help please..

puddin

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I have a Marshall dsl 40 cr. today she plays in the classic, but doesn't play in the ultra gain..is it the board? Thanks in advance..
 

Peegoo

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@puddin I have a Marshall dsl 40 cr. today she plays in the classic, but doesn't play in the ultra gain..is it the board? Thanks in advance..

It could be several things.

Start simple. Unplug the amp. Gently remove each tube one at a time and reinsert it (mind the orientation--they go in one way only). Try the amp. If re-seating the tubes like this doesn't fix the issue, an amp tech is probably in your future.

Another simple troubleshooting step: do you use a footswitch to change channels? If so, unplug the pedal from the amp and try the channel-switching control on the amp's front panel.

Unless you're familiar with troubleshooting, working around electricity/electronics, and soldering, you can zap yourself, or ruin your amp.
 

Tim S

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Here's a breakdown of the functions of the 4 preamp tubes in the DSL40CR:

V1A Classic & Ultra
V1B Ultra-only

V2A Classic & Ultra
V2B Classic & Ultra

V3 Cathode Follower (CF)

V4 Phase Inverter (PI)

The only triode that is unique to the Ultra channel is V1B, so *if* this is a tube problem, it will be V1. Swapping tubes around probably won't help because you'd just be swapping a bad-triode into another socket that both channels need. You should have at least one spare 12ax7 (aka ECC83) preamp tube around for a spare, so you can swap a known-good tube into each socket of a dodgey amp until you find the bad one.

Note: You'll want to use a stout, non-spiral filament tube (like a JJ ECC83s) for V3 (Cathode Follower) . If you don't, that tube will fail sooner than normal.
 

Wally

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I think I’ll change all 12ax7’s tomorrow. I have a full set of jj ECC83s Thanks everyone.
as @Tim S suggested, it is advisable to sub a known good tube into those tube positions one at a time. Start with V1. If a good tube in that socket does not cure the problem, re8nstall the old tube and sub the ‘test’ tube into V2. If and when the substitute tube cures the problem, you have found a bad tube, which can be discarded. If a tube is the problem and you replace all three 12AX7s at one time, you will have three old tubes sitting there.….one of which is bad. You will not know which tube to discard and which two tubes are still good. (;^)
 
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Tim S

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Just in case anyone stumbles into this thread in a future Internet search…. The DSL40CR has two Master Volumes and owners assign each of the 4 voices to either MV1 or M2.

So if both Ultra voices happen to be assigned to a bad Master Volume, then that could cause them to be silent. Make sure at least one of the Ultra voices is assigned to a Master Volume that one of the Classic voices is using (a known-good Master Volume) as a troubleshooting step.
 

puddin

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as @Tim S suggested, it is advisable to sub a known good tube into those tube positions one at a time. Start with V1. If a good tube in that socket does not cure the problem, re8nstall the old tube and sub the ‘test’ tube into V2. If and when the substitute tube cures the problem, you have found a bad tube, which can be discarded. If a tube is the problem and you replace all three 12AX7s at one time, you will have three old tubes sitting there.….one of which is bad. You will not know which tube to discard and which two tubes are still good. (;^)
Yes, thanks Wally. I’m a little slow right now. Recent surgery. Early to bed. I will tackle tomorrow when I’m better rested. I will follow up tomorrow. Thanks for everyone’s help.
 

puddin

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as @Tim S suggested, it is advisable to sub a known good tube into those tube positions one at a time. Start with V1. If a good tube in that socket does not cure the problem, re8nstall the old tube and sub the ‘test’ tube into V2. If and when the substitute tube cures the problem, you have found a bad tube, which can be discarded. If a tube is the problem and you replace all three 12AX7s at one time, you will have three old tubes sitting there.….one of which is bad. You will not know which tube to discard and which two tubes are still good. (;^)
Update.. I've checked all pre amp tubes, one at a time. Starting in the V1, with a known good tube. Tubes are fine. This is the first time ever having a issue with this amp. I think it's time for my tech. Question? can I play in the Classic without causing damage to the amp. I can't lift 50lbs right now to get serviced.
 

Tim S

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Glad you have your Ultra channel back. Operator error? We’ve all been there. When you catch it before you spend any money on a tech, that’s a huge win!
 

puddin

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Glad you have your Ultra channel back. Operator error? We’ve all been there. When you catch it before you spend any money on a tech, that’s a huge win!
I always play in the triode mode. I keep my masters dimed and my volumes around 2 o'clock. The amp would switch, but no sound. Some how my gain on the ultra, got turned down to 0. So embarrassed. To much wine...yesterday.:cool: thanks for all your help.
 




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