help identify vari-mu

[squib]

any ideas on the make / schemo of this vari-mu limiter?

I'm also on the hunt for a schemo of a STC vari-mu limiter ( Australian made )
I've been up to the eyeballs in vari-mus lately, 3 down, 3 to go!!

 

[CJ]

Flip it over. If it has tube turrets, it might be a Fairchild.

 

[squib]

to see the underside of the circuit board requires quite a bit of disassembly. I'll get onto it! Also pardon my ignorance but what do you mean tube turrets?

 

[rafafredd]

Just a guess, nothing more... With UTC transformers, might be an RCA.

 

[squib]

anyone?

it has the following tubes:
2 x 6K7
3 x 6SJ7
1 x 6H6

plus 4 x UTC trannys

 

[Mark Burnley]

Hmm,

Could be an in-house build for a radio station or such like. I think CJ means those tube sockets with the small pole sticking out of the underside with tag terminals. The components are strung between the socket terminals and these tags mounted below. Neat form of construction, but a PITA to service/restore!

An underview would be good.

Great site BTW, I love the Star Wars Vs. QE page!

:thumb:

Mark

 

[Larrchild]

I wanna say RCA MI-10234C but not 100%

does it have 25k input atten or 600ohm?

 

[Crusty2]

I would guess a very nicely done in-house build, too. Stock meter fascia (is that Triplett?), no engraved legends on the controls, ect. It might be a copied design though, most likely U.S (RCA?).

If you started tracing the circuit, I bet one of these guys could I.D. it for you.

Paul

 

[Mark Burnley]

Aw, go on- you know you wanna trace it!

:wink:

Mark

 

[squib]

oh yeah, i'm just itching to trace it!
Maybe i'll just build a psu, fire it up and see what happens

 

[rafafredd]

what are the UTC trafos? Any label on them?

 

[Larrchild]

Audio Cylopedia, 1st edition has an RCA MI-10234C schematic. sure looks close in parts count.

 

[CJ]

UTC used to sleep with RCA, so that's a good possibility.

 

[rafafredd]

Audio Cylopedia, 1st edition has an RCA MI-10234C schematic

Hey, can you scan and post it?

 

[squib]

yep, a scan of this RCA would rock my boat. Give me a starting point for comparison

 

[CJ]

You could almost draw your own schemo with the info and pics, balanced signal chain, twin tube diode side chain with another sj7 to bump it up. UTC's are all twin coil.

insert your favorite .0.047 caps and 100-220k plate resistors and your done.

 

[Larrchild]

Ok.

 

[squib]

thanks Larrchild, close but no cheese i fear.
Still, an interesting limiter design.