Repairing Al Gore's Favorite Tube Amp - Fender Excelsior Pawn Shop Special Series
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- เผยแพร่เมื่อ 3 ต.ค. 2024
- This amp was part of the Fender amplifier series called the "Pawnshop Series". This series included the Ramparte, the Vaporizer, the Greta, and the amp you see here - the EXCELSIOR! It came to me cooking tubes and being generally rude, nasty, and sounding like a WAP. It was like the Cardi B of amplifiers. In this video, we'll troubleshoot and repair what's ailing it, namely some red plating power tubes, then we'll demo it with a PRS and a Stratocaster. Along the way, I'll show you some of the good and bad aspects of this model and we'll perform a couple tiny mods and rebias for early breakup.
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Hi Brad, just a few super serial technical remarks...
1. 6V6 is 12W, 6V6GT and JJ6V6S are 14W
2. the voltage to use in cathode bias calculations is the plate-to-cathode voltage, now you measured plate to ground (correct method for fixed bias amps), so subtract the voltage drop over the cathode resistor.
3. cathode bias is best at about 100% of max plate dissipation because increase in cathode current create a larger voltage drop across the cathode resistor and therefore bias it cooler, temporarily.
in this amp i would leave the 470R bias resistor because:
with Pa max = 14W, Rc = 470R and Vrc = 29,2V :
Va = 369,8V (= 399 - 29,2)
Irc = 29,2 / 470 = 62,1mA
Pa = 0,0621 x 369,8 = 23W
=> 11,5W for 1 tube is already only 82% of max plate dissipation.
with your 1K bias resistor you brought it down to:
36,5V / 1000 = 36,5mA
0,0365 x (432 - 36,5) = 14,4W for 2 tubes, which is ONLY 7,2W per tube
Aiken amps has a good article on everything bias, please read up => www.aikenamps.com/the-last-word-on-biasing
Thanks for the comment. I am aware of the Aiken link already. Great site. You are correct on your math, and I appreciate the effort you put into writing it all out; however, there are some other considerations I think you might be missing with the focus on figures, and I'd like to address them.
I already addressed #1 in the video. You are right that my max dissipation figure was wrong for a glass bottle 6V6GT (or JJ equivalent).
You are correct on #2. That was an oversight on my part. Got stuck on autopilot and whiffed on measuring to cathode rather than ground. The actual effect on the numbers was not excessive in the end. Put me off by maybe 8%? Still a mistake, and I own it.
Now on #3... This is NOT what Aiken says (that cathode biased amps can be biased to 100% dissipation at idle). What he says is you can usually "ignore the 70% rule". That's not the same as saying "bias to 100% at idle". I typically stick to the 70% rule even on cathode biased amps because, at the end of the day, it does not USUALLY affect the tone of the amps appreciably at jamming volumes, the amps run cooler overall (which is good for this guy because he wanted reliability and lower tube maintenance as his main mandate), and if anything, an amp running a bit cold will break up sooner on the dial and at lower volumes, which is what many players are looking for anyway, hence the obsession with attenuators these days. Although the onboard camera mic might not reproduce it faithfully as I'd like, the play test yielded a resulting tone that was acceptable to both TJ and I, and the objective of the customer was achieved.
@Alex Maurice no, no one cares about it.
@@TheGuitologist But you biased this amp to about 50% of max power. Try measuring the output power into a resistive load you loose power as you reduce the bias. 80% is probably a good compromise if you really don't want to replace tubes. It's most likely the screen voltage that's too high, I'd increase the PSU resistor to drop it to 330V relative to the cathode. I'm finding good JAN military tubes used at a decent price and am going to try them in our amp. It would be interesting if you measured power of amps that you work on before and after repair. Just below clipping with a waveform that visibly looks like a sinewave is usually below 1% distortion, give it a bit of clipping since these produce rated power at 10% distortion.
Screw social media! Your live chats are always great.
Glad you enjoy them. I have fun in the chat. There are some funny SOBs in my comments sections.
@@TheGuitologist Sometimes I have too much fun that I have to go back to watch the video. And take the burnt food out of the oven D'Oh!
I watch you troubleshoot and feel nostalgic,even though Im only retired 6 months and still have people bringing work to me.Then I remember all the chasing around,getting nowhere and feel just fine.
I'm here for this "Shoddy ass Shit" LOL!! I love that you keep inserting south park clips as you try to sherlock holmes this mess haha. This is very chill but also funny and educational content. I love it, dude!
Hopefully this is Al Gorithm's favorite too. Let's help him out and leave a comment, eh? Numbnuts.
He INVENTED this amp (just like the internet), so... you know... 🧐😒🤣
@@trubadorphotography2541 Al Gorithm didn't invent "the internet", it was "the internets".. And their tubes 🤡🌍
Dude! You're hilarious! Ha Ha! 🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣
Don't forget Mrs. Gore. What a censoring bitch. Dems fail to mention that. Wonder WAP (sic) her opinion on Cardi B would be, in the 80s?
lmao
"That ground lug just popped right off... Shocking!" ...I see what you did there!!
Thank you Brad! You brought me back from the YT maze of logical distortion!!
Carry on....
Glad to help!
I loved my Excelsior amp! I too had heating issues and ended up installing 4 fans from an old PC to keep it from burning up. After that it was very reliable.
And now you know what to do to fix the core issue!
@@stephenhunter70 I don't have it any more. Notice I said "loved" as in past tense. lol I would like to get another one though. Haven't seen them in my local shops though recently.
I believe the chassis ground studs were spot welded on.
Oh my God you plugged a guitar into the "accordion" input! You just can't do that! I'm super cereal!
Where can I find that super cereal?
@Busta SpeekerI miss toys in my cereal.
@@SuperJiggawhat i miss being able to eat cereal. if i do now, ill shit myself....
@@frigglebiscuit7484 I'm sorry man, that's shite.
I had an Exelsior few years ago. It was ratteling from the very beginning. The ratteling stopped when I changed all the tubes. With an Eminence Legend 1518 and new JJ tubes, the amp was perfect !
Hi, and it never rattled again?
I’m thinking that the frecuencies of the stock speaker in brown Excelsior is the cause of the rattle in the tubes. Because i have found that the people change the tubes and then starts to rattle again, but only with the brown one.
I remember when this series came out. The fender vaporizer was the best amp in the series.It had foot switch, jetson cab and reverb.
I think it was the coolest looking one. Was the Greta also part of this series?
@@TheGuitologist yes she was
@@TheGuitologist Yes Greta was one and a cute little amp. I bought one for my daughter. It breaks up at 1/4 vol. Would love to see you overhaul one of those. Love your vids(guitar and politics)
I regret selling my vaporizer.
@@oneeyeddog6127 that amp had a taste tone. I miss mine too.
These amps were quite affordable a few years ago. After this tutorial I found them very desirable. And this teaching of yours make DIY easy. A few years ago you can buy one of these new for less than 300 CND that was a good deal. Thanks Brad and your friend excellent video. 👍
Brad is the Louis Rossman of Tube Amps 🤟😎
He's the "Bob Ross" of """tube""" amps.
@@TheMentalblockrock "just take the capacitor out and beat the devil out of it...just like that."
@@TheMentalblockrock "titanium hwite resistors, pthalo blue knobs, cadmium yellow wires".
Mosdef the louis rossman
Here's a comment for Al! Thanks, again, for bringing us along for the experience.
Got the chance to try one of these out, and loved the tremolo. Really sounded good to my ears! The amp tone was appropriately bluesy/swampy, too. Almost bought it for the tremolo, but didn't need an amp at the time- it was just one of those "Hey! they got one of these!" moments.
I own one- its a GREAT sounding amp !!! and iv ran mine for years with no problems....its a killer tube amp !!!
I have a excelsior and excelsior pro. Same amp. The pro jist came from fender with a eminence legend speaker. I run both those amps full bore and usually with a full or drive pedal. I absolutely love them. Great stereo rig. Ive mever jad a problem with either.
Also, there is a femal surf music band called the "surfrajets". They all llay through excelsior amps. Bass and guitars
Bass too? I usually see a different rig on hers.
Ohhhhhh gotcha, the South Park bit. Carry on everyone
You can blame that design on the penny pinchers at corporate. Somebody said "we can save .02 cents per unit" and they went with it. I see it all the time on some of the cars I work on.
Corporate Amplifier Companies don't care about the Musicians. They put the shit out there and we buy it LOL.
Thank you for this video!!! Really helped my navigate my own repair. I too lost power to all the filament heaters. At 30:55 in your video the same thing has happened to you. Such a mystery at first. But same as yours - the spade clip on mine was loose or corroded, both of them. But I still had full plate voltage and could hear the transformer working. This filament supply connection is definitely a weak link in the power supply chain. Great tip for any Excelsior owners. A good idea maybe be to put in a soldered connection here..
Wait! My nuts ARE numb! How the hell does Brad diagnose these issues sight-unseen? Impressive.
Nuts are among a group of ailing parts I always diagnose from a distance. ;)
I've never seen one of these it's got a nice voice with a a little bite and sum hair on it .for sure....Brad saves the day
Bonus points for the Jimmy Smith.👍👍
this video is super serial. manbearpig certainly must have sabotaged this amp to get back at the inventor of the series of tubes we call interwebs.
This amp with a JBL D130 is something special.
I have one of these Excelsiors which I use primarily as a harp amp, but also for guitar. An Eminence Legend 1518 is a great speaker for these amps. I swapped the tone switch for a proper treble cut tone control, and modified the preamp stage by dropping the preamp voltage, and changing the 3.3k cathode resistor on V1a to 2.7k. I wanted to keep the "Valco" vibe, snd they used 220k-270k plate resistors with 2.7k cathode. If you change the values to typical Fender 100k and 1.5k you pretty much get a 6G2 Princeton preamp...
Other mods I made were a footswitch jack for the tremolo, and put V1b's bypass cap on a switch, which cleans the amp up, but keeps that budget amp vibe....
MOSFETs are quite neat, they work almost exactly like a triode valve, and if you adjust the voltage in a tube amp design you can substitute all triodes with MOSFETs, Session did exactly that in the 80s.
I have played some really great sounding mosfet amps. SS can be very good.
Still loving my Session Rockette since 1986 !
I really was especting at min 10 to see some smoke getti g out of the nice resistor box. You replaced the 10W cathode resistor for a who knows how much dissipation can hold those inside the box...
I was thinking the same thing !! The resistor boxes I have had contained 1/4 watt resistors !! Seems they would burn out quickly !!
I looked it up. The box has 1W resistors. (I was halfway expecting 1/2W.) Still, I wouldn't run it for very long.
Great stuff Brad, I'm super cereal! The repair and the SP clips....too funny
Mike Campbell is a big fan of the Excelsior
You had me at that shot of bourbon at the beginning ... lol ... That amp sounds great to me and I have a PRS CE 24 with the knob that has 5 positions , black faced head stock ... Good vid ...
I'm not sure, but this one is a 2002 CE24, and it probably originally had a 5-way rotary too.
love these videos Brad. Can't wait to see the rest of those guitar catalogs that one of your subscribers sent in awhile back:)
Tip the cabinet on its side to lengthen the umbilical cord.
Great tip! Sometimes you just gotta look at things from a different angle.
@@TheGuitologist Remove it and sell the stem cells to Nancy Pelosi.
@@adamimberti6948 Nancy gets the adreno chrome.
@@adamimberti6948 Not if Christopher Butthole Reeve gets the cells first!
Sounds great after the fix, to me. Does the speaker stay? Just thinking that the lower frequencies were shaking the joints/connections and therefore = breakup. I'm Celestion Vintage 30 only. But that's just me. People buy this stuff looking for a "deal" anyway. What I do. If I get burnt, I can take the loss. That's the game. We're here and watchin'. Good stuff. Norm.
Man, modern fender don't make em like modern mesa lol. But seriously good stuff, your amp repair vids are always A++ 110% good. it's like I'm not even learning.
Good troubleshooting and outcome
That resistor was more physically stable down on the board, but is of course better dissipating heat off it. I wonder if a little standoff on each end could be made to keep the weight of that wirewound from working at the leads and solder joints. Only a concern if it's getting banged around. of course.
Cool stuff man, thanks for uploading this. I had a Mesa Boogie Mini Rec that used to cook tubes.The amp ran off of el84 tubes. I was told that el84 are designed to burn hot, and that was the issue but I've always wondered until now. You are a great teacher brother.
Those mosfets have pretty high voltage specs and can essentially be used in place of a triode.
Do not replace the speaker! The Fender Special Design speaker is part of the charm and uniqueness of this amp. Lots of people change this speaker thinking that they're doing themselves a favor, but they're not. Does anyone think that Fender didn't try other speakers in there when they designed it? They were probably designing the circuit with Jensens before they got the first bespoke speakers for this amp. Historically, bespoke stuff ends up being more a lot more valuable to collectors.
Right on Brad......................amp repair and Kentucky Bourbon..........life at it's finest
This is the best video on youtube, and I'm being super serial.
Drinkin devil's blood and guitar... what could possibly go wrong?? Lol
Never got a notification for this one either!
No surprise there.
The thumbnail for the video is hilarious!
When I used to repair vintage electronics I would replace any resistors I saw discoloured on the board with the next wattage up or the one above that depending on space. It sure helped as I had more than few that would blister you as soon as you touched them then go up from say 2W to 5W and mildly hot and go to a 7, or 10W if it would fit, and you could rest your finger on it.
Al Gore said in 2008 the Arctic would be free of ice by 2013. Ooopsie
There have been MANY Ooopsies since, and mostly worse ones, in the wrong direction. Don't catch fire about it, it's just your pants.
He also said ManBearPig would kill us all.
@@TheGuitologist He was super cereal about it.
@@TheGuitologist MBP? 520K is a good start, I would have thought.
That shielding could have been shorting and causing the red-plating.
I noticed the same with my Excelsior.
Also, I did replace the speaker with a custom re-coned that really makes all the difference in the world.
Originally I had planned to add a Tone Control Mod., however after replacing/upgrading the speaker it is fine as is.
Thanks for the Vid...I own a Vaporizer and I had not played it in a couple of years and when I turned it on, the reverb did not work. Got is going by cleaning the RCA jack that goes to the spring reverb unit. Hope the rest of the connections stay good!
A pot in place of that tone switch is another winning mod.
The Excelsior Pro has a few improvements, namely an upgraded speaker. I dig mine; I also have the Vaporizer; both are surf green. Also have a DecoTone. They sound great, and the prices were reasonable, except for the DecoTone. No overheating problems on any of them.
who hasn't said "that accordion needs to be louder".
Those damn amps. Fender never should have put PCBs in those amps.
Great vijeo, Brad and some great noodling by TJ!!
There isn't much to those things. I guess the marketing strategy was based on cosmetics
100%...and it's working. I still want one lol
The definitely got some things right. The chassis mounted tube sockets is superior to about 95% of the stuff in its price range. They didn't skimp on that important feature.
they really should have put a small spring reverb tank on the side of the cabinet for these amps.
Always thought this series of amps was pretty cool for what they were. The Vaporizer was the best out of the three usable offerings (the Greta micro amp was about as useless as hen's teeth) imho, with its "total bypass, full tilt boogie at maximum 11 watt blastage with no pots or controls in the way of the pure raging maxed volume tone" feature...that little bugger absolutely SCREAMED through those twin 10 inchers when you hit that bypass switch! It looked pretty damned cool doing it too, with almost evil "black widow" grill opening. Wouldn't mind getting my hands on one, especially the red tolex version, if anyone out there in inter-webber-fier land wants to part with theirs for the right price (nudge nudge wink wink...)!
Excellent job as per usual, Brad, I'm being thooper cereal!
What, no chicken pickin' ? :) sounds nice to me. Well done.
laughed my ass off at the ground part. good lord.
I just bought one of these last week. Has a fender speaker with a bigger magnet. Hopefully I will have good luck with it. When I got it, I had to tap a power tube for it to work properly. Swapped power tubes and the problem followed the tube
Brad your soldering skills are excellent to watch
Just as I was sure I had seen everything, the Al Gore Rhythm sent me this.
The amp sounds like someone is playing inside a cardboard box. That was the issue I had with the Blues Jr amp too.
Yeah...pretty rough
I mean honestly, this amp sounds like hot garbage mixed with wet dog shit.
Kids: Always drink bourbon when working on electrical equipment.
Fascinating. Shit's way over my head but I enjoy watching you sleuth it all out. And, was that an old PLUSH amp head sitting on the floor underneath the stool your buddy was playing on at the end of the vid? Thought it was a Kustom at first but it didn't look quite right then may have caught a peek at part of the logo. Am I remembering that correctly? If so, man, that takes me back in time a lot of years. Keep up the vids, Brad. I look forward to 'em.
It is a PLUSH indeed. Here is a link to the video where I serviced it a few years back: th-cam.com/video/4tjYK2Ati7Y/w-d-xo.html
@@TheGuitologist [cheech&chongvoice] "Diamond tuck 'n roll man!" [cheech&chongvoice] Thanks Brad!
nice video brad i got one of these amps they sound old and cool i also have the greta great little amp which i use every day would love to see you do the greta man!!
That ground stud looks like it was friction welded, if done properly would give a better connection between thr screw and chassis. Also if I remember right I paid like $200 for mine new then sold it a year ago for $300.
I thought that too. A welded stud that broke because it wasn’t welded properly. Quality control. I’m sure they could have a machine insert an actual screw to save 1 cent per amp. Sheesh.
Just as a thought, when replacing the resistor, how about putting it on the other side of the board so the heat will go up to the chassis and not the PCB?
This isn't a double-sided board, so there's a pad only on the one side to solder to. It's doable, but another solution might be to route out the underside of the resistor area like was done on the other board.
The reason the ground lug wasn’t drilled through is because the protective earth need to be attached to a fastener that can’t be undone from outside the device, and that doesn’t perform any other function. This is usually done by spot welding the stud to the chassis, which seems to have been done poorly or not at all on this device. The safety idea behind that arrangement makes sense, but you can’t stop to wonder if it would just have been better to use a bolt instead.
I think in this case, the regulation failed utterly in its intent.
I gotta say, those chassis look ripe for a point to point project. They could have at the very least spent a few more bucks, get rid of the circuit boards and put in turret boards, it would be 1500 dollar amp all day long. It would be an easy modification to do. Layout is nice and clean.
I know. Why not do the majority of them with the PCB and then do a small run of hand wired ones? Upgrade the transformers a bit and wire on turret boards... Do it in China. Hit a $1000 price point with a better speaker. Could have been cool.
@@TheGuitologist higher wattage speaker too. They barely missed on these. I might have to get one and do it up. The parts are all there. It would just take a little solder.
What I noticed about this amp is that for an amp with a 15" speaker it sure is thin and trebly sounding.
It's got a light/ dark switch if the sound is too bright. Switched to dark, it sounds great with strats.
@@cruelcuts Oh OK, it's been a long time I might have missed seeing that switch.
Very cool little amp nice sav on the heat stroke and cheap ass ground lug 👍👍
Thanks for the great content !!!
Beats me why Fender's marketing department wanted to build a re-issue of a Valco-style amp, when they could have just re-issued the tweed Deluxe: essentially the same guts and similar sound to this scrap pile...good job, Brad...
On your initial test of the bias using your decade box, have you got a speaker or dummy load connected? Is that socket sitting above the board you have piggybacked your decade box to a speaker socket? Could be why you were getting the bias runaway? I've made that mistake once or twice and immediately figured it out before killing something.
I bet the ground lug was supposed to be spot welded in there and they didn’t get a decent weld on it. I imagine a robot welded it together.
Hey, imagine if evolution granted man three hands instead of two? Your mod would have been easier to install. Personally, I prefer the Excalibur amp. It cuts through the mix. Got it?
on those female spade connectors i squeeze the very back of each side so it starts on easy and gets tight all the way on.
Sounds good Brad!
Seems pretty simple to work on compared to most modern amps. Do a few mods to make ot reliable and you're good.
Did they not drill through the chassis for the ground because of appearances maybe? Only reason I can think of.
It's probably on the schedule of CE regulations or something, having to do with a ground lug being accessible from the outside. What was supposed to be a safety feature became a flaw.
Another great video Brad! Who built that Strat TJ was playing?
Behold this shotty-ass shit ! 🤣
Sounds great brother
Not a bad sounding amp. And it definitely sounds like a Fender.
Very cool!!
Papa Lazarou lookin like Phantom of the Opera!
ha ha - had one of those. I replaced the speaker with an eminence. Fender offered a more expensive version that came with the same eminence (but with a fender label on it). So fender did this too. Also, swap out that tone switch (switches in a 470K resistor in and out) with a 470K or 500K tone pot (this is from memory, and memory is not so good - so please verify)! It makes it a nicer amp. I am listening to it now so you have not fixed it yet (in my listening) so I don't know what the fix is yet.
Not sure how I missed this video. Always wanted one of these amps but I have a couple tweed deluxe clones and I figure they're too similar to justify getting one.
I don't understand why half the speaker is blocked by the decorative front-panels. Doesn't that make a difference?
Not enough to matter. It's an open back cab anyway, so you're getting it from all angles really.
28:35 gratuitous League of Gentlemen shot.
"We didn't burn him!"
I have some Black Widows lying around. Would one of those be a worthwhile speaker upgrade ?
I love mine. I swapped the speaker for an eminence red coat
Should have called it the "ManBearPig" amp fix. 🇺🇸
Personally I would take the bias resistor off the PCB and mount it to the chassis, especially to get it away from that electrolytic capacitor.
You're the bearded drinking Bob Ross of amplifiers
The Fender Pro-O-Luxe, everyone!
Tipper Gore will slap a Explicit Lyrics sticker on this channel.
Hi Brad. As always supereb video. The 1K 10W resistor is going to flap around under virbration when the amp is cranked up. Perhaps a means of support to de-stress the leads and more importantly the solder joint would be good. A single ceramic or cheaper metal spacer each end of the lead. What do you think?
Standoffs wouldn't be a bad idea, but I think it'll be ok. This resistor doesn't have that much more mass than the other power resistors which are stood off the board. I doubt the vibrations of notes will dislodge it. The only thing that would dislodge it would be mishandling of the amp, but that kind of force would also dislodge any number of other things, including the ground lugs, apparently.
@@TheGuitologist Hi Brad. Certainly manhandling will cause stress fractures added after heat and sound vibrations after a good session. Having come from 30 years designing and certifying aviation electrical and avionic systems, we would design out a single level failure of this type. Amps are not subject to the same vibrations, but with PCB construction maybe turret terminals so as to provide ventilation and mechanical protection. two problems solved.
I think your solutions are great suggestions.