Jcm 2000 Tsl 122 Bias Help

Discussion in 'The Workbench' started by Sapphire Sounds, Apr 13, 2019.

  1. Sapphire Sounds

    Sapphire Sounds Member

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    Hey later tonight I want to get into my 1999 TSL and check the bias for any adjustments then replace all the tubes.. I have a multimeter and a set of matched power tubes for the amp. I will check youtube out later and browse this forum.



    However the preamp tubes I got with them seem smaller than what I remember being inside the amp, are they okay to use?

    20190413_130946.jpg
     
    Last edited: Apr 14, 2019
  2. Gunner64

    Gunner64 Well-Known Member Premium Member

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    Ecc83/12ax7 are whats pictured and whats in your amp.
     
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  3. ampmadscientist

    ampmadscientist Well-Known Member

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    From where I sit, those tubes look huge.
     
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  4. Sapphire Sounds

    Sapphire Sounds Member

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    Okay I just searched ecc83s and read up, apparently they are nearly the same product.. I dont know my shit yet with amplification. Heres a pic of my Marshall, I'm a stranger to electric land

    20190413_152901.jpg

    Dont they? I thought maybe the preamp tubes were maybe extra small instead but the power tubes are in full chungus sized boxes...
     
  5. Jon C

    Jon C Well-Known Member

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    Love It !!
     
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  6. Sapphire Sounds

    Sapphire Sounds Member

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    I caught a break and popped the amp up on a table took the back off and popped out the dead power tube and one of the pre amp tubes to see the size comparison

    20190413_164401.jpg

    Haha this amp runs on 4 big chungus tubes and 4 little Debbie's

    20190413_164035(1).jpg

    How do I get the metal cylinder off the pre amp tube on the far side?
     
  7. Sapphire Sounds

    Sapphire Sounds Member

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    Update got the sheild off the preamp tube, just turned it pushing up a bit and it sprung out. So is that last socket called the V1 or first gain stage?

    20190413_165745.jpg
     
  8. Jon C

    Jon C Well-Known Member

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    Susceptible to RFI .. shield helps and the spring help reduce microphonic chance …… YMMV
     
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  9. ampmadscientist

    ampmadscientist Well-Known Member

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    It may help to turn the amp upside down, so you can see the pin locations on the sockets.

    The shield is a bayonet attachment.
    Push down lightly and turn counterclockwise to remove the shield.
    Push down lightly and turn clockwise to install the shield.

    The socket which is closest to the input jack is V1, which "is" the first gain stage.
     
    Last edited: Apr 13, 2019
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  10. Sapphire Sounds

    Sapphire Sounds Member

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    Hey yall now I can get to it, should I pop all the tubes in and power it onto standby- warm up?

    20190413_205937.jpg

    Heres the old tubes couldnt believe I smashed the last one I took out on the speaker magnet, oh well. The power section was Svetlana EL34 9916 with one labeled 9920. The preamp section is unbranded tubes, 2 of them went microphonic.

    20190413_210049.jpg

    Ill keep the amp somewhere I can get to those metal pins with my multimeter while I shave a pencil into a flathead for the bias adjustments... I have never done this stuff before
     
  11. Sapphire Sounds

    Sapphire Sounds Member

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    I got the amp used for short money and for a few weeks it would blow the HT fuse consistently but I would just power down and replace the 1 amp fuse to play it while it was still hot. The issue actually went away completely after like 5 fuses for months and it only blew the HT fuse once again, since then its been stable which surprised me. The preamp tube went microphonic so I swapped it and the dead powertube with some from my Blackstar but I put those back a week or two ago so I could retube and bias the Marshall. If my TSL 122 ends up showing that it has a shitty PCB I dont know how I would go about modding it if that hasnt already been done. The issue 20 PCB boards for TSL amps are uncommon to find for sale now.

    Screenshot_2019-04-13-21-18-05.png

    Im not planning on looking at the boards in mine yet as I will give it a chance to prove its stability with a proper set of new tubes and bias adjustment.

    Do I pop the new tubes in and let the amp warm up on standby? I guess I can only use my multimeter to check the bias pins when tubes are warm?
     
  12. Sapphire Sounds

    Sapphire Sounds Member

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    V1 (Blank)

    20190413_222302~2.jpg

    V2 18H0

    20190413_222257~2.jpg

    V3 & V4 are both 14D0

    20190413_222239_HDR.jpg

    I dont know if the lettering means anything but thats what I went with for the preamp section..
     
    Last edited: Apr 15, 2019
  13. Sapphire Sounds

    Sapphire Sounds Member

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    20190413_223959.jpg 20190413_224019.jpg


    So I put those 10G8 ones in the second and fourth power tube sockets

    20190413_224102.jpg 20190413_224133_HDR.jpg

    The 10H8 V tube is in the first, and 18H0 the third socket.

    Going to power on and keep the amp in standby warm up for a bit and look for the values I need to set on the two halves...

    Am I doing okay?
     
  14. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    yep, try 78mv each side. Each side will push/pull on the other side, so, when you go up on 1 side, it'll pull the other side down. So, you'll have to teeter-totter them back & forth.
     
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  15. Sapphire Sounds

    Sapphire Sounds Member

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    Okay cool im going to warm up and make another wooden tool for the plastic part there thanks

    20190413_230004.jpg

    20190413_230500.jpg
     
  16. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I bought me a set of these, because they hook/clip onto the bias wires.

    [​IMG]

    makes it easier. Just clip the black on the center, then move the red one from side to side to test...
     
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  17. Sapphire Sounds

    Sapphire Sounds Member

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    Yeah I like that more than these alligator clips for sure.. I'll look for a set and a multimeter that can actually read mV... Is there a setting I could use on this one I have already?

    20190413_232602.jpg
     
  18. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    try 200mA (DC) on yours...
     
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  19. ampmadscientist

    ampmadscientist Well-Known Member

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    "I got the amp used for short money and for a few weeks it would blow the HT fuse consistently but I would just power down and replace the 1 amp fuse to play it while it was still hot. The issue actually went away completely after like 5 fuses for months and it only blew the HT fuse once again, since then its been stable which surprised me."

    Sounds like this amp may have serious problems and you shouldn't put tubes into it until you test and solve the issues.

    "Im not planning on looking at the boards in mine yet as I will give it a chance to prove its stability with a proper set of new tubes and bias adjustment."

    You measure and prove the stability without any tubes installed, or else the new tubes may just burn up...you are doing this the wrong way.

    "...The 10H8 V tube is in the first, and 18H0 the third socket...."

    Don't ever put mismatched tubes into this amp.
    All the tubes should be EL34, and all the tubes should be a matched set.
    Get 4 tubes that match, test the amp bias stability FIRST, repair any issues, install the tubes LAST.

    Stop what you are doing. Get with the program.
    Measure and repair the board FIRST.
    If there is a problem with the board, or the bias stability you need to address that FIRST.
    DO NOT do this with the tubes installed.

    PS: bias pots are going bad in these amps quite often. It is advisable to install fresh bias pots. Then you can test if the pots are working properly, WITHOUT the tubes in the sockets.
     
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  20. ampmadscientist

    ampmadscientist Well-Known Member

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    Follow the tests, write down all the readings. Report all the readings to the forum.
    Don't skip the tests, do them all.

    1. Install fresh batteries into meter.
    Set meter on 200 ohms.
    Touch the red and black probes together.
    What is the reading?
    Prove that the meter is working. Report the readings to the forum.

    2. Take the tubes out of the amp.
    Turn the power on, and set the standby for "warm-up." Do not turn the standby to "operate."
    Set meter to 500 DC volts.
    Black probe: connect to metal chassis.
    Red probe: connect to pin 5 of output socket.

    Measure pin 5 of all output sockets. Write down the readings as: "pin 5 warm-up."
    What are the DC readings of all pin 5, output tube sockets?

    3. Turn standby to "operate."
    Measure pin 5 of all output sockets. Write down the readings as: "pin 5 operate."
    What are the DC readings of all pin 5, output tube sockets?

    Report your DC readings.
    You should have: 8 DC readings to report. 2X DC pin 5 readings for each socket.
     
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