Marshall TSL

[Valvehead]

Howdy---working on a Marshall TSL 100 today.

Had to replace the power trans , its up and running , voltages look good--bias set , amp works....BUT..

I have a random static / crackling noise. Its on all 3 channels, and I can kill it by removing V1.

I also notice if I ground V! pin 7 the noise is still there......if i ground V1 pin 2 , its quiet .

looks like some filtering there - C10 / C 19 ...maybe the culprit ?

tube has been swapped out also

tsl.pdf

[Jazz P Bass]

Pull Conn 4 at V1.

If it does stop the noise then you have to follow the snakes.

Conn 4 goes to Conn 8 on the Lead board.
Then through photoresistors to the Crunch board.

Here is an awesome file that someone actually spelled out where all the friggin connectors go.

TSL100 TXT NOTES editable.pdf

[Valvehead]

Yes , pulling Con 4 stops the noise

[Amp Kat]

Grounding pin 2 was quiet because you sent the signal to ground.

[Valvehead]

OK, so signal goes thru Opt 2 and 3 ...im not familiar with these - what happens when they go bad? do they get noisy? do they simply not pass signal ? Anyway to test these ? I do not own a scope

[Jazz P Bass]

You can see noise sometimes with a meter.
Either a fluctuating Vdc or Vac. (set the meter accordingly).

I would go beyond the photoresistors.

Are there any connectors that you can pull on the Crunch board?

[Valvehead]

yes--i can get to all 3 boards

[Valvehead]

forgot to mention--i pulled the main pcb, the output jack pcb , and the Crunch pcb , and fixed any bad solder joints.

i measured V1 and V2 tonight for AC

V1 pin 2 = 1mv ac
pin 7 = 20mv ac

V2 pin2 = 6mv ac
pin 7 = 5mv ac

[Valvehead]

I tested some things tonight.
there are no fluctuations with dc or ac at the grids of V1 or V2

so i pulled some of the connectors between pcb's

pulling Con 6 on lead pcb that goes to Con 2 on crunch pcb-----still noise


pulling Con 10 on Lead pcb that goes to Con4 on Clean pcb ---- still noise

pulling Con5 on Lead pcb that goes to Con 1 on crunch pcb ------NO noise

pulling Con 7 on lead pcb that goes to Con Con 3 on clean pcb ----NO noise

i hope this makes sense ???

[Valvehead]

see my first post

[Valvehead]

Im getting absolutely lost with the signal flow on this thing.........

I did find this tonight pulling some connectors off.

If you look at the Clean Channel scem - posted earlier

pulling CON 6 kills the noise
pulling CON 3 kills the noise

pulling the rest of the cons on the clean pcb does not affect the noise

the noise has to be from something in the 2 stages of V1 .. ??

[Valvehead]

UPDATE-----

I played through the amp just to hear the channels and I noticed that the Lead channel had way less overdrive than it should , even with the gain on 10 .

So i measured the plate resistors on V1 . Low and behold the 220k measures 10 Meg !

I replaced it and the other plate res on v1 and now I have plenty o gain AND NO static on Crunch or Lead channels !

BUT..its still on the Clean channel , but its way quieter now....still staticy but about 50% less .

Im going to pull the Clean pcb and check the solder joints next.

Any thoughts on this ??

[Alex R]

I'd be checking the plate resistors again, that's very often where crackles come from. They're pretty wimpy on the DSL/TSL.

[AmpFix]

UPDATE-----

I played through the amp just to hear the channels and I noticed that the Lead channel had way less overdrive than it should , even with the gain on 10 .

So i measured the plate resistors on V1 . Low and behold the 220k measures 10 Meg !

That's weird because the schematic you posted states that the plate resistors for V1a and V1b are 100k, not 220k (R13 and R22). Are you sure that you measured the correct resistors?

Have you established which channel and mode the noise happens in? That would help in narrowing down the faulty circuitry.

[Valvehead]

yes there are 2 versions of the TSL schematic . my amp def had 220k/100k.

noise is on ch.1 / Clean channel