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Marshall Circa 2000 JCM 800 Reissue 100 watt head was under water

Discussion in 'The Workbench' started by mars5887, Sep 2, 2021.

  1. Derrick111

    Derrick111 Well-Known Member

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    I seriously caution against the use of WD-40 on electronics... That stuff is conductive and hasn't got the proper lubrications for pots and contacts. You will end up replacing all the pots down the road because the tracks will wear out without the proper lube additives and you can get screwy resistance changes from the conductivity. I did wipe down part of a corroding chassis with it once though, but you have to be careful not to get it near/on any tube sockets or you get arching and may need to replace the socket(s) if they develop carbon arc traces. Not to mention what an arc can do t the amp...
     
  2. Gunner64

    Gunner64 Emotional Support Animal Gold Supporting Member

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    I thought my Dyna was toast too, I was actually surprised it really didn't suffer any effects of the flooding at all. I didn't even corrode. other than letting it sit all I did was wipe it down and deoxit the pots and switches. I still works perfect.

    Lets face it... Glenn and K.K's Marshalls have been soaked in a lot worse. :agreed:
     
  3. Pete Farrington

    Pete Farrington Well-Known Member

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    Dunno about that.

    The same applies to any cleaner lube, ie that leaves a potentially sticky residue which may cause a build up of fluff etc.

    When I was starting out back in the 80s, WD40 was what got used. I’ve still got a couple of amps from back then, pots and sockets are fine, despite WD40 having 30+ years to wreak its supposed havoc in there.

    Maybe vintage WD40 was better? :rolleyes:
     
    Last edited: Sep 8, 2021
  4. C-Grin

    C-Grin Well-Known Member

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    Mmm vintage WD-40 tone is way better for sure, I prefer the stuff from around 83'.:D
     
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  5. neikeel

    neikeel Well-Known Member

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    What does WD stand for?!!

    What else did I say to do to the pots before you use it?! deoxit G100. :D

    c’mon sir, read all the post ;) I did say only in the pots. I didn’t say any where else - because that gets sun air!
     
  6. Derrick111

    Derrick111 Well-Known Member

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    Neil, I added that other bit about the chassis & tube sockets because harry-home-owner will read above and think, 'Gee, I should use that on my vintage amp'.

    It's conductive. Maybe some have gotten away with it, but I had a client that was getting all kinds of wired issues after using it. The resistances were all over the place on his pots, and several went severely scratchy. Use it if you like though...
     
  7. Pete Farrington

    Pete Farrington Well-Known Member

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    No, it isn’t, it gets sprayed on car ignition systems to get rid of moisture, there’s 10s of kV there.
    Something else must have been going on regarding that amp’s pots, perhaps they were already knackered and shedding track material.
     
  8. thetragichero

    thetragichero Well-Known Member

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    91% isopropyl is the way to go (hell if 197 proof grain alcohol is available in your neck of the woods that could work too... i remember a forum post where someone says use of denatured alcohol or drinking alcohol depends if you're a luthier or a musician). alcohol is extremely hydrophilic (that's why you can't get 100% alcohol: it'll pull moisture from the air) so the higher the percentage alcohol the better. as a plus should clean up any remaining flux residue left on the board. i would not use alcohol on the chassis itself as it is very likely to eat away at the silk screen
     
  9. TassieViking

    TassieViking New Member

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    If you are comfortable in pulling the transformers out, stick them in an oven at a low temperature for a long time, transformers usually get baked after they are dipped in varnish when they are made and then baked for several hours.
    (Maybe I'm showing my age if this is not done anymore ?)
    I would bake them at less then 100 degrees celsius. Maybe 80 degrees ? (176 Fahrenheit).
    You could probably do the same to the rest of the components as well.
    Spray the pots, jacks and tube sockets with a good electrical cleaner (Deoxit).

    https://groupdiy.com/threads/transformer-varnishing-methods.70265/

    If you decide to scrap it, I'll do it for you. Happy to pay for the postage to my place. =)
     
  10. matttornado

    matttornado Well-Known Member

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    I bet the circuit board itself is fine. It's the mechanical stuff like switches, pots and jacks thta could be damaged.

    That would be fun project!
     
  11. ibmorjamn

    ibmorjamn Well-Known Member

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    I would have suggested wd 40 , it is good for dispersing water. However Neikeel is one of many people here that now these amps . It could be harsh on the non metal parts.
     
  12. neikeel

    neikeel Well-Known Member

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    I’ve used it many times on cars, motorbikes, lawnmowers and boat engines. Only place you put WD here is in closed space of the pots and switches because if you dry it out properly you will risk oxidation you cannot see to clean off. The G100 is fantastic (thanks to Ampmadscientist to converting me from D5) at reconditioning these things. Of course the best pots are the AB/RS type as they disassemble well and respond well to clean and lube (the CTS less so IMO).
     
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  13. tschrama

    tschrama Well-Known Member

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    Btw what happend to Ampmadscientist?
     
  14. PowerTube44

    PowerTube44 Well-Known Member

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    Sorry, but I'm afraid it's a goner. I'll PM you my address and even pay shipping for him to send that hunk of junk to me.

    You're welcome!
     
  15. Chris-in-LA

    Chris-in-LA Well-Known Member

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    He went to another site. I think he didn’t like arguing with us.
     
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  16. Pete Farrington

    Pete Farrington Well-Known Member

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    The individual behind the ampmadscientist, soundguruman, crumb etc identities loves arguing, often propounding the cause of hot bias, reverting to a bozo characterisation / trollish tactics to counter opposing views.
    It’s a shame, because as noted above, he seems to know his way around the workbench.
    His MO seems to be having periods of intense activity stirring things up on a particular forum, then dropping off radar for a while and turning up on a different forum, perhaps under a different / new identity. I suspect even 2 identities simultaneously on the same forum thread!
    There’s nowt stranger than folk.
     
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  17. MP+

    MP+ Member

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    Water and tube amps definitely don't mix, but in saying that, it might not be terminal. I've seen drops of condensation all over the internals when moving an amp from ice cold conditions to a warm room and switching on, they can handle a fair bit. No guarantees or certainties on this, but try removing the chassis from the sleeve and throw it in the fridge for about 1 week. This will dehumidify and displace moisture, there's no way any spray could displace the amount of moisture your dealing with. Be sure to pull all the tubes from their sockets. Whatever you do, don't switch it on while there is even a hint of moisture on the tube connectors, that's what will blow it, the rest of it might just bounce back. You're looking at 50% / 50%. Good luck.
     
  18. MP+

    MP+ Member

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    Just a footnote to the above - If you do get lucky, the last step before switching on should be to find a really clean area and give it a light going over with a leaf blower, nothing crazy, just work from a distance, the idea being that you want to displace any grit that might have solidified on the circuit board, the other option would be to give it a going over with a dry super clean paint brush, possibly a light vacuum of the tube connectors for the same reason then plug the tubes in and out about two or three times before switching on. One final but important step, clean the spring contacts on the output jacks where they make or break for different output impedances. Any corrosion on those contacts could change the output impedance that the amp sees. As for the rest of the jacks, including the output jacks, grab a spare 1/4" plug, spray it with a good non corrosive lubricant like Electrolube then plug it in and out a few times - all jacks, same as you might do for a crackling guitar jack. The idea being to get any surface corrosion off the face of the contacts.
     
  19. MP+

    MP+ Member

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    Last thing, in case overlooked, pull all the fuses and leave the fuse holders open until dry, wouldn't hurt to replace them all at power up. Maybe even an idea to leave the output tubes out on the first repower. Work all the switches and pushbuttons also when the time comes in case of contact surface corrosion.
     

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