For those in the know - is surface rust on a transformer perfectly normal, cause for concern, or a sign of hidden mojo? I've seen it on lots of vintage tube amps, and my B-100R has a little, but as I'm shopping around looking at tube SVT's (CL / AV / 2-Pro) I've noticed a couple had some pretty evident surface rusting on the transformers. Oddly, the ones that have the rust seem to be the ones I like the sound of. Not sure if thats just coincidence, or a sign that it was a good amp to start with and has seen a lot of active duty "on the road" and spent time in a high moisture environment like a band trailer, garage, or basement.
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Ampeg - surface rust on transformer
- Thread starter stiles72
- Start date
Interesting question? It is normal and doesn't really cause any concern, but adding MOJO that's interesting? Possible maybe. 
Depends on the amount of rust. In most cases that I've seen (which isn't many, mind you), it's pretty much a non-issue.
Is that the power transformer? Doubtful it's adding mojo.
It just converts AC voltage to the supply voltage.
Haven't seen what their output transformer looks like, if its got the same metal plates in it.
Randy
It just converts AC voltage to the supply voltage.
Haven't seen what their output transformer looks like, if its got the same metal plates in it.
Randy
Some say a little rust is a good thing in that it decreases eddy currents and allows the transformer to run cooler ([Invalid or Expired Link Removed]).
When I want it removed, I carefully brush away any loose rust and dab on either a flat black rust paint or varnish to seal it.
When I want it removed, I carefully brush away any loose rust and dab on either a flat black rust paint or varnish to seal it.
Interesting reading! The only reason I even noticed the "good" amps had rusty transformers, was because they sounded good enough to warrant "checking under the hood" and seeing what they had in them for tubes (all were the stock Sovteks). So the case is there that they could bennefit from the rust, and have somewhat better performance...
Hi.
While I place more trust on MM techs than, say, Aspen Pittman for example, variations like that usually fall well within the manufacturing parameters.
What is true, is that different materials rust differently.
If increasing insulation would help tone considerably, a thicker enamel or shellac or even rusted laminations would be used to produce "heavenly transformers". One might use paper insulating layers also.
I have yet to see any of those methods used. Not publically anyway
.
From the transformers I've dismantled, even the most rusted ones, the surface rust only goes about 1-3mm between the laminates. Even on ones that have been scrapped because of being submerged for a good while. Since the iron path is about as unaffected as can be, it would take a lot of convincing for me to actually believe that the rust makes the tone better. Or worse for that matter.
I'd rather thake Your idea of the amp being a good one in the first place and therefore having been more exposed to the elements.
Regards
Sam
While I place more trust on MM techs than, say, Aspen Pittman for example, variations like that usually fall well within the manufacturing parameters.
What is true, is that different materials rust differently.
If increasing insulation would help tone considerably, a thicker enamel or shellac or even rusted laminations would be used to produce "heavenly transformers". One might use paper insulating layers also.
I have yet to see any of those methods used. Not publically anyway
.From the transformers I've dismantled, even the most rusted ones, the surface rust only goes about 1-3mm between the laminates. Even on ones that have been scrapped because of being submerged for a good while. Since the iron path is about as unaffected as can be, it would take a lot of convincing for me to actually believe that the rust makes the tone better. Or worse for that matter.
I'd rather thake Your idea of the amp being a good one in the first place and therefore having been more exposed to the elements.
Regards
Sam
The laminations may short circuit electrically. Transformer efficiency suffers when that happens. Rust isn't a good thing.
all of my svt's had some rust on the trannys . lets see , ive had 2 old 70s , two mti era , and one cl . all of which had certain amounts of rust . i always just sprayed on some wd40 and wiped off the excess with a rag . never had any issues .
The manufacturer used cheap assed paint on the transformers when the amps were built. Obviously, going in and out of the house, sitting in the garage practice space, in the trunk and getting caught in the rain a few times over the years has pushed the limits of that cheap assed paint.
The function of those transformers is INSIDE the paint on the outside is just taco treatment....
Does rust on my transformers bother me? Heck YES, I'm very anal about how stuff looks. Does it effect the sound? No. Me I'd be pulling transformers out of my SVT and bead blasting them and repainting; including the numbers going back on. BUt then I'm totally certifiable. BOB
The function of those transformers is INSIDE the paint on the outside is just taco treatment....
Does rust on my transformers bother me? Heck YES, I'm very anal about how stuff looks. Does it effect the sound? No. Me I'd be pulling transformers out of my SVT and bead blasting them and repainting; including the numbers going back on. BUt then I'm totally certifiable. BOB
If increasing insulation would help tone considerably, a thicker enamel or shellac or even rusted laminations would be used to produce "heavenly transformers". One might use paper insulating layers also.
I have yet to see any of those methods used. Not publically anyway
The laminations are a grayish black due to "mill scale" which is a form of rust, and somewhat non-conductive..... there may be an added coating, or not. Each lamination is insulated from the next, and it does affect the sound/performance.
if they were shorted together, the unit could just as well be made of one piece. But it would get hot as the dickens due to 'eddy currents" in teh iron, which is what laminations stop.
