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Author Topic: peavey musician series 400  (Read 788 times)

plen

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peavey musician series 400
« on: August 06, 2020, 06:55:55 PM »
i bought a peavey musician series 400 amp about a year ago. i played it for about half an hour then i got a lot of distortion. i turned it off. when i put it back on it would not come on. it just gave a putting sound from the amp and blew the fuse, anyone have any ideas where to look.

thanks.

Enzo

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Re: peavey musician series 400
« Reply #1 on: August 06, 2020, 09:29:19 PM »
BLows fuses?  Start at the start.  DISCONNECT any speaker, if it still blows fuses, then check for shorted output transistors.

joecool85

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Re: peavey musician series 400
« Reply #2 on: August 07, 2020, 08:58:16 PM »
Sounds like shot power supply capacitors to me and/or rectifying diodes.  Regardless, before trying to turn it back on, open it up and look for any burn marks etc.  If all looks good, then build a quick light bulb limiter, plug it into that and start taking voltage measurements with a digital multimeter (we can help here).

Light bulb limiter: https://www.ssguitar.com/index.php?topic=2093.0
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Jazz P Bass

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Re: peavey musician series 400
« Reply #3 on: August 08, 2020, 01:09:50 AM »
!!!"  DISCONNECT any speaker"!!!

plen

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Re: peavey musician series 400
« Reply #4 on: November 18, 2020, 05:58:56 PM »
i have not done anything with the amp till today. i checked all the power transistors and hfe is 20  8  20  17  22  21  10  18  i will change 8hfe and the 10hfe ones. are the other ones alright.  thanks.

Enzo

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Re: peavey musician series 400
« Reply #5 on: November 18, 2020, 09:02:26 PM »
Oh, don't sweat any that are off a bit.  We are concerned they are shorted or not.   I'd wager your testing is not done at full current, but rather with a meter, and that is like tuning a race car engine at idle.   You are blowing fuses, and gain variation will not cause that.

If you are blowing fuses, suspects will be:  output transistors shorted.  Bias string open somewhere (perhaps at the sensing diode connector).  Shorted rectifier.


plen

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Re: peavey musician series 400
« Reply #6 on: November 20, 2020, 09:04:19 PM »
thanks enzo for the reply. i have read a lot of the resistors caps and transistors in the amp. so far 2 1n 4003 diodes are bad and two of the four lay down transistors. i have 1n4005 diodes i will put in. i cant see any of the transistors for sale. is there substitutes for them. there was also a orange disc capacitor not soldered. i will test the rest tomorrow.

Enzo

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Re: peavey musician series 400
« Reply #7 on: November 20, 2020, 10:47:38 PM »
I am not where I can post at the moment, but google "Peavey semiconductor cross reference"  or "peavey semiconductor guide".   Many places will have it for download.

Jazz P Bass

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Re: peavey musician series 400
« Reply #8 on: November 21, 2020, 11:59:23 AM »
Here is the Cross Ref sheet.

dmeek

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Re: peavey musician series 400
« Reply #9 on: November 22, 2020, 03:23:29 PM »
The last few Peaveys of this vintage that I've seen had either shorted or open main filter capacitors.