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Author Topic: Shunt Regulator from Stereomour II on Stereomour?  (Read 625 times)

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Offline tumble2k

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Shunt Regulator from Stereomour II on Stereomour?
« on: December 29, 2020, 01:44:55 PM »
Hi all,

I've been wondering if I can put the shunt regulator circuit from the Stereomour II onto my Stereomour.

I would need to physically drill (or laser cut) a new hole for the other tube. I might need to add an additional terminal strip.

But I'm wondering if there are any circuit incompatibilities that would make this impossible (like for example, the DC heater supply on the SII won't work on the SI because of 2.5 VAC transformer secondary won't pass enough current).

Thanks for any information!
Clif

Offline Paul Joppa

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Re: Shunt Regulator from Stereomour II on Stereomour?
« Reply #1 on: December 29, 2020, 03:05:35 PM »
It might be possible, but it sure wouldn't be practical! The bias voltage, current, and plate voltage of the driver are different, so you'd have to strip the old circuit and replace it with the new one. The old power transformer cannot support a DC filament supply.

Basically, the reason for the new Stereomour II was to make these upgrades (plus the input control upgrade and 120v/230v power) possible. To do that we had to revise the chassis layout and the power transformer.
Paul Joppa

Offline Paul Birkeland

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Re: Shunt Regulator from Stereomour II on Stereomour?
« Reply #2 on: December 29, 2020, 03:19:25 PM »
Some years ago I was cleaning out the boss's basement and he handed me the remnants of the first Stereomour prototype.  It had all the iron there and as a bonus it had an octal socket hole in the chassis.  I installed a 12 pin compactron socket and used a 6AC10 driver tube to do just what you're thinking of, though I had to settle for one shunt regulator for both driver channels. 

So, if you want to do this on a Stereomour I, you'd need PJ to weigh in on how much extra current there is on the 12V heater winding, as I think that will be a big restriction.  There are some 2.5V 6V6 equivalents too I think, so perhaps there's enough current headroom on the 2.5V windings to pull that off, maybe not.  I do remember that the PT-6 power transformer on the Stereomour I was a hefty little number. 

You'd need to be really comfortable reading schematics to be able to take the S2 SR kit we sell and graft it onto something else. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline tumble2k

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Re: Shunt Regulator from Stereomour II on Stereomour?
« Reply #3 on: December 31, 2020, 04:17:30 PM »
Thank you both for your information. I forgot about the heater winding in the transformer. Argh. Your idea to use the 2.5 V heater winding from the 2A3 heater is interesting ... but my understanding was that I don't have a lot of current on that supply either.

I suppose I could add my own 12.6V transformer for the heater. I suppose I could just create my own shunt regulator...

Will study more before asking more questions. Thanks again,
Clif