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B&W TV RE: KB Royal Star; PVP20

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sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 3971

WE ARE BACK IN BUSINESS!! Mike Barker has done an absolutely superb rewind. The transformer is 'transformed'!! It's been cleaned up, the primary has been rewound and sealed with what looks like a potting compound and new leads have been soldered on. It even came with a brand new R19 EHT rectifier fitted. I couldn't resist not fitting it tonight despite the fact that I couldn't find the wiring diagram that I made. There are only 5 connections and I figured it wouldn't be difficult to work them out so armed with the circuit diagram and the transformer I set to work. Fortunately once the transformer was in place, several of the unsoldered wires had stayed more or less in place and it was fairly obvious where they went. However I checked carefully on the circuit just to make sure. There are some capacitors mounted on the transformer and a 3.9k resistor and this helped hugely in confirming where the wires went. Once I was satisfied that all was well, I connected the Aurora and the mains and switched on, hand ready on the mains switch for a quick switch-off if necessary. I needn't have worried. After about a minute, up came the picture. I didn't need to adjust the width, it just worked. 

Top marks to Mike Barker.

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Two pictures. The rewound transformer looks superb. I'm hoping the tube will improve again with use. It's still better than when I first got the set working but not as good as it was after boosting. I might look around for a better tube....

If Mike Edwards is looking down from his workshop in the sky, I hope he's pleased the set has been resurrected yet again....

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Topic starter Posted : 21/04/2022 10:52 pm
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 3971

Just a quick update. The CRT has improved with use. A quick check on the CRT tester shows the emission is just into the green area so it might improve even more. I think it's the best I can expect from it so now I'll concentrate on fixing the speaker mounting and then reassemble. Had it running for a couple of hours tonight....watched 'The Repair Shop' in B&W.....that was interesting when they were talking about the 'vibrant colours' on a restored painting....!

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 Looks pretty good on the testcard now. The line lin isn't quite right but probably not worth messing with.

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Topic starter Posted : 21/05/2022 11:44 pm
ntscuser, Cathovisor, colourmaster and 1 people liked
lloydwells93
(@lloydwells93)
New V-Ratter Registered
Posts: 1

@sideband I'm mid way through a royal Star but needing a new Lopt as the Overwind had a massive short amazingly it was still giving EHT 

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Posted : 24/05/2022 12:19 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10844

Hi and welcometo VRAT 👍 

Sorry to hear about your LOPT, it's so disheartening when that happens. I think at one stage or another we've all encountered this horrid situation, whether it be the primary, the overwind or sometimes both.

Personally, for me, it's with a Philips G6. The original LOPT was missing, I managed to get a spare and that failed. With no more available and unlikely to ever find a new one, I decided to transplant in a CVC5 LOPT.  It came out of a less than well stored set. It worked for a while, I had a raster and testcard displaying, unsurprisingly it too failed. 

Since then, I've managed to purchase and other 3 CVC5 LOPTS, all in much better condition. One allegedly NOS, and being the super reliable Weyrad version. The plan is to get to try the transplant again, some time soon, it's just finding the time and motivation to get back in the saddle.

What are your plans to tackle your failed KB LOPT? Are you going to look for another, or perhaps temporarily do the "tripler trick" to at least get the set running until a new LOPT comes along?

p.s.

I might be wrong, but I don't believe it's possible for Mike B to rewind the overwind, only the primary is do-able.

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Posted : 24/05/2022 12:39 pm
sideband
(@sideband)
Famed V-Ratter Moderator
Posts: 3971

The overwinds are completely encapsulated on these transformers (see photo's of mine) so I doubt it's possible as crusty says. In my experience of these, it was only the primary that failed but of course I didn't see so many when I started in the trade as they were all pretty old by then. If it is the overwind at fault, these can be removed and you can use the tripler trick or you can make a doubler or tripler with diodes and capacitors....well insulated of course. You could also try transplanting an overwind from another transformer (I have done so with success). Alternatively ask on the forum and see if anybody has a good one they can part with.

 

You could always ask Mike if he can do the overwind. He may have some solution given his vast experience. In theory, an overwind could be wound and then encapsulated but how much work that would involve I have no idea.

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Topic starter Posted : 24/05/2022 1:55 pm
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