Marshall TSL 100 Tubes glowing bright orange and loosing volume

Discussion in 'The Workbench' started by mesaray, Dec 9, 2009.

  1. Landshark

    Landshark Well-Known Member

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    I had the same thing happen to me, Here's what you need to do. Take it to a tech because it more likely has more going on with it then just the tubes going bad. This is exactly what mine did back in may. You may have some parts on the tube board that have burnt up and need replaced but if there is a problem with your output transformer like a short in the output transformer, then no matter how many times the components are replaced they'll keep on blowing.

    This is what happened to my TSL. Basically the exact same scenario, I tried fixing it myself, same components that I replaced kept on blowing. Took it to a tech named Deric, he fixed the same components, same components blew. He tried to blame it on my cab saying it was wired wrong, I took his word for it, got curious, went to celestion's website, and found out that it wasn't a miswired cab like he said it was. He sent the head off to have the transformer looked at and that was the culprit all along.

    That's not saying that this is exactly what the problem is with your amp but I remember posting a very similar thread about mine back in may. Our descriptions match up almost perfectly. There's so much going on indise this head though that saying to replace one power tube and try that first, is probably not going to work.

    Here's something to try though... The bias probes that come out of the back of the head behind your back grill... lay the metal grill across the 3 probes and see if the head comes to life. If so don't continue playing this way (it's bad on the other components) take it to the tech and tell him what happened. Kindly suggest the transformer get thoroughly tested.:D
     
  2. MartyStrat54

    MartyStrat54 Well-Known Member

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    Jon gave a very good explanation. There are some older style tubes that exhibit more of this type of glow. 300B's give off a good glow. I think a lot had to do with how good of a vacuum was pulled on the tube. Some of the better power tubes had dual getters. Of course the getter is the halo device in a tube that is activated on the tube line after the vacuum is pulled. It results in the chrome looking area usually on the top of the tube. The getters main ingredient is barium. Once activated, the getters keep any unwanted gasses under control in the tube.

    Before this technology was improved, a lot of the vintage tubes were gassy by today's standards and therefore put off quite a glow. Needless to say, the tubes of that era didn't last as long as say a Mullard xf2 EL34.

    I have an obscure amp that uses four, 8417's and they have a very noticeable bluish glow.

    I think it dependes on when the tube was made and the type of tube. You can't pull a perfect vacuum, so you are going to have a little unwanted gasses in there and this is what adds to the effect.
     
  3. Landshark

    Landshark Well-Known Member

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    I get this after Mexican food:fingersx::naughty::fingersx::naughty:
     
  4. Iron Mang

    Iron Mang New Member

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    LOL I get the same thing after Filipino Food. :lol::lol:
     
  5. RA2

    RA2 New Member

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    I've got that bias drifting problem what should I do?
    please help quick

    -RA2
     
  6. Wilder Amplification

    Wilder Amplification New Member

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    More details needed. What makes you think you have bias drift? Are your plates glowing red?
     
  7. jcmjmp

    jcmjmp Well-Known Member

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    As Wilder alluded to, you have to confirm that you are in fact seeing bias drift. Some amount of drift is normal as the tubes heat up and many people get confused with this.

    If your tubes are red plating, that's a bad sign and the #1 cause for that (as far as I know) is over biasing. Assuming they are NOT red plating, get a bias reading at startup and after 15 minutes and again after 30minutes. If the tubes red plated, your tubes are probably toast by now and I wouldn't run the amp too long with those tubes in there.

    Getting the tube board number and issue number would be helpful so we can determine which components to check.
    The board number is something like JCM2-60-02 (where the last two digits could be different) and the board issue number is the first visible number after the word "Issue".
     
  8. MartyStrat54

    MartyStrat54 Well-Known Member

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    That's because it is a dog or a cat.

    Hey I wanted to ask you about your avatar. Is that a real tube device, or just something made up? I ask, because it has three identical tubes. Now I have worked on vintage tube organ amps that would have (2) EL84's for the bass and then a Left and Right Single-Ended amps for a total of four EL84's. The amp would have three OPT's. I've also seen big organ amps with 6L6's or 7027's for the bass and then 6V6's or EL84's for the midrange and highs.

    So what "is" that three-headed monster?
     
  9. musicman

    musicman Active Member

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    If the bias is drifting upwards and you can't pull it back down then take it to a tech & have a new main board fitted.
    My tech tried everything but a new board sorted it out.
    Not too expensive either (in the UK).
     
  10. RA2

    RA2 New Member

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    thanks Wilder & JCMJMP for getting back to me so quick
    and sorry I didn't clarify I bias one side it stays & I try to bias the other side but the meter volts keep going up and way up. no extra tube glow just no strength from the tubes it all sounds distorted :( what tips do you have

    btw I bias my amp @ 90mv please get back to me

    -RA2
     
  11. Wilder Amplification

    Wilder Amplification New Member

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    Move V4/5 into the V6/7 position and vice versa, and see if the problem switches sides. If it does, you've got bad valves. Even if they're brand new they can still be bad.

    If the problem does not switch sides, then there's an internal issue and time to take it to a tech.
     
  12. MartyStrat54

    MartyStrat54 Well-Known Member

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    OH DEAR WHAT CAN I DO, MY TUBES ARE ALL TRASH AND THEY ARE BRAND NEW. TELL ME, OH WHAT CAN I DO?

    Current production tubes give me a headache. Will they last a day? A month?
    Six months? That sucks. That's why there is only a couple of power tubes I'll recommend based on info I obtained from The Tube Store and The Tube Depot.

    On the other hand, if it's just a bad tube, that beats it being something serious.

    Sad that you have to get another set when just one goes bad.
     
  13. Kunnz

    Kunnz Active Member

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    .
     
    Last edited: Oct 1, 2019
  14. Iron Mang

    Iron Mang New Member

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    I think its the dog Adobo that gets me! lol

    Um that was just kind of a Novelty discussion piece, not functional. I don't have much experience with Organ setups, but did work on a Wurlitzer organ that had a very similar setup with all the freq ranges having their won tube section. Nice stuff.
     
  15. RA2

    RA2 New Member

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    nope it didn't switch sides :(
    any ideas maybe something i can clean or replace on the inside?
    any tips will be very helpful

    -RA2
     
  16. Wilder Amplification

    Wilder Amplification New Member

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    Bias it colder until it stops redplating. Or drop the value of the phase inverter plate resistor on the V4/V5 side to lower the gain on that side of the PI.
     
  17. jcmjmp

    jcmjmp Well-Known Member

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    Dip them is snake oil. That ALWAYS works for me.
     
  18. robertlatham1

    robertlatham1 New Member

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    hit up the guy working on it and ask him about the tsl's problem with bias drifting. it was a big problem with these amps... i had to get a lot of components replaced in mine to control it. personally i think it sounds better too, it's now way more consistent with the tone. but check into that, its a bummer having to pay 100+ for replacing tubes every time it starts messing up.

    this only happened to the early model runs. the latter boards where replaced with proper boards and components. it sounds like your board is on the edge of the date of the fix.

    a blue glow in a tube is gasses. it's ok if it's between the glass and the metal plate structures. but if you are getting a deep purpleish blue glow inside the plate structure this is not good and the tube should be replaced.

    bias for these amps should be done with the shunt method. the voltage drift on the bias pins is too unstable to acurately set the bias. the dual pot bias is a good thing, but can be tricky. one trim pot controls the top half of the push pull power section and the other trim pot controls the bottom side of the push pull power section. each side of the push pull section should not be biased over 70ma.(not 70mv we are using the shunt methode of biasing here) if you bias over 70ma you must be willing to replace tubes at least twice a year and dont expect the other components in your amp not to show signs of heat distress. these amps are not designed to run at %80 to %90 of max power dissapation of 4-EL34's, which can easily pump 120w rms!
     
  19. Wilder Amplification

    Wilder Amplification New Member

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    Actually I think you got that backwards. All valves will have that blueish glow inside of the cage assembly and some will have a slight amount of it between the bottle and the cage assembly. It's when the brightness of the glow between the cage assembly and the bottle is more prominent than usual that the valve is considered "gassy".
     
  20. robertlatham1

    robertlatham1 New Member

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    i stand corrected.
    in fact
    the coils inside the cage of my Tung Sol EL34's are glowing very deep blue.
    really very pretty!

    i have a svetlana 6L6STR that's a little gassy and has that blue flouresent glow. which is pretty as well.

    i have read that the getters are the defense for gasses and sometimes don't
    "get'er done!" HA! HA! HA! Ok OK I'll stop now. lol
     

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