Marantz 8B New Transformer Install - Potting Material?

[Kingsin7]

Hey AK

I just got a new transformer for a Marantz 8b in the mail from J&K Audio out of Singapore.

It looks like they did a great job, and they even labeled and matched all the colored wires as they relate to the 8B.

My question is, what material should I use to pot the transformer in its housing?

The original potting was done with tar. I had to place the old transformer housing in a pot of water and boil it to remove it from that tar, which was messy and aggravating... Would RTV work? Silicone?
Thanks,
Steve

 

[Lavane]

Not sure that would properly transfer heat?

 

[Kingsin7]

Not sure that would properly transfer heat?

Oh, I did not consider heat - I was more worried about vibration/noise...

 

[Brice]

Tar is the best, as removable even if it is messy.
Polyurethane, epoxy are great, but final so you can't remove it easily.

 

[Retrovert]

Not sure that would properly transfer heat?

Tar has higher thermal conductivity than air by a factor of ten. Still very poor, of course, but air is terrible.

 

[Retrovert]

Oh, I did not consider heat - I was more worried about vibration/noise...

Vacuum-applied polyurethane varnish will fill in the space and prevent vibration of the turns.

 

[Retrovert]

Tar is the best, as removable even if it is messy. Polyurethane, epoxy are great, but final so you can't remove it easily.

The windings should not be cast in a block, but instead impregnated with varnish to reduce or eliminate noise.

 

[Kingsin7]

The windings should not be cast in a block, but instead impregnated with varnish to reduce or eliminate noise.

Retrovert,
Here is a picture of the New transformer and housing FWIW. Is there a type of shop where I could have it vacuum filled with varnish? Is this something that can be handled with a run to the Home Depot?

 

[Brice]

Before you put it back in its can, I would test it on the amp itself.
You don't know if the voltages are on specs.
I had that happening to me with Heyboer, and these guys were nice enough to replace it.

 

[Retrovert]

Here is a picture of the New transformer and housing FWIW. Is there a type of shop where I could have it vacuum filled with varnish? Is this something that can be handled with a run to the Home Depot?

You'd need a vacuum pump.

Any local business which handles motor rebuilding should be able to impregnate a transformer for you.

I did a quick search for Sacramento and found this one:

http://www.rosenaumotors.com/​

Like I said, just found it with a search. So no guarantees.

It's been my experience that commercial establishments will do one-off jobs if you offer to pay in cash. Nobody needs the hassle of collecting Net 30 for a tiny job.

 

[Kingsin7]

Before you put it back in its can, I would test it on the amp itself.
You don't know if the voltages are on specs.
I had that happening to me with Heyboer, and these guys were nice enough to replace it.

Well, that would be a lot of work soldering and desoldering... The transformer was delivered from halfway around the world in less than ten days from when I placed the order, and they were very attentive and reasonable. I am sure I could send it back if there was an issue.

 

[Kingsin7]

You'd need a vacuum pump.

Any local business which handles motor rebuilding should be able to impregnate a transformer for you.

I did a quick search for Sacramento and found this one:

http://www.rosenaumotors.com/​

Like I said, just found it with a search. So no guarantees.

It's been my experience that commercial establishments will do one-off jobs if you offer to pay in cash. Nobody needs the hassle of collecting Net 30 for a tiny job.

Awesome
Thank you - they are only about 10 minutes from me. I'll see what they say.

 

[Kingsin7]

Awesome
Thank you - they are only about 10 minutes from me. I'll see what they say.

They said they'll have a look at it on Monday.
Thanks!

 

[Retrovert]

You're welcome.

Ten minutes away is hard to beat.

Do report back on how it works out.

 

[Altecboy]

You might ping Jim McShane over at mcshanedesign.net
He works with Harmon Kardon potted transformers and may have some guidance for you

 

[Retrovert]

They said they'll have a look at it on Monday.

So how did the visit turn out?

Did you have the transformer impregnated?

 

[Kingsin7]

So how did the visit turn out?

Did you have the transformer impregnated?

No, sorry - I've been slammed with work all week. I should have a chance next week.
I'll report back with pics just as soon as I can.

 

[Retrovert]

Was curious about what happened...

 

[Kingsin7]

I dropped it off at the motor rewinding place before the weekend. They had thoughts about how to go about it and they decided to impregnate the transformer and then bake it - The owner was worried about the actual temp thresholds for the wiring, so he assured me he would do some experimenting first.

Cost should be around $100, which is plenty fair considering their liability.

The owner was impressed with the quality and cost of the replacement transformer, so he took down J&K Audio's contact info to possibly outsource future customer requests.

I'll report back with a pic once I get it back.

Was curious about what happened...

 

[Retrovert]

Thanks for the update.

Cost might drop after the mechanics of impregnation for the first one has been worked out.