New Dsl20hr, And A Problem...

[Javimart1212]

I just wanted to update y'all on this repair. I had some time off this spring break to try the replacement of the C4 cap, and what do you know, it solved that wind blowing / crackling / noise that plagued these amps. So much respect to Sixstring63 for the fix. I still have to change the two resistors, R56 and R70, but obviously they weren't the culprit, nevertheless, I'll do it anyway. So I hope people try this one out as it helped my little practice amp.

 

[Armando]

I just wanted to update y'all on this repair. I had some time off this spring break to try the replacement of the C4 cap, and what do you know, it solved that wind blowing / crackling / noise that plagued these amps. So much respect to Sixstring63 for the fix. I still have to change the two resistors, R56 and R70, but obviously they weren't the culprit, nevertheless, I'll do it anyway. So I hope people try this one out as it helped my little practice amp.

Hi, What have you done? Have you replaced it with New but same or what? Tell me a little more please. Regards.

 

[Armando]

I understand what this C4 is and you have to change it for another one the same (but it works well of course).

Does anyone know how to find oline this piece exactly?

Regards.

 

[Matt_Krush]

I kinda set my DSL 20H on the shelf and haven't played it in a year.
Decided to play it again since I build a single 1x12 cab for it.

Yep...still had that noise. All volumes/dials at zero, and it sounded like the OPs video.

Glad I decided to return to this thread and check it over..

@Sixstrings63...was that the only bad coupling cap you found?
Guess I'd just assume replace them all, like others, I'd appreciate the schematic

 

[jeffb]

So is this still an issue with current production amps?

 

[Matt_Krush]

I don't know if newer ones still have the problem.
Bought my DSL in Nov of 2018 (should have waited...since it was deer season, I never even tried until like January/Feb 2019)

I changed out the C-4 Coupling Cap ...made no difference for me.
I just used a .01uf Mallory I had on hand.
Noise still persists.

Probably just buy another.

 

[calzone]

I struggle with noise problem on my DSL20CR. It's steady uniform white type noise coming from speaker with both channels (gain & volume) set to zero. I found this thread and had a hope that it's all about C4 cap, but it seems different issue.

I found a schematic from DSL40/100HR series which seems similar to DSL20 in regard to "famous" faulty R70 and R56 placement:

Sch

• calzone
• May 15, 2020

For me it looks like R141 & R148 in this are the same as R70 & R56 in DSL20CR/HR. Both 1MOHm in resonance circuit. My question is - how is it possible that these are responsible for the static noise? Why changing them to another set of lower tolerance (5% insread of 1%) can be a solution to the problem?
@Sixstring63 would you help me on this?

 

[calzone]

To sum this up - I can confirm that the above schematic is the same for DSL20CR, just different part numbers. I did the "fix" but it didn't help my noise issue. Looks like there are in fact different "noise" issues. Mine was steady, uniform "gain-like" white noise. It's different from popping, windy, crackling noise issue which is generated by faulty resistors in resonance circuit.

 

[Sixstring63]

Here’s the schematics guys. I know it says DSL15 but it is the 20. By the number of revs they must of had many issues with this design.

 

[Sixstring63]

To sum this up - I can confirm that the above schematic is the same for DSL20CR, just different part numbers. I did the "fix" but it didn't help my noise issue. Looks like there are in fact different "noise" issues. Mine was steady, uniform "gain-like" white noise. It's different from popping, windy, crackling noise issue which is generated by faulty resistors in resonance circuit.

Yeah, that is totally different from the issue the one I worked on was doing. Just got another in for some tone mods. No noise issues. Customer wants more of an old school tone without the fizz and mud.

 

[Sixstring63]

I struggle with noise problem on my DSL20CR. It's steady uniform white type noise coming from speaker with both channels (gain & volume) set to zero. I found this thread and had a hope that it's all about C4 cap, but it seems different issue.

I found a schematic from DSL40/100HR series which seems similar to DSL20 in regard to "famous" faulty R70 and R56 placement:

Sch

• calzone
• May 15, 2020

For me it looks like R141 & R148 in this are the same as R70 & R56 in DSL20CR/HR. Both 1MOHm in resonance circuit. My question is - how is it possible that these are responsible for the static noise? Why changing them to another set of lower tolerance (5% insread of 1%) can be a solution to the problem?
@Sixstring63 would you help me on this?

Posted the schematic. Hopefully it will help.

 

[calzone]

Thankyou @Sixstring63. I already returned DSL20CR and got DSL40CR. This one has no noise issues, still there is some room for improvements

 

[dslman]

I don't know how I missed this thread, but I have a open box DSL20hr on the way, probably someones return with these same issues. This stinks.
I notice there are not many available, I wonder if they stopped production to try and solve the issues.

 

[Musicmaniac]

It looks like you missed a few threads and not all of these have issues. Also, they're probably sold out and back ordered because of C19.

 

[Gene Ballzz]

@Sixstring63
Thank you so much for sharing that schematic! Is there a chance that there is a page missing? It seems there may be a missing piece of the puzzle that would include AC mains and power transformer.
Just Askin' & Thanks Again!
Gene

 

[RickyLee]

Interesting. That schem is very close to what I did to my modified JCM 800 Studio 15. Just the topology layout and switching scheme basically.

Thanks @Sixstring63 for posting the schems, very cool to see the changes Marshall made on that design.

 

[dslman]

Replacing C4, is easy enough, but what exactly needs to be done to R56 & R70?
How can I tell if my DSL20HR resistors are correct or not?

 

[RickyLee]

@Sixstring63
Thank you so much for sharing that scematic! Is there a chance that there is a page missing? It seems there may be a missing piece of the puzzle that would include AC mains and power transformer.
Just Askin' & Thanks Again!
Gene

Is that the amp that switches into low power mode by cutting the voltage to the power tubes plates and screens?

Yeah, would be very cool to see how they are implementing that.

 

[dslman]

I struggle with noise problem on my DSL20CR. It's steady uniform white type noise coming from speaker with both channels (gain & volume) set to zero. I found this thread and had a hope that it's all about C4 cap, but it seems different issue.

I found a schematic from DSL40/100HR series which seems similar to DSL20 in regard to "famous" faulty R70 and R56 placement:

Sch

• calzone
• May 15, 2020

For me it looks like R141 & R148 in this are the same as R70 & R56 in DSL20CR/HR. Both 1MOHm in resonance circuit. My question is - how is it possible that these are responsible for the static noise? Why changing them to another set of lower tolerance (5% insread of 1%) can be a solution to the problem?
@Sixstring63 would you help me on this?

So you've done the C4, and resistors, and still have noise? This is terrible.

 

[Micky]

Is that the amp that switches into low power mode by cutting the voltage to the power tubes plates and screens?

Yeah, would be very cool to see how they are implementing that.

Yeah, it is there in the schematic.
Power transformer page is missing tho, just like the new DSL40CR schematic that is available.
Can anyone fill in the blanks?