Rust on chassis and transformer

[Steve Blackdog]

I am restoring a ProAmp Viper 210 combo, which is around 40 years old.

There is surface rust on the chassis and tranny bodies. My plan is to give it a going over with steel wool and wax polish. That will kill the rust, but leave a heavy “patina”. I am wondering about taking the steel parts down to the metal and removing the rust completely.

I guess it’s all a matter of taste. So what would you do?

[Helmholtz]

I'd give wipe the transformers a thorough wipe with Ballistol (gun oil) on a cloth and leave them alone otherwise.

The chassis should be clean where it makes contact, but be careful to not remove intact plating. You might try car polish.

Forget wax polish inside an amp.

[Chuck H]

Trying to clean rust off transformers with any abrasion will only do further damage to laminate isolation. I've never used gun oil, but since it's a Helhmoltz suggestion I'm sure it's fine. I assume this is a polymerized oil and not a lubricant? Or, if you want to hide the rust you can just use some rust inhibitive spray paint. And like Helholtz said, the chassis should be cleaned to bright wherever there's a contact for ground or it needs to be soldered.

[Mick Bailey]

I don't like steel wool anywhere near transformers or anything else electronic. With transformers I use a Scotchbrite pad to remove any scaling and dirt, then Kurust rust converter over the rusty areas (it dries dark purple). Then I use Upol Acid #8 primer then whatever top coat is needed. Generally these days I use a moisture catalyzing urethane paint that I get mixed up in a rattle can from my local automotive paint supplier, which dries very hard and is tough. I also sometimes use Rustoleum Hard Hat spray enamel.

For galvanized chassis I remove the rust completely and use ZG-90 cold galvanising spray. it dries fast, adheres very well and prevents further rusting. Can be overpainted if the chassis is black

[Steve Blackdog]

That’s interesting. I have not come across Zg-90. The pro-amp chassis is galvanised steel, so that might be the way forward.

[Chuck H]

I don't like steel wool anywhere near transformers or anything else electronic. With transformers I use a Scotchbrite pad to remove any scaling and dirt, then Kurust rust converter over the rusty areas (it dries dark purple). Then I use Upol Acid #8 primer then whatever top coat is needed. Generally these days I use a moisture catalyzing urethane paint that I get mixed up in a rattle can from my local automotive paint supplier, which dries very hard and is tough. I also sometimes use Rustoleum Hard Hat spray enamel.

For galvanized chassis I remove the rust completely and use ZG-90 cold galvanising spray. it dries fast, adheres very well and prevents further rusting. Can be overpainted if the chassis is black

I've used Scotchbright pads for surface rust on transformers. I didn't notice any problems, but I'm not rigged up to test for for losses due to laminate continuity either. Something I read somewhere basically said that any abrasion whatever can only serve to further break down the already compromised insulation between transformer laminates, expose more metal to oxidize and potentially create more conduction between laminates from the abrasion. And that the best course of action is to just seal up the oxidized area to mitigate further oxidation. It made sense to me. Rust doesn't beget rust. In fact it's an oxide layer that acts somewhat to protect against further oxidation. I've also read that "Rust Reformer" type products can be used prior to painting/sealing to at least get rid of the red oxide appearance. Those products turn the rust black-ish. Probably not dissimilar from the Kurust converter you mentioned. Anyway...

I've also read that surface rust on transformers isn't generally a problem because there's typically only a shallow level of saturation in the laminates.?. This goes beyond my station but it was a discussion here and some higher minds were in on it. So if that's the case then I suppose some rust removal prior to paint or sealer wouldn't be a problem either.

[J M Fahey]

NO mojo whatsoever, 40 years is not old enough to qualify and it was NOT used by Eric, Jimi, Jimmy, etc. so why bother?

I hate rust, it´s self catalyzing and eventually eats everything iron, just give it time.

Gun oil is that, lubricating oil, good only in guns which get cleaned and lubricated at least once a year or better, not a long range solution.

I would follow Mick Bailey´s suggestions to a T.

The proper path is to remove rust but without further compromising metal below, either raw metal or galvanizing or paint, and *neutralize* any remaining one with some kind of rust converter which makes it chemically stable.

FWIW that amp did NOT sell on UK EBay for 170 GBP and to boot just speakers alone make up most of its value, so raher than a revered Icon I would turn it into an everyday workhorse and use it.

[Steve Blackdog]

NO mojo whatsoever, 40 years is not old enough to qualify and it was NOT used by Eric, Jimi, Jimmy, etc. so why bother?

I hate rust, it´s self catalyzing and eventually eats everything iron, just give it time.

Gun oil is that, lubricating oil, good only in guns which get cleaned and lubricated at least once a year or better, not a long range solution.

I would follow Mick Bailey´s suggestions to a T.

The proper path is to remove rust but without further compromising metal below, either raw metal or galvanizing or paint, and *neutralize* any remaining one with some kind of rust converter which makes it chemically stable.

FWIW that amp did NOT sell on UK EBay for 170 GBP and to boot just speakers alone make up most of its value, so raher than a revered Icon I would turn it into an everyday workhorse and use it.

I beg to differ on the subject of Mojo (whatever that is). It is a classic British small manufacturer amplifier. It is very well put together with excellent wiring and components- from the days when you could still make stuff without having to “off-shore” it to the PRC.

I have swapped in new tubes and everything appears to be okay, subject to cleaning pots and replacing the odd capacitor, etc. Once I have eliminated all the crackles and quirks it will be a decent little amp.

Re EBay and things not selling for £170 - not entirely sure what this is about, but I am not particularly interested in the value. For me the satisfaction is about finding a piece of equipment that is one step from the dumpster and turning it back into something decent that will continue to give years of service.

I am a hobbiest - when I die my relatives will inherit a shed load of guitars I have built, home made effects pedals, a bunch of DIY valve amps, and beautiful hand-crafted speaker cabs - none of them will make them rich!


All the best..

steve

[g1]

Re EBay and things not selling for £170 - not entirely sure what this is about, but I am not particularly interested in the value.

I think he was referring to the first link that comes up when you google search the model. 0 bids at £170.
https://picclick.co.uk/Proamp-Viper-...841852079.html

[Mick Bailey]

Peavey welded up some PT laminations right along the two bottom corners to fix the stack to a baseplate. What would the comparison be if the stack was cleaned off completely to remove rust? See #20 - #23. https://music-electronics-forum.com/...r/35154-/page2

[Chuck H]

Peavey welded up some PT laminations right along the two bottom corners to fix the stack to a baseplate. What would the comparison be if the stack was cleaned off completely to remove rust? See #20 - #23. https://music-electronics-forum.com/...r/35154-/page2

We no longer seem to have the option to view in a format that shows who responded directly to which post. I'll assume this is in response to my post #6 above?

I did put the disclaimer in my last paragraph. That was actually referring to a thread other than your link too. So it seems the subject has come up more than once. And that it's no great shakes if the outside edge of a transformer is marginalized for laminate insulation. Along the same lines as your welded transformer I've noticed that some manufacturers don't trouble to insulate their bell cover screws. The long ones that go all the way through the laminates and basically hold the transformer together mechanically. There's every likelihood that the screw, on insertion or with time and vibration could damage lam insulation and become part of a conductive path between laminates. So whatever I said above about conduction between laminates would, I suppose, only be idealizing. And without noticeable benefit for that matter.

[Steve Blackdog]

Along the same lines as your welded transformer I've noticed that some manufacturers don't trouble to insulate their bell cover screws. The long ones that go all the way through the laminates and basically hold the transformer together mechanically. There's every likelihood that the screw, on insertion or with time and vibration could damage lam insulation and become part of a conductive path between laminates. So whatever I said above about conduction between laminates would, I suppose, only be idealizing. And without noticeable benefit for that matter.

Don’t manufacturers insulate the inside of the long screw hole? Presumably it would be designed to withstand a little wear and tear from the screw?

I am working on the assumption that for rust to form the varnish insulation on the edges of the laminations that are accessible from the outside are already compromised.

FWIW, the transformers are working well. I have now tested them for continuity. The OT has no continuity between laminations, but the PT appears to have continuity all over them.

[Helmholtz]

Single point contacts between laminations don't allow for significant Eddy currents.

[Steve Blackdog]

Single point contacts between laminations don't allow for significant Eddy currents.

So that’s why they still work, is it? By the way what’s the problem with wax?

[Chuck H]

So that’s why they still work, is it? By the way what’s the problem with wax?

Wax presents the risk of melting (or if it's a polymerized floor wax type product, blistering) if the transformer gets stressed for any reason and becomes quite hot. It happens. Not to mention that most wax products will become at least soft at typical transformer temps. So you'd be smelling the wax slowly atomizing any time the amp was hot.