Treating rust on transformers?

[Humbucker]

I just bought a 1983 Marshall JCM 800 2204 50W head, when I looked under the hood, I noticed that there's a fair amount of surface rust on one side.

I know that you shouldn't sand of scrape off this rust, apparently it's a good idea to spray this with some Tremclad rust paint. I don't have a spray can of Tremclad but I do have a can of the stuff. Can I slop this Tremclad paint onto the rusty transformer with a brush or will that potentially cause some problems? Is a spray can the way to go with this kind of a fix?

[Mark Black]

Check out this take on rust from one of the more respected transformer builders - kind of surprised me but makes sense...

http://www.mercurymagnetics.com/page...ansformer_Rust

[Tom Phillips]

PT Claims

Interesting. That does kind of make sense. However just blow that Mercury Magnetics has the following posted
"The PT has a profound affect on your amp's sonic characteristics especially its ability to handle musical dynamics. What this means to you is crisper note attack, better note separation, and added sparkle in the upper mids and treble frequencies. And keep in mind that with a properly-designed power transformer you'll hear all-around higher definition with the amp's clean and dirty tones."
This is starting to sound like hype to me and it reminds me of the stuff posted by audiophile sites trying to sell you $300 line cords. I'm not saying that the PT saying isn't important but an improvement in ALL of the characteristics mentioned would have to mean that you were starting with a REALLY bad PT. Also, there are lots of other things in an amp that can affect note attack, note separation, sparkle in the upper mids and treble frequencies plus clean and dirty tones. I can just hear someone asking "will a PT upgrade add more sparkle and better definition to my amp?"
End of comment,
Tom

[bob p]

As a coincidence, it turns out that I recently had a similiar discussion about rusty transformers over lunch with a friend who is a retired design engineer from Motorola's tube R&D department. We talked about surface rust, and he made it very clear that surface rust was not at all bad on a transformer, and that you shouldn't let surface rust bother you. He emphatically stressed that you should not try to remove surface rust, for the same reasons mentioned in the FAQ on the MM site.

He also agreed with Tom's assessment that there's an awful lot of hogwash being espoused by the boutique transformer companies who are trying to sell you custom built replacement trannies at ridiculously high prices. I'm not about to say that a transformer is a transformer and they're all the same, but in reality most power transformers are less different than most people would believe. There is an awful lot of bogus HiFi-type hype that surrounds the marketing for replacement iron for guitar applications. I think that this is primarily because the markups are substantial and because most people have been conditioned to pay for tone, don't know enough to dismiss the hype, and can easily buy into the guru mojo BS.

Keeping some of this in perspective, I'm a dealer for MM and in the past I've bought LOTS of their iron. (Some people may remember the group orders that I would put together on the old Ampage site.) I am troubled by the fact that in the past 3 years, their prices have skyrocketed. My 25-unit cost for anything from a Tweed Champ to a Plexi OT is a LOT higher than it used to be. The typical transformer that I'd buy from MM now costs 146% of what it cost me 3 years ago. IMHO that kind of price increase represents a marketing department that is exploiting the sudden rise in their reputation in order to "brick" the customer. There's just no excuse for it. There's some definite gouging that goes on in the name of voodoo, mojo and tone.

You might ask why I'm so upset. Well, I just thought about buidling a Marshall 18-watter, which is a simple, modest amplifier design. I looked at the prices for MM repro iron and I was shocked. The retail prices for the PT and OT are $230 EACH! Even at 25-unit quantities, the prices for the 18-watt PT and OT are still $130 each. That is just obscene. Rather than being bent over, I'll shop somewhere else.

[Humbucker]

Wow!

That's really interesting stuff indeed! Thanks for sharing that info, that's news to me.
8^)

[Alex/Tubewonder]

Transformer price increases over past 3 years are caused by close to 70% global rise in raw materials prices i.e. core laminations and copper. That said I do not see why an excellent quality OT should cost 230$ in retail. That's being taken for a ride. IMO a 50W OT on EI102 core should not cost today more than 100-120$ in small quantities from manufacturer direct. BTW "hand wound" means "wound on winding machine operated by a human".

[bob p]

Transformer price increases over past 3 years are caused by close to 70% global rise in raw materials prices i.e. core laminations and copper. That said I do not see why an excellent quality OT should cost 230$ in retail. That's being taken for a ride. IMO a 50W OT on EI102 core should not cost today more than 100-120$ in small quantities from manufacturer direct. BTW "hand wound" means "wound on winding machine operated by a human".

The commodity prices argument doesn't adequately explain Mercury's price gouging behavior. Commodity prices have risen and fallen during that time period while MM's prices have risen, but not fallen. Hammond relies on the same global commodity prices to produce their transformers. In that same time period Hammond's prices have not risen 150%.

Let's do some math: Assuming that the 70% figure is correct, MM implemented a permanent 150% price increase to cover an increase in materials cost that peaked at 70% and then retraced back to lower levels. That difference amounts to a gratuitous gouge of the customer. Even if MM may have increased their prices to reflect an increasing market trend, they haven't bothered to decrease their prices to reflect the decreasing market trend. Just in case anyone hasn't noticed, the global commodities markets for iron and copper aren't what they used to be. All of the global commodities prices have collapsed as the result of a) speculators leaving the market, and b) collapsing demand in China. The commodity-based cost excuse just doesn't hold water.

For comparison, look at the price of Hammond transformers. Have they risen by the same proportions in the same period? No, they haven't.

It used to be that when I bought MM iron at 25-unit prices I could buy iron much more cheaply than I could buy it from any of the Hammond distributors. It was cost-effective and a good business decision to buy wholesale from Mercury. Now its cheaper for anyone to buy Hammonds in single unit quantities from a place like AES or Angela than it is for a Mercury dealer to buy MM in the wholesale market at the highest discount level.

That kind of difference is not attributable to input costs. It based solely upon a premium product marketing strategy. I'll let you in on a secret: Mercury's stuff is good, but its not THAT good. The Emperor is naked.

[Alex/Tubewonder]

Thanks for elaborating and providing update on commodity prices. It gives me some ammo to renegotiate prices with my supplier I have no personal experience of MM transformers as I deemed their prices excessively hyped.

Anyway, this has gotten way OT. Don't bother with rust on transformers.