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...and the Pye 11U bounces back yet again.

 
sideband
(@sideband)
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Older members of the forum that followed over from VRAT 1 will be aware of the restoration of my 11U. It's been working well but when analogue closed down I only used it on 405 via the Aurora since at the time, I didn't have a good UHF source...in fact the only way I could use UHF was via a VCR which was a bit of a fiddle. Last year I bought a 'Multiview' which was designed for hotel use and converts Channels 1 to 5 to normal analogue so at last I had a good UHF source. Well to cut a long story short, when I tried the Multiview on the Pye TV I found that the Pye wasn't working on UHF..well at least it was trying but the line stage seemed to be under great stress with only a small unlocked raster which faded away after a few seconds. It continued to work normally on 405. 

Tonight I decided to have a look at it. Rather than get the scope out I decided to to use the multimeter in frequency mode and check the line oscillator. Spot on at 405 10.125k  but reading something like 19.5k at 625. Start with the simple....check the line hold pot (separate ones on this set for 405 and 625). The frequency jumped all over the place and I eventually managed to get it somewhere near 15.625 and a bright raster. So all that was wrong was the 625 line hold pot. Well it was the original so I suppose it hasn't done bad at 54 years. It's a 100K pot and fortunately I have a supply of these 'self-assembly' pot kits by EGAN. For some reason I have a large number of 10K but did manage to find four 100K types. The only problem was that they were not printed circuit types. However with a slight modification they can be fitted without trouble. The 11U is now working on 625 again and displaying good UHF pictures for the first time since 2012....is it really 6 years since analogue was switched off....?

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The original pot. To replace it you remove the spire clip that holds it together and remove the knob and the wiper disc...

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...like so.

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The pot removed.

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 The replacements I have are not the PCB type so they will need modifying....

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...Judicious trimming and careful bending....

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...and the pot fits.

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Solder in, fit the new wiper disc and a new spire clip from the kit and....

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...it all works so now I have 625 (5 channels tunable) and...

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405.

This 11U never ceases to amaze me. It always seems to bounce back and the picture continues to be superb. 54 years and counting....

I think I'll repeat the exercise with the 405 line pot as that is a bit 'twitchy' as well. 

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Topic starter Posted : 21/08/2018 11:38 pm
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Nuvistor
(@nuvistor)
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Always liked the 11u and it’s later version with slightly more IF gain , EF184 instead of a PCF80 last video IF amp if I remember correctly.

I used to have those pots, as spares on the van, is it Egan and Egen?

 

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Posted : 22/08/2018 7:31 am
sideband
(@sideband)
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Well I tried a quick clean of the pot and it made little difference so as I have some spare pots, I may as well use them. 

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Topic starter Posted : 22/08/2018 10:12 am
Nuvistor
(@nuvistor)
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A problem I had with those pots was the spring clip losing tension and slipping down the shaft. The shaft became damaged so a new clip and knob were required, it was just as easy to change the lot to save call backs.

The high level contrast control although a different design also failed.

 

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Posted : 22/08/2018 10:42 am
PYE625
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Posted by: sideband

Well I tried a quick clean of the pot and it made little difference.

The thin carbon coating of the track often wears away with use, and if combined with a high voltage, the wear is probably worse. I read somewhere that tracks can sometimes be repaired with a pencil, but I can hardly see that being any good long term. No, replacement is often the only option.

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Posted : 22/08/2018 6:51 pm
sideband
(@sideband)
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After the successful replacement of the 625 line hold pot I decided to do the same with the 405 pot as it was also a bit touchy. The set now has two new pots fitted and the line is stable on both systems. 

Now that I have a viable 5 channel UHF signal, it's prompted me to sort out my aerial distribution system where I can have 5 analogue UHF channels and (admittedly only one) VHF 405 channel. I also have a UHF modulator so plenty to play with....but that's for another thread....

js1024 SAM 1682

 

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Topic starter Posted : 23/08/2018 10:34 pm
sideband
(@sideband)
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Does anyone have the full service manual for this? I have some sheets that I rescued from Philips years ago that cover the circuit and PCB layout but I have no information on how to set most of the pre-sets. Most are easy to work out but I notice there are two slider pre-sets in the line stage marked 'SET EHT', one for 405 and 0ne for 625. I remember the full manual was in a blue folder. 

Otherwise can anyone advise on the two 'SET EHT' pots?

 

Cheers.

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Topic starter Posted : 25/08/2018 6:55 pm
PYE625
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Hi, I believe the EHT is meant to be 16-17KV with 500 volts on the CRT first anode.

Below is some info from the Ekco data that might help....

IMG 4602 50
IMG 4603 50
IMG 4604 50
IMG 4605 50
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Posted : 25/08/2018 8:21 pm
sideband
(@sideband)
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Posts: 3971

Thanks to Chris and Freya alerting me to a manual on eBay I have now purchased same and it should be here by next weekend.

I also have some 3kv capacitors on their way so I'll be able to change the bodge of several parallel capacitors I fitted (line EHT tuning) to just two single capacitors (one for 405 and one for 625)

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Topic starter Posted : 26/08/2018 9:48 pm