1998 Marshall DSL 401 original schematic dl40 60 00

[Smitty02]

I am looking for the the DSL 401 schematic board # dl40 60 00 I believe I have a copy of the dl40 60 02 with the reverb not working in that amp there is no ZD5 no t15 or t16 Any one have a line on the original 00, I cant find it anywhere I got signal to the return or red line , it will buzz when touched but no output signal OR I may have gotten that backwards I dont feel like running back down stairs LOL to the work shop But I believe the red is the return .. swapped out IC1 and IC3 got voltage diodes are good resistors are good that I can see replaced the pots bad trace maybe ?? I went over the joints nothing looks bad would like a correct print if anyone has a copy Thanks all I hate working on these, you gotta rip it all apart to check anything or fix .....

[Enzo]

Those parts are mutes - "ducking" as they call it on the print - it is there to momentarily mute the reverb during switching. Since yours lacks that addition, they won;t get in the way. Pretend they are not in your schematic and you should be fine.

You have two circuits in the reverb, the drive and the recovery. If you can touch one of the plug tips and get hum, then the recovery seems to be working, and that plug goes into the OUTPUT jack on the reverb pan.

Have you checked the pan itself? Unplug the cords and measure resistance across each jack. The INPUT jack will probably read something low, and the OUTPUT should read like 150-200 ohms. Here is the thing: it won't be wrong, it will either be right or it will be open. Open is bad, and will not make reverb.

If the pan is good, and you get hum when touching the plug tip, then shaking the reverb pan opught to make spring crash sounds. Does it?

These drive circuits can get screwy if they are not connected to the pan, so hook it up. And play a signal through the amp and see if it is present on the drive output to the pan.

[Smitty02]

Yes I got spring rattle and hum when you touch the red/output issue seems to be in the send as I replaced the IC3 and IC1 I got 15v + and - at both IC's 3 and 4 and 12v on the left top pin of IC4 not on IC3 though, cant find any bad diodes or resistors suspect one or some of the transistors j174's or mpsa13's T8 T6..but having a hard time neither have 12v present not sure if they are sapose to.. print dont have many voltage points other than the rails and im still cutting my teeth on reading schematics getting better though.. nothing getting to the pan

[Enzo]

Pin 1 of IC4 is a control voltage. If you get hum when touching the plug or you get spring crash, then IC4 circuit is working, and we move on to the drive side.

IC3 is the drive. Its two halves are paralleled. When signal in playing through the amp, you should see it at pins 1 and 7 of that IC. Those ICs got the signal fromk IC1b, pin 7. Got signal there?

And don;t overlook that between the drive at IC3 and the jacks for the reverb cables, there is a connection and some shielded wires. Make sure any signal output at IC3 makes it over to the jacks.

[Smitty02]

Thats where ive been tracking to the rca jack board but no shielded wires involved unless you mean the pan cable, just a plastic jumper set, which is ok , that I did check right off.. this is a pita job lol thanks for you help as always..

[Enzo]

OK, wrong mental image, no shields. But it remains that the signal path for the reverb drive diverges from the main signal path through IC1 then IC3 to the jacks. Follow the signal along that route and see where it disappears.

And don;t forget the cables down to the pan could be bad.

[Smitty02]

yes I noticed IC3 has + & - 15v and then the rest of the pins have minor voltage readings IC4 has the same except it has 12v at the top (end with the dot) left pin IC3 dont have 12v but does have the + & - 15v, should this be a concern or is there any conclusive way to test a IC as i have swapped this one out with one I had already, it could be bad too came out of a scrapped out dsl 201 I had gutted and built into a 18 watt... Hey I just gave myself a idea.. If you say the schematics are pretty close I can use the 201 board to trace the path, it may be helpful as it is impossible to do without flipping the board over trying to follow the schematic is pretty hard for me, a layout would be priceless specially with these amps and all there issues. I hear they are/or already are Re-issuing these amps Joy !

[g1]

Don't bother comparing voltages between IC3 and IC4 as they are not the same type of chip. Only the supply voltages should be the same (pins 4 & 8).
In post #2 Enzo asked you to measure the resistance of the input jack of the tank. You did not mention what you measured, was it a low resistance?

[Smitty02]

Oh yes I am sorry input is 25.6 ohms output is 223.9 ohms my bad I edited was not .3 I had to fix those little angel hair wires

[Smitty02]

yes those little angle hair wires going to the connector on the return they look like they are connected but are the cause i had a extra tank that was the same issue. with a soft touch and low heat I was able to track solder down the pin and onto the plastic with rosin and both tanks came to life and the plus side thanks to Enzo and a lot of posts. Ive learned the reverb path and more for these little beasts, all is well reverb again. I dont know how long they will last but I hope forever LOL clean it up get it out thank you good fellows.