Amp chassis & transformer bell rust

Discussion in 'Tube Audio' started by ggizzy, Nov 13, 2017.

  1. ggizzy

    ggizzy Well-Known Member

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    I have been slowly taking apart and diagramming an older EL34 UL PP amp from the late 50s/early 60s. I have it almost down to the chassis, with just the sockets and transformers remaining to be pulled.

    The amp has been sitting unused for around seven years and was filthy with dirt and dust when I picked it up. There is a bit of rust in spots on the outside of the chassis and I am wondering how to go about filling them without repainting the whole chassis. I would hate to lose the lettering and other identifiers of the amp.

    The good news is that underneath the chassis looks fine.

    The transformers are coming all the way out anyways. But after soak testing the transformers though, I will know more definatively. Everything on both transformers below the chassis looks great too. The rust on the transformers is only on the silver bell topside. The laminations are protected by some sort of cardboard and plastic material. The amp was top of the line back in the day and the components inside are all top notch and this thing is built like a tank!

    I read over several threads about restoring/deep cleaning and so I'm thinking -

    -Cleaning with the water/ammonia solution. (I've only cleaned with isopropyl 91%)
    -wire brushing the transformer bells, being very careful to tape and seal off the rest so no slivers get in the housing. (Laminations are covered very well)
    -using the black shoe stuff. Or I could try the above but then spraying them with primer and repainting with a similar gloss silver. I'd like to keep the original paint color on top, but that is purely cosmetic and if the shoe black works and will protect it better, I have no qualms.

    The chassis rust concerns me more- I am open to any and all suggestions, no matter how lengthy they may be. I could follow the above on those spots as well? Maybe with a wax coat on top to prefent further rust?

    I have a pair of these amps and will be thoroughly enjoy restoring both to proper condition. Thanks for any help.
     

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    Last edited: Nov 13, 2017
  2. knockbill

    knockbill Addicted Member

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    I would disassemble the chassis and media blast the rust off, if you are removing the txs anyway... May as well start with a clean slate...Gray hammertone would look good on them and you can replace the lettering/numbers with rub-ons, decals, rubber stamp or something similar, if you like... I think the rust on the chassis will still show thru regular paint, and hammertone looks cool!! The tx bells may sand out smooth enough for regular paint...
    Good luck with the project...
     
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  3. macyjrm

    macyjrm AK Subscriber Subscriber

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    What Knockbill said.
     
  4. primosounds

    primosounds AK Subscriber Subscriber

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    You can remove the transformer end bells and sand and paint them. It would be easier doing it that way. be sure to replace the long screws to keep the lams together, do not overtighten the nuts or drop the trans.
    I would not clean any part with water except as a dampened rag. A little rust on the trans lams is not really a big deal except visually. So just removing the surface rust with a brass bristle brush and repainting is ok.
    If you are going to keep this unit and want to repaint the chassis to make it last you will need to completely remove all the components and work with the bare chassis. I have done this before and not have access to a bead blaster i used sand paper and elbow grease. The results as with all painting jobs, depends on how good your preparation of the surface to be painted is. the more glossy the paint, the more perfect the surface has to be. Otherwise you will see all the imperfections, like the sand paper scratches and any deformations in the metal. I also mostly use hammertone paint because it forms a thick layer which covers defects well. The picture in my avatar is all repainted with hammertone chassis and trannys. It is not bad (from about 2 feet away) and some people like the "industrial" look. And it is a thousand times better than rusty metal cancers on a chassis.
     
    Last edited: Nov 13, 2017
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  5. arts

    arts Super Member

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    You could always go with the ''distressed'' or ''rat-rod'' look.Just clean it up as best you can then shoot it with clear:)
     
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  6. restorer-john

    restorer-john Super Member

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    'rat rod' look maybe for the garage, but in the house? :)
     
  7. jharris

    jharris New Member

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    You might want to Google instructions for cleaning old cast-iron pans. People go to great lengths to get rust off them.

    Among things you likely have (or can get easily), vinegar will dissolve rust better than isopropyl alcohol. I wouldn't bother until you're ready to repaint, since you can put a lot of effort into rust removal and the bare metal you expose will just rust again.
     
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  8. restorer-john

    restorer-john Super Member

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    What's wrong with just bead blasting the entire chassis and bells and painting? It's not cast iron.
     
    Last edited: Nov 14, 2017
  9. jharris

    jharris New Member

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    If OP has the equipment and space for bead blasting, or can use/borrow it, that would work great.
     
  10. ggizzy

    ggizzy Well-Known Member

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    I appreciate all the replies and information presented.

    Unfortunately, repainting the entire chassis is probably not an option even if I redo the decals. I believe it would destroy the monetary value of the amp(s). And while I do intend to use both monitors as my main stereo system, I do not want to negate my investment by repainting the entire chassis. I got a helluva deal on them thanks to a forum member here, and I want them to retain as much possible value for a potential rainy day fund.

    I do not have a bead blaster or access to one so that is out of the question as well. I am familiar with metal corrosion, prevention, and treatment from my time working around aircraft. I just bought a new house and will be moving shortly. The new house definately has the space for blasting and I may end up as a last resort doing just that. (The amps are housed below the speakers in the back of a four foot tall cab and aren't visible during use)

    I will have to do some further research and forum crawling. If I can clean and spot paint the rust, color matching or not, I would still prefer to do that.
     
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  11. N8Nagel

    N8Nagel AK Subscriber Subscriber

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    I would take the bells off, electrolytically derust, and respray and reinstall.
     
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  12. BuzzK

    BuzzK AK Member Subscriber

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    People have given you a lot of good advice. If it were me, I'd at least remove the trannies; have the bells bead-blasted or buy replacements; and repaint them with a semi-gloss. I'd also paint the outside of the lams with a flat black, and re-assemble with stainless steel hardware. You can make them look brand new.

    I question your belief that the chassis -- in its present and [as you choose] irremediable state -- is worth preserving as-is. The sockets look rough and probably need replacing too.

    What I would do -- and I'm sure you wouldn't -- is cosmetically fix the trannies and install them on a new chassis, and essentially "start from scratch" with new components. I'd keep the old chassis with all of the old, original parts, in case you want to sell it later, you can give a buyer the best of both worlds.
     
  13. knockbill

    knockbill Addicted Member

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    Saving the old chassis as is and rebuilding the amp on a new one is another way to go,,, Closer look shows the sockets bolted on,,, was this a kit? possibly homemade?
    Regardless, the original chassis is pretty well rusted, maybe a new owner would want it as, can't imagine that scenario in its present and declining condition tho!
     
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  14. ggizzy

    ggizzy Well-Known Member

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    Thanks for your opinion, BuzzK, but starting over on a new chassis would be a fool's errand. I would bust rust, repaint and topcoat the entire chassis before I did that.

    I appreciate all the advice given, that is why I asked the question on a forum. I am not arguing against the advice and I may end up going that route in the end. The purpose of the inquiry was to establish if there were "homebrew" remedies that would fix the problem without resorting to stripping the entire chassis. The idea is not to make them look new but to prevent further corrosion. They will be operated in a professional studio environment devoid of humidity, smoke, excessive heat, etc.

    The sockets are bolted to the chassis, entirely the same way the Leak and other UK hi-fi amps of the era were. I don't think manufacturers during the era wasted isolation sockets on non-line amps. Obviously the sockets will be replaced if they are corroded and V1 isolated on rubber grommets or with an isolation socket.

    The amps were not a kit. They were manufactured for EMI by an associated company called STD. This company did all of Orthotone amps which were sold to the NY area market in the US through Scope Electronics. They were marketed overseas as well. They were considered professional studio monitors. I don't have a schematic so I am having to diagram the entire amp.
     
    Last edited: Nov 14, 2017
  15. primosounds

    primosounds AK Subscriber Subscriber

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    While you believe that a complete rebuild with a new paint job might decrease the collectible value of the amp. The value of the amp is also related to the cosmetic appearance. It is not like antique furniture where refinishing the piece will ruin its value. En contrare, if you can replicate the paint color and have the rest of it clean and functioning properly that will make it attractive to most.
    While you believe that a complete rebuild with a new paint job might decrease the collectible value of the amp. The value of the amp is also related to the cosmetic appearance. It is not like antique furniture where refinishing the piece will ruin its value. En contrare, if you can replicate the paint color and have the rest of it clean and functioning properly that will make it attractive to most. The value of the piece is mostly in the transformers and to a certain extent if the circuit is original. But most collectors will not pay much for a rusted chassis and it will certainly detract from the price.
    You can use a "rust conversion" solution which will turn the rust into a stable form but you still would need to disassemble the chassis as that stuff should not get into any circuitry. And the other areas of the chassis will still rust away. You either need to deal with the rust or live with it.
     
  16. cademan

    cademan Addicted Member

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    Leave it as is. That way if anyone might break in and decide to steal anything, they will look at that old rusted tube thingy and pass on it. :D
     
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  17. maxhifi

    maxhifi Super Member

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    You could always just stabilize it, rub a little 3 in one oil into the rust, so it doesn't keep rusting, and fix it electrically. What kind of amp is it anyway?
     
  18. Leland47

    Leland47 AK Subscriber Subscriber

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    It is possible to spot repair rust....and thereby perhaps save the lettering.

    This would require a Foredom flex shaft or similar tool and tiny brass/steel rotary wire brushes...or tiny grinding tools.

    Then spot fill with bondo.

    Then a tiny airbrush rig like artists use to spot spray and feather into the original paint....

    Have to get paint matched...

    Then fix lettering with rub on.....and clear coat.

    Think auto body work on a miniature scale.
     
    Last edited: Nov 14, 2017
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  19. BuzzK

    BuzzK AK Member Subscriber

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    I am certainly a fool, and to prove it here is an Eico HF87/89 rebuild, on a chromed chassis. I supplied most of the parts for a friend to assemble it; this is his work thus far.

    Granted, the Eico 87/89 is a low-end product compared to many other vintage amps, but it can be made to be incredibly musical with Dave Gillespie's FB loop mods -- as good as any I have heard.

    Would you pay more for a ratty looking Eico or for something that might be more pleasing to the wife in her living room? :)

    I've included a pic of another mostly-stock amp that I rebuilt. It was in decent cosmetic shape, so I kept the (original) chassis. DSCF1812.JPG

    unnamed-1.jpg unnamed-2.jpg unnamed-3.jpg
     
    Last edited: Nov 14, 2017
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  20. BuzzK

    BuzzK AK Member Subscriber

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    PS: I think Leland's suggestion is the best so far . . .
     

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