When would you call an eyelet board 'cunductive'?

Discussion in 'Amp Tech Center' started by trouserpress, May 7, 2021.

  1. trouserpress

    trouserpress Tele-Holic

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    For example I can measure 100 to 600 mV all across the waxed upper eyelet board of my SF-Deluxe Reverb. The lower board shows near to none.
    Lack of experience lets me wonder if that's the source of hiss and oscillation in this amp. How much volts have you got on the surface of your boards? Please share your observations. I'm about to get me a new board from the Tube Amp Doctor and a whole lot of work (I could really do without).

    Edit: Sorry I meant conductive
     
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I am not sure how many volts are OK-ish. Has the amp lived in a wet environment? Do you notice left over resin around the eyelets? Perhaps heating the board will get rid of moisture and redistribute the wax. Maybe clean around the eyelets and add a little wax before heating.
     
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  3. SomeGuyNamedRob

    SomeGuyNamedRob Tele-Meister

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    I would never call it "cunductive" because the correct spelling is "relicked"
     
  4. trouserpress

    trouserpress Tele-Holic

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    The previous owner said he had the amp stored in his cellar for 35 years. That might very well have been a wet environment. But I can‘t see any corrosion on this amp anywhere and shouldn‘t have the normal operational temperature gotten rid of moisture during the 4 years that the amp is at my (dry) place?
    On most parts of the surface the wax seems to have turned into a kind of thin and dusty, oily smear - like somebody had sprayed WD over it trying to get rid of the wax.
    I‘ll start cleaning it with brushes, alcohol and a cloth and check how that affects the conductivity.
     
  5. trouserpress

    trouserpress Tele-Holic

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  6. RLee77

    RLee77 Friend of Leo's

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    How difficult would it be to remove the wax completely? My guess would be that the wax has absorbed particles & moisture over the years and turned into a slightly conductive goop.
     
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  7. trouserpress

    trouserpress Tele-Holic

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    That's exactly what I am thinking.
    Well I just took a shot at removing it and ... resigned. You'd have to scratch it off and even then you'd never know if that conductive debris hasn't found its way into the board itself.
    I'll transfer the components to a replacement board.
     
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  8. Dacious

    Dacious Poster Extraordinaire

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    I think the designated cure for this is a hairdryer or judicious application of a heat gun.
     
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  9. trouserpress

    trouserpress Tele-Holic

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    Thanks Dacious. I've read about putting boards in the oven. That I won't do but my hairdryer and I will have a go. Although for no concrete reasons I don't expect it to work. Maybe it's because I tried sooo much over the years. If only that darned amp didn't sound so good...
     
  10. Dacious

    Dacious Poster Extraordinaire

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    Amps from colder regions stored in unheated spaces I have read are prone to this.

    You can't remove the waxiness, it's all through the thickness of the board.
     
  11. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    There's another word for impregnated that begins with f. I only ever use solid boards for amp builds now.
     
  12. trouserpress

    trouserpress Tele-Holic

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    and ends with riggin - right?

    OK, hairdryer and Q-tips made a difference!
    Overall noise/hiss seems a little better and far more important: the evil oscillation is no more!! mVolts between board and chassis are more than 10 times less (down to 2-70 mV). Great proposal from @Dacious - thanks - that saved me a lot of soldering.
    I'm going to repeat that at least one more time. Hairdryers provide plenty of heat. I reckon a heat gun would be overkill.
     
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  13. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The board was impregnated by those who worked for CBS. It was f 'd on a later date. With a hairdryer and a good waxing it can continue the process of being relicked.
     
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  14. Dacious

    Dacious Poster Extraordinaire

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    If you are going to have a hot dry day sometime soon, it's worth unshipping the chassis and prop it so the sun's rays hit the board for a few hours. Nothing is as good as the sun and it's UV rays for removing residual dampness. Then make sure the amp is never left in the damp again.
     
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  15. theprofessor

    theprofessor Poster Extraordinaire

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    Can you say a bit more about what you did? Did you simply open up the chassis and run a hairdryer over everything? Or did you take some components off the board, or...?
     
  16. trouserpress

    trouserpress Tele-Holic

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    With the hairdryer in one hand I went slowly from east to west and back while I was brushing the surface with Q-tips - taking up as much of the liquid wax as possible.
    I have to say that while the amp settles into working temperature some of the current still comes back - especially around the eyelets to which B+ is soldered to (up to 90mV). But it is like 10 times less than before and the oscillation has not come back yet.

    I tried 10 good tubes in V2. All of these seem super microphonic but not at all in V1. Igot a brand new socket in V2!
    The leads to the knobs of the reverb channel are super microphonic too. I can hear every little tap as clear as a bell through the loudspeaker. Ground soldering is solid. Got to get this sorted out....
     
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  17. trouserpress

    trouserpress Tele-Holic

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    No I didn't. I shoved the Q-tips under the components wher this was possible. As Dacious pointed out there's most likely no way curing such a board to a 100%. Since the hiss level (my main problem now with the oscillation gone) was fairly unimpressed by my latest efforts I'm about to leave the board be as it is now.
     
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  18. theprofessor

    theprofessor Poster Extraordinaire

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    Is this the amp you drove to Rheinland-Pfalz for? I'm very glad to hear that you like the way it sounds (other than the hiss and oscillation)
     
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  19. trouserpress

    trouserpress Tele-Holic

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    That would be tomorrow then - I'm going to position it on my balcony.
     
  20. trouserpress

    trouserpress Tele-Holic

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    No, no, the Rheinland Pfalz amp is a Super Reverb that I have not picked up yet. My car is still in the garage where the mechanics are having problems to find the cause of the fault (yet another current leakage that drains the battery). I made a downpayment to the seller to ensure he doesn't sell it in the meantime.
    The amp in question is a SFDR I bought 4 years ago. It was very clean and unmolested but hissing when I got it. With every measure I took it lost some of its originality as well as some of that hiss.
     
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