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Author Topic: Peavey XR600b with 400b/g low volume output  (Read 6455 times)

Enzo

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Re: Peavey XR600b with 400b/g low volume output
« Reply #15 on: July 19, 2016, 11:22:16 PM »
OK, that says to me something from Q9 on back is not right.

I am not concerned with C11 and C21. Those voltages look normal anyway. I recommend lifting CR10 and CR15 to disable those limiter circuits entirely.  Though they are likely OK if injecting at Q9-C is strong.

If C8 is not doing its job, you don't have to remove it, just tack on a parallel cap of anything remotely close.  All we would want to find out is if adding a cap there increases the sound level or not.  Just a quick thing to eliminate it.

If injecting at Q9 worked, can I assume you injected through a cap to block any DC?  Please do use a cap and try at the base of Q9.  Q9 is your voltage amp, so it may have lost its ability to amplify.  And as I said, Q10 can come out in cse it is messing with us.

There are only so many places between U1 and Q9.

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #16 on: July 22, 2016, 07:19:15 PM »
Ok  I lifted cr10 and cr15 and removed Q10 and tacked a cap on C8.

No change in volume output.  So using sig gen with a cap on the end and started probing Q9 base an signal is still low. So I probed Q2 emitter which caused L1 and R61 to burn.

Jason

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #17 on: July 23, 2016, 10:03:01 PM »
Any suggestions on what else to check when i replace the 2 burned components?

Thanks,
nosaj

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #18 on: July 30, 2016, 09:46:32 AM »
Enzo,
Maybe this helps you wrap your head around this.  For the most part eavey Molex pins are keyed from what I've seen so I have been plugging the speakers in to the connector by c26 instead of by L2.  I noticed this last night by pouring over the schematic. I've still got L1 and a resistor to replace for sure though and maybe other parts?

Thanks,
nosaj

Enzo

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Re: Peavey XR600b with 400b/g low volume output
« Reply #19 on: July 30, 2016, 08:26:21 PM »
Oh.  Then that explains everything.  It never occurred to me it was connected wrong.

The C26 pins, if you view the schematic, are for the heat sensing dual diode on the heat sink.  With nothing connected there, the bias string is open, so the V+ and V- sides both can turn on full.  With a speaker there, it is like a 4 or 8 ohm resistor, and the amp would function, but wouldn;t make much sound, I;d think.   

The diode ought to be on the heat sink and have a twisted pair of wires coming up to a molex that should go n those pins.  Where have you been connecting that?

If tiny L1 burnt up, just replace it with another 4.7 ohm like the resistor in parallel with it.  If you look at the VERY similar 400BH board, the factory has already done that.


Get that diode plugged in where it belongs and see if the amp starts working right.

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #20 on: July 30, 2016, 11:47:07 PM »
And another 2 pictures of what I believe are the heat sensing diode and where it is hooked up(not a molex connector but one lead to a fuse and the other to the on/off switch)  This is how I found that connection it was soldered So I had left it there. 

Let me know what you think. I'll be replacing L1 in the morning and hooking it back up to see where we're at and if there's any updates.

Thanks so much
,
nosaj

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #21 on: July 30, 2016, 11:50:32 PM »
Here they are

Enzo

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Re: Peavey XR600b with 400b/g low volume output
« Reply #22 on: July 31, 2016, 01:52:53 AM »
We are confusing two things here.

The thing you are calling the heat sensor is in fact a thermostat, not a diode.  it is bolted to the heat sink, and if it gets too hot, it will turn off the main AC power to the amp.  But it isn't what I am talking about.

The black and white wires go to the heat sink and are wired to a special diode there., and they do end in a molex on the main board.  That is what plugs on by the cap where you previously had the speaker.  On the power transistor board, you have the two 3-wire connectors, and then the 2-wire connector.  The special diode is right next to that 2-wireconnector.  The two connector pins are wires to either end of that diode and nothing else.

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #23 on: July 31, 2016, 10:04:31 AM »
Well I'm glad i did pics and asked then.

Thanks,
nosaj

nosaj

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Re: Peavey XR600b with 400b/g low volume output
« Reply #24 on: July 31, 2016, 02:00:49 PM »
Replace L1 with a 4.7 ohm, tacked 2 diodes back in, put Q10(?) back in circuit .
And we're rocking and rolling again. Loud like it should be.  Another piece of usuable equipment rescued from the trash.

Thanks so much Enzo

nosaj

Enzo

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Re: Peavey XR600b with 400b/g low volume output
« Reply #25 on: August 01, 2016, 03:46:32 AM »
Great!

phatt

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Re: Peavey XR600b with 400b/g low volume output
« Reply #26 on: August 03, 2016, 02:13:04 AM »
Sounds like you got lucky as it could have been a melt down. :tu:
Phil.