SB-620 pwr transformers?

[MVD@MVD]

Oops - return key.

HO-10 and maybe HO-13 had a power transformer with 1200 V winding using a
single (1V3?) tube half-wave rectifier. There may alsos be a 200-some volt
winding, as well as one or two filament windings.

SB-610, 620, & maybe -614 (???, or was that just a clock) had 54-182 with
600 vac @ 1 mA DC winding into a solid state voltage doubler. This hits the
1500 V caps a little hard. SO the HO-10 type and SB-610 type do not have
compatible power transformers. The remaining windings on the SB-610
transformer (54-182) are 6.3 @ 3.0 A and 6.3 @ 0.6 A.

I can't remember if 54-130 was the single primary version of the 54-182, or
of it was the HO-10 1200 V transformer, but the number sticks in my head..I
think the former rather than the latter.

I have a part that has been used by two people who were able to overlook
cosmetics, safety and a need to keep it original, in the case of having ONLY
the hv winding open, and the filament windings intact and still working. It
serves as a substitute hv source only, and it's not likely there is room to
fit it in the cabinet.

Less often, a primary fault renders the entire transformer unusable.

The part I have sold people is not without downfalls - if all remaining
windings on your original 54-182 are working, you need to retain it for
those voltages. It will not fit in the SB-610, and has to be 'contained'
safely externally, and the hv routed in safely. One guy used a Tupperware
container and fish tank tubing...ugly but effective.

What I have are 54-282 from the Heath/Bell & Howell scope. It has a 660 V 3
mA winding and a 6.3 @ 0.6 filament. This results in 10% higher B+, already
a bit on the high side in the original design. I've suggested using the 6.3
secondary wired to 'buck' the primary, as this should reduce the overvoltage
to only 5% high. I doubt that increase will harm the CRT, but the capacitors
(more hard-to-find stuff) should be upgraded to higher voltage rating
(usually happens when you use what you can find nowadays). My guess is a
little more acceleration on the electron beam will give a brighter trace out
of a tired old CRT.

I've thought about using these transformers to create a totally external B+
supply, with new rectifiers and 2 kV capacitors. This would require routing
into the cabinet 1850 VDC or so instead of 660 vac. I'm not sure I want to
sell a complete kit of parts because it's a bit more hazardous than your
average 12 V project, and I prefer to have aquaintence vs. business
relationships with attorneys.

So maybe I should just offer the transformers and the idea. If one has a
totally bad transformer and wanted to go one step further and
outboard/outrig separate 6.3 filament transformers, be very careful with the
0.6 A winding - I think it may float at B+  level for the CRT filament. Use
the schematic rather than my rusty memory to assess this.

The 54-282 differs from the 54-182 also in that the 54-182 has a 5 kV DC
hi-pot (dielectric withstand) spec, and the 54-272 has a 4 kV spec. Both
were intended for small CRT applications, so make your own decisions. I
imagine most attempts to find a solution don't consider this because it was
never public knowledge (until now!).

I should scan an image of the 54-282 and find my specs for the hi-pot
ratings for all windings on both 54-182 and 54-282 so people can make their
own conclusions.

I had been selling the 54-282's for $15 + $3.85 Priority Mail.

Murray

----- Original Message -----
From: "Peter A Markavage" <pmarkavage at JUNO.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Tuesday, July 23, 2002 1:30 PM
Subject: Re: SB-620 pwr transformers?


> We need a  mod plan, source, etc. This seems to be an on going problem
> for the 610, 620, HO-10, HO-13, etc. How about one of those little high
> voltage sealed high voltage modules they use for some of the small screen
> TV's (non LCD)?
> Pete
>
> On Mon, 22 Jul 2002 07:17:57 -0700 Guy Giacopuzzi <ggg3dds at JS-NET.COM>
> writes:
> > Well, its the old problem...found a 620, but with a bad 1500v
> > secondary
> > winding...didn't we have someone that had a source for these...been
> > searching the archives manually (can't get the auto search to work),
> > but
> > haven't found the source yet..Anyone remember?
> >
> > ggg, WA6OQQ, lake arrowhead, ca
> >
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