Polytone power transformer?

**paulkogut** · 08-30-2016, 01:55 PM

Anyone know where I can find a power transformer for a Polytone Mini Brute IV? I bought the amp from what I thought was a reputable Brooklyn used gear/repair joint. The amp blew soon after purchase, and has been back in the shop for months, as the guy has supposedly been unable to find the correct power transformer. He now tells me he's given up looking, and it's up to me to track the transformer down. Any leads would be appreciated.

Thanks,

PK

**mercosound** · 08-30-2016, 04:49 PM

Hmmm, looks as though that is a currently available model - I'd be surprised if Polytone couldn't supply a power xfmr for it. I may be wrong though, since your tech hasn't been able to locate one... I'd give it a try - call/email Polytone directly, with your amp's serial # handy just in case they need that. Good luck -

**Papawooly** · 08-30-2016, 05:12 PM

Hi Paul...

Don't know if this will help, but here (from Electronics-forum) I found a number of links to Polytone schematics.

Polytone Schematics

And here...

Polytone Schematics - Tube amp Schematics

Have Fun!

Papawooly

**icr** · 08-30-2016, 05:18 PM

I don't think any of those schematics show the specifications of the power transformer.

**neatomic** · 08-30-2016, 05:49 PM

when all else fails, try approaching it from another direction..contact the transformer manufacturer!

mercury magnetics makes transformers for just about any amp...plus they will rebuild your old one if needed...

contact-

Mercury Magnetics -- The Guitar Amp Transformer Company

luck

cheers

**BigDaddyLoveHandles** · 08-30-2016, 06:15 PM

Originally Posted by mercosound

Hmmm, looks as though that is a currently available model - I'd be surprised if Polytone couldn't supply a power xfmr for it. I may be wrong though, since your tech hasn't been able to locate one... I'd give it a try - call/email Polytone directly, with your amp's serial # handy just in case they need that. Good luck -

They are no longer in business, right?

**MaxTwang** · 08-30-2016, 06:57 PM

Originally Posted by BigDaddyLoveHandles

They are no longer in business, right?

Polytone's been gone for years. Tommy Gumina died in 2013.

**MaxTwang** · 08-30-2016, 07:12 PM

Neatomic's suggestion of contacting Mercury Magnetics is a good one. Rewind/rebuild is usually possible but not cheap.

I would also try to find an amp tech that knows Polytone amps, they would know the specs of the transformer and may know of a suitable replacement or one that could be adapted (it's possible Hammond Manufacturing makes something 'close enough').

I scanned through a few of the schematics and the secondary voltages vary a bit, what isn't specified is current.

Something new from Hammond would probably be a LOT cheaper than rewinding the old one.

**neatomic** · 08-30-2016, 07:19 PM

yes..merc mag, hammond and the other old venerable usa made transformer manufacturer heyboer....

Heyboer Transformers - Audio Transformers

the chances are good that one of these companies made the originals for polytone to begin with!!

cheers

**Naquat** · 08-30-2016, 10:25 PM

First I would try and contact the X'former manufacturer. If they don't have a replacement they can probably give you the specs so you can source something similar. It's not a tube amp so it shouldn't be too difficult.

**Herbie** · 08-31-2016, 12:51 AM

And when rewinding a new transformer becomes an option, buying a second Mini Brute just for spare parts might get even cheaper.

**Little Jay** · 08-31-2016, 01:06 AM

Maybe Franz 1997 knows?
Polytone amplifier 220v electrical conversion

**GNAPPI** · 08-31-2016, 03:04 AM

A quick check of the xformer for signs of burn would be advisable. If there is none there is a possibility that the primary or secondary windings are protected with a thermal fuse which is easily either bypassed or replaced.

To check for an open thermal fuse a simple continuity test should isolate it. If a fuse is open the reading will be infinity, if the coils are burned there will likely be SOME resistance reading.

Peavey uses protected transformers which I personally think is an idiotic design since the primary and secondary windings can be fuse protected with a replaceable fuse saving a major repair.

PS. Any decent tech should know this.

**Franz 1997** · 08-31-2016, 06:02 AM

Originally Posted by Little Jay

Maybe Franz 1997 knows?
Polytone amplifier 220v electrical conversion

The 1978 manual ( diamond-tolex era) specifies a 46v centre-tapped transformer. The current is not specified, but looking at the electrical consumption rating of the unit ( which should be on the panel somewhere, in watts ) will help a tech approximate it.

I don't know if later models are the same, but they might well be.

**Greentone** · 08-31-2016, 08:45 AM

I will look it up for you today.

**Max405** · 08-31-2016, 09:16 AM

It's incredible how much you guys know, about everything.
Im in awe just reading this.
JD

**GNAPPI** · 08-31-2016, 10:03 AM

Originally Posted by Papawooly

Hi Paul...

Don't know if this will help, but here (from Electronics-forum) I found a number of links to Polytone schematics.

Polytone Schematics

And here...

Polytone Schematics - Tube amp Schematics

Have Fun!

Papawooly

Thanks for the links, Polytone is one of the few makes that I do not have a good selection of prints for.

**Franz 1997** · 08-31-2016, 11:04 AM

Originally Posted by Joe DeNisco

It's incredible how much you guys know, about everything.
Im in awe just reading this.
JD

We probably need to get out more...

**MaxTwang** · 08-31-2016, 12:56 PM

Originally Posted by Franz 1997

The 1978 manual ( diamond-tolex era) specifies a 46v centre-tapped transformer. The current is not specified, but looking at the electrical consumption rating of the unit ( which should be on the panel somewhere, in watts ) will help a tech approximate it.

I don't know if later models are the same, but they might well be.

There should be 2 secondaries, this Reverb listing should be close (that transformer would probably read high as it was tested w/o a load). Looking at the schematics - either the transformer specs changed a bit over the years or there's variance in the measurements by the people writing the schematics.

https://reverb.com/item/1277059-poly...-36v-50v-100va

**MaxTwang** · 08-31-2016, 12:56 PM

Originally Posted by Franz 1997

We probably need to get out more...

Reading amp schematics is 'getting out'. Isn't it?

**neatomic** · 08-31-2016, 04:54 PM

Originally Posted by MaxTwang

Reading amp schematics is 'getting out'. Isn't it?

way out!

haha

cheers

**Engine Swap** · 09-01-2016, 09:35 AM

Find a new tech.

you'll need a transformer with two, center-tapped secondaries. These are rectified and regulated to provide the positive and negative DC voltages for the ICs and power transistors.

As long as the transformer can deliver enough current, there should be plenty of replacement options out there. Since both seconaries are regulated, the voltages don't have to be an exact match.

Are you 100% sure the transformer is bad? I don't have a lot of confidence in the tech. If the problem lies elsewhere, replacing the transformer would be a waste of time. Did the tech provide any details? Open windings, short?

**paulkogut** · 09-01-2016, 09:48 AM

Thanks, all. Some good leads to run down. At this point, "Polytone' appears to be just a voice on an answering machine, but I should be able to track down a reasonable replacement from some of the other sources mentioned. The transformer caught on fire pretty spectacularly, so I'm confident it's out of commission for good. I am for sure disappointed that the tech has washed his hands of locating the part for an amp he sold me a few months earlier, not the kind of thing that inspires confidence for any repeat business.....

PK

**Cunamara** · 09-01-2016, 07:27 PM

If he's going to fix it for free, that's one thing. If he's going to charge you, find a better tech. Maybe someone here could recommend someone, if it comes to that.

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