Marshall TSL

[Valvehead]

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

as in V2 ??

[AmpFix]

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

noise is on ch.1 / Clean channel

Which board "issue" number do you have? You need the correct schematic as there are many different variants. Maybe the amp was previously modified? The Schematics (TL-10_60_02 board, issue 4, 5, & 7) I've seen all call for 100k on V1.


Looking at the general tube board schematic, it seems like if doing one either one of:
. Grounding pin 2 of V1(a) makes the noise go away
. Pulling CON4 also makes the noise go away,

maybe you should follow the signal path through CON4. I don't have a TSL in front of me and the schematic doesn't specify where CON4 from the tube board goes. (I have seen the TSL110TXT file but the terminology it uses is different from the one that Marshall uses, leading to more confusion). Looks like its the "Overdrive" board it goes to (CON8)?

Just to rule the relays and switching circuit out, pull CON14 on the main tube board. You should still get signal through, just no reverb or channel switching. I would also pull CON10 on the main tube board.

[Valvehead]

The scem that matches my tSL is JCM2-60-02

V1 - R13 is 220k

Con 4 from main pcb goes to CON 8 Lead pcb

pulling con 10 main pcb --still noisey
pulling con 14 kills all signal-no noise --it goes to bias supply

[Tom Phillips]

...pulling con 14 kills all signal-no noise --it goes to bias supply

The same raw AC that powers the bias supply also is used for the amp's +/- 15V supply. Therefore, another way to think about it is that the the cable connected to Con 14 is sending the voltage to the ±15V power supply circuit which resides on the rear panel jack board. The ±15V is then used in various places in the amp. So when you disconnect Con 14 the ±15V supply turns off and parts of the signal path goes dead.

Edit: I have a DSL100 on the bench right now so, rather than spending the time to trace the signals through all the pages of the schematic, I disconnected the AC feed to the ±15V supply and checked the amp's operation. So.. for the DSL100, without the ±15V, the clean channel and the front panel LEDs are dead and the amp defaults to the ultra gain channel mode. Just some interesting information and the operation of the TSL, of course, may differ. For the current noise troubleshooting effort I think that pulling the connector just turns off the signal from V1 and that's why the amp goes quiet. Unfortunately, it doesn't provide any additional useful diagnostic information since the noise has already been isolated to the circuitry associated with V1.

[AmpFix]

The same raw AC that powers the bias supply also is used for the amp's +/- 15V supply. Therefore, another way to think about it is that the the cable connected to Con 14 is sending the voltage to the +15V and -15V power supply circuit which resides on the rear panel jack board. The +/- 15V is then used for all the ICs in the amp. So when you disconnect Con 14 the signal path goes dead.

The ICs should not be part of the signal... with he relays in the default position ... but maybe I missed something (could be different than the DSL) . I'd have to go through the signal path again.

Sounds like maybe part of the switching circuitry might be acting up (things left open that should go to ground), especially if the Crunch and Lead OD channels don't exhibit this noise.

[AmpFix]

The scem that matches my tSL is JCM2-60-02

V1 - R13 is 220k

Do you have the schematic that matches your board? You have to match the board number (JCM2-60-02) AND the issue number (Its printed on the PCB close to the board number). I see that the Issue 7 of that board does have R13 as 220k.