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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 message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
stevem
Messages: 4758 Registered: June 2004 Location: NY
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Senior Member |
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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] Report message to a moderator
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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 message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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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 #27793 is a reply to message #27785] |
Fri, 26 June 2020 12:26 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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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 #27796 is a reply to message #27785] |
Sat, 27 June 2020 13:48 ![Go to previous message Go to previous message](/FUDforum/theme/vk30/images/up.png) ![Go to next message Go to next message](/FUDforum/theme/vk30/images/down.png) |
chicagobill
Messages: 2005 Registered: April 2003
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Senior Member |
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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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