DSL100H Help

[Jack W.]

Marshall DSL100H (2012 issue) has a burnt resistor R60 off V3, someone else worked on it and replaced it with (2) 470 ohms for a total of 223 ohms. This just doesn't seem right. The amp still blows fuses and it was brought to me.
We are unable to acquire the schematics.
Can anyone verify what the correct value of this resistor is,
or provide a copy of the schematics for this release?

Thanks.

[Pedro Vecino]

R60 is a screen grid resistor. The original value is 1K/5W. When this resistors melts or open, always check the tube. It may be due to a malfunction in it.
http://www.drtube.com/schematics/mar...%29%20iss5.pdf

In your case it would be appropriate:

- Replace the resistor.
- Check that the fuse is the proper value and slow blow.
- Connect the amp without EL34īs.
- After that, install them in pairs trying to detect a defective. Firstly a pair. Then the other pair.

[Jack W.]

Thanks Pedro, but this amp is a newer issue - the V3 tube is a 12ax7 preamp and the designated R60 is off pin3 a cathode.
They seem to have redesigned the DSL100 it has plenty of TL072 ICs and a digital reverb FX.

[Pedro Vecino]

I don't know the model. I'm sorry

[Jazz P Bass]

So, without a schematic, what is the function of V3?

Is it the Phase Inverter?
If it is, the Cathode resistor should be 470 ohm.

If the amp came in blowing fues, remove the power tubes & see if the fues holds.

[Jack W.]

The V3 preamp tube hasn't been clearly ID'd yet..It doesn't seem to be the driver. V4 pc traces have the familiar look, and plate resistor values, of a typical Marshall driver. The PCB is heavy in traces very little wiring...it's going to take some time without prints to get the layout of things. Not sure the customer's gonna like it....
Thanks guys.

[Jazz P Bass]

The tube layout, 3 12AX7 preamp, 1 12AX7 PI is supposedly the same as the DSL100.
Though not neccessarily the same circuit.

I would look at the posted DSL100 file & see if it is close.

[Mark Black]

And too, look on the PCB's for a silkscreened board number like "JCM2-60-02" and issue number or some such. Might help to narrow down which schematic is pertinent.

[Jack W.]

This thing is much different to the original DSL's. Has "Clean" & "Classic" digital reverb controls, "classic" and "Ultra" channels, lots of TL072 IC's and a different switching matrix. Totally revamp PCB. According to Marshall service (ie Musicorp) only authorized centers have access to the service info on these and they are bound to confidentiality which no one has breached as of yet. So no prints have leaked out, haha. As a former Auth. shop..none of our Marshall cataloged prints even come close to this newly revamped model. Just hoping someone was able to call out these resistors to confirm proper values.
No worries as we will pass the unit on to the local Authorized dealer.
Just another hump in the repair buissness thanks to Dealers (esp Internet sales) and Manufactures with poor customer support systems. I'm sure the whole amp will be obsolete by next week and all parts no longer made...