Marshall DSL40C (new version)

[The Dude]

You need to trace the signal with a scope if you have one. If not, AC on a DVM. I'm thinking you have signal up to the input side of R46 or there would be no signal to the reverb. It could even be R46 itself is bad or is not soldered properly. It could also be that RL2B is not switching. Some simple signal tracing would tell you what's going on.

[Valvehead]

are you referring to the scem posted above? Thats a 2011 ...i think mines a 2015? Vietnam made. R46 in mine looks to be 4 meg ?

also that scem looks like it has a master volume ? after the tone stack . My amp doesnt have a Master--each channel has a volume

[The Dude]

Yep, I was referring to that schemo. Apologies. If it's not the right one, our first order of business would be to post the correct one so we are all on the same page.

[Valvehead]

Ive looked everywhere Dude---cant find one

[The Dude]

I've been hunting myself. No luck so far.

[The Dude]

Is there a possibility that, despite circuit board designations being different, the circuit is similar enough to get you started? Is there a 560K coming from the center tap of the treble control? Maybe you can find your way using the schematic ignoring designation numbers. Or there's the possibility they redesigned much of the amp.

[Valvehead]

Ill take a look tonight Duder

[Valvehead]

this thing has the 4 pin pots...and traces on both sides of the board...going under relays ..etc...all over.... .ill have to pull it out to really trace anything--maybe tomorrow

[Enzo]

Didn't Doctor post the schematic in this thread:
http://music-electronics-forum.com/t38684/

Post #4?

[Valvehead]

different circuit to a point Enzo....I think ? ......my amp has 2 separate volumes--no master...and some of the stuff doesnt match up--let me pull the pcb back out and trace some as suggested .

[Enzo]

I see two volume controls upper right, VR2 and VR4. I don;t see a master on there. I also see two gain controls VR1 VR3 and one set of tone controls. That sounds like what you want so far.


And what happens if you pull the reverb board, do the reverb controls no longer boost the volume? Do the other controls then function correctly?

[Valvehead]

correct........Dammit....i didnt zoom in on the pdf enough.....i just saw the very large Bass/ mid / treble/ Volume lettering.... and missed the 2nd volume.....my fault.

Pulling the reverb board = amp acts the same--barely any volume, and now no reverb of course, reverb pots dont affect it.

My extremely uneducated guess is Relay 2 or 3B is stuck on fx output ? So i would just be hearing the fx return...but something isnt sending voltage to switch them?

i will pull the pcb and see if i have 5+ vdc to them .

[Valvehead]

so far ive tested the following

i do have 5vdc at the + of C80

reg3 has 15.8v / 0v / 5v

3vdc at both reverb pots

EDIT -------- I have 5v at rly2 and rly3 --one does switch when pushing the fx loop switch , and the other switches when i press the channel select

[Valvehead]

i found it boys---a bunch of cracked solder joints --hard to see .

thanks for your time-----amp is working fine so far !!