A little HV poswer supply I disected today

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Butterylicious

Well-known member
Joined
May 17, 2005
Messages
520
Location
Austin
Here's the schematic
275V-PS-Schematic.jpg


C1, L1, & L2 are not marked. C1 measured .75uF which seems like an awfully low value for this application.

Here's a picture of C1
C1.jpg


I haven't a clue what values L1 & L2 are. L1 is the larger inductor with the callipers on it, L2 is to it's right. the transformer to the left of L1 is a Merit P1353.
Inductors.jpg



I slapped a little load on this power supply and everything seems fine. My main concern is that capacitor C1. I think it's "scarey uh oh". This power supply is for a pair of Western Electric 121A preamps so I wanna make sure it's groovy B4 I connect it to rare circuits.
 
That little amp has a nice input transformer. Actually, it's an output transformer reversed.

Specs:(as per package, not installation)
Triad JO-23
50:15,000
20KΩ Pirmary
250Ω Secondary

The output transformer has no markings.
 
Just to press the question about the power supply:

Does anyone else find the value of C1 = .75μ? odd?

It seems low to me, but that's what I measured it to be.
 
Buttery,

Just check your connections to the 5Y3GT from the transformer- you've got it wrong in your diagram. Take your B+ from the cathode of the rectifier.

e.g:

cyclo_psu.jpg


I wouldn't worry too much about the caps- let them re-form and then see how you're looking for ripple on the B+ line. And look out for "ooze" from the caps.

Mark
 
[quote author="Butterylicious"]Just to press the question about the power supply:

Does anyone else find the value of C1 = .75μ? odd?

It seems low to me, but that's what I measured it to be.[/quote]

Basically, this is a choke-input supply; the real work is being done by C2 and the inductors. I assume C1 is there just to absorb a bit of switching noise.

Or, of course, it's defective. But I suspect it's really supposed to be 0.75uF, and the filter's a choke filter.

Peace,
Paul
 
Buttery;

Cool put it back together and use it!

Watch out with that oil cap.
If it is leaking or starts leaking it has PCB's in it.
It is no problem until it leaks!
Dispose of PCB's correctly.
Remember PCB's have a great affinty for fats in the human body.
If you get PCB's into you you will not get them out of you.
Very similar to Mercury.

Just use it and be happy.
 
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