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Finicky repaired 1974 Ampeg V4B

#41
Even if the tubes are bad the tech should've returned them with the repair job. I can't believe that a bedroom player who may have done 20 regular gigs has worn out his Ampeg V4 tubes even if they are 45 years old. If an amp spends most of its life in storage are the tubes going to go bad? Maybe , maybe not. We are not able to judge without testing them.
Do I think that you would make guitar amps with marginal tubes? Absolutely, if you had no choice in tube quality.
You will manufacture what you have to build to satisfy demand for Tube amps.
Perhaps you have great tubes for your Mesa amps, I hope you do, I own two Mesa amps, but you won't convince me that the average tube coming out of China today is better than what GE or RCA produced back in the 1960's and 70's. The prices don't bear that out.
 
#44
agedhorse said:
Ok, it's been a long time since I worked on these, but those caps look awfully long even for a 240.

I would leave everything that tests properly alone myself, ESPECIALLY the parts on the terminal board that almost never fail unless monkeyed with. But then again, many folks think it's an upgrade to drop a small block into an old GM stovebolt and call it an upgrade and a restoration at the same time too. What do I know?
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I didnot replace any parts or started any repair on this amp .
I just took photo of the inside of a unpaired amp.
Yes the long caps are the right size for the MC240 check around.
I was just showing the inside of the amp before I start the repair.
 
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#45
IMG_8166.jpg
I just serviced an 1977 ampeg V4-B with horrible hum issues. The only thing wrong was the original 12DW7 was bad, (and there was an open resistor preventing the standby light from coming on). I replaced it with a new production JJ 12DW7 (and new resistor) all was good. Caps were fine so I wouldnt automatically jump to that conclusion. I assume your tech checked all the preamp tubes but you said only replaced one. This is just a shot in the dark. As Agedhorse said, it needs to be methodically diagnosed with proper equipment to determine the root cause, but its easy enough to swap preamp tubes. Just my experience. I got lucky on this one and didnt have to dig any deeper... .
 
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#47
bcbassman said:
Do I think that you would make guitar amps with marginal tubes? Absolutely, if you had no choice in tube quality.
You will manufacture what you have to build to satisfy demand for Tube amps.
Perhaps you have great tubes for your Mesa amps, I hope you do, I own two Mesa amps, but you won't convince me that the average tube coming out of China today is better than what GE or RCA produced back in the 1960's and 70's. The prices don't bear that out.
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That's quite an assumption you are making, and I can give concrete evidence that when we can't get good quality tubes that we will either change suppliers or we will in fact discontinue a product. The Strategy/Prodigy amps are an example of where we could not get an acceptable quality new production tube and simply discontinued production of the amps. The same applies to the Carbine and Walkabout, we could no longer get an acceptable quality lateral MOSFET with tight enough tolerances so we discontinued the product.

Yes, there are some outstanding tubes coming from eastern Europe and China IF you are willing to pay the cost of the highest grade tubes. Where do you think the lower grade tubes we reject (we parameter test and burn in every tube we use) end up? It's no different than in the old days when we used American and European tubes, no different though the yields were probably a little higher on the average but not by as much as you might think.

Shadi said:
Sounds like your tech should have replaced some capacitors....those lose their value over time and are a #1 cause for hum.
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Actually, capacitors are probably closer to number 3 and certainly NOT number 1, not by a long shot.
 
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#48
MichelD said:
Thanks for the replies folks. I feel like I've been kicked in the guts though, after hearing about the original tubes possibly being more than I paid for the repair.

This place has good reviews on line, and it was recommended to me by another bass player on the Vancouver BC bass player Facebook page. I chose this shop partly because it was so close to me too. Possibly a mistake.

I'm only out $263 so far, but I expect if I took it elsewhere then I'd have to pay that again. I think I'll write a detailed explanation of continuing issues with the amp and email it to tech for starters to see where that goes.
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Hmmm, now that I see you’re in Vancouver I want to know who the tech is...
 
#50
As an owner of a couple tube amps, I am trying to follow this and get educated, but true to form there are wildly differing "opinions" being circulated for fact. Without naming names, I'm going to follow the advice of the pros here, thanks for hanging in there and combating the ignorance.

Believe it or not, I am gleaning some good information here.
 
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#51
agedhorse said:
The Strategy/Prodigy amps are an example of where we could not get an acceptable quality new production tube and simply discontinued production of the amps.

The same applies to the Carbine and Walkabout, we could no longer get an acceptable quality lateral MOSFET with tight enough tolerances so we discontinued the product.
.
Click to expand...

Always wondered why some Mesa amps were disco'd when it appeared that sales were OK.
Disappointing that the Carbine went that direction, especially when you look at what they go for on the used market.
OTOH, hard to make and warranty them if you can't buy decent components.

Andy, big picture as labor prices rise and amps get more complicated, I'm thinking that the idea of owning an amp and keeping it running for 10-40 years is just not reasonable anymore.
The shortage of techs and the modern amps being very difficult to bench repair (without special training) is not encouraging.
At the speed everything changes in the world of electronics, can we assume that parts will be discontinued sooner due to being outdated by newer, better, parts?

Ultimately, this may not be a bad thing as few of us are lucky enough to have top quality, factory authorized techs in their area that are stand up knowledgeable guys.
Maybe board swaps are the future of MI repair?
(Said the guy who hated it when you couldn't rebuild alternators, carburetors, etc. in the 70's as it was cheaper to the customer to replace. Hard to get many labor hours swapping instead of repairing although the quality of the repair was generally better when done on site.)
 
#52
Frankie Fender said:
As an owner of a couple tube amps, I am trying to follow this and get educated, but true to form there are wildly differing "opinions" being circulated for fact. Without naming names, I'm going to follow the advice of the pros here, thanks for hanging in there and combating the ignorance.

Believe it or not, I am gleaning some good information here.
Click to expand...
You are not alone based on the PMs I receive.

Jim C said:
Always wondered why some Mesa amps were disco'd when it appeared that sales were OK.
Disappointing that the Carbine went that direction, especially when you look at what they go for on the used market.
OTOH, hard to make and warranty them if you can't buy decent components.

Andy, big picture as labor prices rise and amps get more complicated, I'm thinking that the idea of owning an amp and keeping it running for 10-40 years is just not reasonable anymore.
The shortage of techs and the modern amps being very difficult to bench repair (without special training) is not encouraging.
At the speed everything changes in the world of electronics, can we assume that parts will be discontinued sooner due to being outdated by newer, better, parts?

Ultimately, this may not be a bad thing as few of us are lucky enough to have top quality, factory authorized techs in their area that are stand up knowledgeable guys.
Maybe board swaps are the future of MI repair?
(Said the guy who hated it when you couldn't rebuild alternators, carburetors, etc. in the 70's as it was cheaper to the customer to replace. Hard to get many labor hours swapping instead of repairing although the quality of the repair was generally better when done on site.)
Click to expand...
Agreed, this is a frustratingly disturbing trend and I fight with it every day. I write service manuals and have to consider the often declining education and experience levels that service techs posses. This is not a new thing, but appears to be getting worse.

I am also seeing perhaps an even more disturbing trend, where a tech who is obviously not grasping the fact that he is not understanding the concepts yet enthusiastically argue with those who designed the circuits. If they already know it all, then by gosh fix the problem rather than begging for help.
 
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#57
MichelD said:
OP here with a follow up:

I emailed the tech explaining the remaining issue with chronic persistent hum in both channels and as soon a she got back to work after the long weekend he asked me to bring the amp back in tomorrow.
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Make sure you ask for the original power tubes back.
If the amp is not any better, there is a good chance those are good tubes.
Cheers
 

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