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Old 18th March 2008, 11:09 PM   #1
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Question Help for my Peavey PV8.5C

Hello Everybody!

I bought in stock 3 Peavey PV8.5C.....
All the amp had the same problem.... 1 channel broken, the same channel
I repaired the driver board with exactly the same components (this it could be ok) and the power board with the equivalents transistor MJ15024 and MJ15025.
All the power resistors on power board are ok now but with the new one power board I have a problem with DDT protection..... with a very low input signal the light DDT turn on and I can't to understand what happens.....

Can you help me?

Thaks for all replay.
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Old 19th March 2008, 07:04 AM   #2
Tarzan is offline Tarzan  Belgium
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Do you have a schematic?
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Old 19th March 2008, 07:50 AM   #3
Netlist is offline Netlist  Belgium
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In the CS series, on the driver board near the input, a small capacitance (.1F) is often the problem.
It is connected between ground and the gate of the FET.
There's only one FET per board (hint) and the PV8.5C has the same circuit. From the (very bad) schematic I have, it would be a electrolyte of 2.2F.

/Hugo
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Old 19th March 2008, 08:20 AM   #4
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Hi guys,

thanks for fast reply!!

Yes, I have a full schematics with a good resolution...... (for NETLIST... if you need I can send you by email my pretty good schematics...)

This evening I test the capacitor near the fet.....


Thanks!!!

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Old 19th March 2008, 08:31 AM   #5
Netlist is offline Netlist  Belgium
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You have mail.

/Hugo
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Old 19th March 2008, 08:59 AM   #6
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Sorry netlist.....

I don't understand what do you mean.......

Thanks!
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Old 19th March 2008, 09:03 AM   #7
Netlist is offline Netlist  Belgium
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I have sent you a mail so now you have a reply address to send the schematic.

/Hugo
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Old 20th March 2008, 07:59 AM   #8
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Hi guys

yesterday I tested the capacitor near the fet but it's all ok.....

I tried to change the new power board with the old one, that original and with the original one it's all ok..... the DDT led don't turn on.
I tested the output signal and I saw this.....
with very high impedance (just with oscilloscope) it's all ok but when I placed the low impedance (4R7 power resistor) I have a problem with the clip of DDT circuit.

I have this problem just with the power board with MJ15024 / MJ15025
with the old board it's all ok....

What do you think about?
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Old 21st March 2008, 08:17 AM   #9
Netlist is offline Netlist  Belgium
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Check if the output coil is well soldered.
Check the Triacs in the protection circuit.
Make sure the TO3 cans are well tightened (but not too hard, too). Don't solder the screws.

/Hugo
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Old 1st April 2008, 08:53 PM   #10
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Hi guys!!!!!!!

I found what's happen on my power amp!!!!
I bought the power transistor on Ebay shop by chinese seller...... and all the transistors was fake
I bought others transistor MJ 15024 / MJ 15025 and now my PEAVEY has a great sound!!!

In this case in Italy we say: CHE SOLA!!!!!

So guys look where you buy transistors and all the others electronic parts for your circuits!!

Thanks for all !!!
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