Replaced Jcm Dsl 100 Board... Still Having Problems!

[0caria]

Bad bias pot will cause excessive current draw.
I think you should start there and get the bias steady.

Agreed. Unfortunately, Pro Audio's web shop is closed until January, so I'll have to wait it out another few weeks, cause I can't find the replacement bias board anywhere else. Oh well. Thanks again for all your help and detailed instructions. I appreciate it.

 

[ampmadscientist]

Agreed. Unfortunately, Pro Audio's web shop is closed until January, so I'll have to wait it out another few weeks, cause I can't find the replacement bias board anywhere else. Oh well. Thanks again for all your help and detailed instructions. I appreciate it.

I think you could order this part from any Marshall service Center or Marshall dealer:
JCM 2-64-02-01-S
But it may turn out that there is no choice but to change the pots on the old board.

Sorry I do not have a part number for replacement pots yet.

 

[0caria]

I think you could order this part from any Marshall service Center or Marshall dealer:
JCM 2-64-02-01-S
But it may turn out that there is no choice but to change the pots on the old board.

Sorry I do not have a part number for replacement pots yet.

Unfortunately, the only available option for me online is the Pro Audio Uk, and at least where I am, their web shop's closed until early January, so I'll either look for a retail store that can order them, or just wait it out till January to buy the bias board. In the meantime, you mentioned that the pots are very poor quality. Would cheap pots like that be a concern in the long run if I just buy the replacement bias board and not change out the pots it comes with? If it is a concern, do you know anyone I can talk to on this forum who knows where to get better quality pots to replace the ones on the new bias board?

 

[anitoli]

Go here and scroll down a bit you will see the pots:

https://amprepairparts.com/marshalldsl100.htm

 

[ampmadscientist]

Unfortunately, the only available option for me online is the Pro Audio Uk, and at least where I am, their web shop's closed until early January, so I'll either look for a retail store that can order them, or just wait it out till January to buy the bias board. In the meantime, you mentioned that the pots are very poor quality. Would cheap pots like that be a concern in the long run if I just buy the replacement bias board and not change out the pots it comes with? If it is a concern, do you know anyone I can talk to on this forum who knows where to get better quality pots to replace the ones on the new bias board?

Can you take the board out and measure the foot print in mm?
That's what you need to know to find a better part.

 

[0caria]

Go here and scroll down a bit you will see the pots:

https://amprepairparts.com/marshalldsl100.htm

Thanks for the link man. Checking it out right now.

 

[ampmadscientist]

Thanks for the link man. Checking it out right now.

If you cannot find somebody to change the pots on the board, send it over here and I will solder them on for you. Pack the board good so it will not be damaged.
(PM me) This is your Christmas goodies. Happy new year.

 

[0caria]

If you cannot find somebody to change the pots on the board, send it over here and I will solder them on for you. Pack the board good so it will not be damaged.
(PM me) This is your Christmas goodies. Happy new year.

Thanks man I appreciate it, but I'll just buy the new bias board with the pots on it, that way I know the whole bias board is new. The bias board in the amp is very old (says issue 2) is faded and seems to have some weak solder joints on the back. Merry belated Christmas and Happy New Year Mad Scientist. Thanks again for your help.
Mike

 

[ampmadscientist]

Thanks man I appreciate it, but I'll just buy the new bias board with the pots on it, that way I know the whole bias board is new. The bias board in the amp is very old (says issue 2) is faded and seems to have some weak solder joints on the back. Merry belated Christmas and Happy New Year Mad Scientist. Thanks again for your help.
Mike

Persistence makes impossible possible, have a good new years.

 

[Craig Robichaud]

The new board did not solve all the problem for some people.
For other people the new board did solve it.

So I recommend you do this test...
B, and I recommend you consider the Dr Tube modification.
This is a test to see if the bias voltage is affected by insulation breakdown on the circuit board:

1. Take the output tubes out.
Turn the amp power on, leave the standby OFF. No high voltage is turned on.

2. Measure the DC voltage at the power tube control grid. This should be negative voltage (on pin 5 of DeathAdders amp)
Note the bias voltage. - write this down.

If there is no bias voltage, you need to trace back in the circuit to see where the bias path is broken.

3. Continue to monitor the DC bias negative voltage at the socket pin. Turn the standby ON. (high voltage is now ON.)

4. How much did the bias voltage change when you turned the high voltage ON?
If the bias voltage changed substantially (dropping the voltage down) when the standby was turned on...
you got problems!

Example: if the voltage changed from minus 42 volts DC ------ to minus 35...you got problems.

5. This test allows you to check the bias stability without burning up any tubes. I hope you try the test to see what the condition of the board is.

If you have no bias voltage:
trace and troubleshoot with the standby turned OFF. (no high voltage is turned on)

6. Do not turn the high voltage on. Standby remains OFF.
Do not put the output tubes into the sockets, Do not operate the amp, until you prove that the negative DC bias voltage remains steady (standby ON -OR- standby OFF) at the power tube sockets FIRST.

Hey dude...caught you saying standby “off”!!!...Joking with ya!

 

[ampmadscientist]

Hey dude...caught you saying standby “off”!!!...Joking with ya!

Oh shit, did I?

 

[mickeydg5]

I think it should be called the PLAY switch. Play or not to play, that is the question.

 

[ampmadscientist]

I think it should be called the PLAY switch. Play or not to play, that is the question.

Whatever.
That will work too.
as long as "operate" (play) and "warm-up" are clearly defined.

"Standby on"," standby off" are too confusing. People interchange the terms and it's not clear.

 

[mickeydg5]

I agree.

 

[anitoli]

Whatever.
That will work too.
as long as "operate" (play) and "warm-up" are clearly defined.

"Standby on"," standby off" are too confusing. People interchange the terms and it's not clear.

I don't see why this is so confusing. Standby on means to "wait"............

 

[Gunner64]

This dsl100 I have been working on here ....... says on..and off....just like the power switch.

 

[anitoli]

Marshall customer service prolly got fed up with all the questions about how to use that friggin switch so they dumbed it down just a bit.

 

[Gunner64]

Marshall customer service prolly got fed up with all the questions about how to use that friggin switch so they dumbed it down just a bit.

But when the standby is in the "on" position the standby function is actually off..lol...hence the dumbness. I never seen or had any confusion until this here internet thingy happened,.. then boom!..almost instant dumbness.

 

[anitoli]

But when the standby is in the "on" position the standby function is actually off..lol...hence the dumbness. I never seen or had any confusion until this here internet thingy happened,.. then boom!..almost instant dumbness.

Yes Marshall got it backwards. LOL.

 

[Adieu]

Power: off/on
Standby: standby/play