Changing electrolytic caps

  • Thread starter Thread starter peterc52
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peterc52

peterc52

Well-known member
Any special way to do it?

My VH4 sounds off. And was told it might be the caps.

Or is it simply solder new ones in and turn it on

IMG_5804.jpeg
 
Those are probably a giant pain in the ass, I think they probably used bus wire to ground them so you won’t be able to pull them out without pulling the board.
But yes once you get new ones in you can fire it right up, no need to “form” the new caps.
 
peterc52 said:
Any special way to do it?

My VH4 sounds off. And was told it might be the caps.

Or is it simply solder new ones in and turn it on
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Take it to a reputable tech. It's poor practice to replace components without a proper assessment. Yes it's possible those caps need replacement, but given the amount of dust on that thing it seems a like an overall health-check would be very wise.
 
Just for understanding. Is it possible to measure a electrolytic capacitors without soldering? Or it's better to replace anyway, if amp is older than 10 years (for example)?
 
IDDQD said:
Just for understanding. Is it possible to measure a electrolytic capacitors without soldering? Or it's better to replace anyway, if amp is older than 10 years (for example)?
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Looks to be the same cap, or similar (Diezel uses Tube Amp Doctor electrolytic caps).

If you check the datasheet, they're rated for 5000 hours, which if you played an hour every day, should last around 15 years. I think caps will last a lot longer than that in most cases, but parts can always fail unpredictably or fail more quickly under specific conditions. Lots of decades-old amps out there with original caps in them that are working beyond spec. I suppose your question at its core is about the value of preventative maintenance. Differing opinions on that, of course, but better for electrical engineers and amp techs to be giving the advice, in my opinion.
 
Sermo Lupi said:
Looks to be the same cap, or similar (Diezel uses Tube Amp Doctor electrolytic caps).

If you check the datasheet, they're rated for 5000 hours, which if you played an hour every day, should last around 15 years. I think caps will last a lot longer than that in most cases, but parts can always fail unpredictably or fail more quickly under specific conditions. Lots of decades-old amps out there with original caps in them that are working beyond spec. I suppose your question at its core is about the value of preventative maintenance. Differing opinions on that, of course, but better for electrical engineers and amp techs to be giving the advice, in my opinion.
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Even if you play more than an hour a day, it's worth mentioning that the rating is likely for specific operating conditions and the data sheet may (or may not) provide the curves and formula to convert the rated lifetime to the expected life in your application. In short, I agree that the caps will likely last for longer than 5000 hours of runtime, possible a lot more.
 
7704A said:
Even if you play more than an hour a day, it's worth mentioning that the rating is likely for specific operating conditions and the data sheet may (or may not) provide the curves and formula to convert the rated lifetime to the expected life in your application. In short, I agree that the caps will likely last for longer than 5000 hours of runtime, possible a lot more.
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Yep, agreed on the above. An EE could better quantify the lifespan no doubt, but at least the datasheet helps to put things into perspective.
 
Looks to me like that's just the plastic spacer used on top of the cap to hide any exposed metal. The plastic cap is put on first than the side sleeve is put on afterwards. Since the plastic cap is near the tubes it expands when heated, but doesn't easily slide back into place since the sleeve is overtop. I bet you can push down on that rippled top and it will go flat. I want to see the underside of the cap.

As for the amp sounds off, first thing I would check would be the preamp and power tubes and bias. Also, what is the voltage in your music room? Does the voltage change? A few volt shift can easily make an amp sound different.
 
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psychodave said:
Looks to me like that's just the plastic spacer used on top of the cap to hide any exposed metal. The plastic cap is put on first than the side sleeve is put on afterwards. Since the plastic cap is near the tubes it expands when heated, but doesn't easily slide back into place since the sleeve is overtop. I bet you can push down on that rippled top and it will go flat. I want to see the underside of the cap.

As for the amp sounds off, first thing I would check would be the preamp and power tubes and bias. Also, what is the voltage in your music room? Does the voltage change? A few volt shift can easily make an amp sound different.
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I have 230 volts here in denmark and its pretty stable too.

It sounds really good now! New set of tubes and a new circuit board. Made all the difference in the world!

The caps are okay - only cosmetics
 
why did they replace a board? Cold solder joints or something?
 
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