Crappy customer service really ticks us all off but seems to be the norm.
Intermittent issues can drive you more crazy than whatever is passing for normal today!
The tech shouldn't pay if he fid repairs proper, i.e. IT'S NOT THE TECH'S FAULT. And 20 month s is way beyond warranty. Frankly customer should have used the amp sooner, within the 90 days. So the customer SHOULD PAY since it's way beyond warranty. We all would be SOL, TS, and get screwed, if it's our own dam fault.
that's kinda what I was thinking, brad repaired the amp, dood sat on it and his tube warranty expired, owner is on the hook here, but that's what kinda guy Brad is.. solid
I am a bit confused. so the problem wasn't with the tubes?
The tubes did fail under a bias setting where I would not have expected them to fail. The customer was cranking the amp and using an attenuator, which was pushing the amp into dangerous levels of dissipation. I believe it was a combination of things.
Aside from who or what is at fault, here in New Zealand we have a very good piece of law called the Consumer Guarantees Act (CGA). It basically states that all goods and products must be fit for purpose, of acceptable quality and last for 'a reasonable period of time'. The CGA works over and above any warranty by the retailer or manufacturer. Example - you buy a TV with a 12 month warranty. 18 months or two years later it develops a fault. The retailer has to repair, replace or refund because an item like a TV would be expected to last at least 5 years. Whether they repair, replace or refund is up to the retailer, unless:
• the problem can't be fixed
• the problem is of "substantial character", e.g. the item is unsafe
• the retailer takes too long to act on your complaint.
Then you get to choose what action you want.
The act only applies to things bought for personal use, it doesn't apply to goods purchased for commercial use, trade purposes or where you are making an income from their use.
I don't know what laws you have in the US, but would be interested to know if there's anything like the CGA.
When I bias my JMP 2203 with 6550s I calculate as if the 6550 is a 25 watt tube(EL34). These amps are designed to run EL34s and it has to do with impedance of transformer why you do it this way.
Just stuff I’ve seen in the net.
Quote:
You bias 6550's in that amp just like you would bias EL34's. The transformers were spec'd out around EL34 tubes so they aren't going to put out enough juice to run 6550's at their full potential. You also run the risk of running your PT too hard if they are biased too hot.
This is exactly why I set idle current according to what the amplifier is asking for. NOT what the Tube Receiving Manual says they will produce. A 100 watt Marshall is asking for 25 watts each, so that's what I use for my calculations.
Interesting, thanks for this information!
@@GranvilleGuitars Thanks for sharing your knowledge Scooter, great tip!
Ken Fischer always told me and I agree that some Marshalls actually sound better on 6550's. Yes, the Dagnall 100w output and power transformers are wound for EL34's, but over the years it hasn't seemed to have been a huge problem with replacing power transformers if running 6550's were really causing damage. Bias is completely subjective and finicky from amp to amp... some sound better at 15mA per tube, some at 35 or 40mA per tube. I remember the thrash metal guys in the 80's running 6550 powered JCM800/JMP 2203's liked a really high bias with hardly any current... thin, but super crunchy.
Interesting how the two 150K ohm resistors which value is shown as is on the schematic is shown as 82K ohm on the board.
You could do like the guys I work with, if a truck keeps blowing a 10amp fuse they replace it with a 15-20amp. That’s the proper way to fix it, Right?
Well, there's foil...
@@camilo1455 when all else fails jamb a paper clip in
I'm a fan of the foil in a cigarette pack lol
@@gford8551 And a fire extinguisher? 🍻😎
You can fix it Permanently by cutting a small bolt to use as a Fuse!! Never worry about Restrictions again!!
Brad, please don’t take this the wrong way. I’ve noticed that your attitude has gone from you being a guy on TH-cam, to you using TH-cam as a source of power in your life. Also noticed that you got yourself in trouble with that school board member or whatever he was virtually the same way, by you by claiming that that you have power through your social media, and that you will wield it. Karma is action. Mindfulness rules in this time of chaos. Peace! Stay kewl little brother! But also know your audience are not your pawns. We won’t be used.
Dude how dare you txt that to Brad..you are blocked from alot of us now
I was doing them a favor making them aware. It would be worse NOT to tell them and just blind side them with criticism. It’s honorable to be up front.
The guy on the phone is like "we will survive".
26:54 Brad's channeling his inner Karen...lol
My inner Garen.
@@TheGuitologist perfect!
@@TheGuitologist LMFAO
Wow, i watched an hour before you changed the resistors that you had noticed that they are wrong value hour earlier, and even after that there is a problem that never get solved if you have to tell client not to turn the volume past 7.
So it is not fixed even.
Where is this guy gigging that he can run a 2203 over 7 on the master volume?
Stadium!
@Busta Speeker LMBO!!!!
That there's funny, I don't care who ya are!
What you need to do is CONFIRM the problem before getting too upset here....sometimes it is just out of your control...
You mentioned some " residue " on the Outside of the Tubes???
That sounds like something to consider...maybe a short from some contamination???
Ewww...i just rethought what i wrote!!
😱
"It's not my fault...." Dude I was in 3rd grade when I found out life is not fair. The girl that asked to be my "girlfriend" (we'd hold hands on the playground but I started missing my friends, I "broke up" by saying, I don't want to be your boyfriend, I just want to hang out with my friends..) she ran to the Duty Teacher and said I hit her. I did not.
But nevertheless I feel my ear being tugged suddenly and an angry woman telling me I'm going see the Principal. I actually had to grab my ankles and take 3 smacks from a leather belt to my ass and was completely innocent.
How to turn your heavy metal 🤘 amp into a smooth jazz machine…. LOL 😂 Brad, my man, you was put between a rock in a hard place. Learned a lot, great video.
The power supply of that amp is in fact too good. It does not sag and is able to deliver more power to those 6550s than they can dissipate.
I agree. That's part of the problem. I also think the OT primary impedance might not be ideal for 6550.
@@TheGuitologist That is possible too. But when you look at the output tube load lines, most output stages seem to go easily to overheat zone but in real world don't, because the power supply is not rigid enough.
Maybe just adding a 100-200 ohm power series resistor to the power supply to kind of emulate a tube rectifier could solve the problem and even could make the sound nicely compressed and make tubes last longer.
Probably wouldn’t hurt.
@@TheGuitologist And as a bonus, it (series resistor) makes B+ filter caps last longer as well.
@@TheGuitologist If the plate to plate impedance of the OT is around 1750 ohms, which I presume, it is in fact too low for a 6550 quartet if B+ is more than 400V and does not sag at full power. The p to p load of 6550 quartet should be around 2000 -2500 ohms if plate voltages are over 450V because if the power supply does not sag, the load line goes over max allowed plate dissipation at low voltage side of the load line.
I absolutely love your channel but whenever you bring up your viewer count in a threatening way (second time that I've seen now) its pure cringe.
Sorry to see you have these type of problems. Back in the 70's I was a 2way tech and was grateful that the local RCA parts house treated me like royalty when it came to returns. That tube with the interment loose element is an obvious manufacturing defect. Your supplier should have treated you like you were an extension of their business and not like the end user. They have now made their bed and have lost your business for life.
You might contact Sovtec directly, they might exchange them so they can have their techs examine them...
Yep. Senseless move.
@@TheGuitologist On a funny note, I once had my 3-500 power tube develop a grid to cathode short in my Linear amplifier at my ham station. It was on standby for a 1/2 hr and looked over the Plate Voltage was sagging from 3200v to 2300v. I took a peek in the vent and the graphite anode was a white as the sun. Cost me $238 for a replacement. That old Amperex is now a Christmas ornament Lol...
I disagree. What if Marshall is pushing beyond the spec of the tube? Is it still the tube manufacturers fault?
@@ethanspaulding6067 Hmmm
@@ethanspaulding6067 Some suggested reading;
*The Tube Amp Book by Aspen Pittman
*The Marshall Book by Mike Doyle
These will explain the decision by the Marshall distributor in 1974 Rose-Morris to use GE 6550A tubes in all amps shipped to the US, Canada, and Japan. A Google search will also help.
"I have a youtube channel"
*check*
"Can I speak to your manager?"
*check*
boy this was embarrassing
Was working sorry I missed this live but man you had me cracking up a couple of times
You missed it, deal with it and move on. Personally I think you should call the wholesalers and apologise for dissing a valve that has clearly been taken over its limit.
I dealt with it and I’ve moved on to another supplier.
@@TheGuitologist it's called cutting your nose off to spite your face here in the UK. Never burn bridges. Keep it real 👍
you handled this immaturely and myopically. All too common American emotional & manipulative hothead. AND you got it wrong! Your 126k subscribers got to hear this. Hubris has backfired.
It’s telling how often you repeated your emotionally driven rationale. It was as if you were not only trying to convince us of you being in the right but also convincing yourself because you KNOW you were on very shaky ground.
At least you made this public.
..i dont get it..he had amp fixed since 2019 and never used it untill he get onstage? ...right..
Maybe he has the amp without use, since covid the bands dont play so often, besides that, maybe the owner didnt blast it out in that time
So he wants longer than a new amp's warranty on the replacement valves? Purchased more than the warranty period before the pandemic began? Good onya, champ.
Well... from watching the whole thing... Your still driving the tubes past their specified limit. And yea I agree that he runs it all the way open. He still will too.
I warned him not to exceed 7 in the Master for long and to use a fan.
house voltage is usually 120 -124 in Cal. GENERATORS at gigs can be more /
50 years checking these numbers
motion picture company sold to Disney 1996
Dream Quest Images
LOVE WATHING YOU trouble shoot
wire tied built computers for motion control
specials effects 1976-1989
Cool history. Cool time to be in movies.
You should contact Sovtek, and im sure they'd comp the tube after seeing this.
My first real amp was a '74 Marshall MKII with 6550s. I can tell you from experience that if you're playing loud enough to get those tubes distorting it will part your hair and probably your scalp.
@Orandy lol..youre an idiot that didnt read the description or get the point of that video you are linking into your comment.
@Orandy read the damn video description.... you have no freakin clue what you are babbling about.
@Orandy its a pro-woman video you bonehead. He just added some humor into it to take the edge off of the subject. He used the images you are bitching about to raise awareness of women being abused but he " just wants them to have fun" and be happy. You are just trying to brand it as something its not about.
@Orandy Thanks for that impromptu game of "spot the idiot".
@Orandy Don't make it too easy, though ;)
I used to bias those old Unicord distributed Marshalls using the 6550 specs and some of those amps kept coming back. Mostly with tube related issues until someone scolded me for it. The PT is what can't handle the extra current draw when using the 35W plate dissipation figure. You almost have to ignore the 6550 specs and bias the amp like it was using EL34's. The amp would have had a 5A mains fuse if it were designed to run 6550's like the Marshall Major, which does have a massive PT and OT to boot.
I noticed the PT getting super hot in the amps I was biasing using 35W max dissipation. Once I started backing off, the amps stopped coming back to the shop and had less tube failures as well. Hopefully this helps. I think that cold biased sound of those tubes is why people get it in their head that 6550's and KT88's sound a certain way, when in reality they're just cold biased and have a lot more perceived headroom as a result.
Tubes are getting expensive and a lot of times I've just converted those amps back to EL34's by changing those 82K or 150K grid leak resistors to 220K and adjusting the bias range resistor if needed. It was a strange reason Unicord got Marshall to make that change to U.S. imported amps in the first place and I think they gave it up around 1984 or so.
As always, your mileage may vary. You know what you're doing. I'm just sharing my experience with you in case it helps your issue. I enjoy your channel so keep up the good work and have a great day.
I appreciate you sharing the benefit of your experience. Thanks for the comment. Loads of others in the comments also concur with you. I have learned a valuable lesson on this one. I'm not immune to learning.
@@TheGuitologist Thanks for the kind response. For the record, I don't believe that biasing in anyway had anything to do with those tube failures, especially the one that had the toasted white getter flash. I agree you got sent some bad tubes. I had three modern "Mullard" EL34's from a matched quad arc internally and blow in an amp that had no other faults. That was probably the most astounding set of failures in new production tubes I've seen.
Oh for chrissakes! Some days you get the bear and some days the bear gets you. Grow up, Guitologist - you're acting infantile . . You wasted more time with your hot air on the phone then the amp costs
You clearly are not a man of principle then. That’s all this was about.
I've been buying from CE Distribution for close to twenty years and they're the nicest, friendliest company I deal with on a regular basis. Your treatment of them with demands and foul language is uncalled for, especially when your own lack of knowledge and experience is to blame. Third time's the charm? Hope so for your customer.
They should have taken care of the issue. The problem of people not being able to play due to covid was pretty unprecedented and they refused a return on a stupid technicality with a dealer who had been with them for years. Lack of experience? I have HUNDREDS of videos repairing amps. How many you got?
23:53 Karen entered the chat ^^
I would have rather you keep the rings on. If you get zapped it will make a great video.