Egnater Rebel 20 Mk I - Blown PT

[J M Fahey]

This is what I think you will need:

EDIT: looks like we simulposted
anyway quite close to what you see there.
Only problem is what you mention about lack of real estate space there

*Any* increase of core size will be a step in the right direction.
Thicker stacking solves magnetic problems (larger core area) but keeps window size, so does not help much on copper resistive loss ... what killed your HV winding, while next larger EI size will solve both, even if stacked same thickness.

Measure available space and check this with your winder ... or pay thru the nose for MM iron ,unless you find another transformer with similar specs.

HV and filament windings are critical, bias and LV can use wire as thin as the winder can handle without breaking, both need less than 10mA each ... and thatīs already overkill.

[nickb]

This is what I think you will need:

EDIT: looks like we simulposted
anyway quite close to what you see there.
Only problem is what you mention about lack of real estate space there

*Any* increase of core size will be a step in the right direction.
Thicker stacking solves magnetic problems (larger core area) but keeps window size, so does not help much on copper resistive loss ... what killed your HV winding, while next larger EI size will solve both, even if stacked same thickness.

Measure available space and check this with your winder ... or pay thru the nose for MM iron ,unless you find another transformer with similar specs.

HV and filament windings are critical, bias and LV can use wire as thin as the winder can handle without breaking, both need less than 10mA each ... and thatīs already overkill.

I'm coming up with about -55VDC for the bias supply so a 40V tap on the transformer will be on he safe side.

So, I've got

(I have updated this after some calculations)

50/60Hz estimate 150VA
Area 2.625in sq
VA = (area * 5.58 * 5/6)^2 ~= 150VA


PRI 230 BROWN
117 BLACK
100 BLUE
0 SILVER (OR WHITE OK)

SEC 1 RED 285 200mA*
WHITE 40V 10mA
RED/YELLOW 0 CT
RED 285 200mA*


SEC 2 3.15 GREEN 2.5A
0 CT GREEN/YELLOW
3.15 GREEN 2.5A

SEC 3 16 BLUE 0.6A
0 CT BLUE/WHITE
16 BLUE 0.6A


*SEC 1 worst case is 350mA. 200mA based on 25% duty


We'll see what Mercury say and I haven't given up on Egnater as I really would like a confirmation. I might have to use some charm on them

What I find oddest about secrecy by manufacturers in general is that if they give me the data under NDA then I get what I need and they get what they want. If I have to work it out for myself I'm free to share with the world. Seems they are not really thinking very far ahead.

On the winder, I have a pretty good relationship with someone here already - they've done a few for me before. They will happily strip down to clone when that is possible. I've found things go much better when I have a target spec too.

Thanks to all contributors. What a great bunch of guys.

[g1]

Don't know if this is of any use but someone mentioned 288VAC here: http://music-electronics-forum.com/t38856/
Seems that was loaded, though there was a filter cap issue.

[nickb]

Don't know if this is of any use but someone mentioned 288VAC here: http://music-electronics-forum.com/t38856/
Seems that was loaded, though there was a filter cap issue.

Good info - thank you.

He also saw the bias at -65VDC whereas I was estimating 55V.

[nickb]

Just to put some closure on this. After two emails and one phone call to Boutique Amps distribution I was not able to get the specs from them, as is of course their right. But, they were nice enough to give me Bruce Egnater's email , so I asked him. WHAT A NICE GUY He was so helpful. I got everything I needed plus some background stories on the project.

I could have bought a replacement through Boutique Amps, kudos to them as it's more than many will do, but with shipping and duty it was more than the owner paid for the amp. The new wind is going to be about half of that.

[jfxberns]

So if Bruce shared the information with you, why don't you share here with everyone?

I am sure there are quite a few people that would like to know what you learned about the Power Transformer specs--including me.

[nickb]

So if Bruce shared the information with you, why don't you share here with everyone?

I am sure there are quite a few people that would like to know what you learned about the Power Transformer specs--including me.

Because it was not clear to me that I was at liberty to share the info.

[J M Fahey]

Fair enough.
If Bruce or whoever runs the Company today were keen on sharing publicly, they wo do so or even print values on available schematics.
But so far it looks that Bruce was helpful, no doubt about that, but he shared that info on *one* Tech only.
In general, that is not meant to be publicly shared, unless specifically stated.

In any case the reverse engineering analysis used earlier must be close enough.
So estimating and some Math gave us possible 285V and somebody had measured 288V?
Wow!!! ... that's 1% precision!!!!

[glebert]

It seems to me the problem with replacing these Egnater PTs (I've got a Renegade 65 on my bench right now) is the 12V for filament and for reverb. Has anyone tried to use a "normal" PT to get all of the voltages other than the 12V and a separate PT just for the 12V? I am probably going with the Mercury Magnetics for mine, but it burns me to pay that much for a transformer.

[nickb]

So if Bruce shared the information with you, why don't you share here with everyone?

I am sure there are quite a few people that would like to know what you learned about the Power Transformer specs--including me.

Good news (and curse my failing memory)...

I found the original emails from Bruce. He did say it was OK to share. Here is the schematic with values, the PT spec and the correct power tube drive mixer circuit.

He also told me this about the mixer design:

"The story is funny. The original version just had a switch to select the pairs. We found out Boogie had a patent on this (surprise) and we didn't want to deal with that. I was asked to come up with something else. I was on vacation at the beach with my family at the time. I sat down and just somehow came up with this scheme and it looked like it would work....and it did. People think we sit around and just come up with cool ideas. As you know I'm sure, most out born out of necessity as opposed to random creativity. I used to read discussions about how the tube mix was done. Some of their "guesses" were creative too, though most would not work."

PT-20_.pdf
REBEL20sch 8-09 with Values.pdf
REBEL MIX MOD V2.pdf

Enjoy and thank Bruce..

[jfxberns]

Very cool of him to share the specs and the story!

Also, thanks for getting his OK and sharing, @nickb!