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Quad 303 power transformer lamination varnish

mygoggie

mygoggie

New Member
Hi, maybe one of you have an answer to this.

I am currently restoring a 1969 Quad 303 which was severely abused and then abandoned.

The question has now arisen whether the main transformer's laminations were varnished before assembly or was the whole unit assembled and then varnished?

The reason for this point is that I am worried that cleaning the very rusted external faces of the laminations might destroy the insulation resistance of the plates in the core.

Your kind assistance will be greatly appreciated.
 
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Pretty sure they have to be varnished or have an oxide layer (alternative to varnish) before they are assembled. Rust IS an oxide layer, so if you take it off, you'll need to re-varnish or lacquer those spots afterward. I've read that spar varnish is similar to what most companies used to use, but that is admittedly home-brew speculation.
 
mygoggie said:
Hi, maybe one of you have an answer to this.

I am currently restoring a 1969 Quad 303 which was severely abused and then abandoned.

The question has now arisen whether the main transformer's laminations were varnished before assembly or was the whole unit assembled and then varnished?

The reason for this point is that I am worried that cleaning the very rusted external faces of the laminations might destroy the insulation resistance of the plates in the core.

Your kind assistance will be greatly appreciated.
Click to expand...

Also, it may have been dunked in varnish after the transformer was assembled in addition to the varnish already on the core pieces.
 
Thanks for the reply. Yes it was dunked in varnish after assembly.

Is there anyway to test if the lamination insulation is functioning as required?
 
No, it was just badly rusted which I cleaned and one of the followers of this thread mentioned that I need to be concerned due to the fact that the resistance measured across the outer side faces of the laminations read zero, it might very well get hot when in use.

Otherwise the windings are good and the secondary voltage values are correct.
 
Wish it was a Duesenberg Berlin ! Anyway I decided to go the chemical insulation layer route and then do the varnish thing. I am confident it will turn out better than new.

Thanks for the confidence and advice offered. Much appreciated!
 
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mygoggie said:
No, it was just badly rusted which I cleaned and one of the followers of this thread mentioned that I need to be concerned due to the fact that the resistance measured across the outer side faces of the laminations read zero, it might very well get hot when in use.
Click to expand...

Outer rust doesn't really hurt a transformers inner windings, and as long as the primary and secondary windings ohm out okay, it's fine!

I have an amp with all rusty transformers and chassis and it works fine

The zero ohm reading is normal and is most likely on the primary side.

IMHO, I wouldn't worry about the transformers for now. Aside from moisture on the outside producing rust, the innards are usually fine unless the whole thing was submerged under water and if that were the case, the end bells would have to be removed so you could inspect the innards for water and find a way to dry it out totally before use. I have found receivers down dead end roads in mud puddles that worked fine when dried out thoroughly.
 
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There was a company called Deuesenberg that built guitars and amps. I'm okay with Rickenbacker geeters and bass geeters.
 
I would just power it up. If it doesn't hum excessively it should be O.K. If the laminations have separated it would tend to rattle.
 
The transformer will very likely have been 'vacuum impregnated', (not just painted or immersed), this is a very effective system to get the varnish into every nook and cranny, by removing the air. Once you have re-varnished the rusty spots I think the transformer will be fine.
 
If you want to follow my progress on this restoration you are welcome to read it here

Thanks for all the advice and motivation guys, I really appreciate it as this is the first time ever I am doing such an amplifier restoration. I am learning an awful lot!

Just for interest sake, the transformer looks pretty good after being chemically insulated, baked and two coats of varnish.

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