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Forum 141

Anyone know the number of turns on Bush/RBM mono Overwind?

Black & White Television

Last Post by Refugee 11 years ago

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Alastair

(@alastair)

Posts: 294

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Just got a Murphy 2015D set--dual std, 19" transistorised IF and one of those complicated dual-standard tuners.

The set is alive, but only for around 5 minutes before the usual RBM mono LOPT issue causes it to quit...
I could just build a doubler, but would like to give winding an overwind a try.

Rather than trying to count the number of turns on its pitch covered overwind, I know some guys have re-wound these, and would know how many turns approx these have....

I have a small transformer winding machine and could probably manage it.

Worth a try anyway--Just need to know the number of turns--probably several thousand over several dozen layers!

Posted : 03/05/2013 12:51 am

Brian Cuff

(@briancuff)

Posts: 2063

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I think you will need a wave-winder for an EHT over wind Alastair. The winding is narrow and high and an ordinary layer wind will not be self-supporting. I think it also has something to do with self-capacity.

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Posted : 03/05/2013 1:11 am

Alastair

(@alastair)

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Hmm--Interesting.

The plastic one that I had out of the TV125 was a narrow straight layered winding approx 1/4" wide, but due to the plastic type construction and potting defied unwinding to assess the number of turns The winding was pretty thick having loads of layers.....

Guess I could rig up the transformer to give 1V per turn and measure the voltage, after a period in the airing-cupboard, and measure it quick!....

Hmm--There's an idea!

Posted : 03/05/2013 1:25 am

Refugee

(@refugee)

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I would go for a much lower HT voltage while testing.
On a VGA over-wind I have been getting 6KV from an HT of 20 volts.
100mv per turn would be more like it for testing the turns ratio if it is at all leaky.
1 volt per turn may well kill your DVM even with a leaky over-wind.
I have posted more details of why I have been tinkering with this kind of testing.
viewtopic.php?f=15&t=4933

Posted : 03/05/2013 2:26 am