New old amp day and questions (TSL 100 content).

Discussion in 'The Workbench' started by TheLoudness!!, Feb 18, 2020.

  1. TheLoudness!!

    TheLoudness!! Active Member

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    I recently had gotten a TSL 100 from a local pawn shop that had probably been there well over a year. It was cheap and figured it was something to work with. I knew right off the bat that the reverb was non functional. I guess I will figure out eventually what that is. I know it needs some new power tubes for sure. The amp is loud but seems like it could be louder as far as it being a 100 watt Marshall.

    The amp is from 1999 which makes it a pinch over 20 years old. I had only recently learned that the TSL suffers from the bias drift like the early DSL did/does. Does the TSL need the speaker jack ground issue fixed as well? Are the caps for these located on the motherboard? If so, I'm guessing that a revision 20 board will fix quite a few issues. I'm using it with a single 8 ohm cabinet.

    Also, has anybody done any upgrades on these such as a Classictone transformer or choke? Lots of other amps that I had a choke added to...only helped the sound for sure.

    Any tube suggestions? A JJ in V1 seemed to help it out. The Gold Lion 12ax7 that was in there sounded awesome in a Mesa but in the Marshall, it just wasn't anything to exciting.
     
  2. South Park

    South Park Well-Known Member

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    So how much electronic back ground do you have . Get the bias mod when it needs it . That model amp is not easy to work on
     
  3. TheLoudness!!

    TheLoudness!! Active Member

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    Not a whole lot honestly. There is tech guy who has worked on most of my amps but don't get to take much to him because he is quite expensive.
     
  4. South Park

    South Park Well-Known Member

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    I hope that amp works for you . If you want to do amp mods a 2204 is great for that. You should go to school for this stuff it is well worth it
     
  5. TheLoudness!!

    TheLoudness!! Active Member

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    Yes, that would be awesome. I've got to play through two JCM800's that were just incredible. The downfall is the expensive of a JCM800 these days.
     
  6. South Park

    South Park Well-Known Member

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    If you go to night school for eletronics you can build one it is that easy .
     
  7. TheLoudness!!

    TheLoudness!! Active Member

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    One day...I might just do that lol
     
  8. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    unfortunately, you bought an amp that has a history of problems...

    Is there any warranty on it?
     
  9. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I'd say, before you do anything to it, give it a diagnostic test. You'll need to pull the amp chassis out of the head case box.

    You'll need a decent multi-meter.
     
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  10. TheLoudness!!

    TheLoudness!! Active Member

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    Good advice. I have a decent one so I guess it's time to do some learning!
     
  11. TheLoudness!!

    TheLoudness!! Active Member

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    Holy crap...I was afraid of that. No warranty unfortunately. Live and learn....
     
  12. Drinkingdeath01

    Drinkingdeath01 Well-Known Member

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    Your TSL may not have the bias drift issue since not all of them seem to suffer from it. I've had two for years and never had any problems with them. My local Marshall tech told me that over the last 20 years he's worked on over 100 TSL's and only two have had that issue. I would do a tube swap and a good once over and see how she sounds.
     
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  13. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    well, you did seem to know about the motherboard/drift issues. The bias board also can have issues & the way it was designed.

    You can get the ISS 20 board, but, you still might need to get a new bias board & mod the motherboard to fit it. Unfortunately, the bias board does not include the bias pots, which also go bad...

    https://www.hotroxuk.com/marshall-tsl100-main-board.html

    https://drtube.com/modifications/jcm2000-stable-bias-mod

    https://s4360.americommerce.com/store/shopcart.aspx

    before any of that though, it's best to give it a diagnostic w/ multi-meter to see if any of that is necessary...
     
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  14. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    pull the chassis out & give it a good visual inspection, to see if anything looks like it's fried, any soot, etc. Pull the tubes 1st.

    Use a sharpie to mark the power tubes 1-4/ L-R You can clean the marker off w/ alcohol later...
     
  15. TheLoudness!!

    TheLoudness!! Active Member

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    Thanks. I will have it looked at and see where it goes from there. I probably got in over my head with this one...but maybe not.
     
  16. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    get a schematic. Find one closest to the ISS # of your board.
     
  17. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    diagnose it yourself, otherwise it could cost you a lot...
     
  18. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    can I ask that you keep this conversation consolidated in 1 place... (here)

    having it fragmented, all over the place, you will have multiple conversations going on, when someone will be trying to help, they won't have all the info.

    thanks...
     
  19. ampmadscientist

    ampmadscientist Well-Known Member

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    Don't do anything to the amp until you have passed diagnostic tests.
    If the amp won't pass the tests, there is no point in spending money to repair any other issue.
    If the board is bad, it has to be corrected first or the tubes can burn up.
    If you are not capable of doing the measurements, hire a technician who is qualified.

    TSL DSL 50 100 board insulation test

    Un-plug power from the amplifier. Disconnect Mains power entirely from the amplifier.

    Set meter for ohms. Set meter for highest ohm scale:

    Your scale may vary.

    Remove all output tubes.

    Connect red meter probe to pin 4 of the output tube socket.

    Connect black meter probe to pin 5 of the output tube socket.


    This is what you should read:

    Ohm Reading will climb up, up up. Then meter will read infinity (or "OL.")

    "OL" means: Open Load. No Resistance.

    This reading is a normal reading.

    Test all output tube sockets and make sure that you get the same normal reading as above.


    Fail Reading:

    The meter reading will not climb up, up up. (as above)

    The reading will stay low, and steady. It will not climb.

    Example: reading between pin 4 and 5 of the output tube socket is 658 ohms, steady and is not climbing.

    Example: reading between pin 4 and 5 of the output socket is 250K ohms and steady.

    This indicates the board may be bad.

    All output tube sockets must be tested as above. Be sure to test all of the of the output tube sockets.

    Write down your readings for each socket as you test.

    The board must be repaired or replaced (options) before any other tests are made.

    If the test reading above is Fail: stop here.

    TSL DSL 50 100 Bias stability test

    Part I

    Take out all output tubes for this test.

    Set meter for DC volts. Connect DC volt meter black probe to metal chassis ground, use clip lead if possible etc.

    Connect red probe to pin 5 of output tube socket.

    Turn on power, but leave standby switch in warm-up position.

    Do not turn the standby to operate position.

    Note DC voltage of pin 5 for each output tube socket, test all output tube sockets.

    Write down the DC voltage reading for each socket and keep track of the readings.

    Part II

    Adjust bias controls and observe DC voltage on pin 5 of output tube socket.

    You should be able to adjust the two trim pots for -42 volts DC on all output tube sockets pin 5.

    The voltage should hold steady ---and-- adjust up and down smoothly for both bias adjust pots on all output sockets.

    Monitor the pin 5 voltage with your meter and adjust the pots up and down.

    Make sure that your DC voltage on pin 5 does not drop out as you adjust the bias pots. If the DC pin 5 DC bias voltage is missing, or if the voltage will not adjust up and down smoothly, replace the bias pots and or repair bias power supply and retest for correct operation.

    HIGH voltage stability test

    Adjust pin 5 DC voltage to -42 volts for all output tube sockets.

    Monitor pin 5 voltage with the DC volt meter.

    Turn standby to Operate position (high voltage is now turned ON !!!)


    Important: When you turned standby to “operate,” how much did the DC voltage on pin 5 change?

    Verify that DC voltage on pin 5 of all output tube sockets remains steady when standby switch is turned to “operate” position.


    Fail Indication: the voltage on pin 5 changes substantially when the standby switch is turned to operate position. This indicates that the circuit board may be defective.

    Do not install tubes or operate the amplifier if this test result is FAIL.

    Do not install tubes or play the amplifier. This could damage new tubes or cause more damage to the amplifier.

    A. Replacement Board is available.

    B. Dr. Tube stable bias modification kit : which will repair the existing board.

    Next Step: bias stability test. Do not skip this test.
     
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