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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 8th Aug 2017, 3:58 pm   #81
matspar
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Default Re: Pye VT2 EHT problems

Yes I use a variable attenuator with my Aurora as the signal is a bit strong but only on certain sets. Adjusting this isn't making any difference to what I'm seeing on the screen apart from the reduce in signal. The CG12E diode was o/c when I first had the set and I replaced it with a 1N4148.
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Old 8th Aug 2017, 4:01 pm   #82
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Default Re: Pye VT2 EHT problems

Thanks Lawrence I'll check the wiper voltage shortly and see what I'm getting
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Old 8th Aug 2017, 4:01 pm   #83
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Default Re: Pye VT2 EHT problems

With a signal supplied to the receiver check the voltage present at pin 7 of the ECC81 sync separator valve. At normal contrast settings more than 20 volts negative should be measured at the grid if the sync separator is working correctly.

DFWB.
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Old 8th Aug 2017, 4:56 pm   #84
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Default Re: Pye VT2 EHT problems

Lawrence - wiper voltage is showing 96-155 volts. Slightly higher than the 68v quoted. David - pin 7 of the ECC81 does show a negative voltage which goes from around 20 -36v. Advancing the contrast right up makes this voltage disappear.
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Old 8th Aug 2017, 6:25 pm   #85
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Default Re: Pye VT2 EHT problems

Can you lock the line timebase? If you can my thoughts lean towards the frame frequency.
You say it was OK before the frame blocking oscillator went O/C. Make sure you haven't reversed the primary and secondary connections.
It is possible that the transformer is out of tolerance. This could lead a merry dance to nowhere. Worth a check. John.
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Old 8th Aug 2017, 6:48 pm   #86
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Default Re: Pye VT2 EHT problems

Hello John,

Hope you are well. The line timebase is working quite normally and locks fine, along with the width/linearity etc. It had the same fault 5 years ago before the blocking oscillator went o/c so I'm not immediately suspecting this although I can't rule it out. The chap who rewound it did a top job and all the turns were counted and resistance readings taken. The connections are all ok. I'm pulling my hair out with this one! As you're not far from me would you be interested in having a look if I bring it to you in a few weeks time?
Matt
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Old 8th Aug 2017, 7:01 pm   #87
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Default Re: Pye VT2 EHT problems

No problem. PM sent. J.
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Old 10th Sep 2017, 8:32 pm   #88
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Default Re: Pye VT2 EHT problems

The final part of the Pye VT2 saga

Well, it's all working, and working well!!

Yesterday myself and the Pye went to visit the legendary John W, and it was a fantastic day all round.

John worked his magic on the frame timebase and after a while a very agreeable test card began to emerge. There was a bit of head scratching, and it led us a merry dance as once the frame oscillator was running at the correct frequency, the sync separator valve ECC81 decided to pack up and all line hold was lost! to cut a long story short the set needed a replacement ECL80. I'd previously fitted a new one which turned out to be duff. John also discovered an iffy valve holder, a resistor which was off at one end, and an o/c cap buried away in the i.f. enclosure. The frame circuit was returned to original spec but the sync pulses were still a bit weak. A resistor was added which gave much better control of the frame hold pot and the picture now locks perfectly with plenty of travel each way.
The EHT was also a bit low at 6kv. I'd fitted a 270pf cap from the anode of the line output valve as the Pye has a tripler fitted. This was reduced to 180pf and lifted the EHT up to just under 9kv. The picture is certainly bright and test card C looks beautifully crisp!!
Today I refitted the chassis on its timber base and put it all back together with the proper screws. It's been playing early carry on films for most of the day entertaining all my house guests (and it hasn't put a foot wrong!)
So I'm very very pleased it's finally up and running. I'm extremely grateful to John for his help and expertise on this one, was a total pleasure spending time with a real master who's probably forgotten more than I'll ever know!

Here's some pics of the finished set. The 2 off screen shots don't do it any justice, I need a decent camera!

Best wishes to all
Matt
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Old 11th Sep 2017, 9:28 am   #89
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Default Re: Pye VT2 EHT problems

We had a great day Matt! Thanks for bringing it over together with the GEC 2147.

I will work my way through the GEC. I woke up at 3am with a cluster of 2147's floating in the bedroom..

The VT2 does work quite well as can be seen by your pics. The trick with taking pictures is to reduce the contrast setting to below that of normal room viewing so that the picture is slightly washed out. Keep the brightness setting as low as possible consistent with a slightly lower than normal display.
The camera will then autoset the exposure more correctly. It helps to have a lamp [60w] aimed at the wall behind the receiver. A little experimentation will perfect the procedure.

The decoupling capacitors in the screened IF unit look exactly like 3000 ohm resistors and are easily overlooked causing a bad IF response.

Tuning the tripler was an easy one and has given remarkably good results. With the faulty overwind previously removed by yourself together with the 90m/a at 6.3v required for the original EY51 EHT rectifier, the remaining section of the LOPT with it's reduced strain should be OK.

Regards, John.
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Old 14th Sep 2017, 6:29 pm   #90
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Default Re: Pye VT2 EHT problems

Good write up. Glad you have got it working. Hopefully soon I will get a suitable specimen to cut my teeth on.

Regards, Robin.
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