Tube Amp (Rivera guitar amp) repair gone wrong - diyAudio
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Old 11th February 2012, 05:18 PM   #1
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Default Tube Amp (Rivera guitar amp) repair gone wrong

Guys
I have a 15 year old Rivera amp that started smelling when I played it. I took it to an amp repair shop and they diagnosed it, told me the power tubes were bad and that I needed them replaced and biased. A day later he called back and said it failed on the bench.

There is ow no power and he wanted more money to diagnose (already payed him to diagnose) and finally said that he wants out and does not want to repair.

Questions maybe you all can help with

It played fine then started smelling, Tubes replaced, now no power at all.
Is this right? How can it work before tubes no no power and nothing lights up?

Could he have messed something up? Makes no sense for it to work, before the tubes and fail after.
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Old 11th February 2012, 06:19 PM   #2
jjman is offline jjman  United States
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Could be a defective tech. Or bad OP tranny. Or several other things. Interesting he wants out. Are they a nightmare to work on?

Expect to have this thread moved to the Instrument forum by the internet police.
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Old 11th February 2012, 06:22 PM   #3
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not sure. He said he had to order the schematics to troubleshoot. It was a red flag because he said he has worked on many of these amps and that they are all the same.

If he is not going to tell me what's wrong and wont fix it I am going to ask for my diagnostic money back and find another place.

Just really interested in how this could happen or if the tech is the one who caused it
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Old 11th February 2012, 10:35 PM   #4
kevinkr is offline kevinkr  United States
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Per forum directive this belongs in the Instruments & Amplifier forum so I will move this thread there. (Moved.. )
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Old 11th February 2012, 10:39 PM   #5
kevinkr is offline kevinkr  United States
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Sounds like the problem started before you took it in for service, but I suspect a short in the power transformer as the most likely cause given what followed.

This failure could be due to a quality defect in the transformer, exposure to excessive moisture over a long period of time, incorrectly biased output stage, or a failing supply capacitor. Note that this is by no means an exclusive list. (Impossible to know without actually working on said amp.)

This sort of problem is fairly obvious on the bench so this does not speak too well of the particular tech, right move to ask for your money back and take it elsewhere.
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Old 11th February 2012, 10:58 PM   #6
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Quote:
Originally Posted by kevinkr View Post
Sounds like the problem started before you took it in for service, but I suspect a short in the power transformer as the most likely cause given what followed.

This failure could be due to a quality defect in the transformer, exposure to excessive moisture over a long period of time, incorrectly biased output stage, or a failing supply capacitor. Note that this is by no means an exclusive list. (Impossible to know without actually working on said amp.)

This sort of problem is fairly obvious on the bench so this does not speak too well of the particular tech, right move to ask for your money back and take it elsewhere.
Great advice!

What exactly did it smell like? In my experience a runaway power tube smells different than a transformer frying. If the tubes were original the tech probably just assumed that it was a bad power tube for it being it's age and put new tubes in and then the real problem reared it's ugly head. My advice is that if the tech can't tell you what the problem is you should look for a new tech. I don't bring any of my amps to techs anymore because of issues like this, I was lucky enough to have worked in the field of electrical generation and know a thing or two about electricity so it was a matter of reading some material and having the very nice DIYAUDIO community to lend a helping hand.
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Old 11th February 2012, 10:58 PM   #7
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I did a search for 'Tube Amp Rivera' and found some schematics. I would have no faith in him.
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Old 11th February 2012, 11:04 PM   #8
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I did a search for 'Tube Amp Rivera' and found some schematics. I would have no faith in him.

I don't think you should even need a schematic to diagnose such problems. Tube amps are actually quite simple and most topologies in the guitar world should be easily recognized without a schematic. If you are good with a digital multimeter it can tell you a lot more than a schematic.
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Old 12th February 2012, 12:01 AM   #9
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Originally Posted by famousmockingbird View Post
I don't think you should even need a schematic to diagnose such problems. Tube amps are actually quite simple and most topologies in the guitar world should be easily recognized without a schematic. If you are good with a digital multimeter it can tell you a lot more than a schematic.
Until you get into some of the switching amps. But even then you should be able to isolate the problem in general terms, power supply, output stage, driver, preamp. To say it is dead and I need more money to find out where the problem lies is bs.
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Old 12th February 2012, 12:49 AM   #10
kevinkr is offline kevinkr  United States
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Originally Posted by Printer2 View Post
<snip> To say it is dead and I need more money to find out where the problem lies is bs.
Yep, and all too common unfortunately..
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