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Drying out an RBM Pitch Overwind.

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Black & White Television

Last Post by freya 10 years ago

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Spot-Wobble

(@spot-wobble)

Posts: 735

Honorable Member Registered

I am about to try the same on my PYE V4 LOPT.
It is currently producing around 10KV but drops down to 8 KV after a short while. It should be 14KV
The EHT drops and the width reduces after about 10 minutes.
I tried removing the pitch off one of the other faulty LOPTs overwind by heating it with a hair dryer.
It heated the pitch enough to remove it easily but without it melting to the point of going gooey.
Obviously need to heat the winding up afterwards to drive off any dampness, then re-coat it.

Andy

Posted : 01/02/2014 10:31 pm

freya

(@freya)

Posts: 1312

Prominent Member Registered

The lopt in my pye LV20 underwent a bake off just before Christmas, it was put in the fan oven on a wire rack with a tray below lined with foil.
The temperature was increased to the point where the pitch started to run out, after about 4-5 mins it stopped so using an old oven glove I rotated it 45 degrees to allow more to pour out from another pocket, then again until all surfaces had been down.
It does make a good stink that lasts for 2-3 days so if you can do it outside I recommend that.
After doing this the EHT is stable at 6.6 Kv (it was 4.4 Kv before) the focus wandering was also remedied by replacing the rectifier mounting paxoline board with a new fiberglass one.
Nothing was used to recoat the windings.

Posted : 01/02/2014 11:09 pm

Marc

(@marc)

Posts: 2753

Noble Member Registered

The lopt in my pye LV20 underwent a bake off
Nothing was used to recoat the windings.

Hi Freya,

Wouldn't that leave the LOPT vulnerable to damp ingress in the future ?
I did a Bush TV22 LOPT a while ago but I spayed it with Lacquer to protect it.

Marc.

Marc
BVWS member
RSGB call sign 2E0VTN

Posted : 01/02/2014 11:18 pm

freya

(@freya)

Posts: 1312

Prominent Member Registered

No, even with the amount that came off there is still more that could not be removed from the overwind. The primary and secondary are both cloth taped anyway.

Posted : 01/02/2014 11:28 pm

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