TSL 100 mods

[Texasbluezman]

I've been looking on here for a couple of months, trying to figure out WTF was wrong with my amp. I got really discouraged. I had never soldered on a pcb before, and was a little nervous about trying. I got a really good deal on this amp and a 1960BV cab. $500. The cab is worth that, but without a head, it's just a bunch of speakers. This head is a 1999 model.

About a month ago, another TSL 100 head come up on CL for cash or trade. I jumped on it. Got rid of a combo, that I didn't use, and some cash, and I was the owner of another head. A 2006 model.

So now I felt better about taking my head apart to see if I could fix it. Not the head on my body, that one's totally f@#$ed.

I read various threads on here for 2 weeks straight. Still being a little reluctant. I started by labeling the wiring and taking out the mother (tube) board. I planned on doing the bias drift mod, and a few others. See, the problem was, that I would turn the amp on, let the tubes warm up, flip it off stand by, play it at bedroom levels, with VPR off, and after about 5 mins, the volume would just fade away to nothing. After about 5 mins, it would come back on from 1 to sometimes 5 mins, and repeat. It seemed like a heat related issue. Oh, and it was biased at 85mv.

All mods were done to the motherboard (MB). I plan on doing more to the MB and the OD board later, but it sounds really good for now.

Here's what I've done so far:

C43, C44- 22uF, changed from 50v to 100v
C6, C7- changed from .022uF to .068uF, 630v
R7, R10, R66, R70- changed from 220 ohms to 5.6k ohms. 1 watt metal film.
C46- 22pF, changed from 500v to 1KV
R2- 100k ohms, changed from 1/2 watt to 2 watt
R3- 82k ohms, changed from 1/2 watt to 2 watt

All of the mods can be found on this forum. If these mods didn't work, tubes were the next thing to buy. I don't know how old they are. It has Svetlana's in the power section and no names in the preamp. The 2006 has a full set of JJ's in it. They both sound great now, with a few minute differences. Most of the time I like the '99 more than the '06. Can't really explain it, but it sounds better to my ears.

Also, I tried to fix the footswitch on the '99, and was unsuccessful. I had a thread going about it, but I gave up. I then built my own 2 button footswitch. Again, from a thread found here. The '06 head had a working footswitch, but I really like my 2 button. Takes up less real estate. I don't use the switches for the reverb or the effects loops anyway. Gonna try to upload a couple of pics.

Thanks to everyone here on the forum. Keep up the outstanding work. Thanks, also, for putting up with the countless noobs like myself! Peace!

 

[tubes]

Did you figure out what was causing the volume fading?

 

[Texasbluezman]

I did not pinpoint exactly which mod or repair fixed the problem. I should have done one at a time. I just know it's working now.

 

[Texasbluezman]

WELL, I thought everything was fixed. I went to jam with an old high school drummer buddy today. We played in a band back in day, and I'm looking for a drummer now. I basically went to audition him. I took both, 1999 and 2007, of my TSL 100 heads. I set volumes for all channels on both amps. I first was playing the '99. It was sounding sweet. Then about 15-20 mins of jamming, with the volume on about 3, the volume just faded away and didn't work again for the rest of the time that I was there. Which was about 3 hours. My thoughts? Possibly the tubes. I'm not sure. Good thing I brought the '07, it performed flawless. With the exception of a hum that did get louder as time went on. (Any idea what that could be?)

Anyways, I'm gonna try an experiment. Take the JJ's out of the '07, put them in the '99, bias them up and play through it, at the same volume as the jam, for as long as my wife will let me. LOL. If it still does it then I'm going to start changing out preamp tubes one at a time. The '99 has Svetlanas and no name pre's, which I know are what comes in them originally, but I would think they would have been changed by now, BUT, there's always that possibility that they could be original. The amp hasn't been played much through the years, so it is a semi high possibility. Will post results.

Of course, any, and all, suggestions will be appreciated.

 

[RickyLee]

Sounds like you are on the right track with swapping the power valves/tubes.

 

[Texasbluezman]

I hope so RickyLee. If it is the tubes, it'll have to wait. Need some make some extra dough. But it gives me time to research. I want the amps to sound similar, but a little bit different. After the jam session, my buddy said he preferred the '99 over the '07. He said it had a little bit more balls. I agree somewhat. It was different, but not much. I did prefer the '99 also, over the '07. But the '07 is just as awesome, and most importantly, it did not die!

 

[Texasbluezman]

Since the band jam was cancelled today, I decided to to do some testing and troubleshooting. I took the metal guard off the back of both TSL's. I first checked the bias on the '99. It was pretty steady around 85mv. Then I checked the '07, it was on 60mv! WTF! Who would set a bias that low in this amp? No wonder it sounded like it had no balls. Anyways, it's set at 85mv now. Can't wait to check it out at the next band jam.

So, I went back to the '99. Was playing through it for about 10 mins, at a very low volume. Volume on 1, VPR off also. Then the fading thing happened. I just happened to have the lights off (was admiring the tube glow) and noticed that V2 was not glowing. I wiggled it a little and nothing. Then I took the cover off V1, it was not glowing either. But, when I wiggled it, both V1 and V2 lit back up. In fact they had a much brighter glow than V3 and V4. V4 was a little brighter than V3, but still not even close to the brightness of V1 and V2. The Svetlana's were glowing just as bright as the JJ EL34's in the '07. I think those are newer and not original, like the preamps I believe are.

So, I thing I'm gonna look at getting some new preamps. I read so much about them here and have come up with a few candidates.

A Tungsol, an EH, a Mullard CV4004, a regular Mullard, and a 12BZ7. I know that's only 5. I would like to get more, but pocket says that's enough for now. Of course, these are all CP's. I would love to get NOS. I have a NOS 12AY7 in V1 of my Fender Blues Deluxe Reissue, and I always get comments about the amp's sound. Especially, if there's someone with another BDRI.

Oh, and the TSL's are gonna be used for hard rock and metal, with different tunings that include: standard, drop d and drop c, I may also use drop c#, but not sure about that yet, depends on the singer. Would like to go lower but I need some bigger strings for that. 10's don't really like to be tuned lower than drop C.

 

[The Dose of Harmony]

Did you fix the problem???

Did you try the fx loop?

 

[SG~GUY]

-curious why ya didn't put the "known good tubes in the 07 from the 99"????

-could be bad/dirty/corroded tube-(pre)-socket,... or?

-I love the 12bz7's!!! but ya know they draw twice the heater current right?

 

[Texasbluezman]

The problem appears to be something totally different. I took both heads to a band audition recently. Was playing the '07 first. Then I switched to the '99. Got about 10 minutes of playing again, it faded out, again! Wiggled V1 again and it was brought back to life again.

A question for the masses: does this seem like a loose or bad tube socket? After resetting the tube and carefully putting on the metal cover several times, I was able to jam on it for the whole rehearsal yesterday for 3 hours. But it seems like a temporary solution.

 

[Texasbluezman]

The same problem persists! I have tried every tube I have. It is the amp. I don't believe the pins need tightening, cause the tube is hard to pull out and push in, just like the others. It was doing this before I ever put in the 12BZ7. Is there something else on the board going to V1 that I should be checking?

Edit: I just did an experiment. The amp is on. I took out V1 and measured DC voltage between pins 5 & 9. It started out at -4.72 volts, then slowly climbs to -4.33 volts. Then V2 suddenly lit up and the voltage climbed to -2.44 volts and slowly climbed to about -1.7 volts. Then I put V1 back in and about 5 seconds later V1 and V2 are out again.

Another Edit: Now when V2 comes back on, the voltage reads 2.05. I've read this should be around 6v, or a little more. Have also read, it could be a rectifier.

 

[Texasbluezman]

Now the amp has no sound at all. The last time it made sound was right after I changed the bridge rectifier. I am 110% positive I replaced it correctly. I triple checked. It played for about 3 seconds, then faded out. I have since changed C1 thru C4, on the main board. Thinking that the power supply caps were getting old. I don't have the right meter to check caps.

I still have no sound. All the tubes light up, as they always have. I have swapped power tubes between the two heads. There's nothing wrong with any of them. It's still the amp.

 

[RickyLee]

I missed your post in December but I see you replaced the bridge rectifier. Did you put a robust high rated one in place for the old one?

These amps are a pain to check voltages on while powered up.

V1 and V2 should indeed measure 6VDC - 7VDC across pins 4 or 5 to pin 9. Pins 4 and 5 are tied together.

Did you check the obvious of speaker cab/cables ect? See if you had correct bias voltage on pins 5 of the EL34's?

And the speaker out jacks on the back are known to have issues on the switching contacts on the 4 and 8 ohm jacks. Using the 16 ohm out should always work and bypass that problem. The fix for that is to solder in a ground buss wire across all the speaker out grounds.

Also make sure the problem is not that mute function switch.

But I would say you need to check all the main running voltages on all the tubes. Then after that it would be start tracing the guitar/audio signal going through the amp

 

[Texasbluezman]

1. This is the bridge rectifier that I used. It's better than the stock:
http://www.mouser.com/Search/ProductDetail.aspx?R=BR62virtualkey58300000virtualkey583-BR62

2. V1 & V2 both measure 7.42v across pin 5 & 9. A little higher than you said.

3. Used the same cab and cable as the other head. They work perfectly.

4. Have not checked bias across pin 5 of the EL34's. That needs to be done with the chassis removed, and powered up?

5. Speaker jack mod was performed on both heads, on the board side. But I only use the 16 ohm jack.

6. How do I go about checking that mute function switch? I've never used it. But I did just push it several times, still no sound.

If you have the time, could you explain what exactly I need to check for "main running voltages for all tubes"?

Thanks RickyLee for your responses and help.

 

[RickyLee]

1. This is the bridge rectifier that I used. It's better than the stock:
http://www.mouser.com/Search/ProductDetail.aspx?R=BR62virtualkey58300000virtualkey583-BR62

2. V1 & V2 both measure 7.42v across pin 5 & 9. A little higher than you said.

3. Used the same cab and cable as the other head. They work perfectly.

4. Have not checked bias across pin 5 of the EL34's. That needs to be done with the chassis removed, and powered up?

5. Speaker jack mod was performed on both heads, on the board side. But I only use the 16 ohm jack.

6. How do I go about checking that mute function switch? I've never used it. But I did just push it several times, still no sound.

If you have the time, could you explain what exactly I need to check for "main running voltages for all tubes"?

Thanks RickyLee for your responses and help.

That bridge rectifier is 6A so you are covered there. But that 7.4VDC does seem quite high. What is your wall voltage there?

To check all those running voltages including the bias voltage on the EL34's pins 5, you would have to have the chassis out and the inside exposed. You would have to have it powered ON with the speaker cab plugged in of course. I used an RCA extension cable so I could keep my reverb plugged in as well.

Now keep in mind that this is a very dangerous task, as there is 500VDC inside that amp. No joke for sure. Getting your meter probe on some of these areas to check for voltage is not only dangerous to your health but you can very easily short two circuits together (heater/power supply high voltage) with just a slight slip of the meter probe. The problem is all the PCB's crammed in there along with wiring connectors and such that are in your way to access to traces and connections you would need to check.

A much safer way is to pull one EL34 tube, leave three running at one time and check voltages on that socket from the outside with your meter probe inserted into the tube pin holes on the socket. You would have your Ground or common meter lead clipped to the ground terminal in the amp. This would be an easy way to at least check the pins 3, 4 & 5 voltages. Check the bias at pins1/8 as well. (I am assuming the bias is already set properly?) And you might be able to do that without completely pulling the chassis out. But this is still VERY DANGEROUS. That pin 5 should be a negative DC for the bias. Pin 3 is the plate voltage close to 500VDC and pin 4 is the voltage on the screen grids, close to the same 500VDC.

As for checking the preamp 12AX7 voltages, that is very tough as well. You have to get your probe in there between the wiring and under that rear PCB then it is tough still to get the probe tip to contact the back of those tube sockets. And then being careful not to get shocked or short anything out with a slip of that meter probe.

And then tracing the signal, you would have to reference the schematic and start at the input. Did you check to see if you can get a signal out of the FX loop send? Remember to always have your speaker load plugged in. Or try plugging your guitar into the FX loop return to see if you can get output to the speaker? Not sure, but you might have to have a patch cable inserted into the FX loop send while plugging your guitar cord into the return. Or maybe not. But also try inserting a patch cord to jumper that FX loop as well.

Another problem that could arise is you could lose the low voltage 24VDC circuit that powers that FX loop and some other relays.

As for that MUTE switch, you would have to check that on the PCB. It should be between your phase inverter and the power tubes as it breaks the audio signal path there.

But there is quite a bit to troubleshoot on this amp. Start with the easiest and obvious things first.

 

[Texasbluezman]

Been so busy, just now getting to check out the amp. I checked all pin 5 power tube voltages. -34.5 for V5 & 6. 34.2 for V7&8.

Wall voltage is 121.3vac

I stopped for a second and thought about your post. Check the easiest and obvious. I turned off the amp, and pulled the ht fuse. Black, burnt, and blown. I thought to check this cause, I wasn't getting any voltage readings for any of the other pins. But, what caused this to happen? I'm not putting another fuse in there just to blow another. I've only got 1, and it's in the other head. I'll be a sitting duck with my band if i don't have an amp. What's next?

 

[mickeydg5]

How did the preamp tube DC heater voltage go from -4.72 to 2.5 and now to 7.42?

Strange happenings.

Get some more fuses. Pull all tubes and replace fuse. Turn it ON, play mode. Record voltages at power tube socket lugs and V1 socket lugs.

Lets have a look at that. Remember power tube heaters will be AC while V1 heaters are DC.

Some nice pictures of the replaced preamp bridge rectifier and V1-V2 tube area would also be helpful.

 

[Texasbluezman]

How did the preamp tube DC heater voltage go from -4.72 to 2.5 and now to 7.42?

Strange happenings.

Get some more fuses. Pull all tubes and replace fuse. Turn it ON, play mode. Record voltages at power tube socket lugs and V1 socket lugs.

Lets have a look at that. Remember power tube heaters will be AC while V1 heaters are DC.

Some nice pictures of the replaced preamp bridge rectifier and V1-V2 tube area would also be helpful.

The voltage was fluctuating from -4.72 to 2.5 before I changed C1 thru C4. Afterwards it was stable at 7.42.

Plan to go get a handful of fuses tomorrow. Thx for the reference of AC on the power tube heaters and DC on V1. I knew that already, but still a very good reminder.

I'll get some pics tomorrow also. I have the chassis placed upside down in my shop on some stable 2X4's to make clearance for the tubes. Makes me feel better knowing the amp will not move when probing around high voltages.

 

[Texasbluezman]

I've been reading several topics on here about fuses. Mr. Wilder says he uses fast blowing fuses, even though Marshall installs slow blowing. I trust Jon, he's been a wealth of info for this site. What do y'all recommend?

 

[Texasbluezman]

I changed the HT fuse. Pull all the tubes. Turned on. All was good. I did not check voltages till I put the tubes in. Here is what I got.

V1- pins 5 and 9, was the same 7.42v


pin4 pin5
V5- 463v 471v
V6- 462v 469v
V7- 462v 469v
V8- 462v 470v

I believe that all looks really good.

I then played on it for about a 30 mins. Took a break and came back later to play on it again for an additional 30 to 45 mins. Performed flawless.

My best educated guess is this. After putting in new caps in C1 thru C4 and a new bridge rectifier, it pulled the normal voltage that was required, but the old, original fuse was weak and couldn't handle it and burnt. But, I'm still open to other ideas as to what caused the fuse to blow. I'm just happy it plays again. Oh, and here are the pics I promised: