I recently had a Peavey Stereo Chorus 400(The Beast) come in for repair, this amp did nothing. Step #1 visual inspection. The thing had this large steel wheels mounted on it it , If a amp has wheels it's being moved CHECK FOR LOOSE SOLDER JOINTS. I check this thing from input to speaker output before it dawned on to me to check the @#$%  solder joints. I have been doing this for more years than I care to talk about , so in short always check the basics. The loose solder joints where on those 4700uF caps that give you the -43(not 53) and +43 volts the power the power transistors.


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386 are great for the low power amps , however , you can make a little gain monster with the addition of a TL072 or 4558 which ever you like the best(I prefer the TL072 ).
Like ENGR shows in his pic . I built one years ago (we won't even talk about how long ago). but it yeilds a nice overdrive/distortion.

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Teemuk is dead on  :tu:
I used to have 1 of them myself , they a paralleled

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Cool , Thanx Bro

Yes that sounds about right the Voltage is a + and - 53 voltges on 2 sets of 4 in push-pull config , to reach 200 watts output power. Thanx Bro .
By the way if you don't mind saying where did you find the Peavey Cross-reference I couldn't find one?

What's Up

        I'm repairing a Peavey Stereo Chorus 400, 1 of the of power amps transistors (marked 6357B) is bad (smoked, fried, and toasted) took out the emitter resistor with it. anyway I have seached online for this transistor , looked in my Allied cat. , it isn't listed. anybody hear have any idea what this thing cross ref's. to.

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Nothin to it bro , that's what where here for.

                             
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I just checked it out , it will work , heck I have seen one built , however if recommend you check the 12AX7A data sheet before starting this project. They respond better to a slightly higher voltage(around 190V to 240V). It does have a nice tube overdrive though.

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Sounds cool Darwin, changing the coupling caps does voice an amp(any amp tube or SS) also the bypass caps will as well.

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  yes sir red indicates positive.

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Check the transistors support components and check you suppy current to them, I never limit current while testing an amp, if it won't hang when you turn it on under normal condition , then it's not right you still have a problem to solve and limiting current just would make it harder to do so. Good Luck, Bro

Quote from: teemuk on July 03, 2008, 03:07:25 PM
I use the same diagram and I see a SPDT switch. What comes to shielded wire run …well, it could work - and if it does, good – but I have my doubts: With all the high gain and the high load impedances involved I think a few meter wire run to a foot pedal is not such a good idea - even if shielded, which would be mandatory anyway. As I mentioned, that configuration could easily add more unwanted noises - or at worst burst into oscillation. If I would try to implement something like that I would at least buffer that wire run.

I yes I see the what your saying , loads of gain, after looking at it further, I don't know , it is possible , you would have to build a buffered relayu circuit ( to prevent RF oscillation and pop when switching) as Teemuk stated, hoever all this can be done by the a DIY'er if the person really wanted to, myself I would just plug my TS9DX in more than enough gain from it or most any good OD or Distortion pedal. With the same footprint(stuff on the floor).

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It looks fairly simple to me from the scematic I have , I don't see a SPDT on my diagram it shows a SPST, looks real simple take out the switch run some sheilded cable to a footswitch, looks simple to me. Which diagram are you going by Teemuk I'm looking at the Supertramp& Twin Tramp diagram ?

Basically most amps are built like this:

Input-------(PREAMP(Gain,Volume and Tone controls live here))-----Driver(this stage either split the phase for push_pull power amps or just boost he current for power amps)-----POWER AMP-----the Speaks



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Quote from: joecool85 on June 06, 2008, 07:14:46 AM
I figured I was on the right path, and other tubes that I didn't mention?  Like I said, 2-5 watts and capable of running properly around 100v.

Yeah, 50C5's are fairly good at lower voltages , however running your preamp tube(or tubes) at lower voltages (although it is possible) can produce problems(12AX7's) like voltages ranging from 190V to 240V.

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