tsl100-f3 blew-large 330uf cabs are discolored

[wyomingrocks]

Hi group, another TSL problem. Problem started with a heater gone bad on tube 7 it ended up being a fuse and that brought the heater back to life. but what caused the fuse to blow???? While inside I noticed it has had a 5 watt resistor as well as the c46 cap replaced in the amp, which seems to be a common problem with these amps.

When I noticed the tube wasn't glowing I checked the bias and it was 150mv on one side and I was able to adjust to normal on the other. I am ordering some large 330uf caps but can't find there component number printed on the board to tell you. They are the largest ones on the board I believe they are the ones tied to the BR1, I will be checking that and more after I pull the board out a little.


I am looking for a common problem that is not allowing me to adjust my bias, and connected to fs3 blowing. And possibly related to the large caps.

When I bought the amp the man said he had just installed an output transformer, maybe the two large caps were discolored (smoky) looking back then and never got replaced?

What areas can you think of that I should be looking at, thank you each and everyone who contributes to this board you are such a major help to so many people.

[Enzo]

The first second and third things coming to my mind are a bad power tube. The heater fuse blows when some internal element of the tube shorts to its heater. The 5w 1k resistor is the screen resistor for the tube, that usually only blows when a tube shorts internally.

If C46 shorts, that can also toast that resistor.

If your amp makes B+ voltage up to level and relatively free of ripple, then the large caps are OK.

[Mars Amp Repair]

hello Wyomingrocks,
F-3 is in the filament ckt one one of the power tubes. It usually blows when the tube shorts. Unless the tube is new, I'd think about replacing it & probably the entire Quad.

As far as the caps go, It would be unusual for a filter cap to actually get blackened unless it melted down. I'm thinking that cap may be right next to the little disc cap that you mentioned has been replaced. that little cap will turn black when it shorts...is it possible that that blackening got on the larger filter cap? I doubt the 330uf cap is actually bad.

Try a new(s) tube & fuse. you're probably ok after that. glen

[Enzo]

Or maybe we are looking at the glue they smear on the caps to hold them down.

[wyomingrocks]

thanks for the feedback

Thanks alot for the feedback guys, let me reclarify my problem.

When I bought the amp the guy said it had a new transformer installed. When I took it apart for the heater not working is when I noticed by a visual inspection that the screen resistor had been replaced previously and the small cap burned the pads off the board.

The large filter caps are pretty far away from the little cap that smoked like 4 to 5 inches, there is a white 5 watt power resistor that is in front of them that is as white as can be.

I was an electronics tech for about 10 years in a whole different industry but have seen my share of stressed components, other than the severe smoky discoloration there is no leakage of any kind. They may have been made that color but I have never seen anything from a manufacture with that particular color.

Do you think those caps could have been damaged when the the man changed the transformer and he just didn't replaced those caps. I guess another way of saying if the transformer went bad does it ever take the filter caps with it or when the filter caps go bad does it ever take out the transformer. I will dig out my o-scope and check for ripple if I can find my leads.

Mean while I will rob the tubes out of my dsl and give that a go and see if I can reset my bias. Thanks again for your time guys.

[wyomingrocks]

I couldn't find my scope leads but

I couldn't find my scope leads but I did change out my tubes with some known good ones from a DSL. I am still having the same problem of not being able to bias, even with good tubes. It is still running high on the v7, v8 side. I then went to two tubes, trying to isolate it to a socket, still only adjusting to around 80mv on v7, v8 side.


I next took some measurements and found a couple diffrences.
Pin 5 on V7 and V8 = -34V, and Pin 5 on V5 and V6 = -44V. I had to quit after measuring the socket, but tomorrow I will take some resistance measurements.

also yesterday before I replaced the fuse.
I measured pin 7 to ground on all the tubes v5, v6,and v8 were all 50 ohms
and the tube that blew the heater fuse had an open. I will check that again tomorrow along with some other parts that I can with my meter. If anything catches your eye please let me know. Thanks

[Enzo]

I don't know how an output transformer could stress filter caps. If it shorts to ground, all that does is remove the voltage from across the caps. If excess current flows through the OT, all that does is drop the voltage across them. They won't have the ability to hold up, so ripple will increase. If it opens, then they sit there charged with little to do.

If a filter cap shorts or gets real leaky, it will tend to ground off the B+, thus removing it from the output transformer. If they simply get leaky, then the B+ is real ripply, this makes tons of hum, but I don't see it stressing the transformer.


Here is something you may not have realized. Looking at the rear of the amp chassis there are the three pins for the bias readings, right? And a trimmer on either side of those. Looking at the rear of the amp, the pin and trimmer on the left are for the tubes on the RIGHT end of the row. And the trimmer and pin on the right are for the tubes on the LEFT end of the row. If you assumed the trimmers adjust the tubes closest to them, you'd be wrong.

You have a 10 volt difference in bias voltage between the two sides. That alone is more than enough to make one side melt and the other idle clean.

On the schematic. look just left of the power tubes. The bias trimmers are off hte page through the 7 pin connector, but those three small filter caps and the few resistors there are your bias distribution circuit. Any of those 220k resistors off value? Any of those 47uf caps leaky?

[wyomingrocks]

thank you

Enzo thank you very much for getting back to me. What you pointed out is exactly what I was going to work on tomorrow. The kids finally get off of Christmas vacation and I have some free time again. I read some where, it is very possible that is was something that you wrote about the pots adjusting the opposite sides so I am good to go there.

I think I will hold off on messing with those large filter caps until I get my bias circuit fixed. I am really afraid of applying power to this amp while my bias is out of wack. I certainly don't won't to replace those caps and if there is no ripple I won't, I can live with a little discoloration for what ever reason it is there. I have another TSL and the large caps in it are what I have always typically saw, color wise.

Thanks for spelling out how the power supply wouldn't affect the caps that eases my mind. I am now working mostly with my ohm meter at the moment until I can get the bias situation under control.

Tomorrow I will ohm out those bias parts and do comparisons between the bad side and the good side. I sat down tonight and highlighted all common parts for the bias circuit.

I love your signature about education, it feels pretty much where I am right now. Between what I have forgotten and what I actually never fully grasp, sometimes it feels like all I have left is my education. My Aunt used to tell me that my education is the one thing nobody can take from you. So these amp problems are doing me alot of good with helping me dust off some old cob webs. I have a long, long way to go, but I am really enjoying learning about amps.

Anyway thank you again for all your help. I will take some readings tomorrow and report back any strange findings or hopefully find the faulty component and put this one to rest.

[rabies]

I had a TSL100 for about a year and cranked the hell out of the masters on all channels with EMG loaded guitar with high gain, etc. Only problems I had with it were with the footswitch.

My amp tech had worked on a lot of Marshalls and said he had a client with a TSL100 that kept blowing OT's. All he set it at was clean channel only with gain and volume max'd out.

So be very wary with these newer Marshalls. Other thing was that the footswitch cable/jack is mounted directly onto the PCB board itself (read harmony-central reviews), so if you mess that up connecting it, say goodbye to your amp.

I have a JMP1/monobloc rack now with no problems yet, seems pretty bullet-proof but keeping my fingers crossed...

[wyomingrocks]

thanks rabies

I haven't worked on many amps maybe 5 or 6 but have worked on alot of boards. I am not sure how this compares to most other amps, but it definately is a maze of wires and boards. Seems like a troubleshooting nightmare waiting to happen. I have went through about a dozen or so amps in the past two years, trying to get a feel for what I like tone wise/feature and price wise. I really like these tsl's, I can get pretty good tone out of them depending on what type tubes I run, they sound really good with an eq or sonic stomp in the loop and I use g12h heritage speakers in my cab. The footswitch I have read about, I have tie wrapped mine in several places to stop movement, it seems to be holding so far, don't look the best but it seems to be working. I like the tsl so much I bought two of them, I figured trouble shooting would be easier this way and I always have to have a spare amp. I had a JVM and the inside of it looked so much more orderly than the tsl. I had a road king, that thing seems like it would be a monster to work on. But for features/price I think I will ride it out with my tsl's they seem to do about everything I can ask and not totally break the bank. I am hoping to get this unit up and running (with some outstanding help from this forum) pretty soon and I can't wait.

[rabies]

FWIW, the guys in the band really liked the sound... JJ E34L are highly recommended for that amp... cleans were decent for a marshall too.

[wyomingrocks]

still working on it

Today I got in the parts for my other tsl and it seems to be working again. But this unit is a different story.

I measured alot of resistors today. One area I found interesting was.

R67 and R69 are supposed to be 220K. I measured across R67 and it was right on but R69 measured 169k, I ended up pulling one side and it measured 220k, now ???, thanks for any input.

[wyomingrocks]

finally back

Hi group, I am finally back to working on this amp. I get good readings on the bias circuit, C37 compared to C36 neither are open or shorted and measure right on my cap meter. R69 measured 169K and R67 measured right on at 220k. I pulled R69 and measured it out of the circuit and it was right on at 220k.

I put the resistor back in and pulled CON12 and R69 rose back up to 220k, so next I went to the overdrive board and measured the caps and resistors there. The connector on the overdrive board is CON20 on the top right of the schematic. R41 and R42 measure 680k, but I get different readings on C36 vs C37.

On C36 I get 103nf and on C37 I get .703nf

My question is on C37 do you think this is enough of a difference to mess up my bias and not allow me to bias one side below 150mv, I do not have a 100nf cap so I will have to order one?

While I have the boards out, can you think of anything else I should check??

Thank alot for any help or insite you can provide.

[Enzo]

That circuit is the feed to the DI. The cap value doesn;t matter. if the cap was very leaky on DC, then it could be involved. Otherwise doubtful.

Your problem is getting the amp to bias. Pull CON12 off the main board there. Does the amp now bias right? If so then something on the other end of the CON12 cable is involved. If the amp still won;t bias, it is not.

There are two switches on the other end of that cable - the low power switch and the mute. DO NOT try to set teh bias with the mute on. It connects thetwo sides of grids together.

C36,37 may measure OK on a meter, but that doesn;t tell us they are OK up at operating voltage. They could be fine at the couple volts from a tester and leak like a sieve at 50v.

And don't overlook something right in front of you. Disconnect the little bias adjust board and verify the pots are 100%.

[wyomingrocks]

Thanks Enzo

I ended up replacing C36 and C37 as a set on the lead channel board. It now allows me to set my bias to 80mv on both sides. The amp appears to be working ok. I guess time will tell. My question now is, I know you don't normally monitor the bias while playing but I had my leads still hooked up and I started playing on the lead channel. I was running volume pretty high along with lots of gain and was putting the amp through the paces. I was measuring 200 to 400 mv while playing then it would settle back down when I would stop. Is it normal to get so high of a reading, if so I will button this back and call it good. If not I will keep plugging along. If this is truely fixed thank you very much group expecially Enzo. I appreciate the time you spend to help us all out. Sometimes all I need is a little reassurance that I am going in the right direction and I am very thankful for your help.