Yorkville-Traynor YCV40 preamp noise troubleshooting (2nd try)

[bsco]

Let me know how you make out with that.....I'm sure that you will figure it out....
Cheers,
Bernie
P.S. When I changed out those caps I put in 105 degree ones as there were 85 degree ones from the factory

[scopetrace]

Let me know how you make out with that.....I'm sure that you will figure it out....
Cheers,
Bernie
P.S. When I changed out those caps I put in 105 degree ones as there were 85 degree ones from the factory

I bought the caps yesterday so I should check this out this week.

[scopetrace]

And I bought an used in circuit ESR meter for testing. I am soooo happy to have found one.

[bsco]

For now I am using a scope and signal generator to check the capacitors along with a cap checker....After the new year I am going to look at getting one of these esr metersand also a vacuum de-soldering station to make that chore easier. Especially when working on double sided and multi-layer boards. Please let me know how you make out.....
Cheers,
Bernie

[olddawg]

Imhe...in practice ESR meters and cap checkers are pretty useless. I used to repair a lot camcorders along with just about everything else. For a couple of years everyone thought an ESR meter was a magic bullet. It turned out that you were better off replacing all suspect caps if you didn't want call backs. There are some good expensive cap checkers out there that will check a cap at working voltage. They have long setup procedures and if you don't get the parameters correct or the cap is failing, the caps can explode in your face. IMHO it is cheaper, more efficient, more reliable, safer, and less time consuming just to replace suspect caps in the long run. They aren't that expensive.

[scopetrace]

Please let me know how you make out.....
Cheers,
Bernie

Thanks my friend !

PS: I think the ESR meter is better with an analog dial. I changed the bias capacitor in a power amp section of an other amplifier (yesterday) and what I could see is that the cap had in fact two values of ESR and flicked back and forth the needle to the two very distinct values. If you leave the cap without moving anything (probes, board, wires, etc.) and the needle move by it's own: the cap is dead. The cap in question was the cause of cherry color plating in one of the power tube.

So perhaps, if you find time to build one of the circuit that is floating on the net (solid strate with no micro controller) on which you can plug an analog dial, it could be IMO a good tool.

See ya Bernie.

[scopetrace]

Imhe...in practice ESR meters and cap checkers are pretty useless. I used to repair a lot camcorders along with just about everything else. For a couple of years everyone thought an ESR meter was a magic bullet. It turned out that you were better off replacing all suspect caps if you didn't want call backs. There are some good expensive cap checkers out there that will check a cap at working voltage. They have long setup procedures and if you don't get the parameters correct or the cap is failing, the caps can explode in your face. IMHO it is cheaper, more efficient, more reliable, safer, and less time consuming just to replace suspect caps in the long run. They aren't that expensive.

Yes I understand that. What I understand also is that most of these low cost tools test at a given frequecy (so, 100 or 150KHz). But ESR is not a single value but a range of values given the condition in which the cap is tested. This can include frequency, voltage, temperature, etc. If you make a living out of repairing electronics it is a thing. It's clear that you'll take no chances. But perhaps that if you fiddle on your own equipment for learning and pleasure, it's an other thing. Anyways, I already tested some old caps that have been sitting in the bottom of my drawer and it's clear that those are no good anymore. So for 50 bux I quite happy to have bought this. It can still weed out the ones that are really bad. Now, it's clear that I am no expert but I'll take any tool anytime to fiddle around. Well, that is my point of view for now. But, yes, when it does not work, take the burnt earth policy: fire all those old elctrolytics. And someone could also use a higher voltage signal generator and scope it to see the form of the ripple. I wonder if some guy check out the form of Lissajous figures to spot some defects in them...

And ESR is only one of the parameter that can be checked for unreliability of the device in question.

Thanks OldDawg !

[Enzo]

Not to mention the voltage at which the ESR is of interest.


Large caps are not so cheap, but I agree with olddawg, if a cap is in doubt, replace it. If you are just testing evey cap in something hoping to find a problem, well, I suggest there are better methods. I charge for my labor, and if a customer is paying me a dollar a minute or more, how much time should we put into testing a 30 cent cap?

[scopetrace]

Not to mention the voltage at which the ESR is of interest.


Large caps are not so cheap, but I agree with olddawg, if a cap is in doubt, replace it. If you are just testing evey cap in something hoping to find a problem, well, I suggest there are better methods. I charge for my labor, and if a customer is paying me a dollar a minute or more, how much time should we put into testing a 30 cent cap?

It's not my profession, so I'll listen to you guys.
I am on two troubleshooting right now so I am going to post results as soon as I have them.

Thank you Enzo.

[Prairie Dawg]

I was able to buy a new Chinese analog ESR meter off of Amazon for about fifty bucks. After a little surgery to repair something the guy with those white "QC passed" stickers missed it's fine.

[scopetrace]

I was able to buy a new Chinese analog ESR meter off of Amazon for about fifty bucks. After a little surgery to repair something the guy with those white "QC passed" stickers missed it's fine.

What did the guy missed ? Is it that there were no 'out of spec' stickers from a quality guy ?

-------------

Okay,
so before changing the caps in the power supply, I decided to to clean thoroughly every jacks and switches once more. To my surprise the noise dropped quite a bit. So I went with a third cleaning especially on the channel switching switch, boost switch and bright switch.

No noise seemed to want to reappear. So I used the amp for a three hour practice and everything seemed to be fine except for a micro-phonic tube. So, what I will do is continue to use it this weekend and if the noises come back, I'll grab those caps I bought for the preamp powersupply and jump back in the topic.

Thanks to all of you guys.