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Old 25th Jul 2018, 8:31 pm   #21
Jac
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Default Re: TV Philips 1426, 819 lines 1952

Thanks for the photos of the line output transformer Roger.

This is a type I have not seen before, and it is not what I am looking for.
I see now, now that I read your posts better, that you already mentioned that it is a round can. I oversaw that. Sorry.

(I'm only looking for the transformers in the square cans.)

Does the transformer have any markings, or codes on it?

Jac
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Old 25th Jul 2018, 9:49 pm   #22
FERNSEH
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Default Re: TV Philips 1426, 819 lines 1952

The attachment shows details of the substitute line output transformer.
This is the transformer that was fitted in the Pye CTM4. The EHT was 10KV in the 405 line receiver so it's possible that the EHT will be higher in the 819 line Philips TF1426. The transformer was originally designed for 819 receivers.

DFWB.
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Old 25th Jul 2018, 9:50 pm   #23
rogerdup
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Default Re: TV Philips 1426, 819 lines 1952

For Jac:
after cleaning the top of the can, I saw a number which is a Philips part reference I think.
Interesting to notice on the photo of the same model that the lopt enclosure has been completely redesigned. I don't know when Philips decided to change the can for this one on the 1426A model.

For David:
Thank you for the schematic. It will really help me for the restoration. The TF1426A schematic indicates 12Kv, but checking the crt characteristic of the MW36-22 shows it work with 10Kv EHT.
Are 7 and 8 wound for the EY86 heater and EHT?
Thanks for the Help!
Roger

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Old 25th Jul 2018, 10:12 pm   #24
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Default Re: TV Philips 1426, 819 lines 1952

Hi Roger,
The winding to tags 7 and 8 was used to supply the reference signal to the line flywheel discriminator circuits in the CTM4. Also after delay to the vision AGC.
The EY86 filament is supplied from a highly insulated winding.

DFWB.
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Old 26th Jul 2018, 3:14 pm   #25
rogerdup
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Default Re: TV Philips 1426, 819 lines 1952

Hi David,
Attached the schematic of the line time base of the Philips 1426A.
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Old 26th Jul 2018, 4:10 pm   #26
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Default Re: TV Philips 1426, 819 lines 1952

Hi Roger,
I foresee no difficulties with the substitution of the transformer with the one I posted off yesterday. The easy bit is the connections to the PL and PY. I presume that coil S75 is the width control (largeur). What is the function of coil S66? An extra winding exists on the replacement transformer.
C96 is the energy reclaim capacitor. A higher value than that indicated in the diagram may be required, suggest 0.1uF.

DFWB.
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Old 26th Jul 2018, 7:39 pm   #27
rogerdup
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Default Re: TV Philips 1426, 819 lines 1952

Hi David,
Thanks for this added info regarding the C96. I don't know what is the purpose of the S66 coil. It seems to correspond to the extra winding of the replacement transformer?
A lot stuff to do on this TV but in mind a good replacement of the EHT !
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Old 27th Jul 2018, 8:15 pm   #28
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Default Re: TV Philips 1426, 819 lines 1952

Hello.
I've been carefully studying this thread and would like to know how anyone has come to the conclusion the transformer contains PCB's.
Has a chemical analysis been done and is there written proof of the nature of the oils chemical makeup.
I'd be very surprised that a domestic TV would contain such an oil.
I would agree that industrial transformers would contain a PCB chemical mix but in domestic environment a big No.
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Old 27th Jul 2018, 8:53 pm   #29
rogerdup
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Default Re: TV Philips 1426, 819 lines 1952

I don't know what kind of substance this can contain. My concern is actually how to get rid of it in a safe way for the environment.
Roger
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Old 27th Jul 2018, 11:14 pm   #30
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Default Re: TV Philips 1426, 819 lines 1952

When I was at school we found an old Murphy TV with one of those transformers in it.
We took the old telly to bits and found the transformer with oil leaking out and became so curious that we had to look inside so down the drain with the oil and the can was opened to reveal a coil that did not impress us all than much...
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Old 28th Jul 2018, 6:54 pm   #31
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Default Re: TV Philips 1426, 819 lines 1952

Hi Gents, I suspect that the oil would NOT be PCB as it was an expensive substance.
PCB at normal UK temperatures would be pretty gelatinous, not very runny. Most LOPT cans contain a runny mineral oil, but it should not be disposed of casually.

The design of these transformers was often not very good as the oil insulation made up for many of the design flaws in the insulation department.

Ed
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Old 29th Jul 2018, 8:15 pm   #32
Pieter H
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Default Re: TV Philips 1426, 819 lines 1952

I doubt the oil was to conceal "design flaws" of the transformer designers. The period that these oil-filled transformers were used was from 1947 to roughly 1951-52, when at least the first commercial Philips TV's in the Netherlands already used standard LOPT's without a can.
There are a few arguments why this should, at the time, be considered standard practice.
First, at least within Philips, the first prototype TV sets were the famous rear projection sets, with a 25kV anode supply to the picture tube. These sets had as much as three EY51's in the oil-filled drum. See here. I expect the oil-filled can was simply copied even in the first direct view sets, at least in my father's 1947 set.
At the time, 1946-47, 25kV was not a regular voltage for a consumer product, and for two reasons I can imagine that the responsible designers preferred to put the LOPT in an oil-filled can. First because of safety reasons, making it less accessible. And secondly to avoid sparking and the like. Not because of design flaws, but because transformers for consumer applications at the time were simply not yet reliable enough at those voltages.
As said the TX400 already introduced a newly designed "dry" LOPT, but he 1426 was the last design based on the 1948 TX380 platform, and thus the last one to use the oil-filled can.

As to the oil, I doubt that any new developments took place for this application, and I assume that the oil that was used for industrial HV transformers was simply re-used for the TV sets. It wouldn't surprise me if it contained some PCB's, but if so it was probably more accidental than intentional. I would therefore still recommend to be cautious when handling the oil.

Cheers, Pieter
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Old 29th Jul 2018, 8:25 pm   #33
rogerdup
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Default Re: TV Philips 1426, 819 lines 1952

Hi Everyone,
Thank for all those interesting considerations about this oïl can lopt.
Today, I go to the club and check most of the 18- 9pins tubes of this set. Was not surprised to notice that most of them, if not all, are to be replaced. Hopefully we still have a good stock of 9 pins TV tubes.
Roger
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Old 30th Jul 2018, 2:18 pm   #34
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Default Re: TV Philips 1426, 819 lines 1952

How did you notice that most were to be replaced? Emission measurements are only a quick indication and hardly predictive for if they work and when they fail.

Let's say, I wouldn't be suprised if some of the output valves and rectifiers were really bad and maybe one or two signal valves dubious. I would be very surprised if all valves were bad. If they really are, prepare to replace the picture tube as well, as it will certainly be low emission if the set has played that many hours.
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Old 30th Jul 2018, 6:06 pm   #35
rogerdup
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Default Re: TV Philips 1426, 819 lines 1952

From Maarteen: "How did you notice that most were to be replaced?"

Well, using a Metrix pro tube tester, that we use widely at our worshop. It is proven to be very accurate.
I did not had time to test every single tubes but check mainly the two power tubes EL41; shows 17mA and 19mA anode current instead of the 36 mA. Some EF80 have to be checked and those PY81 and PY82. The line power PL81 is dead and to be replaced.
As far as the CRT MW36-22 is concerned, yes this TV has a long time use behind it. We just hope that it is still good enough for demos.

Roger
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Old 10th Aug 2018, 10:45 pm   #36
Maarten
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Default Re: TV Philips 1426, 819 lines 1952

Ah yes, the valves you checked are indeed the ones I would suspect and test. I'll keep my fingers crossed for your CRT.
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