Amplifier Transformer Core Surface Rust

[tbonesullivan]

Like all gear junkies, I'm a member of various amp groups on Facebook and elsewhere, and yesterday someone posted an amp for sale, and someone was a little down on it due to some surface rust on the output transformer core. It was a Mesa MkIIC+ with an Export Transformer, so people were worried about that, considering it's a major selling point of the amplifier.  I've never really considered thinking about it before, as most amps I have seen that are 20+ years old have some level of rust on the core, which forms when the original paint or lacquer degrades, if they had that at all. A lot of smaller transformers also have a covered core, so you can't really see it anyway.

So, I looked around, and found a Mercury Magnetics blurb about it, saying it was essentially no big deal: https://www.mercurymagnetics.com/transformer-rust-friend-or-foe/

But, this was after reading another guy say: "well it's not horrible, but it means that eventually your transformer will rust through and die".

Then I went through a bunch of Hi-Fi forums where people had various opinions, some who had tried to remedy the rust due to appearance, and others who said "just put some rustoleum over the rust and call it done.", while others were all about the WD-40.  Anyone have any thoughts on this?

[DaveH]

I'd leave it as-is, not a big deal. I definitely would not spray it with WD40 tho... If it really bothered you, you could get a can of rust reformer at Home Depot and hit it with that.

https://www.homedepot.com/p/Rust-Oleum-Stops-Rust-10-25-oz-Rust-Reformer-Spray-Paint-215215/100392541

 

[Bloozguy]

Just leave it alone. Don't spray anything on it because the performance of the transformer depends upon the core laminations being separate from one another. Paint, rust remover or WD-40 will get between the laminations and potentially degrade the performance of the transformer.

[tbonesullivan]

Well, aren't most transformers vacuum dipped in lacquer to begin with? Mercury Magnetics even offers to redip transformers for free if you send them in.

[crunchee]

I agree with leaving the rust alone, and definitely NOT using WD-40 on it.  One thing rust will indicate, is what kind of climate or surroundings the amp's been in since it was made, so I'd approach any future/potential maintenance with that in mind if it was me.

[tbonesullivan]

Yeah, a definitely no on the WD-40. Only one of my amps really has the issue, and it's minor, nothing close to what the Mesa had. Looks like some of the varnish/lacquer chipped of somehow in places, so it's got a little on the OT, and some on the PT as well. It's a 90s carvin X-100B, so it's not like I couldn't easily replace the whole thing if it went up in smoke. I haven't noticed any rust progression in the 10 years I've owned it, and now it's in a moisture controlled environment.

I do know that over time, with the heating/cooling cycles, the lacquer will degrade somewhat and flake. You can see that on the transformers from my Rivera. It's not rust, just the orange/yellow electronic lacquer kinda flaking:

[texwest]

Hey I think that might be my amp your talking about! 

[texwest]

On 2/19/2019 at 10:17 AM, tbonesullivan said:

Like all gear junkies, I'm a member of various amp groups on Facebook and elsewhere, and yesterday someone posted an amp for sale, and someone was a little down on it due to some surface rust on the output transformer core. It was a Mesa MkIIC+ with an Export Transformer, so people were worried about that, considering it's a major selling point of the amplifier.  I've never really considered thinking about it before, as most amps I have seen that are 20+ years old have some level of rust on the core, which forms when the original paint or lacquer degrades, if they had that at all. A lot of smaller transformers also have a covered core, so you can't really see it anyway.

So, I looked around, and found a Mercury Magnetics blurb about it, saying it was essentially no big deal: https://www.mercurymagnetics.com/transformer-rust-friend-or-foe/

But, this was after reading another guy say: "well it's not horrible, but it means that eventually your transformer will rust through and die".

Then I went through a bunch of Hi-Fi forums where people had various opinions, some who had tried to remedy the rust due to appearance, and others who said "just put some rustoleum over the rust and call it done.", while others were all about the WD-40.  Anyone have any thoughts on this?

Hey I think that might be my amp your talking about!  Yeah those boogie guys don't know much about amps and get all picky about stuff that is irrelevant.  There are so many old Fenders and Marshalls out there with much much worse rust and they work great.  I need to take better pics of the amp.  The flash really brought out the rust. Its really light surface rust and I didn't even think about it until they mentioned it.  I've definitely seen a lot worse on some old vintage amps.  This one is about 35 years old now.

This is a killer amp!!  The other day one of my guitar students and I opened it up and really played it. Great clean tones.  As good as a twin IMO. I actually sold my vintage twin when I acquired a couple of these.   You can dial in anything with this amp from jazz clean to edge of distortion to super high gain lead tones. The simulclass really does make it have more character for rock rhythm guitar.  He really wanted it and it made me waiver about selling it.  He's a rich Chinese international student so he might spring for it.  I have two C+'s and I'm keeping the one with the nice hardwood cabinet.   I don't need a backup anymore.

I lowered the price to $3200 plus shipping for it.

[texwest]

Here's a new reverb listing with better pics   

Vintage Mesa Boogie Mark IIC+ DRX head - Simulclass, Reverb, very rare X101 Export Transformer $3300 https://reverb.com/item/19775087-vintage-mesa-boogie-mark-iic-drx-head-simulclass-reverb-very-rare-x101-export-transformer?publish_confirmation=true

[Thundersteel]

I had trouble selling a like-new Mesa, because of the same "problem." Even after some up-close pics and an explanation, a lot of potential buyers still balked.

[tbonesullivan]

Yeah, they really don't know much. The people on the Facebook groups are kinda jerks, IMHO.  The original price was good, and not out of line, but everyone there wants a deal.

Right now though the market does seem pretty soft for some reason. It is tax season, and a lot of people are finding out that the refund they were expecting is not the same as the refund they are getting.

I would just keep listing it until it finds the right buyer. The amp looks great, and the guts look great. Surface rust on the transformer core is minimal. You would always have MM relacquer it, but that would require pulling it from the amp, which can be a pain.

[tbonesullivan]

14 hours ago, gtrdaddy said:

Rust on iron is very normal. Iron is a component of rust. Iron is the compound in steel that causes steel to rust. Oxygen alone,  causes iron to rust. Rust by definition, is iron oxide, which is the compound of oxygen and iron combined. Rust on an iron core transformer is not indicative of an amp's past surroundings or climate. Just oxygen being in contact with iron can cause this, and oxygen with any amount of humidity will expedite this process. Even relatively low humidity of 35-40%. Ever pull a cast iron frying pan out of the kitchen cabinets after not using it for a long time? Rust. It was dry though? Oxygen.

So, the amplifier is FINE! Go get it 😉

 

Looking at most of the transformers in my amps, and from reading, I think most are oxide coated during the creation process, which helps insulate the laminates. Then they lacquer them, with that lovely orange electrical insulating lacquer. This also means that half the time you take a picture of a transformer core, it looks kinda rusty anyway due to the orange lacquer.

I unfortunately have to put all my amp and other GAS on hold because car needs new brakes.

[texwest]

On 2/24/2019 at 8:35 PM, tbonesullivan said:

Yeah, they really don't know much. The people on the Facebook groups are kinda jerks, IMHO.  The original price was good, and not out of line, but everyone there wants a deal.

Right now though the market does seem pretty soft for some reason. It is tax season, and a lot of people are finding out that the refund they were expecting is not the same as the refund they are getting.

I would just keep listing it until it finds the right buyer. The amp looks great, and the guts look great. Surface rust on the transformer core is minimal. You would always have MM relacquer it, but that would require pulling it from the amp, which can be a pain.

You're right the market is soft right now.  These sold for bigger prices last year.  I lowered the price again, but if I can't sell it for a decent price I might wait.

[tbonesullivan]

23 hours ago, texwest said:

You're right the market is soft right now.  These sold for bigger prices last year.  I lowered the price again, but if I can't sell it for a decent price I might wait.

Definitely wait. Maybe in 6 months the prices will go back up.  Right now I'm spending money on getting better tubes overall. I've got some nice old production tubes, but I don't have any mullards or Amperex.