Strange Marshall 8200 Issue:

Inspector #20

Inspector #20

Ambassador of Tone
Fallen Star
Country flag
My 1993 Marshall Bi-Chorus 200 has been my go-to amp for my work in this Halford/Fight Tribute. When my marriage recently fell through, i called the guys up and went full-time with them.

So, during a recent live show in Huntington Beach, i noticed that i was getting less and less gain from the amp, despite having the TS-9 running.

Atthe break, i fiddled around with it and noticed that the Boss Compressor was sucking a lot of volume out of the amp, and when i switched it off, the amp got louder.

I got through the show by crlanking the amp gain and the TS-9's controls to full.

Before last night's marathon show at The Doll Hut, i borrowed a Marshall 8100 from another musician froend and ot hs TONS of gain AND the Boss Compressor again behaves normally.

The amp tech at Orange County Sound Studios suspects a "Bad IC Chip."

I would like to get it back online.

(Oh and a local radio ststion blares through your amp at The Doll Hut. Its a long-standing problem)

Thoughts???

No.noise, just very low gain level.

No Chug!!!

20230729_115422.jpg

20230730_141226.jpg20230730_141132.jpg20230730_141314.jpg
 
Inspector #20 said:
My 1993 Marshall Bi-Chorus 200 has been my go-to amp for my work in this Halford/Fight Tribute. When my marriage recently fell through, i called the guys up and went full-time with them.

So, during a recent live show in Huntington Beach, i noticed that i was getting less and less gain from the amp, despite having the TS-9 running.

Atthe break, i fiddled around with it and noticed that the Boss Compressor was sucking a lot of volume out of the amp, and when i switched it off, the amp got louder.

I got through the show by crlanking the amp gain and the TS-9's controls to full.

Before last night's marathon show at The Doll Hut, i borrowed a Marshall 8100 from another musician froend and ot hs TONS of gain AND the Boss Compressor again behaves normally.

The amp tech at Orange County Sound Studios suspects a "Bad IC Chip."

I would like to get it back online.

(Oh and a local radio ststion blares through your amp at The Doll Hut. Its a long-standing problem)

Thoughts???

No.noise, just very low gain level.

No Chug!!!

View attachment 94305

View attachment 94306View attachment 94307View attachment 94308
Click to expand...
I have no answers my friend.
 
Funny, this exact issue popped up on another forum years ago but long story short here's the 3 areas to inspect and some info on what's occuring:

The issue seems to be a sag in power. I'd be willing to wager the loss is happening on one channel and not both? ( I.e OD1 is normal but you see it over on OD2 or vice versa?) The compressor creates this sagging effect on its own by its design in smothering peaks, so already having the issue internally is making the compressor draw it further down. But the solution? One of 4 if not all options


These first two came from @Amp Mad Scientist himself but over there

#1 the Supply Filter Caps have begun to age and are no longer delivering enough stored power, thus robbing from the power supply directly.

#2 The Zenner diodes are going bad and only allowing lesser voltages pass thru them

#3 You have a bad preamp tube possibly

#4 IC3 chip has begun to fail. It's a dual switching opamp. So it could be failing on one sides input, thus not allowing it to deliver the proper power. This part is no longer made: M5201S but it's direct replacement is now (NJM2121D).

Hope this helps
 
Clockworkmike said:
Funny, this exact issue popped up on another forum years ago but long story short here's the 3 areas to inspect and some info on what's occuring:

The issue seems to be a sag in power. I'd be willing to wager the loss is happening on one channel and not both? ( I.e OD1 is normal but you see it over on OD2 or vice versa?) The compressor creates this sagging effect on its own by its design in smothering peaks, so already having the issue internally is making the compressor draw it further down. But the solution? One of 4 if not all options


These first two came from @Amp Mad Scientist himself but over there

#1 the Supply Filter Caps have begun to age and are no longer delivering enough stored power, thus robbing from the power supply directly.

#2 The Zenner diodes are going bad and only allowing lesser voltages pass thru them

#3 You have a bad preamp tube possibly

#4 IC3 chip has begun to fail. It's a dual switching opamp. So it could be failing on one sides input, thus not allowing it to deliver the proper power. This part is no longer made: M5201S but it's direct replacement is now (NJM2121D).

Hope this helps
Click to expand...

Filter caps were recently replaced.
 
Inspector #20 said:
Filter caps were recently replaced.
Click to expand...
There are no known schematics of the 8200 I can find but apparently the 8280 combo schematic is used to reference this amp. In that case, here ya go.

But as you'll see, you got 2 IC3s ( IC3A and IC3B) which are heading to OD1 and OD2 respectively. Just before them is ZD3 at 5.6v. You could check there in that area and kill 3 birds with one stone.
 

Attachments

Clockworkmike said:
There are no known schematics of the 8200 I can find but apparently the 8280 combo schematic is used to reference this amp. In that case, here ya go.

But as you'll see, you got 2 IC3s ( IC3A and IC3B) which are heading to OD1 and OD2 respectively. Just before them is ZD3 at 5.6v. You could check there in that area and kill 3 birds with one stone.
Click to expand...
Appreciated!!!!!
 
Inspector #20 said:
Filter caps were recently replaced.
Click to expand...
You’re in a tough situation without a backup amp. Your 30 year old Valvestate deserves a good look from a professional amp repairman who can properly trace the signal to the offending part, or parts. In the land of millions that you live next to, there’s got to be some good choices to pick from that will tuneup that old solidstate amp to perfection!
 
Clockworkmike said:
There are no known schematics of the 8200 I can find but apparently the 8280 combo schematic is used to reference this amp. In that case, here ya go.

But as you'll see, you got 2 IC3s ( IC3A and IC3B) which are heading to OD1 and OD2 respectively. Just before them is ZD3 at 5.6v. You could check there in that area and kill 3 birds with one stone.
Click to expand...
Appreciated!!!!!
syscokid said:
You’re in a tough situation without a backup amp. Your 30 year old Valvestate deserves a good look from a professional amp repairman who can properly trace the signal to the offending part, or parts. In the land of millions that you live next to, there’s got to be some good choices to pick from that will tuneup that old solidstate amp to perfection!
Click to expand...

I need to come pickup the RH-2204. This unexpected turn of events took all my surplus cash, so recovery time is needed.
 
You must log in or register to reply here.
Back
Top