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PC 5129 R3 [message #27785] Mon, 22 June 2020 17:54 Go to next message
sunnhead is currently offline  sunnhead
Messages: 221
Registered: June 2010
Location: Minnesota
Senior Member
Got a lead 2 and the 5129 is not getting any signal. Just hum. Looking for the schematic.

-S

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Re: PC 5129 R3 [message #27786 is a reply to message #27785] Tue, 23 June 2020 05:46 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4774
Registered: June 2004
Location: NY
Senior Member
I do not have a schematic for that amp, nor does this site so I need to ask if that 5129 is the driver board with the square Transistor heat sinks on it and box style 5 watt resistors, or is it a preamp board?

Also if you hook up a voltmeter set for D.C. Volts to the amps speaker output do you read any voltage?

[Updated on: Tue, 23 June 2020 05:48]

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Re: PC 5129 R3 [message #27787 is a reply to message #27786] Tue, 23 June 2020 15:44 Go to previous messageGo to next message
sunnhead is currently offline  sunnhead
Messages: 221
Registered: June 2010
Location: Minnesota
Senior Member
this is a preamp board

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Re: PC 5129 R3 [message #27788 is a reply to message #27785] Tue, 23 June 2020 23:24 Go to previous messageGo to next message
chicagobill
Messages: 2006
Registered: April 2003
Senior Member
Do you mean that the preamp board is not passing signal?

Check the two power supply voltages. Then read the voltages at the outputs of the preamp chips. There normally is no (or little) voltage on the output pins.

The schematic is a the Music Electronics Forum.

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Re: PC 5129 R3 [message #27791 is a reply to message #27785] Fri, 26 June 2020 11:00 Go to previous messageGo to next message
sunnhead is currently offline  sunnhead
Messages: 221
Registered: June 2010
Location: Minnesota
Senior Member
The amp was used to play a stereo through before I got it. Im sure the person blew the transistors out plugging in the stereo. The preamp signal is just hum, and increases hum when turning the reverb pot up. The board has 2 IC chips, unsure if they are damaged. I would like to rebuild with new transistors and maybe the IC chips. Looking for a parts list to order up the parts.

-S

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Re: PC 5129 R3 [message #27792 is a reply to message #27785] Fri, 26 June 2020 12:08 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4774
Registered: June 2004
Location: NY
Senior Member
How are you determing that the preamp signal is all hum?

If the preamp signal is all hum, then so will the output into the speaker sound the same , is that what you mean?

You seem unwilling to do the test outs that Bill and myself. Have asked you to do so that we might help you out better!

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Re: PC 5129 R3 [message #27793 is a reply to message #27785] Fri, 26 June 2020 12:26 Go to previous messageGo to next message
chicagobill
Messages: 2006
Registered: April 2003
Senior Member
That board should have 3 ICs. Only 2 of them will stop the signal from passing, I1 and I3. I2 which is a dual opamp is used for the reverb driver and for the trem low frequency oscillator.

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Re: PC 5129 R3 [message #27795 is a reply to message #27785] Sat, 27 June 2020 09:52 Go to previous messageGo to next message
sunnhead is currently offline  sunnhead
Messages: 221
Registered: June 2010
Location: Minnesota
Senior Member
http://49live.com/amp/k5.jpghttp://49live.com/amp/k1.jpghttp://49live.com/amp/k2.jpghttp://49live.com/amp/k3.jpghttp://49live.com/amp/k4.jpg

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Re: PC 5129 R3 [message #27796 is a reply to message #27785] Sat, 27 June 2020 13:48 Go to previous messageGo to next message
chicagobill
Messages: 2006
Registered: April 2003
Senior Member
Yeah, that's the right board. I1 has been replaced earlier and a socket has been added.

I2 is the 8 pin 1458 in the center of the board and I3 is the round TO-5 (I think) one near the edge of the board. I3 is a house numbered LM3080 transconductance op amp.

Check transistors T1 and T2, then check for dc voltage on the in/out pins of the 3 ICs.

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Re: PC 5129 R3 [message #27916 is a reply to message #27785] Tue, 10 November 2020 11:00 Go to previous messageGo to next message
sunnhead is currently offline  sunnhead
Messages: 221
Registered: June 2010
Location: Minnesota
Senior Member
Ok so The amp is now fixed, turns out one of the ziner Diodes failed and was putting 40 volts into the board. Replaced that now the board gets the 12 volts. The bigger IC was fried replaced that. Amp is working great now!

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Re: PC 5129 R3 [message #27917 is a reply to message #27785] Tue, 10 November 2020 12:22 Go to previous message
stevem is currently offline  stevem
Messages: 4774
Registered: June 2004
Location: NY
Senior Member
Good news to hear!

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