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Old 19th Feb 2007, 9:32 pm   #1
Mikey405
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Default Tripler to replace 25KV overwind

Hi everyone.

What are people's thoughts on using a tripler to replace a 25KV EHT overwind in an old Philips colour TV? Does it put any undue strain on the primary of the transformer? I kind-of assumed that it wouldn't, but I've been talking to a pal of mine who says that it might, so I thought I would check. I have a very small "Universal" tripler which would fit nicely inside the cage and hopefully provide the required 25KV. If it wouldn't hurt the set, I would like to be able to use the TV regularly.

Thanks everyone.

From Mike.
PS. Just in case of a minor miracle, the part number of the original transformer is A328059 and it will be written on the paxolin terminal board.
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Old 19th Feb 2007, 9:40 pm   #2
Mr Hoover
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Default Re: Tripler to replace 25KV overwind

Hi

There was an article in Television magazine many years ago about doing this
with a Decca CTV 25.

I recall it worked fairly well but the EHT regulation wasn't as good compared with the original PD500 shunt stabiliser arrangement.The original LOPT
never died,I recall selling the set around 1979 and subsequently doing the
same with another CTV 25

There may have been a later article In TV Mag regarding doing the same with the Philips G6 chassis.

Good Luck
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Old 19th Feb 2007, 9:56 pm   #3
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Default Re: Tripler to replace 25KV overwind

Not really, Mike. In fact, it'll probably put less strain on it in a way. No GY501 heater, for example. You might possibly need to mess around with a few caps but as a rule, 25kv should come out of it okay.

Best to try it with the PD500 if it's there.

Cheers,

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Old 19th Feb 2007, 10:54 pm   #4
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Default Re: Tripler to replace 25KV overwind

Hi Mr Hoover and Steve.

The set is the Philips K4 and the EHT regulation is done in the low-voltage side of the line output section so I would not have too much problem there hopefully. My mate read my post earlier and immediately phoned up and said "Don't do it".

From Mike.
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Old 19th Feb 2007, 11:06 pm   #5
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Default Re: Tripler to replace 25KV overwind

Can't think why? Is he a member on here, and if not, can I have his E-Mail address.

The set in question, the K4, is probably never going to get a LOPT, unless the one you have is re-wound or one is re-manufactured for the set. So I fail to see why he says what he does.

You can't send me a circuit of the area in question can you?

Cheers,

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Old 19th Feb 2007, 11:30 pm   #6
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Default Re: Tripler to replace 25KV overwind

I think my mate is a traditionalist Steve. He's actually the chap whose set it was before mine, so I feel a certain responsibility. He's a member on here, but wishes to remain an omnibus.

We've been poring over the circuit to see if a G6 tranny would go in as the circuit is so similar, but the biggest problem is space really. Personally I think a tripler will be fine, but I'll bow to my mate's decision as he is a K4 expert. (Or I'll snook it in when he's not looking.)

From Mike.
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Old 20th Feb 2007, 12:02 am   #7
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Default Re: Tripler to replace 25KV overwind

See if it'll work in a G6 then, and if it does, you can try it in the K4. If the circuits are similar. Have you still got that Single Standard G6, you could use that, and have it working too.

Cheers,

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Old 20th Feb 2007, 9:50 am   #8
Mike Phelan
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Default Re: Tripler to replace 25KV overwind

Mike
The G6 LOPT is slightly unusual inasmuch as the anode current from the PL goes through a choke (blue thing with a ferrite core) instead of all going through the LOPT primary. Is the K4 like that?

I am not sure how a tripler can cause strain - the beam current is no different and it is probably more efficient that the leakage inductance of the overwind.
Was he thinking of the harmonic tuning, maybe?
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Old 20th Feb 2007, 8:25 pm   #9
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Default Re: Tripler to replace 25KV overwind

Quote:
Originally Posted by Mike Phelan View Post
Was he thinking of the harmonic tuning, maybe?
I'm not entirely sure Mike to be honest. I'll see my pal soon so I'll try and persuade him then...

From Mike.
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Old 20th Feb 2007, 8:27 pm   #10
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Default Re: Tripler to replace 25KV overwind

Quote:
Originally Posted by Steve_P View Post
Have you still got that Single Standard G6, you could use that, and have it working too.
I have Steve, but it's the primary that went up in flames in that set...

From Mike.
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Old 20th Feb 2007, 9:22 pm   #11
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Default Re: Tripler to replace 25KV overwind

Mike, have you seen the thread "Philips G6 Tripler Conversion" relating to my 502 set?

Cheers,
Brian
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Old 22nd Feb 2007, 7:27 pm   #12
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Default Re: Tripler to replace 25KV overwind

Hugh's CTV25 tripler conversion article is excellent, as is Keith Cummings one on the B&O Hybrid series, although I don't remember an article specifically on converting Philips sets to tripler conversion. LL-J mentioned he has a tripler running in a G6 in the 1980s.

There was also excellent guidance in Mike Phelan's article on early CTVs in the January 1979 issue. He made the important point about the beam limiter not working after such modifications, with the suggestion of a simple circuit in the luminance feed.

Chas E Miller's Babani book, "The Practical Renovation of Colour TVs" has a chapter on this too. Wish I still had a copy of this excellent book.

In the "Philips G6 tripler conversion" thread I noticed my mention of harmonic tuning capacitors, I should of course said the 60pF was from the PL509 top cap to chassis.

Cheers,
Brian
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Old 22nd Feb 2007, 10:03 pm   #13
Mikey405
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Default Re: Tripler to replace 25KV overwind

Hi Brian.

Thank you for those comments - I'll certainly take a look at those articles. My mate said that he didn't recommend using the tripler as he already tried it in another K4 and had little success - The width was always very poor and the primary of the lopty burned out within a week...

Thanks Brian.

From Mike.
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Old 23rd Feb 2007, 12:46 pm   #14
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Default Re: Tripler to replace 25KV overwind

Hmmm... Interesting point that Mike. I wonder if the primary burn out was co-incidental and would've happened anyway? Certainly I put in a BRC 1500 doubler into a Bush TV161 series with success initially but only for the primary to fail a few weeks later.

I admit I very seldom use the G6 in either its original and current modified form so I can't personally confirm either way.

Certainly Hugh's Decca CTV25 was reliable following such modification.

I can't see any harm in trying this if there's nothing to lose. Just a pity some makes use unreliable LOPTs!

cheers,
Brian
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