[Heathkit] O-12 power transformer

[Ian Wilson]

Interesting. I have had exactly the same experience with a Heathkit
scope power transformer (I forget the model number, but many of them
are similar), and with an Eico (maybe) scope power transformer that
I salvaged to repair a project using the Heathkit xfmr.

The problem was with the wire at the high voltage end of the EHT
winding. This had burnt its way through the insulation where the
hot end of the winding wrapped around the core and made its
way away from the transformer.

This was causing intermittent loss of EHT, hadn't taken out the
transformer. I think I recollect teasing the last turn away from the
laminations. Not exactly a perma-fix :)

73, ian K3IMW


On Tue, Mar 10, 2015 at 9:02 PM, Kevin Ward <n2ie at arrl.net> wrote:

> Richard -
>
> Once upon a time someone gave me a piece of equipment (Knightkit I
> believe) which he said "just quit operating."  The filaments powered up but
> as the saying goes, "the lights were on but nobody was home."  My friend
> said there was no flash, bang, or smoke - - it just quit!
>
> A quick check with the VOM confirmed an open winding in the power
> transformer.  I made a quick sketch with notes on where all the wires went
> and dug out the transformer.  I pulled off the end bells and had a look.
> The winding had parted, right at the end of the last turn of the winding.
>
> I had to unwind a single turn to get a free end I could work with, but I
> was able to restore operation.  I replaced both electrolytics because one
> had a bulge, even though both tested OK, and never had another problem with
> that unit.  I recommend you replace those caps.
>
> If you're going to replace the transformer anyway, you have nothing to
> lose by pulling it and having a look.  Just don't forget to document your
> work as you go.  Especially if you don't have the manual and schematic.
>
> Kevin  N2IE
>
>
>
>
>
>
>
>
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