Re: Refurbishing a 465 (earlier serial) with a strange intensity issue

Fabio Trevisan
 

Hi John and Sigurdur (did I spell it righT?).

I've been down this road with my 464 and tried the rejuvenation and also
played with the filament winding.

If you look at the tekscopes pictures, look for "Tek464 CRT Double-Peaking"
or just click on the link:

https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/1813474623

The schematics are for reference only, as it employs a computer
voltage-stabilizer transformer, which had many taps and was suitable for
this project, but you won't probably find any alike.

As a comment for Sigurdur's comment:
"It might be simple enough to add a winding or two to the heater
output?"

1st. It's indeed easy to add windings (at least on the 464 is and as far as
I could see, the 465 xfromer is alike. It's a separate bobin/former.

2nd. Just be cautious about the number of turns you add, because the full
winding may be just 3 turns (like on the 464), so, if you add 2 turns, you
may be adding 66%.
You can always unwind the original and count of how many turns it's made of
and take from there. Never fear, they come out easily and can be rewound
just as much.

3rd. Mind to use wire with HV insulation because, as though the winding
voltage itself is low, it's at -2500V potential and if it gets near or in
contact with other parts of the circuit and its insulation is weak, you can
get a spark where that high-voltage shouldn't get. I immediately think of
the low-voltage side of the DC restorer and the Unblank and Z axis
amplifier, because they're all nearby the HV circuitry.

Rgrds,

Fabio



2017-07-06 14:31 GMT-03:00 Sigurður Ásgeirsson siggi@... [TekScopes] <
TekScopes@...>:



On Thu, 6 Jul 2017 at 04:19 Sigurður Ásgeirsson <siggi@...> wrote:

Is there any way to sneak a couple of extra windings on the HV
transformer? It would be necessary to figure out the phasing and the
volts/turn, and insulation will be terribly important.
I've never been inside a 465, but I found some images from inside the HV
shield here <http://www.vintage-radio.net/forum/showthread.php?t=96958>.
It's not a super-great image, but it looks like the heater winding is
outermost on the core, and it looks like there'd be plenty of gap to feed a
couple of turns through.
It stands to reason that the heater winding would be next to the HV output
tap, as that minimizes the voltage differential between the two. It might
be simple enough to add a winding or two to the heater output?

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