peavey musican 400

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plen
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peavey musican 400

Post by plen » Sat Feb 08, 2020 6:53 pm

i bought a peavey musican 400 head and a 4x12 marshall cab. i bought it for the4 marshall cab. my son played the amp and i liked it. it made funny noises. the next time i turned it on it blew the fuse. i changed the 15a fuse and put a 4amp fuse in. the amp wont come on and makes a putting sound from the transformer. the pilot light keeps going off and on. could this be a bac transformer or could it be something else.

thanks.

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Enzo
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Re: peavey musican 400

Post by Enzo » Mon Feb 10, 2020 3:45 pm

Anything is possible, but "bad transformer" is just about always the very last thing on the list.

Look at the schematic, the fuse has a series thermal breaker on teh heat sink. I suspect that is tripping. And as it is self-resetting, it resets itself, then trips again...over and over.

First suspects are shorted output transistors.

plen
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Re: peavey musican 400

Post by plen » Mon Feb 10, 2020 3:52 pm

enzo thanks for the reply. is there 2 of these amps. mine is the series 400.

plen
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Re: peavey musican 400

Post by plen » Wed Feb 12, 2020 2:26 pm

does anyone know substitutes for the output transistors.

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Enzo
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Re: peavey musican 400

Post by Enzo » Wed Feb 12, 2020 4:55 pm

Peavey does, and they publish a cross reference. See below
PV Semi Cross Ref.pdf
(96.59 KiB) Downloaded 133 times

plen
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Re: peavey musican 400

Post by plen » Thu Feb 13, 2020 7:11 pm

i have got a peak dca55 meter. can i test the output transistors in the amp wired up.

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Re: peavey musican 400

Post by plen » Fri Feb 14, 2020 7:39 pm

i just took the output transistors and tested them. leakage is 0.000ma on all of them. hfe is 17 9 21 21 16 19 7 19

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Enzo
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Re: peavey musican 400

Post by Enzo » Sat Feb 15, 2020 7:07 am

OK, there will be some wires from the transformer to the main board, probably red, with a molex connector. (White plastic connector that disconnects from the board) Unplug that connector so the transformer wires are hanging in the air. Now turn on the power switch. Does it still cycle off and on? I realize there will be no amplifier function this way.

plen
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Re: peavey musican 400

Post by plen » Sun Feb 16, 2020 9:11 am

enzo i cant try that at the minute as when i turned it on the 4a fuze was blown. that is the second one. it did not blow them right away. it was after it was turned on a few times. i just put in a 2a fuse and it blew right away. i will try to get 4a fuses tomorrow. i can see 2 white connectors. each has three wires. two of the wires on each white connector are going to the big capacitors and one wire from each looks like they are going to the transformer. one wire is black and the other is blue.

thanks peter.

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Enzo
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Re: peavey musican 400

Post by Enzo » Sun Feb 16, 2020 11:41 am

Black and blue are probably the mains connection. I could be wrong.

Look up "light bulb limiter", it is simple. Make one and use it. We don'tt need to be blowing lots of fuses.

plen
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Re: peavey musican 400

Post by plen » Thu Jan 07, 2021 9:54 am

about 4 weeks ago i got the amp working. reverb does not work. when i first got the amp it was working. will reverb work with the knobs or does it have to be turned on by a foot switch.

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Pappy B
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Re: peavey musican 400

Post by Pappy B » Thu Jan 07, 2021 1:35 pm

Should work without footswitch. Take a look at the reverb pan and see if any of the tiny wires are broke off at the connectors. Also clean the plugs and jacks if they are dirty.
The more I learn the more I realize how much I don't know.

plen
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Re: peavey musican 400

Post by plen » Thu Jan 07, 2021 1:39 pm

thanks pappy B i have checked the wire springs and the wires,they are ok.

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Enzo
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Re: peavey musican 400

Post by Enzo » Thu Jan 07, 2021 9:36 pm

ANy chance the cables are plugged in backwards?

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Re: peavey musican 400

Post by plen » Fri Jan 08, 2021 9:21 am

i have changed the wires on the reverb tank already.

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