Repaired Plexi died in 10 mins

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Hey, all,
I bought a 1967 Super Bass in December but at the time it wasn’t functioning. I took it to an amp tech I’ve never used before and he fixed a blown tube socket, replaced the caps, retubed it and gave it a grounded power chord. It took a month. Thing is, I finally brought it home tonight, played it for 10 minutes and it just went silent. Died without a sound. The mains fuse is clearly blown. No idea beyond that. Needless to say I was incredibly pissed. Do you think this is an instance of bad repair work? What could be wrong?

There were some potential red flags. The tech told me the amp sounded “anemic” because of the design and I’d probably want to use it for pedals. What?! Anemic Marshall Plexi?! A `67 Plexi for pedals?? When I brought it home, the amp wasn’t as loud as I expected. Maybe a bit quieter than my `87 JCM800, which is 50 watts. It only got drive when everything was dimed. And there was an odd squishy sound in the low register when I’d chug on chords. Also the indicator light wasn’t working. Any advice? Insight? Should I take it back to the same shop? I’ve already sunk $550 into repair work. Thanks!
 

StrummerJoe

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Hey, all,
I bought a 1967 Super Bass in December but at the time it wasn’t functioning. I took it to an amp tech I’ve never used before and he fixed a blown tube socket, replaced the caps, retubed it and gave it a grounded power chord. It took a month. Thing is, I finally brought it home tonight, played it for 10 minutes and it just went silent. Died without a sound. The mains fuse is clearly blown. No idea beyond that. Needless to say I was incredibly pissed. Do you think this is an instance of bad repair work? What could be wrong?

There were some potential red flags. The tech told me the amp sounded “anemic” because of the design and I’d probably want to use it for pedals. What?! Anemic Marshall Plexi?! A `67 Plexi for pedals?? When I brought it home, the amp wasn’t as loud as I expected. Maybe a bit quieter than my `87 JCM800, which is 50 watts. It only got drive when everything was dimed. And there was an odd squishy sound in the low register when I’d chug on chords. Also the indicator light wasn’t working. Any advice? Insight? Should I take it back to the same shop? I’ve already sunk $550 into repair work. Thanks!
I would certainly take it back. Very next day if not possible on the same day.

I wouldn't wait for advice.
 

South Park

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The indicator light is the heaters . You should check for voltage at the socket 6 v AC . If the transformer is bad nothing the tech did to cause this the heaters worked when the repair work was done .
 

paul-e-mann

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Hey, all,
I bought a 1967 Super Bass in December but at the time it wasn’t functioning. I took it to an amp tech I’ve never used before and he fixed a blown tube socket, replaced the caps, retubed it and gave it a grounded power chord. It took a month. Thing is, I finally brought it home tonight, played it for 10 minutes and it just went silent. Died without a sound. The mains fuse is clearly blown. No idea beyond that. Needless to say I was incredibly pissed. Do you think this is an instance of bad repair work? What could be wrong?

There were some potential red flags. The tech told me the amp sounded “anemic” because of the design and I’d probably want to use it for pedals. What?! Anemic Marshall Plexi?! A `67 Plexi for pedals?? When I brought it home, the amp wasn’t as loud as I expected. Maybe a bit quieter than my `87 JCM800, which is 50 watts. It only got drive when everything was dimed. And there was an odd squishy sound in the low register when I’d chug on chords. Also the indicator light wasn’t working. Any advice? Insight? Should I take it back to the same shop? I’ve already sunk $550 into repair work. Thanks!
Really it could be anything, take it back to the guy, he owes you a working amp!
 

Matthews Guitars

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For one thing, 550 dollars for that amount of work is OBSCENE. Unless most of the money went into expensive NOS vintage tubes. That job is two, maybe three hours bench time MAX. I'd have charged not more than 225 labor plus parts and felt bad about charging that much. I charge 75 dollars an hour labor and would most likely charge 2 hours for that work.

Unfortunately I'd be focused on your output transformer at this point, and give it a full diagnostic by disconnecting it and checking its per-winding DC resistance and inductance. I'd really HOPE that the OT is still good but I'd be prepared for the worst.

If it is a bad OT, then your best option short of having the original rewound, is a Heyboer, since Chris Merren (Merren Audio) apparently is all but out of the business due to now working a "day job".

Heyboer does rewind original transformers, apparently. If the OT is bad, this would be the way to preserve as much originality as possible. But at a higher price than simply replacing the OT with a correct new replacement.
 

Chris-in-LA

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The indicator light is the heaters . You should check for voltage at the socket 6 v AC . If the transformer is bad nothing the tech did to cause this the heaters worked when the repair work was done .
I don’t think there are any Marshall amps that run a 6 volt lamp off the heaters. Also not sure what you’re suggesting in terms of troubleshooting or repairs.
 

Spanngitter

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Beside the fact that it is impossible to point you here into any direction of TS (unless somebody owns a really good working crystal ball) there is still some kind of warranty for the work this tech has to give to you, especially after charging an obsessive amount of money for the repair already conducted. However, it could be simply a foul tube (which can occur from time to time) but do not TS on your own here, take it back to the tech and explain calm what occured and that you want him to have another look to verify his work.
Regarding this repair bill it would be really interesting what the itemization was as for that price I'd expect a complete overhaul plus a real good full set of tubes which provides me an amp which lasts again for decades.
 

Seanxk

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As has been mentioned, get it back to the tech, I would also hope he has given you everything he took out of the amp inc the valves.
If he finds it's a transformer, 1, I would not expect to pay for the labour for that and 2, I would take the amp away and say thankyou, goodbye.
 

PelliX

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I don’t think there are any Marshall amps that run a 6 volt lamp off the heaters. Also not sure what you’re suggesting in terms of troubleshooting or repairs.

Just ignore S.P. - he clearly didn't read what was going on, as usual, and spouted some random "tech tips". It's a little annoying, but you get used to filtering it out.

As far OP is concerned: it's all been said - the price is pretty damn high for what was done. I'd certainly return (it) and have a word with the tech. It could be a stroke of really bad luck, i.e. fix one thing and the next one breaks or he could have buggered something. Handing a customer an amp back without a working indicator light (and no mention of this) seems odd. It's probably one of the easiest things to fix, provided you have the right part. Best of luck with that amp!
 

StingRay85

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If you put in fresh tubes, running it for at least half an hour on a signal generator and a dummy load seems to be reasonable if you want to check if the bias remains stable. Having it break down in 10 minutes is really unacceptable.
 

neikeel

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That is a steep bill.
Lamp is 6.3v off the heaters on the PT if a 67 with Drakes or off heater chain if Dagnalls.
Take it back, explain, give him a chance. Ask him to check it over - not shotgun repair. If he can’t tell you what is wrong/what he needs to do then walk away. I work on these for cost of parts and some decent wine but am on wrong continent for you!!
 
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That is a steep bill.
Lamp is 6.3v off the heaters on the PT if a 67 with Drakes or off heater chain if Dagnalls.
Take it back, explain, give him a chance. Ask him to check it over - not shotgun repair. If he can’t tell you what is wrong/what he needs to do then walk away. I work on these for cost of parts and some decent wine but am on wrong continent for you!!
It has the Drake transformers.
 
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I talked to the tech today and he said he's going to take another look at it tomorrow. He said it could be a bad power tube (it has a quartet of new, matched JJs). That's a reasonable first assumption, I guess. I can't physically see anything wrong with the power tubes, no blackening or burning. Not sure that means anything though. I also mentioned that the indicator light didn't work, and he said it didn't work from the beginning. ?? Well, yeah, that's why I brought the amp to be fixed. One of my main concerns is the amp didn't have the push you'd expect from a 100-watt Marshall. The tone seemed weak. I told him that it felt like something is wrong with the output, before the fuse blew. He said he went over the preamp pretty closely, which I didn't really understand. God, I just want to get this Plexi playing in tip top shape. It's turning into a marathon.
 

Dblgun

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That is a steep bill.
Lamp is 6.3v off the heaters on the PT if a 67 with Drakes or off heater chain if Dagnalls.
Take it back, explain, give him a chance. Ask him to check it over - not shotgun repair. If he can’t tell you what is wrong/what he needs to do then walk away. I work on these for cost of parts and some decent wine but am on wrong continent for you!!

@neikeel , what do you consider decent wine and does that eliminate everything with a screw on cap rather than a cork?
 

PelliX

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I talked to the tech today and he said he's going to take another look at it tomorrow. He said it could be a bad power tube (it has a quartet of new, matched JJs). That's a reasonable first assumption, I guess. I can't physically see anything wrong with the power tubes, no blackening or burning. Not sure that means anything though. I also mentioned that the indicator light didn't work, and he said it didn't work from the beginning. ?? Well, yeah, that's why I brought the amp to be fixed. One of my main concerns is the amp didn't have the push you'd expect from a 100-watt Marshall. The tone seemed weak. I told him that it felt like something is wrong with the output, before the fuse blew. He said he went over the preamp pretty closely, which I didn't really understand. God, I just want to get this Plexi playing in tip top shape. It's turning into a marathon.

Wow, certainly not a mind reader, that tech... :shrug: If a customer brings you a defective device and there's more broken than anticipated, generally you have two strategies; fix everything because that was what the customer wanted or inform the customer of the situation and let them decide. I see @neikeel has offered to do this for decent wine. I'm also on the wrong continent, but let the record show that I would do it for reasonably cheap beer... :rofl: I know next to nothing about wine, so I'm looking forward to neikeel's input - maybe I can pick up a thing or two! I know that the cartons are bad, and I've been told anything under a tenner a bottle is Chateau Migraine...

As for the power tubes, no - there doesn't have to be any obvious visible sign of them being bad - so the theory stands.
 
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Beside the fact that it is impossible to point you here into any direction of TS (unless somebody owns a really good working crystal ball) there is still some kind of warranty for the work this tech has to give to you, especially after charging an obsessive amount of money for the repair already conducted. However, it could be simply a foul tube (which can occur from time to time) but do not TS on your own here, take it back to the tech and explain calm what occured and that you want him to have another look to verify his work.
Regarding this repair bill it would be really interesting what the itemization was as for that price I'd expect a complete overhaul plus a real good full set of tubes which provides me an amp which lasts again for decades.
Beside the fact that it is impossible to point you here into any direction of TS (unless somebody owns a really good working crystal ball) there is still some kind of warranty for the work this tech has to give to you, especially after charging an obsessive amount of money for the repair already conducted. However, it could be simply a foul tube (which can occur from time to time) but do not TS on your own here, take it back to the tech and explain calm what occured and that you want him to have another look to verify his work.
Regarding this repair bill it would be really interesting what the itemization was as for that price I'd expect a complete overhaul plus a real good full set of tubes which provides me an amp which lasts again for decades.
Here is the itemized repair list …
 

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DaDoc

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$550 for repairs? That's ridiculous! WAYYY overpriced IMO, even with a new set of tubes!

Hell yeah, I would take it back, and demand it be done right!

I had the local tech go through my '73 JMP last summer, he did a great job, and it cost me around $200.00..Although my tubes were still good, so he didn't have to change those.

Those old amps are some of the easiest in the world to fix, no excuse for any competent tech to not get it right.

Last night one of my Twin Reverbs died on me, so I'll be taking that one to him soon..I'm hoping his prices haven't skyrocketed like everything else!
 
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PelliX

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$550 for repairs? That's ridiculous! WAYYY overpriced IMO, even with a new set of tubes!

Hell yeah, I would take it back, and demand it be done right!

Three and a half hours at $96 per hour - that's the bit that gets me. And a $14 power lead.

EDIT: In those three hours, he apparently didn't squeeze in the replacement of the pilot light...
 


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