Monitor xfmr

[Multi-Volti Devices]

Hello:

Regarding monitor scope hv winding alternate solutions:

If I remember, the HO-10 and similar use a 1200V or so winding, with no
doubler, and the SB-610 and it's ilk use a 600 V winding with a voltage
doubler.

Since I am familiar with the SB-610 transformer (most recent vintage used
54-182, and in my mind 54-130 keeps coming up. Don't remember if it was for
an earlier SB-610, or if it's the H)-10 xfmr). If your interest is in fixing
the HO-10 and similar (1200 V winding), read on anyway, as this may help if
you are considering an outboard fix.

Anyway, the 54-182 has the following windings
600 v @ 1 mA
6.3 v @ 2.6 A
6.3 v @ 0.6 A

I proposed a solution to the "open hv winding" problem to a couple of guys
locally, and I had three 'field testers'. One never got back to me, the
second reported it worked with no further communication, and the  third said
it worked and he put it in a Tupperware container to insulate it
(interesting...but I think Rubbermaid is fine too :o)  )

The alternate part (54-282) was for the a Heath/Bell&Howell 'scope, and
doesn't have sufficient windings to serve as a "drop-in" replacement.

54--282 windings (dual primary)

660 v @ 3 mA
6.3 v @ 0.6 A

I think the 54-182 had a 5000 VDC hi-pot spec and the 54-282 is 4000 VDC, if
I remember right.

Considering the similarity of application, and the implication that the
designers were happy with 4 kV for the -282, which actually has a higher
voltage in operation, leads me to believe that it's a reasonable substitute.

The bad part is having the hv running around externally. Perhaps a minibox
could be bolted to the cabinet of the monitor scope.

For the SB-61x people, if you have a problem other than an open wiinding
(like an interturn short), you're out of luck, or at least back to square
one like wa0bka, in that you need an additional external transformer. The
54-282 in an external application could be supplemented by a 6.3 v @ >2.6 A
transformer. I do not know which windings have the hipot (dielectric strengt
h) concerns, so I would play it safe and find an old type filament xfmr
intended for power tubes (and thus rated for hv series connection). I think
the main issue is the filaments being in series with the hv circuits. So I
wouldn't recommend a Radio Shack 6.3 v 3A job, as it's anyone's guess what
the hipot/dielectric withstand rating would be. If you're an "old-timer",
you may have heard of the crude technique of mounting the transformer on
ceramic insulators! But, I don't want to encourage risky tricks. If you know
what you're doing and come up with them on your own, that's your path to
pursue.)

The slightly higher voltage could be accommodated by utilizing sufficiently
rated external filter capacitors in the doubler, or buck-winding the 6.3
winding in series with the primary (would drop about 5% to 630 or so), or
rationalize that it will give a brighter trace.

My imagination further thinks that if the other windings are ok, or suitable
lv substitutes are available for the ugly outboard approach, that the 660 @
3 mA winding with a doubler could replace the 1200 and conventional
rectifier in the HO-10.

I got a quote once on having 54-182's wound by a local company, but it was
prohibitively expensive due to setup costs. I think I would have to buy
50-100 to get them down to about $35-50. That's quite an investment, so I
shelved the idea.

If any brave, high-voltage-experienced individuals want to use the 54-282 I
have a couple boxes of them. They're clean and early 90's vintage. ($15+$3
ship).

Didn't mean for this to come across as an ad, but I think it may help some
people out, if they can deal with the safety factors and layout issues.

Murray


-----Original Message-----
From: waobka <waobka at TDS.NET>
To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
Date: Wednesday, July 01, 1998 9:45 PM
Subject: Monitor xfmr


>Contact with Tom Hand in GA. for assist in obtaining a
>transformer for the Heath Monitor  was a no go.. Tom works on
>BIG stuff. So request out again for a used working HO 10
>monitor scope or a power transformer for it. If this isn't in
>the works then I guess I will have to build an outboard supply
>unit- with one or more transformers. It has two 5 volt
>secondaries, a 210/220  ac to provide  LV DC and a secondary HV
>1200 V and a tap to give about 625.. Have the low voltage units
>and can contrive the 210 V  but the 1200 volt is a sticker  The
>DC conversion is with diodes - no problem here  Any comments
>-suggestions or whatever solicited..
>
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