issues with JCM 2000 TSL100 fx loop

[Marsi]

Hello everyone,
There might be very similar threads going around about the TSL100 fx loops, but after searching on the internet for days I haven't found a solution to the specific problem I'm having and I decided to sign up to this forum and try my luck since there seems to be a lot of knowledge in this place.

Any help would be greatly appreciated.

I am currently working on my first analog pedalboard. The pedal chain going into the input of the amp is about done and sounds exactly how I want it to. The amp sounds great, and very alive and bright.
Now, I want to start adding some time-based or modulation effects in the fx loop and I have ran into some trouble.

I switched on the fx loop through the foot controller, and the result was a massive drop in volume and tone (very dull and boring sound) which really needs to be fixed to be usable.

So I started experimenting, with the following results:
- First I thought it might be my true bypass pedal chain, so I tried to put a buffer before and/or after the other pedals. This did improve the tone issue slightly, but not nearly enough, however it has an effect.

After this I went on to try things out without pedals connected, using just a jumper/patch cable between send/return to exclude any thing in the chain to be the cause of the problems.

- as soon as I engage the fx loop (patch from Send A to Return A) I experience the same loss in tone and volume. (fx mix at 10)
- I toggled the loop level switches, the IN position (recommended for floor pedals) produces a little more hiss/noise than the OUT position, however that seems to be the only difference. (fx mix at 10)
- I can play with the fx mix button and as expected; the further it is turned clockwise the worse are the problems. (there seems to be some sweet spots around 3 and 8 which actually produces a sound very similar to when the fx loop is off, however I would like to run some effects at 100%) (phase issues?)

- When I plug in a jack ONLY in Send B, I already experience the problem, before even plugging the other end into Return B... which is strange, right?
For Loop A I need to complete the loop before the problems occur.

I have also tried running the amp without the foot controller connected, just in case.


So, I have now been searching the internet for a plausible cause or fix, and have so far been unsuccessful.
Most of the discussions are about the usual volume drop, which I would be able to put up with, but the loss of tone really is a problem
Generally threads end in the conclusion that the parallel fx loop on these just aren't great, or people don't have issues after turning the fx mix control to 100% (where my problems are worst).

Is there something wrong with my fx loop, or is it a 'normal' problem? Did anyone experience this and found a solution?
I would be happy with any help I can get, since I love the sound of the amp and this is the last step I'm working on to create my sound.

(also, searching for easy parallel to true series mods for the tsl100 has not been very successful, or the mods either come with very few reports of actually working good. Since this is an option I might consider if I can't get my problems fixed I would like to hear any recommendations)

 

[Mitchell Pearrow]

Hello everyone,
There might be very similar threads going around about the TSL100 fx loops, but after searching on the internet for days I haven't found a solution to the specific problem I'm having and I decided to sign up to this forum and try my luck since there seems to be a lot of knowledge in this place.

Any help would be greatly appreciated.

I am currently working on my first analog pedalboard. The pedal chain going into the input of the amp is about done and sounds exactly how I want it to. The amp sounds great, and very alive and bright.
Now, I want to start adding some time-based or modulation effects in the fx loop and I have ran into some trouble.

I switched on the fx loop through the foot controller, and the result was a massive drop in volume and tone (very dull and boring sound) which really needs to be fixed to be usable.

So I started experimenting, with the following results:
- First I thought it might be my true bypass pedal chain, so I tried to put a buffer before and/or after the other pedals. This did improve the tone issue slightly, but not nearly enough, however it has an effect.

After this I went on to try things out without pedals connected, using just a jumper/patch cable between send/return to exclude any thing in the chain to be the cause of the problems.

- as soon as I engage the fx loop (patch from Send A to Send B) I experience the same loss in tone and volume. (fx mix at 10)
- I toggled the loop level switches, the IN position (recommended for floor pedals) produces a little more hiss/noise than the OUT position, however that seems to be the only difference. (fx mix at 10)
- I can play with the fx mix button and as expected; the further it is turned clockwise the worse are the problems. (there seems to be some sweet spots around 3 and 8 which actually produces a sound very similar to when the fx loop is off, however I would like to run some effects at 100%) (phase issues?)

- When I plug in a jack ONLY in Send B, I already experience the problem, before even plugging the other end into Return B... which is strange, right?
For Loop A I need to complete the loop before the problems occur.

I have also tried running the amp without the foot controller connected, just in case.


So, I have now been searching the internet for a plausible cause or fix, and have so far been unsuccessful.
Most of the discussions are about the usual volume drop, which I would be able to put up with, but the loss of tone really is a problem
Generally threads end in the conclusion that the parallel fx loop on these just aren't great, or people don't have issues after turning the fx mix control to 100% (where my problems are worst).

Is there something wrong with my fx loop, or is it a 'normal' problem? Did anyone experience this and found a solution?
I would be happy with any help I can get, since I love the sound of the amp and this is the last step I'm working on to create my sound.

(also, searching for easy parallel to true series mods for the tsl100 has not been very successful, or the mods either come with very few reports of actually working good. Since this is an option I might consider if I can't get my problems fixed I would like to hear any recommendations)

I am truly sorry for your fx loop issues, I am not a tech bye any means, but I can tell you be patient your answers will come, and to the forum!
Cheers Mitch

 

[EADGBE]

Could an effects jack(s) be dirty and or corroded?

 

[The Dose of Harmony]

Its a common problem for TSL ‘s
There is alot on info on the mods of this amps!

I will send you the link later !!!

Thats the one if the Tsl’s weak spots
I dont know in you specific case but it sounds like the same problem to everybody else!
There is more info in this page
In the mean time!!! Catch up on this link!!
Post you serial and year ?
If you open it find out what isseu number you have in your boards, that will help us to date your amp .
http://www.marshallforum.com/threads/tsl-effects-loop.104075/

If you have more questions let us know

 

[Marsi]

I am truly sorry for your fx loop issues, I am not a tech bye any means, but I can tell you be patient your answers will come, and to the forum!
Cheers Mitch

Thank you! much appreciated

Could an effects jack(s) be dirty and or corroded?

There is no visibly observable corrosion or dirt from the outside, however later today I will open up the amp and also check the insides. Thank you!

Its a common problem for TSL ‘s
There is alot on info on the mods of this amps!

I will send you the link later !!!

Thats the one if the Tsl’s weak spots
I dont know in you specific case but it sounds like the same problem to everybody else!
There is more info in this page
In the mean time!!! Catch up on this link!!
Post you serial and year ?
If you open it find out what isseu number you have in your boards, that will help us to date your amp .
http://www.marshallforum.com/threads/tsl-effects-loop.104075/

If you have more questions let us know

Thanks a lot for your reply!
I've noticed by the number of reported issues in other threads that the fx loop is a common cause of problems for the TSL. I encountered a lot of threads especially about the volume drop and noise.
However, a lot of times I read that people just sold the TSL for the DSL to get the series fx loop, or buy clean boosters to counter the volume loss which I would not consider a 'real solution' but more like a last resort trick when nothing else works.

What bothers me the most is the devastating change in tone.
I'm familiar with the thread from your link. There are some good ideas in there, but overall I find it hard to derive conclusions about effective solutions. However, there is a successful report in there of someone who changed all the boards in the amp for new revision ones, which is interesting but also quite a radical procedure for just the fx loop issues.

I thought my specific problem might differ because of my observation of a simple buffer circuit in the chain slightly improves the tone/volume problems, plus the strange observation of only plugging into loop B send already causes problems in contrary to them only starting to exist when both Return and Send are connected for loop A.
This made me suspicious of a problem with the OP-amps/'buffer' from the amp's fx loop since they appear to share components in the schematic.
Any ideas on this?

I would love the links to good mods!

Later today I will open the amp up and check the numbers (I think from memory the year was 2002).

Thanks again!

 

[The Dose of Harmony]

Thank you! much appreciated



There is no visibly observable corrosion or dirt from the outside, however later today I will open up the amp and also check the insides. Thank you!



Thanks a lot for your reply!
I've noticed by the number of reported issues in other threads that the fx loop is a common cause of problems for the TSL. I encountered a lot of threads especially about the volume drop and noise.
However, a lot of times I read that people just sold the TSL for the DSL to get the series fx loop, or buy clean boosters to counter the volume loss which I would not consider a 'real solution' but more like a last resort trick when nothing else works.

What bothers me the most is the devastating change in tone.
I'm familiar with the thread from your link. There are some good ideas in there, but overall I find it hard to derive conclusions about effective solutions. However, there is a successful report in there of someone who changed all the boards in the amp for new revision ones, which is interesting but also quite a radical procedure for just the fx loop issues.

I thought my specific problem might differ because of my observation of a simple buffer circuit in the chain slightly improves the tone/volume problems, plus the strange observation of only plugging into loop B send already causes problems in contrary to them only starting to exist when both Return and Send are connected for loop A.
This made me suspicious of a problem with the OP-amps/'buffer' from the amp's fx loop since they appear to share components in the schematic.
Any ideas on this?

I would love the links to good mods!

Later today I will open the amp up and check the numbers (I think from memory the year was 2002).

Thanks again!

Boodoo amps offers a solution for that problem but its expensive because they sell a mod but you have to purchase the standar mode too

I am actually updating all my boards i already have the main and the rear boar but the rear board its only compatible with the new ones !!!

And just to give you heads up the drop in volume its almost the same from what i understand but no noise and you have the right values of caps and resistors all across the board!!!

 

[GT08]

Patch from "Send A to Send B"...……...think you need to read the Manual.

 

[Marsi]

Patch from "Send A to Send B"...……...think you need to read the Manual.

Oops, I wrote that down incorrectly, should of course be Send A to Return A. Already edited the original.

 

[GT08]

Give the jack sockets a good rodgering using a jack plug soaked in cleaning fluid.
I never use my fx mix above number 3.
I only ever use delay in fx loop.

 

[Marsi]

A bit later than expected, but I opened the amp up today.

The motherboard reads JCM2-60-00
Crunch channel TL10-66-00
Lead channel TL10-61-00
Clean channel, unable to read due to a sticker on the plate.
The board connected to the outputs and fx loops reads TL10-62-00
Serial: M-2003-37-0107-A

Upon closer inspection in better light I did spot a fair bit of corrosion on the fx loop jacks...
The cleaning fluid didn't really seem to do much. I am now considering replacing the just fx loop jacks instead of that whole board, any thoughts on that? Soldering would be no problem at all.

 

[Hutch]

Well I might be doing things all wrong but I always leave my loop on and use a boss ES-5 to turn on and off effects and loops to front of amp or loop. works fine for me with no drop in volume.

 

[The Dose of Harmony]

A bit later than expected, but I opened the amp up today.

The motherboard reads JCM2-60-00
Crunch channel TL10-66-00
Lead channel TL10-61-00
Clean channel, unable to read due to a sticker on the plate.
The board connected to the outputs and fx loops reads TL10-62-00
Serial: M-2003-37-0107-A

Upon closer inspection in better light I did spot a fair bit of corrosion on the fx loop jacks...
The cleaning fluid didn't really seem to do much. I am now considering replacing the just fx loop jacks instead of that whole board, any thoughts on that? Soldering would be no problem at all.

You have old numbers on you board
Do you know What issue are they?

The issue number its the last digit in the code that is printed on the boards sometimes close tho the number of the board !

Replace the rear board its not an option for you !!!

the new rear board its not compatible with old issue number!

If you replace the rear board you have to replace all of them and if i remember right by the number on your main board you are gonna suffer the bias drift sooner or later!!!

 

[Marsi]

I took a quick look, I cannot really see any issue number, except for 'issue 3' being printed on the board near the schuko connector. Is that what you mean?

I have not yet had any problems with the bias drift, but so far the longest I have used the amp in one session was 3 hours.

I am considering to just order the two jack bus connectors and soldering them onto the rear board too see if this will fix anything, before spending a large amount of money on all new boards.

I have a second TSL100 stored at a different location (year 1999), which sounded slightly better to me somehow, even though I biased them at around the same voltage. And that is the amp which I will use for gigs when the analog pedalboard is done, so soon I will check the board numbers in that one, and check for fx loop issues. Which might be a nice comparison. If I would exchange boards I would rather do it on the 1999 amp.

 

[The Dose of Harmony]

Yeah the last number its the issue number!
You have one of the early ones

 

[marshalltsl]

I took a quick look, I cannot really see any issue number, except for 'issue 3' being printed on the board near the schuko connector. Is that what you mean?

I have not yet had any problems with the bias drift, but so far the longest I have used the amp in one session was 3 hours.

I am considering to just order the two jack bus connectors and soldering them onto the rear board too see if this will fix anything, before spending a large amount of money on all new boards.

I have a second TSL100 stored at a different location (year 1999), which sounded slightly better to me somehow, even though I biased them at around the same voltage. And that is the amp which I will use for gigs when the analog pedalboard is done, so soon I will check the board numbers in that one, and check for fx loop issues. Which might be a nice comparison. If I would exchange boards I would rather do it on the 1999 amp.

My TSL100 it's from '98. IMHO the best solution it's replace all boards to new ones, issues 20. Exist a kit to do It. The new boards are much better than the early ones. No noise, much better FX, better overall sound.

I think that the best way to use the TSL 100 fxloop it's with pedals or multieffects that they are build in vol. Level input and vol. Level output. You get a perfect volume balance, no drops in volumen when FX loop it's on.

 

[Jeff Hudson]

If everything sounded good through the front, why worry about the effect loop?