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Author Topic: Peavey Filter Caps  (Read 1408 times)

Tennerondack

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Peavey Filter Caps
« on: November 10, 2018, 04:43:43 PM »


Hey folks,

Thanks for the help already received on this fine forum.

My latest question : I have an old Peavey 260 Standard that has a good bit of hum in the output so it seemed replacing the ancient filter caps would be a good start , (right ? ).
i am aware by search that the originals are no longer available, 5000 uf 55 volts and that some have used these higher values. Will they work ? Thanks.


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Enzo

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Re: Peavey Filter Caps
« Reply #1 on: November 10, 2018, 05:59:40 PM »

May or may not be those caps.  Scope the supply, is it full of ripple?  Are the connections or solder to those caps good and solid?


5000uf is  non-standard value, 4700uf would be the current thing to use.   You want to use 6800uf instead?  go ahead, it is just a guitar amp, not lab gear.

55v is also non-standard, so 63v would be the thing to use.

But look at the low voltage supplies, are they ripple free?  Are the main voltages ripple free?  Are the DC voltages wher they ought to be - ie none on the speaker.
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Tennerondack

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Re: Peavey Filter Caps
« Reply #2 on: November 10, 2018, 06:33:57 PM »

Thanks for the info  Enzo.

I'll go with what you suggested, I just saw the alternate value suggested in an old post. I'll give the other stuff a try as well.

Thanks !
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Tennerondack

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Re: Peavey Filter Caps
« Reply #3 on: November 19, 2018, 05:42:59 PM »

Update, I don't have a scope but do have a decent meter. I'm reading up on how to use it to check for ripple voltage.

I did go ahead and changed out the  filter caps because it was an easy first step as I learn. The old ones discharged a good zap but when the new ones went in everything quieted down a lot,
I do want to learn the test procedures too, I'll be  puttering when I have the time.

This old beast sounds remarkably good with guitar, the distortion circuit is more over- drive voiced IMHO, and gets a nice grit w/o being harsh or tinny. It has a short reverb tank that sounds a little funky, but fine in my view.

It's a little thin for bass in my view, but I like a fat tubey tone. Actually I think this old beast would fit right in with the modern voiced bass amps such as class D etc. but with my Harke bass driver in front it sounds great !
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Jazz P Bass

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Re: Peavey Filter Caps
« Reply #4 on: November 19, 2018, 09:33:43 PM »

" I'm reading up on how to use it (the volt meter) to check for ripple voltage. "


Easy. Peasy. 8|

Set your meter to read Volts ac.
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Tennerondack

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Re: Peavey Filter Caps
« Reply #5 on: November 19, 2018, 11:16:37 PM »

I like that. Simple is good.  :dbtu:
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Tennerondack

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Re: Peavey Filter Caps
« Reply #6 on: November 27, 2018, 11:41:13 AM »

Well fellas, as I practiced putting filter caps In a second Peavey amp head I bought to tinker with and learn on,  I made the bonehead move of getting one of the cans reversed and when I fired it up it blew the fuse.

I rewired them correctly and everything powers up fine, but the amp has no output power.
I get a very weak signal to the speakers that is very distorted .

Is it likely I just cooked the caps, or that other things got cooked as well ?
Any clues appreciated, and ridicule richly deserved 
« Last Edit: November 27, 2018, 11:44:42 AM by Tennerondack »
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Enzo

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Re: Peavey Filter Caps
« Reply #7 on: November 27, 2018, 06:43:49 PM »

Find out.  The backwards cap may well be damaged.  Is it doing the job?  Are both power rails up to voltage and clean?
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Tennerondack

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Re: Peavey Filter Caps
« Reply #8 on: November 27, 2018, 08:00:15 PM »

Thanks for the push,  now I shall learn. I found a schematic in another thread, I am green as a gourd.
The schematic said + - 39 volts, I see where the transformer feeds the rectifiers and the leads off the f.c.'s on the same connector ?
Where do I read the rail voltage ?
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Enzo

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Re: Peavey Filter Caps
« Reply #9 on: November 28, 2018, 01:36:03 AM »

"Rail" just means power supply.  SO if this has 39v rails, look for something like 35-50vDC plus side and minus side.

For future, you can get any schematic for the asking from customer service at Peavey.
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Tennerondack

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Re: Peavey Filter Caps
« Reply #10 on: November 28, 2018, 06:55:17 AM »

It seems erratic. A couple of times, it read 48 volts on plus and minus, but then was all over the place.
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Tennerondack

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Re: Peavey Filter Caps
« Reply #11 on: November 28, 2018, 09:12:08 AM »

On a related tangent I have this 150 watt power section from a KB 300 amplifier. Visually it seems a more modern version of the same theme.
If I can connect it to the existing preamp, maybe I would do this. It is dimensionally almost exact.
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Enzo

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Re: Peavey Filter Caps
« Reply #12 on: November 28, 2018, 08:33:18 PM »

That almost sounds like a problem with your meter probes.
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Tennerondack

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Re: Peavey Filter Caps
« Reply #13 on: November 28, 2018, 09:07:46 PM »

Could be. I also discovered one of the solder joints on the cap repair failed. I've had to steal fuses to keep other stuff going, I'll retest and be back.
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Tennerondack

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Re: Peavey Filter Caps
« Reply #14 on: November 29, 2018, 04:34:48 PM »

  Here is my update :
I got some fuses, fired things up and found I was getting plus and minus 42 v.dc on the rails, I could not detect any ac with my meter.
I have a second identical head which works fine, and I tested around and compared things just to get familiar and everything tested very similarly.
I still have the same weak distorted output.

Here's something I discovered I hope will give you a clue :
On the three pin connector that goes to the pre amp, the pa pin reads -0- the minus voltage pin less than 1volt. If I touch the - voltage pin, I get a weak but audible open ground sound in the speaker,, like when touching a live guitar cord.

I compared it to the working unit, which had + 42 v on the pa pin, and less than 1 v on the - voltage pin. There was no open ground sound when touching the - voltage pin.


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