TSL100 Problem.. Amp humming and left pair tubes bias value going crazy..

fortuyn79 · 10-13-2009, 03:03 PM

Hi,

I've bought a used TSL100 and got it delivered today. Problem with this amp for starters was that there wasn't a matched quad in there. There was one EH EL34 in the first socket en 3 Sveltlanas sitting in the other sockets. It seems the Svetlana's were the original tubes in this amp and that the owner (somewhere over the years) changed the first EL34 to something else (??)..

A while back I had a DSL100 with a similar problem, from that experience I've learned to first check the bias before trying out the amp since you don't know where it's been. When I power on the amp, the right pair EL34 bias value is stable, the left pair on the other hand goes past 150mv and going higher and higher. I see the tubes light up blueish and a hum becoming stronger and stronger... Of course I power down the amp before something bad happen

Just to be clear, I've bought a new quad of EL34's for this amp, and I had a used set of 4 12ax7 in storage which I know are good.

I've looked at the PCB but can't discover any burned components.. From looking at it briefly, I've seen the PCB design looks a lot like the DSL100 PCB and I think the bias resistors are R19 and R24 which seem ok (the ones in the DSL were fried because some other part came lose of the board).

Could the unmatched EL34 have caused technical problems in the amp or would that just make it sound weird?

I've read a lot that the TSL100 (this one is a 2001 head) have heat issues causing the solder of the tube sockets to come lose and have bad connections. I'm aware of the wrong resistors in this version of the PCB mainboard. I will replace them but they just make the amp a little unstable, nothing radical like this.

I know the tubes are fine, can anyone steer me in the right direction?

Sander...

American Viking · 10-13-2009, 04:27 PM

Replace all tubes, preamp and power. Whoever owned it before obviously didn't know what they were doing so swap them out, bias and let us know what you come up with. Every head I've ever gotten used the first thing I do is trash the tubes. There's no telling what some yahoos will put an amp through.

fortuyn79 · 10-13-2009, 04:29 PM

Hi,

Thanks for the reply but I'd already tried a different set of tubes (pre and power) with the same result... Could this be cause be a bad solder of one of the power tube sockets?

Any help is appreciated..

Sander...

American Viking · 10-13-2009, 04:34 PM

shit, sorry! I must have misread, you already said that, duh, my bad.

So your big problem is bias drift.... hmmmm. This is common with TSL/DSL's, search these forums for a bit because there are many people here that have been through this before. Some people have had to just replace that PCB with a newer issue one. I think they're a little over $100. Hopefully you can find something that you can correct without having to go that far. If I run back across one of those threads I'll post a link back to you here.

jcmjmp · 10-13-2009, 06:09 PM

The PCBs never had the wrong resistor values. There were set to those values by design. Most people don't even look at the proper schematic for the specific tube board version and issue. PaoloJM says that the has seen 220k grid blockers can cause bias drift. I never had that problem with 220k grid blocker since 1997 but I guess that depending on the tube, it could be an issue.

Do you have the board number i.e. JCM2-62-00 and issue number? That would be a good start. The issue number is the first visible number after the ISSUE print on the board.

And yes, the DSL and TSL tube board are the same. The differences lie in the rear and front boards. The rest is the same.

fortuyn79 · 10-20-2009, 04:59 PM

Hi,

It's been a week, I've been busy as hell but tonight I had a chance to open up the TSL to have a look. First of there is nothing visually off with any of the components. Just the tube socket pins seemed a little dried out so I resoldered those thinking it was maybe just a bad connection, of course that wasn't the problem.

"JCMJMP" thanks for wanting to help, the issue of the board is JCM2-62-00 like you probably figured, it's a 2001 model.

After resoldering the tube socket pins my attention went to the bias pots. I don't know much about electronics but I think one of those could be the problem. Printed on the side of each bias pot is "22K 370". When I measure the resistance of both pots (turned all the way left and all the way right) :

Pot 1 : 0.2-19.83k
Pot 2 : 0.2-18.35k

Shoudn't the maximum Ohms be the same? And shouldn't they reach 22k?

Please note that the previous owner once had a matched quad in this TSL and at some point changed the first tube with a completely different EL34. I would guess this would cause a great imbalance between the tubes. Is it possible this caused a lot of heat causing the pots to go bad?

I don't have a clue where the original owner got the idea of changing the first tube. Maybe he got confused with mixing preamp tubes for different sounds, who knows...

I think I'm gonna run down to the electronic store tomorrow to get some info and possibly replacement pots but any information would be very helpful.

Thanks,

Sander...

MartyStrat54 · 10-20-2009, 05:26 PM

All advice is given with the warning that high voltages are present in your amp. If you do not know how to remove the high voltage by draining the filter caps, take the amp to a qualified service technician.

The bias pot readings are within tolerance. A lot of the components in your amp are + or - 20 per cent. I don't like it when someone changes a tube out with just one good tube. You don't know if that tube red plated and did any other damage. The TSL is a fairly complicated amp to work on unless you have experience. There are several things that could be causing this. If you can unsolder and pull up one end of each of your fixed bias resistors, you can then take a reading on them. One of the fixed resistors could be bad. Another thing to do that is more of a preventive measure, is to spray contact cleaner into the power tube sockets. Also, if you gently bend the pin retainers this will allow them to make stronger contact with the tube pins. After you spray the contact cleaner, run the power tube into the socket and pull it out and stick it back in again. If after this, the tubes are tight, you do not need to bend the pin retainers.

jcmjmp · 10-20-2009, 10:24 PM

Quote:

Originally Posted by fortuyn79

"JCMJMP" thanks for wanting to help, the issue of the board is JCM2-62-00 like you probably figured, it's a 2001 model.

That's the board rev. The issue number is a different number that is printed on the board. The first visible number after the word "Issue" it the issue number.

fortuyn79 · 10-21-2009, 12:29 AM

Hi,

I will try to use contact spray on the sockets, I could just replace the bais resistors. I would have to look up which ones they are but I had a DSL100 before and looking at this PCB I'm guessing they are R19 and R24 (correct me if im wrong). They are coded BROWN BLACK ORANGE GOLD, can anyone tell me what value they should read? Desoldering and reading them I can handle

Also I found printed on the PCB : "ISS 5" so that would probably mean it's a issue 5 board right?

Wilder Amplification · 10-21-2009, 12:35 AM

Quote:

Originally Posted by fortuyn79

Hi,

I will try to use contact spray on the sockets, I could just replace the bais resistors. I would have to look up which ones they are but I had a DSL100 before and looking at this PCB I'm guessing they are R19 and R24 (correct me if im wrong). They are coded BROWN BLACK ORANGE GOLD, can anyone tell me what value they should read? Desoldering and reading them I can handle

Also I found printed on the PCB : "ISS 5" so that would probably mean it's a issue 5 board right?

Nope, those sound like the 10K grid swampers.

Before you do ANYTHING, grab your multimeter, remove the power valves from the amp. Turn the amp on in PLAY mode (as opposed to standby mode) and measure the voltage from ground to pin 5 on all your power valve sockets, and make sure you have the same negative voltage on pin 5 of all of the power valve sockets. If you do, this means that everything from the bias supply to the valve socket is good to go and more than likely one or more of the valves has a leaky/shorted control grid. If this is the case, as you probably already know it is best to replace the whole set.

Just because valves are brand new doesn't mean they're any good. But you need to check that pin 5 voltage before you proceed any further. I've had sets that were bad right out of the box so don't put all your faith in valves just because they're brand new.

jcmjmp · 10-21-2009, 08:21 AM

Quote:

Originally Posted by Wilder Amplification

Before you do ANYTHING, grab your multimeter, remove the power valves from the amp. Turn the amp on in PLAY mode (as opposed to standby mode) and measure the voltage from ground to pin 5 on all your power valve sockets, and make sure you have the same negative voltage on pin 5 of all of the power valve sockets. If you do, this means that everything from the bias supply to the valve socket is good to go and more than likely one or more of the valves has a leaky/shorted control grid. If this is the case, as you probably already know it is best to replace the whole set.

Just because valves are brand new doesn't mean they're any good. But you need to check that pin 5 voltage before you proceed any further. I've had sets that were bad right out of the box so don't put all your faith in valves just because they're brand new.

Yup.

Try heating the bias circuit resistors with a hair dryer while no valves are present to see if the voltages drift. This will simulate the heat from the amp being in use. Worth a try, just to make sure the solder joints are solid and don't move with temp changes and also to rule out neg. temp co resistors that have been found on some Issue 5 boards. You could just use the bias test points on the chassis to do this.

The bias circuit resistors on the issue 5 are R68=33k, R77=10k, R67=220k, R69=220k.

The grid blockers call for 220k on the schematic but they can easily be changed to 5.6k while you're in there. Paolo JM has stated that he's sen these cause bias problems. I've never seen this problem with 220k grid blockers personally, but its worth a shot. The Grid blockers are R7,R70,R66 & R10

fortuyn79 · 10-24-2009, 06:06 PM

Well thank you guys for all your help, tonight I had the time to go over what Martystrat and JCMJMP advised me to look at and something fixed the problem.

I called my local electronics store who told me just like Marty that the tolerance on the variable bias pots was normal.

Things I did which might have fixed the problem :

- Resoldered the tube socket pins;
- Used a little contact spray in the sockets;
- Replaced the grid blockers with 5k6 resistors;
- Checked the existing fixed bias resistors which were all ok.

I'm guessing it was just a bad connection with the tube(s), I'm aware of the grid blockers topic as I've had a TSL for years, but I don't think that could have caused the extreme continuous (fast) growing bias voltage on one of the pairs.

I'm glad it's resolved without it having to go to a repair shop.. Thank you guys a bunch for your help, this is the second time I managed to fix an amp because the info I got on the forum..

Hope not to post any time soon again

musicman · 11-09-2009, 06:02 PM

Hi everyone,
New here and am experiencing the same problem.
2003 TSL122 with what looks like 3 x =C= (probably original) & 1 x JJ.
Waiting for a matched quad JJ's to arrive.
Measured the voltage between pin 5 & ground all sockets at 523v - does this sound right please ?
Thanks.

musicman · 11-09-2009, 06:06 PM

Forgot to mention.
The valve supplier says 90mv bias is far to high and suggests starting at 72mv then increasing gradually to no more than 80mv.
Would you agree please ?

thrawn86 · 11-09-2009, 06:09 PM

You should repost this in the Power Tubes: Who, What, When, Where, Why, and How? thread.

SGed · 11-10-2009, 01:50 PM

Check capacitor C46. C46 is a 22pf 500v capacitor that is present on the DSL100 schematic, but for some reason was omitted from the TSL100 schematic. The capacitor is a coupling capacitor for oscillation between the plate and screen of the last power amp tube, which is V8. Cut the capacitor out of the circuit to see if the hum goes away. If it does, replace the capacitor with a 22pf,1kv rating. Which should be done anyways because the 500 volt eventually fails causing the problems.

fortuyn79 · 11-10-2009, 01:59 PM

Thanks everyone for the tips, but to be clear the problem is solved. It wasn't anything complicated, just lose solder and bad connections.

musicman · 11-10-2009, 03:33 PM

Hi fortuyn79,
I have the same bias problem with my TSL122 that you used to have so tagged on to your thread.
Hope you don't mind.

RA2 · 11-30-2009, 02:11 PM

I did what i saw written here must have missed something any tips about it
my bias is running high only on one side and keeps rising, tips please.

also what is a grid blocker?

-RA2

TSL 100

Wilder Amplification · 11-30-2009, 02:15 PM

Quote:

Originally Posted by RA2

I did what i saw written here must have missed something any tips about it
my bias is running high only on one side and keeps rising, tips please.

also what is a grid blocker?

-RA2

TSL 100

A grid SWAMPER is a resistor (typically 5.6K in Marshalls) that goes between the grid load resistor and the output valve grid. It serves to combat against grid oscillation. It also feeds the negative voltage from the bias supply to the output valve grid so if one is bad, it will cause the valve that it's connected to to go overcurrent and thermal runaway. But this would only affect one valve, not multiple valves unless multiple grid swamper resistors are bad.

Remove the valves from the amp and turn it on, then measure your voltage between the chassis and pin 5 on all 4 power valves. Then report back with your findings and we can guide you from there.

musicman · 11-30-2009, 04:45 PM

I had exactly the same problem.
Had mine to a tech who found an earth connection not connected on one side.
He also replaced "the smoothing capacitors on the bias supply voltage and the screen decoupling capacitor 47pf."
Be careful putting new valves in as I ruined a new matched quad by trying to bias them up.
ps I don't understand the capacitor bits above just posting this for information for those that do.

10-13-2009, 03:03 PM	#1 (permalink)
fortuyn79 Junior Member Join Date: Dec 2008 Location: Holland Posts: 23	TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Hi, I've bought a used TSL100 and got it delivered today. Problem with this amp for starters was that there wasn't a matched quad in there. There was one EH EL34 in the first socket en 3 Sveltlanas sitting in the other sockets. It seems the Svetlana's were the original tubes in this amp and that the owner (somewhere over the years) changed the first EL34 to something else (??).. A while back I had a DSL100 with a similar problem, from that experience I've learned to first check the bias before trying out the amp since you don't know where it's been. When I power on the amp, the right pair EL34 bias value is stable, the left pair on the other hand goes past 150mv and going higher and higher. I see the tubes light up blueish and a hum becoming stronger and stronger... Of course I power down the amp before something bad happen Just to be clear, I've bought a new quad of EL34's for this amp, and I had a used set of 4 12ax7 in storage which I know are good. I've looked at the PCB but can't discover any burned components.. From looking at it briefly, I've seen the PCB design looks a lot like the DSL100 PCB and I think the bias resistors are R19 and R24 which seem ok (the ones in the DSL were fried because some other part came lose of the board). Could the unmatched EL34 have caused technical problems in the amp or would that just make it sound weird? I've read a lot that the TSL100 (this one is a 2001 head) have heat issues causing the solder of the tube sockets to come lose and have bad connections. I'm aware of the wrong resistors in this version of the PCB mainboard. I will replace them but they just make the amp a little unstable, nothing radical like this. I know the tubes are fine, can anyone steer me in the right direction? Sander... __________________ Sander http://www.myspace.com/underdog_79

10-13-2009, 04:27 PM	#2 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,031	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Replace all tubes, preamp and power. Whoever owned it before obviously didn't know what they were doing so swap them out, bias and let us know what you come up with. Every head I've ever gotten used the first thing I do is trash the tubes. There's no telling what some yahoos will put an amp through. __________________ Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp. ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

10-13-2009, 04:29 PM	#3 (permalink)
fortuyn79 Junior Member Join Date: Dec 2008 Location: Holland Posts: 23	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Hi, Thanks for the reply but I'd already tried a different set of tubes (pre and power) with the same result... Could this be cause be a bad solder of one of the power tube sockets? Any help is appreciated.. Sander... __________________ Sander http://www.myspace.com/underdog_79

10-13-2009, 04:34 PM	#4 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,031	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. shit, sorry! I must have misread, you already said that, duh, my bad. So your big problem is bias drift.... hmmmm. This is common with TSL/DSL's, search these forums for a bit because there are many people here that have been through this before. Some people have had to just replace that PCB with a newer issue one. I think they're a little over $100. Hopefully you can find something that you can correct without having to go that far. If I run back across one of those threads I'll post a link back to you here. __________________ Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp. ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

10-13-2009, 06:09 PM	#5 (permalink)
jcmjmp Senior Member Join Date: Nov 2008 Posts: 2,719	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. The PCBs never had the wrong resistor values. There were set to those values by design. Most people don't even look at the proper schematic for the specific tube board version and issue. PaoloJM says that the has seen 220k grid blockers can cause bias drift. I never had that problem with 220k grid blocker since 1997 but I guess that depending on the tube, it could be an issue. Do you have the board number i.e. JCM2-62-00 and issue number? That would be a good start. The issue number is the first visible number after the ISSUE print on the board. And yes, the DSL and TSL tube board are the same. The differences lie in the rear and front boards. The rest is the same.

Today
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10-20-2009, 04:59 PM	#6 (permalink)
fortuyn79 Junior Member Join Date: Dec 2008 Location: Holland Posts: 23	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Hi, It's been a week, I've been busy as hell but tonight I had a chance to open up the TSL to have a look. First of there is nothing visually off with any of the components. Just the tube socket pins seemed a little dried out so I resoldered those thinking it was maybe just a bad connection, of course that wasn't the problem. "JCMJMP" thanks for wanting to help, the issue of the board is JCM2-62-00 like you probably figured, it's a 2001 model. After resoldering the tube socket pins my attention went to the bias pots. I don't know much about electronics but I think one of those could be the problem. Printed on the side of each bias pot is "22K 370". When I measure the resistance of both pots (turned all the way left and all the way right) : Pot 1 : 0.2-19.83k Pot 2 : 0.2-18.35k Shoudn't the maximum Ohms be the same? And shouldn't they reach 22k? Please note that the previous owner once had a matched quad in this TSL and at some point changed the first tube with a completely different EL34. I would guess this would cause a great imbalance between the tubes. Is it possible this caused a lot of heat causing the pots to go bad? I don't have a clue where the original owner got the idea of changing the first tube. Maybe he got confused with mixing preamp tubes for different sounds, who knows... I think I'm gonna run down to the electronic store tomorrow to get some info and possibly replacement pots but any information would be very helpful. Thanks, Sander... __________________ Sander http://www.myspace.com/underdog_79

10-21-2009, 12:29 AM	#9 (permalink)
fortuyn79 Junior Member Join Date: Dec 2008 Location: Holland Posts: 23	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Hi, I will try to use contact spray on the sockets, I could just replace the bais resistors. I would have to look up which ones they are but I had a DSL100 before and looking at this PCB I'm guessing they are R19 and R24 (correct me if im wrong). They are coded BROWN BLACK ORANGE GOLD, can anyone tell me what value they should read? Desoldering and reading them I can handle Also I found printed on the PCB : "ISS 5" so that would probably mean it's a issue 5 board right? __________________ Sander http://www.myspace.com/underdog_79

10-24-2009, 06:06 PM	#12 (permalink)
fortuyn79 Junior Member Join Date: Dec 2008 Location: Holland Posts: 23	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Well thank you guys for all your help, tonight I had the time to go over what Martystrat and JCMJMP advised me to look at and something fixed the problem. I called my local electronics store who told me just like Marty that the tolerance on the variable bias pots was normal. Things I did which might have fixed the problem : - Resoldered the tube socket pins; - Used a little contact spray in the sockets; - Replaced the grid blockers with 5k6 resistors; - Checked the existing fixed bias resistors which were all ok. I'm guessing it was just a bad connection with the tube(s), I'm aware of the grid blockers topic as I've had a TSL for years, but I don't think that could have caused the extreme continuous (fast) growing bias voltage on one of the pairs. I'm glad it's resolved without it having to go to a repair shop.. Thank you guys a bunch for your help, this is the second time I managed to fix an amp because the info I got on the forum.. Hope not to post any time soon again __________________ Sander http://www.myspace.com/underdog_79

11-09-2009, 06:02 PM	#13 (permalink)
musicman Member Join Date: Nov 2009 Posts: 47	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Hi everyone, New here and am experiencing the same problem. 2003 TSL122 with what looks like 3 x =C= (probably original) & 1 x JJ. Waiting for a matched quad JJ's to arrive. Measured the voltage between pin 5 & ground all sockets at 523v - does this sound right please ? Thanks.

11-09-2009, 06:06 PM	#14 (permalink)
musicman Member Join Date: Nov 2009 Posts: 47	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Forgot to mention. The valve supplier says 90mv bias is far to high and suggests starting at 72mv then increasing gradually to no more than 80mv. Would you agree please ?

11-10-2009, 01:50 PM	#16 (permalink)
SGed Member Join Date: May 2009 Posts: 51	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Check capacitor C46. C46 is a 22pf 500v capacitor that is present on the DSL100 schematic, but for some reason was omitted from the TSL100 schematic. The capacitor is a coupling capacitor for oscillation between the plate and screen of the last power amp tube, which is V8. Cut the capacitor out of the circuit to see if the hum goes away. If it does, replace the capacitor with a 22pf,1kv rating. Which should be done anyways because the 500 volt eventually fails causing the problems.

11-10-2009, 01:59 PM	#17 (permalink)
fortuyn79 Junior Member Join Date: Dec 2008 Location: Holland Posts: 23	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Thanks everyone for the tips, but to be clear the problem is solved. It wasn't anything complicated, just lose solder and bad connections. __________________ Sander http://www.myspace.com/underdog_79

11-10-2009, 03:33 PM	#18 (permalink)
musicman Member Join Date: Nov 2009 Posts: 47	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. Hi fortuyn79, I have the same bias problem with my TSL122 that you used to have so tagged on to your thread. Hope you don't mind.

11-30-2009, 02:11 PM	#19 (permalink)
RA2 Junior Member Join Date: Nov 2009 Posts: 5	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. I did what i saw written here must have missed something any tips about it my bias is running high only on one side and keeps rising, tips please. also what is a grid blocker? -RA2 TSL 100

11-30-2009, 04:45 PM	#21 (permalink)
musicman Member Join Date: Nov 2009 Posts: 47	Re: TSL100 Problem.. Amp humming and left pair tubes bias value going crazy.. I had exactly the same problem. Had mine to a tech who found an earth connection not connected on one side. He also replaced "the smoothing capacitors on the bias supply voltage and the screen decoupling capacitor 47pf." Be careful putting new valves in as I ruined a new matched quad by trying to bias them up. ps I don't understand the capacitor bits above just posting this for information for those that do.

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