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Mr.Grumpy

Mesa Studio .22 : Landfill bound!

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I've gotten a good few years from this used amplifier. I've owned it about 9 or 10 years, I think I paid $400 for it back then. It works fine for a few minutes, then after it warms up for a while, it starts hissing and then later, gets this crackling and rumbling noise through the speaker that eventually overwhelms the guitar.  NO, it's not an intermittent effects loop normalling jack; I already have a patch cable on the effects loop. 

I pulled the chassis out years ago to take a look, and the PC board looks like burnt toast. Good ol' board mounted tube sockets. :facepalm: Sure, they're fine until the warranty runs out, and maybe even a few years beyond that. I was reading some amp & electronics forums and although it sounds like a temporary fix MAY be possible, it's due to an ongoing deterioration issue that can't be stopped while using the amp. One forum's advice was to find the burned, carbonized spot on the PC board and scrape it off, as it acts like an extra resistor between random circuit traces. 

The only real long term fix would be to transfer all the existing components to a shiny new circuit board, probably not cost effective for Mesa to do, and probably not for me either. Years ago I saw a foreign, maybe Russian website that was selling "clone" PCBs for many popular tubes amps including Marshall, Fenders and Mesas. Can't find anything now, Mesa seems to do a pretty good job keeping their IP (schematics 'n' such) off the internet. 

I may slide the chassis out, take a few pics, and ask for a quote from Mesa,  just for laughs. But most likely it's bound for the trash heap, the dustbin, garbage dump, landfill....I don't really see any 'rehab' possible that doesn't cost as much or more as just buying another tube amp. 

I've already got a used SS Marshall from GeeSee picked out,  now I have to explain this to the wife. 

 

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Yes, Mesa's "estimated repair chart" shows typical repairs for a Studio .22 to be "$150 - $200" and if that would restore my amp to working condition that price would be a bargain. But if you scroll down on Mesa's repair page, it has a separate entry for "Badly burnt PC board damage" says "need photos for est."  Heck, it would be worth another $400 if Mesa could install a new, fresh board. 

I know electronic stuff doesn't last forever, but we've been spoiled by tweed and silverface Fenders that - of course with maintenance - keep going for 50, 60, 70 years. 

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I used to own a Studio 22, which I really liked when I first got it, but it took a tumble one day and it was never the same, even after they did the repairs. I don't blame them... but I do agree with you that the PCB mounted tube sockets aren't exactly the best approach from a long-term reliability aspect - and their reliability is something they've often pointed to in their marketing.

If that burning is a side effect of the amp's design, it's not your fault... and IMO they should be well aware that it's an issue on older amps if that's the case. OTOH, it's a ~26-34 year old amp now... and it's really not fair to expect things to last forever (old Fenders notwithstanding ;) ) but hey, what do you have to lose by asking? I'd send them a MP3 of what the amp is doing (going from power-up to full noise) and a picture of the PCB and ask for an estimate. The worst that can happen is that they give you a unreasonably high estimate that makes it not worth doing, but then again, you might be surprised. 

BTW, do you have a picture of the PCB that you can post? I'm curious, and would love to see it... :snax:

 

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It couldn't hurt to contact Mesa just for grins. You might be surprised. (Mind, you probably won't but you never know.) Best of luck.

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I'd give Meas a call, there's not really that many folks that work there and they are awesome.

They might be able to fix it and or help you out.

If the board is toast in might just need a jumper wire to kinda get it working again.

 

It's worth a phone call.

 

 

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I opened it up and took a good look inside. It's not as 'toasted' as I thought it was, and although there's "browning" around the tube sockets the worst of the burning is right under a power resistor. It looks like a 2-watt carbon comp type resistor, mounted on the underside of the board. From reading on some amp forum somewhere, it appears this is common and well known occurrence with these amps. I'm sure this is a grid supply that has to be at a particular voltage. My music man amp has something similar - half wave rectifier, a filter cap, and dropping resistor and zener diode. Anytime the amp is on, that resistor probably gets close (or above) 200 degrees F. 

pictures later...

 

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I can't figure out how to put the pics where I want them, or insert text between the photos. :idk: But here they are. The close up picture of the component side shows the charred part of the circuit board by the diode and R131 resistor pads. 

The picture of the solder side of the circuit board shows some browning around the power tube sockets, but I think the real problem is where the large cap and power resistor are. Interesting that the cap is a large value but rated for low voltage, only 16 volts. I think that's the power supply for the LDRs that do the normal gain/boosted gain switching inside the amp. The power resistor mounted under the circuit board may be a repair or re-work, I'm not sure. 

 

Mesa_guts03.thumb.jpg.ad845e55f4e8af15100b26c23ccb4d88.jpg

Mesa_guts01.JPG

Mesa_guts02.JPG

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You'll be happy you dug around a bit and didn't just toss it in the landfill.

 

Tubes do get hot, as do resistors.

Edited by Mikeo
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Obviously I can’t check the PCB traces from here, but they honestly don’t look that bad... you might just need a couple of resistors and maybe a new capacitor or two... I’d definitely consider calling Mesa and getting it fixed.

 

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I played through a Subway Blues for a while and, although I really liked the sound of it (and FOH loved it - especially on the half power setting of ten watts), it ate EL84s (cooked of course) and started making sounds that had nothing to do with my guitar. The PCB is very similar to the Studio 22 with the tube sockets mounted right on the board.

The Fender Hot Rod Deluxe, which I often see in my shop, has the tube sockets mounted on separate smaller PCBs connected to the board with ribbon cables.

 

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I'm with Phil. I'm not an amp guy but that PCB doesn't look too bad to me. Probably well worth having Mesa take a look at it.

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16 hours ago, onelife said:

I played through a Subway Blues for a while and, although I really liked the sound of it (and FOH loved it - especially on the half power setting of ten watts), it ate EL84s (cooked of course) and started making sounds that had nothing to do with my guitar. The PCB is very similar to the Studio 22 with the tube sockets mounted right on the board.

The Fender Hot Rod Deluxe, which I often see in my shop, has the tube sockets mounted on separate smaller PCBs connected to the board with ribbon cables.

 

The repair shop I used to manage had a HRD come in once with a weird smell and supposedly fried output... sure enough, it WAS fried - we found a small rat that got electrocuted inside the amp. You should have heard the yell / scream from the tech who opened the amp and first saw it. :lol: 

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I emailed Mesa, and unfortunately they are not able to replace the board (they're not made anymore), but they think it might be possible to repair the board.  They told me to call & discuss... I have this weird thing where I don't really like to make phone calls, but I got through, and guy at the Mesa factory was very helpful. One of their authorized repair centers was very highly recommended by Mesa's tech,  so I'll probably take it to that guy after calling or emailing him and getting the details. I'd like to avoid the whole disassembly, packing and shipping business if I can. 

 

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I would think at the very least, they could clean the traces and re-solder the connections. I bet that would help alot.

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19 hours ago, seibertdr said:

I would think at the very least, they could clean the traces and re-solder the connections. I bet that would help alot.

I'm pretty sure it uses a multi-layer PCB. It doesn't show up well in the photo, but there's charring of the PCB substrate (presumably epoxy-impregnated fiberglass) so that bits of it are carbonized - which act as extra random resistors in the circuit as the amp warms up. At first it was just hissing, which I could tolerate, but now it's making loud popping and crackling sounds.

I'm going to email the local tech today (he's Mesa's authorized repair guy locally) , see what the fee is going to be and figure out when I can afford to get it fixed.

I've already bought a replacement amp for band practice, a solid state Marshall combo, because volume is more important than tone. :)

* edit * I emailed the amp tech, sent him the same photos posted in this thread. He replied in a couple of hours, and said my amp is in "pretty good condition" and that "I can fix your amp." So he's pretty confident it's repairable. I may have to wait until October to drop it off, that whole paycheck-to-paycheck thing. :rolleyes2:

 

 

Edited by Mr.Grumpy

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