Marshall TSL 100 Problem

[metoharo]

Just the other day my Marshall TSL 100 head stopped working. I investigated the problem further and found that all four preamp tubes and V1 power tube were not firing. The other three power tubes lit up fine. I tried a quick swap out to see if that would fix the problem but it did not. Any ideas why five tubes would just stop working at once? Anybody have any ideas what could be the problem? Any help would be appreciated. Thanks.

[alerich]

When you say "not firing" I assume you mean that you cannot see the tube heaters heating up. If that is the case I would suspect an open circuit somewhere in your heater string. I would suspect open instead of short since some of the tube are still lighting up. Per the schematic http://elektrotanya.com/PREVIEWS/63463243/23432455/marshall/marshall_jcm2000_tsl100_100w.pdf_1.png that amp appears to have fuses in the heater lines (see F1 F2 F3 F4 near the power tubes on the schematic). I would check each side of those for voltage. If any has no voltage on the tube facing side of the fuse then it is probably open. In addition, you have DC heaters for a couple of the preamp tubes. Could be a problem with that DC supply.

[metoharo]

Thanks for the info. From the sounds of it I think I may take the amp to a tech. and have them check it out. I was hoping it would be an easy fix, probably not.

[Davidg]

That may not be a very hard fix.If nothing else open it up and the fuses are plainly visible next to power tubes.I had one in here awhile back with similar problem and actually had an intermittent fuse,it wasnt blown it had just barely seperated or was not making good contact because with amp on I would get no voltage but pull the fuse and continuity check was good.After a few monutes of frustration O turned fuse around and sure enough no continuity-It would connect with the slightest bit of gravity but flip around and no connection and no visible break or sign of damage.My point is if u dont want to work on the amp with voltage simply pull fuses and check for continuity or if one is blown-the fuse going to whichever power tube is out is likely the culprit.Bleeder resistors should take care of voltage after amp is off a few minutes but u shou;d drain the caps anyway and if u dont know what I mean or how to drain them properly then yes u should absolutely take it to a tech.Good Luck either way!

[plexi50]

If you have not worked on these amps before i would take it to a tech and a good one that knows these amps inside and out. This amp is the mother of all amps you will ever work on. The million dollar quest is what year was it made? It will be stamped and or written with model and year on the side of the chassis in paper. And what board number is it? I have had some nightmare bias issues on the pre 2000 models. And even a few after 2000

R67 & R73 Board # JCM-60-00. The 100 ohm heater resistors burn open at times. Those number are different on different boards they made.
Board # JCM2-61-00 is a different schematic and more than likely different part number placement

I feel better now rebuilding a customers butcherd Marshall Super Lead 100. The TSL is my worst memory. Even though i repair them i dread seeing them when they do come in. And the customers know it because not many places if any here will work on them