Rewinding UTC interstage transformer from BA6A

[ciaudio]

Please post updates on rewinding of interstage trannie for Ba6a. I own Ba6a myself although I've not had any trouble myself with tannies in Ba6a I have had to have output trans in one of my Ba861a's rebuilt. Heard a crackling spitting sound that I finally pin down to output trans. Cost me $400.00 to get rebuilt!
Although I love Ba6a it seems everbody that has used both seem to like the Ba861a best. Seems to be faster(after factory mod installed) and puts things right up front in mix. Ba6a has lower distortion wider bandwith less transformers so go figure why. Must say that limiters are good for different things.
Both units have been rebuilt by me with n.o.s. vitamin-q oil caps, photoflash p.s. caps, teflon wiring, creamic sockets and new AB resistors.
I can say that Ba86 has triode output stage and Ba6a is pentode.
Thanks for this post...........On RCA limiters.

 

[Winston OBoogie]

...

 

[Bauman]

Man, this thing looks soooo great! Thanks for the pics!!!!

 

[mitsos]

Resurrection... Did anything ever come of this? 

CJ did you ever do this rewind and if so, is the info still around?

thanks

 

[CJ]

this xfmr is not in my scrapbook, so i guess it never was taken apart unless it was done under a different part number,

let me ask around for some winding data,

 

[mitsos]

awesome... got lots of questions about old RCA stuff. Heard this was the hardest one to do right in the BA6A.

thanks!

 

[vari-mu]

CJ's old information,
interstage transformer PEERLESS 4651 .
May be  give it some thought before :

 

[mitsos]

cool, thanks, didn't have that one.. Is that the input from the 436?

 

[vari-mu]

Is that the input from the 436?

Yes , only used Backwards . We need ask CJ !

 

[mitsos]

yeah, hopefully he'll check back here soon. That's awfully thin wire to hand tension!

 

[CJ]

here is a remake on that 4651 cut sheet, still working on winding details for the BA6a

 

[noulou]

I've got a bad ba6a interstage here as well. Would be really interested in a rewind as well.
The sowter alternative does not sound as nice.  :-\

 

[mitsos]

Noulou (niko?). rikse mia matia sta pm sou. Nice space you guys have.  What's wrong with your trafo?  Is it possible to take some measurements of the original and Sowter iron?  At least it would give us some idea of where to start.  DCR and L if you have an inductance meter, would be great...

FWIW, materials have changed a lot over the years, sometimes to re-create a transformer (soundwise) you might have to make it differently than it was originally done.

thanks!

 

[vari-mu]

  Have done two experimental interstage transformers 
    for  2 Plates to 2 Grids,
2 : 1 ratio , Z ratio 20K / 5K .
Lams 31 UI  , 8 X 15 mm , 120 mm^2 stack  ,
0.2 mm thin , 50% Ni .

This things is wound :

2 coils -  each coil has >

Sec - 1500t  #42 or 0.063mm  , DCR 420 Ohm
Pri  - 3000t  #42 in two section , DCR 930 Ohm

Winding SEC :

Winding PRI :

continue >

DONE :

 

[mitsos]

wow, those look nice. Just Secri, or are they interleaved?  Is the secondary sectioned also or just the primary?  Nice coil formers, hand done also?

 

[vitopower]

Did anyone come across winding info / DCR and L on a BA6A interstage?