Peavey xr-600

[cbass]

Hi guys,I picked up an old PV XR600 mixer at a garage sale for 5 dollars.Its the 400r series power amp.
Of course it doesn't work.
Its not drawing to much current through my limiter.No DC on the speaker outs.
The poweramp voltages seem to be in check.I've tested all the output transistors.They all test good.
The only thing that I've been able to find is that all the inputs on the front have DC on them even the poweramp in.If I plug a cord into any of the inputs I can measure almost 10VDC (still have limiter plugged in).It will pass a very weak distorted signal if i plug into the P.A. in.
My first thoughts were maybe "clamping diodes"? that are on the inputs were shorted but i couln't find any diodes that were shorted.
Sorry don't have an o-scope.I know that would probaly make thing a lot easier.

[Jazz P Bass]

It would be nice to have a schematic, but that one in particular I do not seem to have.
Maybe contact Peavey. First thing in the AM is best.
The diode clamps should be attached to the opamp input pins. (2 & 3 / 5 & 6)
Or relatively nearby.
I have attached a copy of another Peavey input circuit, maybe that will help.
EDIT: Bad pdf file

[cbass]

thanks Jazz I haven't been able to find a schematic .I'll try peavey.Your link didn't work for me

[mozwell]

Here you go

[bkahuna]

You need to check the +15 and -15 volt supplies for the front panel board. It seems unlikely that all channels would be blown the same way. It's possible, if someone plugged some horrifically unsuitable source into all of them, just unlikely. Much more likely to be power supply related.

[cbass]

Thanks I'm wondering if someone plugged one of the connectors on the board in backwards.It looks like they will go either way
I have -15 +15 coming off the powersupply

[jrfrond]

The Molex connectors on those Peavey's generally have an absent pin, and the matching hole in the headshell is usually blocked, so unless someone else monkeyed with it, the connector will match correctly.

Plugging into the POWER AMP IN jack breaks the normal from the preamp, and this is a good way to test your power amp section with a signal generator.

Peavey amps from that era are generally repairable and rarely go down in a catastrophic failure, plus parts are still available. You should be able to get that working with no issues.

[cbass]

I have -15 +15 coming off the powersupply

Scratch that I only had +5 where I should have +15 I found a shorted cap on the power supply.I'm gonna replace it and hope for the best

[cbass]

The Molex connectors on those Peavey's generally have an absent pin, and the matching hole in the headshell is usually blocked, so unless someone else monkeyed with it, the connector will match correctly.

Plugging into the POWER AMP IN jack breaks the normal from the preamp, and this is a good way to test your power amp section with a signal generator.

Peavey amps from that era are generally repairable and rarely go down in a catastrophic failure, plus parts are still available. You should be able to get that working with no issues.

The connectors will definately fit either way and the 2 different connectors will fit on either spot on the board I had to test continuity to figure them out after i unplugged them

[cbass]

Ok I Hvae +15 there was 250 ohm 5 watt resistor that was way out of spec.Closet i had was a 200ohm 10 watt I think it will work for now.

But now there is dc on the speaker jacks about 20 volts.I think i found a bad transistor it test bad but im not sure because I broke it away from its heatsink tab when I was removing the screw

[Enzo]

DO you have an XR600, an XR600B, XR600C, XR600 on through the alphabet? They are not the same adn the schematics do not cross well.

Customerservice@peavey.com would send you what you need, but do specify exactly the model name.

No speaker load for now. Verify both high volrtage and low voltage power supplies are up to voltage and clean. Without that, nothing else matters yet.

[cbass]

Its a plain Xr-600 witha 400-R power amp.Its old. '78 is a date i found in it it doesnt even have xlr nputs just 1/4".
I belive both the high and low voltage supplies are in check.

[Enzo]

OK, I have the prints to look at now.

If the thing is not blowing fuses or drawing excess current, get rid of the limiter and plug it into the wall.

Now verify again that +/-15v are both OK and getting to the ICs. And that +/-50v (more or less) is getting to the power amp. The limiter is great for what it does, but when tryong to operate an amp or take voltage readings it confuses the issue.

It concerns me that all your inoputs have 10v on them. All the input jacks are capacitor isolaed from any DC in the circuit, with the exception of the clamping didoes. Now while it is possible all of them are blown, it is darn unlikely. If they had all been replaced by someone and were in backwards, well then maybe. Is the solder on them disturbed?

SO what comes to mind is to ask where you are grounding your meter to take these readings? A burnt open ground trace somewhere could leave what was supposed to be ground along the board edge to be floating. And that could drift up to most any voltage it wanted, and would also allow a half-assed function of the amp to continue. Or is the board out of the chassis, but you are using chassis as ground? CLip your meter to the bushing of the PA jack for ground, any difference?

Same with the power amp, the input is cap isolated. And plugging into the PA jack should disconnect the entire mixer section, so any DC on that is very suspicious. Try this, if you are clipping to chassis for ground - as we usually do - measure the voltage at the center tap wire from the transformer. SHould be zero volts there, since it is supposed to be grounded. Get any AC or DC voltage ther?

Are ther not two groups of three wires connecting the master board over to the input channels board? I think the three at the bottm are power. Any of those broke off?

[cbass]

Thanks Enzo and everyone else.
I belive the voltages from the supply are in order.I have +50 -50 and + 15 -15.I'll check withput the limiter.Ive got my negative probe clipped to the chassis.ANd the yellow ground wire is still hooked up.
Kind of wierd but I didn't have any dc on the speaker till i replaced a bad 250ohm 5 watt resistor that was messing up my +15 volatage.

I suspected one of the ep 430 transistors was bad so i took it out of the circuit to test it further.I managed to break it away from its heat sink tab when my screw driver slipped.It tests bad but leaving me wondering if it was really bad or i broke it.

I belive the connectors are all ok.I had to test continuity to make sure they went back on right as they will fit either way.
It doesn't look like anyone has messed with the mixer section.Though someone has "reflowed"(more like reglobbed) the joints on some of the .33 10 watt resistors in the PA.

I'll do some further testing but not sure what i can do till I find a replacement trasistor.
Is it likely I broke the transistor or can they still test ok with the heatsink tab broken away?

[cbass]

Belive it or not it Looks like My local radio shack has a replacement for the EP-430.They have a TIP31 npn according to what i can find this is a direct replacement.