Tsl Problems

[Texasbluezman]

I was at band rehearsal Sunday. The other guitar player was running late, so he did not bring his rig. He used what was in the room. It was a Mesa Single Rec with a Diamond cab. About halfway through practice, the Mesa just shut down. No power. Fuse blew. I figured something went wrong with the head. So, I offered my other TSL for him to play. Hooked it all up, started jamming. Then it started cutting out. My buddy started checking cables. And, when he checked the speaker cable, the sound was going in and out.

(Now, this is where I f@#$ed up!)

He pulled the cable over the head, and said, "Look, it's not cutting out anymore". So, I said, "Let's jam". About, 10 seconds in the song, my TSL started making noise that sounded like a tornado was ripping it apart on the inside. Of course, I stopped everything. Upon further inspection, the jack was loose in the cab. It is a single input, 8 ohm cab. And yes, I had it plugged into the 8 ohm jack on the amp. I took apart the input plate and plugged a cable into the jack. The jack was not making good contact. He was using a very expensive, and heavy cable. So, I bent the jack back so it would make contact again. But, it wasn't used anymore for the rehearsal.

The Mesa shorted a tube. One of them was no longer silver on top also. It had a whitish color that was translucent. You could see through the top.



Basically, what I think happened. The cab's input had an open circuit, which in turn, shorted the fuse and a power tube. That's an easy fix.

My TSL was subjected to same open circuit, but did not blow a fuse, and all the power tubes are good, cause I tried them all in the Mesa. My TSL still gets sound, but it doesn't sound good. It does not make any tornado sounds when the tubes are not in.

Does anyone know what damage did occur? Thanks in advance.

 

[Texasbluezman]

Either the right people haven't read this yet, or, I've stunned everyone! LOL!

 

[m1989jmp]

You should check your TSL board for burned components and/or arcing on the tube sockets; if fuse did not blow, something else took the damage.

Just don't try new tubes until you pin the problem down.

 

[RickyLee]

Just to add to what m1989jmp mentioned. Check those 1K 5W screen grid resistors as well, measure them with amp powered OFF. And also check the 1 ohm bias resistors the same way while amp is off. Then check the bias and monitor it for a few. Those 1 ohm bias resistors are known to go bad.

 

[Texasbluezman]

There are no burned components or arcing on the tube sockets. Looks spotless inside. Screen grid resistors (R 60,65,74,76)and bias resistors (R6, R9) all check out good. Will put back together later in the week to check bias.

 

[ampmadscientist]

I was at band rehearsal Sunday. The other guitar player was running late, so he did not bring his rig. He used what was in the room. It was a Mesa Single Rec with a Diamond cab. About halfway through practice, the Mesa just shut down. No power. Fuse blew. I figured something went wrong with the head. So, I offered my other TSL for him to play. Hooked it all up, started jamming. Then it started cutting out. My buddy started checking cables. And, when he checked the speaker cable, the sound was going in and out.

(Now, this is where I f@#$ed up!)

He pulled the cable over the head, and said, "Look, it's not cutting out anymore". So, I said, "Let's jam". About, 10 seconds in the song, my TSL started making noise that sounded like a tornado was ripping it apart on the inside. Of course, I stopped everything. Upon further inspection, the jack was loose in the cab. It is a single input, 8 ohm cab. And yes, I had it plugged into the 8 ohm jack on the amp. I took apart the input plate and plugged a cable into the jack. The jack was not making good contact. He was using a very expensive, and heavy cable. So, I bent the jack back so it would make contact again. But, it wasn't used anymore for the rehearsal.

The Mesa shorted a tube. One of them was no longer silver on top also. It had a whitish color that was translucent. You could see through the top.



Basically, what I think happened. The cab's input had an open circuit, which in turn, shorted the fuse and a power tube. That's an easy fix.

My TSL was subjected to same open circuit, but did not blow a fuse, and all the power tubes are good, cause I tried them all in the Mesa. My TSL still gets sound, but it doesn't sound good. It does not make any tornado sounds when the tubes are not in.

Does anyone know what damage did occur? Thanks in advance.

Open Speaker Circuit Can Cause:
A. Blown tubes
B. Burned tube sockets / arcing and damage to other parts due to arcing...
C. Blown Screen Resistors
D. Burned High/ Low Power Switch (pentode triode switch)
E. Burned output transformer / blown fuses.

Like we say:
The speaker connection is the most important connection.
Make sure the Speaker Cable/ jacks are rock solid. Make Sure the impedance is 100% Correct.

Don't Guess: have a pro test the amp w/ a scope.
That's the best possible advice.

 

[Texasbluezman]

I tried all the tubes in the Mesa. Tube sockets look spotless. Screen resistors check in good. Not sure what you mean by the high/low power switch. All fuses are good. How do I check the OT?

I realize the speaker connection is very important. My head was hooked up a different cab, not mine. Didn't know the jack was loose. I had played through that cab before with no problem. I was just being a nice guy and offered my extra head to keep rehearsal going. I was gonna use the head to power my talk box, but I forgot the power cable.

How am I gonna learn to work on my amp if I take it to somebody else? I want to fix it myself. Changing out parts is easy. The only problem that I'm having, is, I'm still learning how to diagnose. I'm just trying to understand what happened and what is messed up, so I can fix it. Thank you for your advice so far!

 

[Texasbluezman]

bump?

 

[RickyLee]

With the output transformer, I would figure it is working or it is not. There is no in between. I have always wondered myself if there was a chance the windings of wire could get stressed. But then I am figuring you would end up with a meltdown pretty quick after that point. So if it still passes signal I would figure it is still fine and move elsewhere for troubleshooting. Now you can take a resistance reading on the windings. But then do you know what those windings read in the past when the amp was healthy?

 

[mickeydg5]

It will make no sound most likely with the power tubes unloaded because the output amplifier is open circuit.

Does it still "tornado" with tubes loaded?

The tornado thing makes me suspect output oscillation at the time of damage due to the bad output connection. Check the resistances at all of the output transformer's taps.

 

[Texasbluezman]

Yes, it still makes the "tornado" sounds with the tubes loaded. As stated before, this happened while plugged into the 8 ohm jack. It still makes the "tornado" sound when plugged into the 16 ohm jack also.

It seems that resistors measure fairly quickly on a multimeter. EXCEPT, R68 starts off low, (ie. 2.2K) and slowly climbs to 21.9K in a couple of seconds, which is really close. But why would it take a few seconds to climb and settle like that? R64, 72, 73, and 75 do the same, but take even longer. They are 220K. Meter started at 2K and after about 60 seconds, it only made it 150K. Climbing real slow at that point also. Like 1K every second. I know that these resistors are connected to the four biggest capacitors, C34, 35, and C38, 39. My multimeter cannot measure capacitors. Unless, there's another way! All other resistors around the power tubes checked out good.

Am I on the right track? Did I check the right resistances? I followed all the wires that came off the OT, and followed the schematic to check everything in the path till I got to the problem resistors.

Thanks Mickey and Ricky. You guys have been a big help. Even if I don't figure this out, I'm learning how to read a schematic really good. But, I'm not giving up. Mainly because, I really don't have the money to take it to a tech. And, I'm positive, with the right guidance, I can fix this amp!

 

[RickyLee]

R68 is a very critical component. If it is lowering its value in circuit with amp on that is very bad. That basically means your bias supply voltage is dropping its value which in turn is making the EL34 bias run very hot.

Are all the bias components still original to what came in the amp? I upgraded all my bias supply circuit resistors to metal flameproof 1W. I also replaced those two crappy bias trim pots to Bourns 1/2W pots. That fix right there corrects the odd issue of having the trim pots and test points on back backwards to the pairs of EL34's they control. I went with 50K pots but 20K is fine. Would be good idea to replace the caps too. And then you should upgrade those 1 ohm bias resistors to the same metal 1W or 2W if it makes you feel safer. Those are R6 and R9.

 

[mickeydg5]

I do not think it was mentioned yet but I presume this thread pertains to a TSL100 amplifier. Year? Board issue numbers?

Those items really cannot be checked accurately with your meter while in circuit with the amplifier turned ON. Your multimeter will always shunt through connected components in circuit resulting in oddball readings due to components which may charge/discharge.

I was asking about OT resistances.
Turn the amplifier OFF. Pull the power tubes. The amplifier power supply capacitors should be discharged after several minutes. Now measure resistances at the OT taps, both primary and secondary.
Primary from center to each side. Secondary from ground/common wire tap to each output tap.

If needed and possible, provide pictures and ask questions.

 

[EADGBE]

It could be anything. Take it to an amp repairer.

 

[Texasbluezman]

Ricky, I have not checked R68, or any other bias supply circuit resistors with the amp on. This amp has been modded. It is an extensive list, but not as extensive as my other TSL. I've got half a clue, LOL, but I'm not really sure which resistors that you're talking about? What are the designation numbers on the schematic?

Mickey, this TSL 100 is a 2007, with an Issue 10 board. I also have a 1999 TSL 100 with an issue 3 board that has been modded and then some. I think I did this right. The primaries are as follows. W3 to W4-32.6 ohms. W3 to W5-16.2 ohms. W4 to W5-16.7 ohms. The secondaries all read 0.4 ohms. Black is common, 16 ohm is red, 8 ohm is orange, and 4 ohm is green? Did I do the check correctly?

EADGBE, you're right, it could be anything. And, I'll check every single component in this amp to figure out what's wrong with it! It's real easy just to take to it someone, and even easier to tell someone the same. What will I learn from that? I'll learn how much money it costs to get a tube amp fixed! As I stated in an earlier post, that's not gonna happen. I will fix this amp, and it will be better than when I got it. So, how much would all of these mods cost? I've played 4 shows with this amp. All of my mods were done correctly! And, I saved a ton of money doing it myself. I enjoyed the hell out of doing it too. If you don't want to help, or can't, FINE. Then don't post anything in my thread, please!

Here is everything that I've done to it so:

Motherboard mods:
C46- 22pF (500v to 1KV)
R62- (1K to 10K) (1w to 2w) metal film
C18- (100pF to 470pF) 50v
C16- (2n2 to 4n7) 500v
C8- (.022uF to .015uF) 630v mylar film
C9- (500v to 1000v) (100pF to 1000pF)
C43, C44- 22uF (50v to 100v)
C6, C7- (.022uF to .068uF) 630v

OD board:
C36, C37- 0.1 uF (63v to 250v)

ClassicTone 3H choke- 250mA

 

[mickeydg5]

Well it is not power tubes if you are loading new/good tubes with good bias settings and still getting the tornado noise.

According to the resistances the OT primary seems fine. The secondary taps are a bit harder because most meters cannot accurately measure that low. But I do not trust the .4 ohms at each tap. It seems there would be at least some difference. You can compare readings to your other TSL100 OT if you have the time. Also measure across the meter leads, touching only lead to lead, and subtract that from all numbers for a more accurate total.

AmpMad brought up a Pentode/Triode switch. Your amplifier does not have that but does have a form of Hi/Low called VPR I believe. Disconnect the VPR circuit at CON12/CON20 to see if it makes any difference in the noise.

What is the idle bias of each power tube? Does it change after it warms up or the amplifier gets hotter? That is something to monitor.
Those 1 ohm bias monitoring resistors Ricky mentioned are something to check. If problematic, they can heat up and provide higher levels of resistance causing imbalance and bad biasing conditions.

Another thing to document is the power tube voltages, AC at pins #2 and #7 with DC at the rest of the pins.

Does the tornado noise vary, does it increase with time, does it change with volume fluctuations?

When powered ON: High Voltges, Dangerous, read and be acquainted, Be very careful.

 

[Texasbluezman]

MAN, I've been so busy. I'm just getting around to doing something with this situation. I've compared readings to my '99 TSL100, they are almost identical. Only a couple of tenths of an ohm lower. I haven't been able to check anything else due to the fact that my cabinet is not at home. I've got band rehearsal Sunday, so, I'm gonna take it with me and take all the readings then. And take some video, so everyone can hear this horrible oscillation. I'm probably not gonna be able to bring the cab home, due to rain, and I only have a truck. It's a pain to load in the x-cab, but I will if needed.

 

[m1989jmp]

Can you discern the frequency of this oscillation (tornado)? Is it 50/60Hz or something higher?

 

[Texasbluezman]

I have no idea. I guess it would take a scope to find out. Which I don't have. If I can't figure it out with the above suggestions, then I'll take to someone.

 

[Texasbluezman]

So, I put everything back together. Was gonna make a video to let everyone hear the oscillations. Hooked up my multimeter to check bias. Turned the amp on. At first there was a little oscillation, then it quit. I checked bias at the bias points and they were about 8 mv off from each side. I biased up both sides to around 80mv. Picked a guitar, and started jamming. Somehow, it is as quiet as a mouse now. Even quieter than the '99. I'm very pleased that it's working, BUT, how? Could a mismatch bias create such noise? I had a whole day planned of troubleshooting, ie. swapping tubes, taking readings while powered up, etc. What shall I do with the rest of my day now? Can't do yard work, everything's still wet. Houston floods. Didn't get to bad where I'm at, but still got water here and there.

Thanks for everyone's input. I still learned a lot from this experience.