I have two of these amps and schematics. My amp tech had no issues in doing some repairs and adjustements, incl. rewiring a 110V model for 230V usage. Using this beast with 2 ohms load and really pushing it, I'm still happy with it's performance.
I have an old "expensive" de-solder station, (great for IC's), so I used it when I started re caping my older amps. It was tedious and inefficient. but since I was watching your work, I switched to copper braid and ordered some solder suckers. I can confirm your de soldering methods are the most efficient, high quality options available. Happy New Year.
At work, I have an Aoyue desoldering station on the bench, which replaced an 80's era Hakko for which heating elements are no longer available. I actually like the Aoyue quite a lot, and they have several models between $150-$200. I did a few minor mods to the "gun": replacing the spongy-filter in the solder-collection tube with an old-style ceramic wool Hakko filter, and ditching the solder-collection spring, which didn't work well, for the traditional wad of steel wool. It works great, rarely clogs, and is easy to unclog. The tips have a little pipette or nipple on the end, making it gentler on the traces for circuit board work, but also good for sucking solder out of an eyelet board. A spare or replacement gun is 55 bucks, tips are 7 or 8 bucks. The vacuum pump is powerful and has never given me a lock of trouble. The price is reasonable, and you can buy them directly from a US dealer, SRA soldering products, instead of from flea-bay or directly from China. Most of my work at the shop is on old solid state hifi with circuit boards, where the average unit might get 30 parts replaced, and doing all that with solderwick would just take to long, although there are occasions where the gun can't reach into a tight spot and I have to use solderwick. It might be nice to have a vacuum operated desoldering tool that is a straight cylinder and not shaped like a gun, but the straight ones that Pace makes (see Brad's Guitar Garage) are quite expensive. Especially if you're frequently working on double-sided PCB's, you will want a pump-operated desoldering station.
+1 on your comments about desoldering stations. I've had two and always revert back to solder wick and or a plunger type solder sucker. I've been doing this since the 1980s.
So many boards and components crammed together. Not a service friendly amp...yet there you are. Got to be a ton of component killing heat produced from it. Happy new year Lyle.
The most likely reason that original bias trimpot got chewed up is because you, and presumably anyone else who worked on it, *used the wrong screwdriver*. Most mini trim-pots are NOT a standard Philips head; the + slots are actually flat-bottomed !!! If you are going to use an ordinary Philips screwdriver on this type of trimmer, grind the point off of the screwdriver tip, and it will work better. Ideally, you should own the type of RF adjustment & alignment tool made specifically for these pots ----- usually having a non-inductive, non-conductive ceramic or hard plastic shaft and tip ---- but a ground-off Philips screwdriver with metal shaft will work, as long as you're extra careful not to slip out of the trimpot screwdriver slot and contact the board with a metal screwdriver while adjusting the bias! Which is why having a current limiter in line with the AC power is a good idea. (Anybody who aligns radios and FM tuners will already have a selection of non inductive plastic or ceramic screwdrivers, for adjusting the various tuning slugs on the coils, RF and IF transformers, and trimmers). PS, a thousand thumbs up to Lyle for mentioning the ABSOLUTE NECESSITY, in my opinion, of using all three terminals of the bias pot, and wiring it such a way that if the wiper fails the negative bias voltage goes full up; the amp will run "cold" and won't sound it's best, but it will still operate and get you through the gig without blowing up. For Mesa to get this so wrong would be laughable, except that these amps aren't cheap, and whoever spends a small fortune to buy one is not getting anything approaching state of the art construction quality, nor reliability.
Happy New Year, Lyle! Watching your trials and tribulations with this Mess o' Booger, I picture Randall Smith as a footwear salesman shoehorning a size 14 foot into a size 10 shoe.
Soldering stations can be tricky to use. I have never had to clean one but I know it takes a special technique to remove electrolytic capacitors or other components with a soldering gun. I have accidentally pulled a few board traces with one
I watched a video of an amp tech working on a Mesa Boogie amp and he said he usually doesn’t work on them as he ends up popping rolaids like candy while servicing them.Only reason he was servicing it was because it belonged to a relative of his.The inside looked like an amp tech’s nightmare.
The modular boards probably make sense for them from a warranty claim perspective because they can just swap out a whole board instead of diagnosing down to a component level. Bad for long term reliability or serviceability though
Instead of using the relay to shunt the 8 ohm output-transformer tap to ground when there's no speaker cable plugged into the amp, perhaps they should have had the relay essentially mute the amp by grabbing the signal somewhere (just before the phade invertor perhaps) and shunting the signal to ground. Otherwise there are likely to be some inductive surges from the output transformer passing through the relay contacts, and it's probably beating the heck out of the relay....
Muting the signal sounds like a good idea to me. I think connecting the plates of the PI together would be a good place, but I think I'd want to shunt the OT secondary as well. Belt and suspenders. Shunting only the OT secondary would mean a LOT of current on the contacts of the relay if a signal was present, tending to weld them together. Still protecting the primary from overvoltage and a very expensive failure. But if the relay doesn't need to give up it's life defending the OT, that would be good. JMO.
At one time i was under boogies spell . All i wanted was a mark v and my tone chasing quest would be finite. My father rip , he used to say....Be Careful What You Wish For
The LED bias setting showed up on the CJ premier one power amp in the 1981 . Using ic to drive a LED based on cathode voltage across a resistor of set value . That was on EACH tube . Easy to use . The plates where fused . 200 watts for 6 6550 with 4000mfd of power supply caps. 135 lbs . To me setting 4 kt88 with a common bias is at best a very bad idea for an amp that is in the home . For a stage amp it is beyond the pale. Heat and current in a Tube amp well common knowledge from the 1930 to now who would have thunk it . surprised to see the ntc for inrush current. 85 C cap well that will save some money to build and shorting the life of the caps. united chem con is a very good brand at least. Given that bias uses little current a leaky cap is a strong call. The use of those mosfet as a phase inverter for kt88 is a bit backwards . If you are going to use mosfets in the circuit than as outputs and give it the tone from the front end tubes . Much cheaper to live with .
For those who don't recognize it, "CJ" is Conrad-Johnson, tube hifi equipment. Their stuff was generally well designed and well built. John, ever see a Chinese built "Hurricane" monoblock amp with eight 6550's/KT88's? Not well built,, a bit of a kludge, and neither measured nor sounded all that impressive, but it did have one interesting thing about it: individual bias pots for each tube, a digital display for tube current (measured across individual 10 ohm cathode resistors, fusible type in case of a shorted tube) and an 8 position rotary switch to select each tube being biased. Recommended current was approx 48 ma per tube, which read 480 on the built-in digital readout.
Those slotted ribbon cables are weird, I've never seen any quite like those before. Perhaps they are insulated with silicone instead of PVC so that they can handle heat. If so, it's about the only thing inside the amplifier that was actually designed and chosen to work reliabily in a hot environment, other than the tubes themselves. PS, One of the plug-in connectors near the transformer looks to be yellowed and overheated.
At 4:50, " Most guys who are into British sports cars learned to fix 'em themselves". Actually, most guys who own a British sports car own two additional parts-cars so that they can keep just one vehicle running. (How many people own three Mesa amps just to try and keep one amp running?). The British sports car enthusiast also typically owns a plain-jane, boring, everyday car for important things like getting to work and going to the grocery store ---- and for going to the auto parts store to buy some other necessary part for their British sports car which can't be or can no longer be cannibalized from their parts-hulk Scotland-yard cars...😁
Being British born, Richard Thompson decided, why should the Americans be the only ones with fun songs about cars and car culture? Like Mercury Blues and Dead Man's Curve and Little Deuce Coop and Little Old Lady From Pasadena and so on; so,, he wrote "MGB-GT", as well as another song about an outlaw, a Vincent motorcycle, black leather and a redheaded girl....
Here is a non amp-repair question for you, Lyle: do you get any revenue when TH-cam inserts advertisements at the beginning of or in the middle of your videos, and do you get more money if I let the ad play through in its entirety and don't simply hit the "skip ads" button? I usually hit the "skip ads" button automatically, but I'll let them play through if it means you get a little extra money.....
I don't let them put ads in the middle. Just the beginning or end. And only the 4 seconds kind, usually with "skip this BS". Yes, I get revenue, but I don't know if it's any different from skipping vs watching or if anyone actually clicked the link in the ad. I do it more to get YT to promote the videos, not because I get much revenue from them. If you don't have ads, YT doesn't put videos in people's suggested feeds. So I have just enough to tickle the algorithm but not enough to be a whore.
"this amp had caught on fire before." Who buys this stuff? As you well know I am browned off on Mesa and that one is going back to the factory. You're a little harsh on the Britmobiles. I drove the hell out of my Morris Minor and both of the MGAs I had. Course I worked in a foreign car parts store and any time I had to go some distance I'd fill up a milk crate with parts and tools. For pots like that I use a cut down exacto knife I made into a very thin screwdriver. Maybe Randy oughtta take my idea and patent it.
"Browned off"? That's an interesting expression, one which I've never heard before. Is that a reference to what Boogies do, sizzle and smoke like a fry pan? If you load a Boogie with British tubes and let it cook, does the resulting "Mullard reaction" make the tone sweeter and more buttery? 🤣🤔
Working on Mesas products is such a PIA. The pads and the traces are so minuscule. Some of the components are under specd and the layout on the printed circuit boardis abysmal. The circuit board is way overpopulated. Just bad design all the way around. For a “ boutique “ amplifier they are overpriced for what you get. No consideration has been given to the poor technician who has to service these damn things.
Those PCB's are wafer-thin and flex alarmingly while being worked on and manipulated. To board-mount *8* octal ceramic sockets and *8* KT88'S on those boards is negligent, damn near criminal IMHO.
You really hate Mesa Boogie, don't you! Every Mesa amp you work on you have a rag-out title to the video...😄 Why don't you just work on something else for your videos and save the hate-on, just suggesting here. Peace. 🙂
God bless you, sir. Going where no man has ever wanted to go before.
Dude I have one hitting my bench next week. So glad I saw this.
I have two of these amps and schematics. My amp tech had no issues in doing some repairs and adjustements, incl. rewiring a 110V model for 230V usage.
Using this beast with 2 ohms load and really pushing it, I'm still happy with it's performance.
The knowledge your sharing with us is fantastic and your not ragging your just pointing out bad design that can be improved on thankyou
I have an old "expensive" de-solder station, (great for IC's), so I used it when I started re caping my older amps. It was tedious and inefficient. but since I was watching your work, I switched to copper braid and ordered some solder suckers. I can confirm your de soldering methods are the most efficient, high quality options available. Happy New Year.
At work, I have an Aoyue desoldering station on the bench, which replaced an 80's era Hakko for which heating elements are no longer available. I actually like the Aoyue quite a lot, and they have several models between $150-$200. I did a few minor mods to the "gun": replacing the spongy-filter in the solder-collection tube with an old-style ceramic wool Hakko filter, and ditching the solder-collection spring, which didn't work well, for the traditional wad of steel wool. It works great, rarely clogs, and is easy to unclog. The tips have a little pipette or nipple on the end, making it gentler on the traces for circuit board work, but also good for sucking solder out of an eyelet board. A spare or replacement gun is 55 bucks, tips are 7 or 8 bucks. The vacuum pump is powerful and has never given me a lock of trouble. The price is reasonable, and you can buy them directly from a US dealer, SRA soldering products, instead of from flea-bay or directly from China. Most of my work at the shop is on old solid state hifi with circuit boards, where the average unit might get 30 parts replaced, and doing all that with solderwick would just take to long, although there are occasions where the gun can't reach into a tight spot and I have to use solderwick. It might be nice to have a vacuum operated desoldering tool that is a straight cylinder and not shaped like a gun, but the straight ones that Pace makes (see Brad's Guitar Garage) are quite expensive.
Especially if you're frequently working on double-sided PCB's, you will want a pump-operated desoldering station.
A real pro, forge on and fix the mess. Worth your weight in gold.
Great way to start the new year!
+1 on your comments about desoldering stations. I've had two and always revert back to solder wick and or a plunger type solder sucker. I've been doing this since the 1980s.
Happy New Year! 👍🏴👍
So many boards and components crammed together. Not a service friendly amp...yet there you are. Got to be a ton of component killing heat produced from it. Happy new year Lyle.
FIRE and smoke are part of the tone? LOL. Mesa should put that on T-shirts. (shaking my head)
The most likely reason that original bias trimpot got chewed up is because you, and presumably anyone else who worked on it, *used the wrong screwdriver*. Most mini trim-pots are NOT a standard Philips head; the + slots are actually flat-bottomed !!! If you are going to use an ordinary Philips screwdriver on this type of trimmer, grind the point off of the screwdriver tip, and it will work better. Ideally, you should own the type of RF adjustment & alignment tool made specifically for these pots ----- usually having a non-inductive, non-conductive ceramic or hard plastic shaft and tip ---- but a ground-off Philips screwdriver with metal shaft will work, as long as you're extra careful not to slip out of the trimpot screwdriver slot and contact the board with a metal screwdriver while adjusting the bias! Which is why having a current limiter in line with the AC power is a good idea. (Anybody who aligns radios and FM tuners will already have a selection of non inductive plastic or ceramic screwdrivers, for adjusting the various tuning slugs on the coils, RF and IF transformers, and trimmers).
PS, a thousand thumbs up to Lyle for mentioning the ABSOLUTE NECESSITY, in my opinion, of using all three terminals of the bias pot, and wiring it such a way that if the wiper fails the negative bias voltage goes full up; the amp will run "cold" and won't sound it's best, but it will still operate and get you through the gig without blowing up. For Mesa to get this so wrong would be laughable, except that these amps aren't cheap, and whoever spends a small fortune to buy one is not getting anything approaching state of the art construction quality, nor reliability.
This amp just keeps getting better over time. I'm glad I watched this so I can cross this turd off my wish list.
Man, you know your stuff…my 65 Princeton Reverb is gonna be on your bench soon
Happy New Year, Lyle!
Watching your trials and tribulations with this Mess o' Booger, I picture Randall Smith as a footwear salesman shoehorning a size 14 foot into a size 10 shoe.
Happy New Year Sir and wish you the best !
Thanks Lou! Same to you and yours.
What's your opinion about solder suckers? Happy new year Lyle
Soldering stations can be tricky to use. I have never had to clean one but I know it takes a special technique to remove electrolytic capacitors or other components with a soldering gun. I have accidentally pulled a few board traces with one
I watched a video of an amp tech working on a Mesa Boogie amp and he said he usually doesn’t work on them as he ends up popping rolaids like candy while servicing them.Only reason he was servicing it was because it belonged to a relative of his.The inside looked like an amp tech’s nightmare.
Was there a part 2 of this amp? Can't find it on the video playlist. I would like to hear the final results of the repairs.
The modular boards probably make sense for them from a warranty claim perspective because they can just swap out a whole board instead of diagnosing down to a component level. Bad for long term reliability or serviceability though
Your voice reminds me of Neil Pearts voice. That's for another nice video.
Instead of using the relay to shunt the 8 ohm output-transformer tap to ground when there's no speaker cable plugged into the amp, perhaps they should have had the relay essentially mute the amp by grabbing the signal somewhere (just before the phade invertor perhaps) and shunting the signal to ground. Otherwise there are likely to be some inductive surges from the output transformer passing through the relay contacts, and it's probably beating the heck out of the relay....
Muting the signal sounds like a good idea to me. I think connecting the plates of the PI together would be a good place, but I think I'd want to shunt the OT secondary as well. Belt and suspenders. Shunting only the OT secondary would mean a LOT of current on the contacts of the relay if a signal was present, tending to weld them together. Still protecting the primary from overvoltage and a very expensive failure. But if the relay doesn't need to give up it's life defending the OT, that would be good. JMO.
Thank you again for these immensely helpful videos. I wanted to ask, have you done much work on any of the mesa bass 400 or 400+'s?
Thanks. Yes, they are very flawed amps, if not as bad as this one here.
Hello, what were some of the common problems with the 400+'s and do you know if the Ampeg SVT2 Pro would be better to service?@@PsionicAudio
At one time i was under boogies spell . All i wanted was a mark v and my tone chasing quest would be finite.
My father rip , he used
to say....Be Careful What You Wish For
I've spent many a night arguing with Randall Smith myself... you're right, he doesn't care a bit!
The LED bias setting showed up on the CJ premier one power amp in the 1981 . Using ic to drive a LED based on cathode voltage across a resistor of set value . That was on EACH tube . Easy to use . The plates where fused . 200 watts for 6 6550 with 4000mfd of power supply caps. 135 lbs . To me setting 4 kt88 with a common bias is at best a very bad idea for an amp that is in the home . For a stage amp it is beyond the pale. Heat and current in a Tube amp well common knowledge from the 1930 to now who would have thunk it . surprised to see the ntc for inrush current.
85 C cap well that will save some money to build and shorting the life of the caps. united chem con is a very good brand at least. Given that bias uses little current a leaky cap is a strong call. The use of those mosfet as a phase inverter for kt88 is a bit backwards . If you are going to use mosfets in the circuit than as outputs and give it the tone from the front end tubes . Much cheaper to live with .
For those who don't recognize it, "CJ" is Conrad-Johnson, tube hifi equipment. Their stuff was generally well designed and well built. John, ever see a Chinese built "Hurricane" monoblock amp with eight 6550's/KT88's? Not well built,, a bit of a kludge, and neither measured nor sounded all that impressive, but it did have one interesting thing about it: individual bias pots for each tube, a digital display for tube current (measured across individual 10 ohm cathode resistors, fusible type in case of a shorted tube) and an 8 position rotary switch to select each tube being biased. Recommended current was approx 48 ma per tube, which read 480 on the built-in digital readout.
I'm looking at all that ribbon cable and wondering how many feet of antenna / transmission line you have there.
Those slotted ribbon cables are weird, I've never seen any quite like those before. Perhaps they are insulated with silicone instead of PVC so that they can handle heat. If so, it's about the only thing inside the amplifier that was actually designed and chosen to work reliabily in a hot environment, other than the tubes themselves. PS, One of the plug-in connectors near the transformer looks to be yellowed and overheated.
At 4:50, " Most guys who are into British sports cars learned to fix 'em themselves". Actually, most guys who own a British sports car own two additional parts-cars so that they can keep just one vehicle running. (How many people own three Mesa amps just to try and keep one amp running?). The British sports car enthusiast also typically owns a plain-jane, boring, everyday car for important things like getting to work and going to the grocery store ---- and for going to the auto parts store to buy some other necessary part for their British sports car which can't be or can no longer be cannibalized from their parts-hulk Scotland-yard cars...😁
Mess-a ?
Customer: "Hey, I have a problem with my amp. It's a Mesa Boogie."
Lyle (under his breath) "Sonofabitch."
I wouldn't own a mesa if it was given to me.
However, one can completely disassemble an MG Midget with 7/16; 1/2; and 9/16 end wrenches plus maybe a heat wrench! LOL
Being British born, Richard Thompson decided, why should the Americans be the only ones with fun songs about cars and car culture? Like Mercury Blues and Dead Man's Curve and Little Deuce Coop and Little Old Lady From Pasadena and so on; so,, he wrote "MGB-GT", as well as another song about an outlaw, a Vincent motorcycle, black leather and a redheaded girl....
Clearly the R&D department do not speak with the guys in servicing.
Here is a non amp-repair question for you, Lyle: do you get any revenue when TH-cam inserts advertisements at the beginning of or in the middle of your videos, and do you get more money if I let the ad play through in its entirety and don't simply hit the "skip ads" button? I usually hit the "skip ads" button automatically, but I'll let them play through if it means you get a little extra money.....
I don't let them put ads in the middle. Just the beginning or end. And only the 4 seconds kind, usually with "skip this BS".
Yes, I get revenue, but I don't know if it's any different from skipping vs watching or if anyone actually clicked the link in the ad.
I do it more to get YT to promote the videos, not because I get much revenue from them. If you don't have ads, YT doesn't put videos in people's suggested feeds.
So I have just enough to tickle the algorithm but not enough to be a whore.
@@PsionicAudio , good to know, thanks.
@@PsionicAudio Tickling the algorithm is illegal in some states. I say if both parties consent, where's the crime? 😛
"this amp had caught on fire before." Who buys this stuff? As you well know I am browned off on Mesa and that one is going back to the factory. You're a little harsh on the Britmobiles. I drove the hell out of my Morris Minor and both of the MGAs I had. Course I worked in a foreign car parts store and any time I had to go some distance I'd fill up a milk crate with parts and tools. For pots like that I use a cut down exacto knife I made into a very thin screwdriver. Maybe Randy oughtta take my idea and patent it.
"Browned off"? That's an interesting expression, one which I've never heard before. Is that a reference to what Boogies do, sizzle and smoke like a fry pan? If you load a Boogie with British tubes and let it cook, does the resulting "Mullard reaction" make the tone sweeter and more buttery? 🤣🤔
Starting the new year with a colossal pain in the ass! Eight kt88s???? That design alone needs to laughed out of town!
I thought Mesa amps would be perfect in the construction with what they cost
Things will get better for Mesa Boogie now. They’ve “partnered” with Gibson after all. 🙄
Oberheim. Tobias. Slingerland. Etc.
Yeah, and even more efficient bean counters, and screwing dealers out of their franchise too because you have to carry Gibson as well.
Amp catching on fire is bad engineering
mesa 8 kt88 est très loin de la fiabilité d un hiwatt 200 ou 400..sans parler de Laney Nexus Tube 400
Working on Mesas products is such a PIA. The pads and the traces are so minuscule. Some of the components are under specd and the layout on the printed circuit boardis abysmal. The circuit board is way overpopulated. Just bad design all the way around. For a “ boutique “ amplifier they are overpriced for what you get. No consideration has been given to the poor technician who has to service these damn things.
Those PCB's are wafer-thin and flex alarmingly while being worked on and manipulated. To board-mount *8* octal ceramic sockets and *8* KT88'S on those boards is negligent, damn near criminal IMHO.
glad i didnt buy one!
Some techs won't even look at boogie. Can't say I blame them. Overrated, overpriced. Be interesting to see the result now that Gibson has taken over.
You really hate Mesa Boogie, don't you! Every Mesa amp you work on you have a rag-out title to the video...😄 Why don't you just work on something else for your videos and save the hate-on, just suggesting here. Peace. 🙂
There is no ragging in the video title.
I fix the amps sent to me for repair.
Sorry to hurt any fanboy feelings. Reality bites sometimes.