UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

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

Reply
 
Thread Tools
Old 6th Mar 2012, 11:39 am   #41
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

Thanks chaps, very much appreciated!

I replaced the tuner valves and a few of the EF80's all to no avail! The HT to the tuner is correct. I don't currently have a signal generator but as I was working my way round I discovered the 'Sensitivity' control was o/c. This is a 3k wirewound pot which I don't have a replacement for.

I have fitted a 1k pot (non wirewound) in its place. There is only 2v on this pot so I'm assuming its not essential that it needs to be wirewound?

Replacing this has got me a picture of sorts. It seems to be running at twice normal speed and the picture rolls quite a bit. I did replace the frame hold control a while ago as the original slider type had rotted away. This now has a 20k wirewound pot fitted. Original was 25k so not far off.

The volume and gain is also very low, and there is also massive sound-on-vision.

Hoping for a bit of advice! is the sensitivity pot value critical? Advancing it increases the volume but causes the picture to 'white out'

Best regards
Matt
Attached Thumbnails
Click image for larger version

Name:	PYE VT2 078.jpg
Views:	255
Size:	64.1 KB
ID:	63512   Click image for larger version

Name:	PYE VT2 075.jpg
Views:	236
Size:	58.8 KB
ID:	63513  

Last edited by matspar; 6th Mar 2012 at 11:51 am.
matspar is offline   Reply With Quote
Old 6th Mar 2012, 3:43 pm   #42
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

I've also just found a 5k pot (non-wirewound) and fitted it - results are much the same but with a bit more 'range' on the control. I've tried a few more sync seperator valves (ECC81's) as well but with no improvements.
Just to summarise!

The line hold appears to lock but the frame hold will not.
Very low volume and low gain, almost inaudible
Poor definition and an amount of sound-on-vision
Picture seems to white out constantly, adjusting brightness and contrast causes the picture to break up and be lost.

The photos show the best screen shots I can get so far, this needed very critical setting of the frame hold and fine tuner adjustment!

If anyone has any ideas on this I'd be more than grateful!!
Matt

Last edited by matspar; 6th Mar 2012 at 3:57 pm.
matspar is offline   Reply With Quote
Old 6th Mar 2012, 6:41 pm   #43
Lloyd 1985
Octode
 
Lloyd 1985's Avatar
 
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 1,175
Default Re: Pye VT2 EHT problems

Hi,
Just a thought, is the tuner set to the same channel as the standards converter? Also you might need an attenuator if using an Aurora, It might be overloading the set with too much signal.

Regards,
lloyd.
Lloyd 1985 is offline   Reply With Quote
Old 6th Mar 2012, 6:49 pm   #44
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 5,742
Default Re: Pye VT2 EHT problems

Hello Matt!
Looks good to me. Is the frame running at the correct frequency or is it lacking in sync i.e does the picture 'hover' around from top to bottom but not actually lock or is the control one ended?
The sensitivity control value is not critical and will cause 'white out' if advanced beyond the correct operating point. These early receivers did not have AGC and the only way of adjusting gain was to vary the bias on the common RF/IF stage by way of a low value pot. Should be easy to locate the fault. If it is the sync separator it is worth looking at R54 390K R55 220k. If you have not done so, replace the sync coupling capacitor, .01uf to pin 7 of the ECC81. Also R43 .01uf and R50 47k to pin 6 ECC81. Other possibilities are incorrect component value or a accidental incorrect connection. Good luck with it.
Heatercathodeshort is offline   Reply With Quote
Old 6th Mar 2012, 7:36 pm   #45
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

Hi Lloyd,

I'm still in the dark ages using a system A modulator and 405 tapes, played through a nice early VHS player. I do want to buy an Aurora this year so I can run my old sets properly.
The tuner is on Channel 1 to match the modulators output, and I normally have a 6db attenuator between the two. Cheers for the suggestion though, much appreciated!

Hi John,

The picture does indeed have the hovering effect, and like you say will not lock fully. Good news about the sensitivity pot I shall leave this alone now. The caps are all new in this area but I'll double check they're all in the right place and then go through those resistors.
Something else I was thinking - could the EHT (now derived from a tripler) upset this part of the set if the volts are too high? When I first got a picture the width and height had crept right in possibly suggesting high EHT. I put a 270pf cap from the PL81 top cap down to deck and the picture now fills the entire screen. Didn't change the appearance of it though!
Thanks again for your time John

Matt
matspar is offline   Reply With Quote
Old 6th Mar 2012, 9:02 pm   #46
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 5,742
Default Re: Pye VT2 EHT problems

The EHT voltage should not effect synchronization. High EHT will reduce picture size, low EHT will increase it. The cap you have fitted tunes the LOPT for a happy balance. [3rd harmonic] The Line sync looks OK and if it is only the frame it must be around the frame interlace circuit. Check the grid leak R49 2.2M and C44 the 12uf H.T. decoupler. [4-15uf will do for test] It's the sort of fault you actually have to 'feel' to get the sense of it. John.
Heatercathodeshort is offline   Reply With Quote
Old 11th Mar 2012, 3:17 pm   #47
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

Finally had the chance for another go on the VT2. I've been through all the resistors and checked the remainder of the valves by substitution. 2 resistors (R54 & 55) were both slightly high so were replaced. Unfortunately as usual there has been no improvements so I've reached a bit of a dead end again!!!

I've got a stressful week looming at work so won't get another opportunity to look at the set for another week, however I shall have a read up on this type of fault in the meantime (it is my weakest area!)

The set has all the symptoms of a very weak signal, ie loss of sync, low volume etc. I've had a Bush TV24 running alongside it to rule out any faults in my modulator etc. I'm suspecting a possible tuner fault, or maybe alignment? The chap who I bought it from informed me that the original owner was something of a tweaker so I can't rule it out!

I won't give up however, and if the offer of help still stands John I will gladly accept in a few weeks maybe? Thankyou to everyone else who has offered me advice on this set.

With best regards
Matt
matspar is offline   Reply With Quote
Old 11th Mar 2012, 5:54 pm   #48
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 5,742
Default Re: Pye VT2 EHT problems

Any time Matt. Just let me know when you want to call over. Regards, John.
Heatercathodeshort is offline   Reply With Quote
Old 11th Mar 2012, 7:25 pm   #49
Kevin19
Tetrode
 
Join Date: May 2009
Location: Cogenhoe, Northamptonshire, UK.
Posts: 88
Default Re: Pye VT2 EHT problems

Hi Matt

your set is starting to really look good re the case great work these set are such lovely mottle Bakelite! Now just a thought and I might be well off the mark here but my problems which were not a lot different to what you have were down to the two diodes in the set being duff! Have you looked at these maybe you have checked these or tried substitutes! My Pye VT2 set had also been very damp stored for years in a leaking old barn I seem to remember some one on one of my post re my set saying these old diodes do deteriorate with age and damp! I changed both I seem to remember one was one at V5 CG12E maybe I'm miles of the mark here and as I say maybe you have looked at these already. Just a thought anyway. Good luck and hope you get it sorted.

Best wishes Kevin.
Kevin19 is offline   Reply With Quote
Old 15th Mar 2012, 7:22 pm   #50
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

Thanks Kevin that very helpful! I shall have a look at both diodes over the weekend, must admit I have overlooked these so there could be a good chance one is duff. I don't think there can be much wrong now, reckon its something really daft which is staring me in the face!
All the best
Matt
matspar is offline   Reply With Quote
Old 18th Mar 2012, 3:27 pm   #51
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

Well, I've finally got round to checking those diodes, and I have made some interesting discoveries.
The meter I use has a built-in diode tester, and I also took resistance readings of each one.

The CG12E reads 200ohms (direction of current flow) and o/c when reversed. Resistance readings are 9k and 1k respectively.

The CG6E is o/c in both directions!! (on both settings)

The WX6 is o/c in both directions (on diode test) and reads around 3meg each way on resistance!!

So I have two very likely culprits, I don't have anything suitable to replace them with, all I currently seem to have is high voltage rectifier diodes.

I've found some data online which suggests a 1N4148 can be used to replace the CG12E and the CG6E, and an OA81 in place of the WX6.
Can anyone confirm this or suggest anything else? any thoughts are much appreciated as always!

Matt
matspar is offline   Reply With Quote
Old 18th Mar 2012, 6:06 pm   #52
Kevin19
Tetrode
 
Join Date: May 2009
Location: Cogenhoe, Northamptonshire, UK.
Posts: 88
Default Re: Pye VT2 EHT problems

Hi Matt.

I think from memory I used 0A90/91 For both in my set! I did use an old
Mullard OA81 to start with as I found one in a box of spares I had I then brought some new OA90/91 and used those and was OK for me.

Best wishes

Kevin
Kevin19 is offline   Reply With Quote
Old 21st Mar 2012, 6:26 pm   #53
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

Thanks Kev,

I have today replaced the three originals - an OA81 in place of the CG6E, and 2x
1N4148's to replace the CG12E and WX6. Had some very good results - the sound output is now excellent, plenty of volume available. The gain is a hell of a lot better and the tuner is now wide awake, nice loud cracks when changing channels and a lot more activity from the fine tuner.

I'm still stuck with the annoying sync problem however. I can now lock the picture much better than before but the picture information is still wrong - has that jumbled up/twice normal speed type fault quite similar to what you encountered! I have replaced the frame hold control with a wirewound pot as the original was knackered.

Think all I can is go through everything in the sync seperator area again, the sync is weak and there is now a bit of line and frame slip.

Thanks again for the diode idea/advice!!

Matt
matspar is offline   Reply With Quote
Old 21st Mar 2012, 6:38 pm   #54
Boom
Nonode
 
Boom's Avatar
 
Join Date: Jan 2007
Location: Westbury, Wiltshire, UK.
Posts: 2,211
Default Re: Pye VT2 EHT problems

It still doesn't look like a sync problem to me. The picture seems locked but at the wrong speed. This would probably put the problem in the frame oscillator stage.
__________________
Dave
--------------
A lovely childhood. Just me, my mother and the voices.....
Boom is offline   Reply With Quote
Old 20th Jul 2017, 8:18 pm   #55
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default The Pye VT2 revisited!

Greetings to all

Hope everyone in the land of old Tv's is well! I've got a new old set to play with which is my bakelite Pye VT2.

I rebuilt this 5 years ago as a total wreck and after a long struggle I got a raster and a picture of sorts on the screen. It had either a sync or a frame fault which beat me at the time and it ended up being packed away in my parents loft and partly forgotten about. Life then got busy with a classic car restoration and a house move and renovation and sadly I didn't go near an old telly for ages. Now I've got more time and space I've decided to have another go and get this beauty up and running.It had a full recap, new diodes in the front end, a few replacement potentiometers, plenty of resistors, a tripler to replace the original LOPT overwind, and some droppers. The crt was very good and I had a nice crisp raster.

After firing it up 5 years on it now unfortunately has a bad case of frame collapse. I tried the easy approach initially and stuck in another ECL80. No joy. Out came the meter and after a bit of time spent it would seem that the frame oscillator transformer is a bit sick. I've got a copy of the original Pye service data which lists it as the 'vertical oscillator transformers' and shows the resistance readings of the windings as 160ohms and 640ohms. The 640ohm winding is showing open circuit.

After searching around in the telly graveyard (parents loft again) I dug out a scrap chassis from a Pye V4 which I broke up years ago in the hope that it contained a suitable donor transformer. It has two similar ones but I think the characteristics are too different to be of any use. One is in the frame stage the other is in the line stage.

A bit stuck now so wondering if any of the masters of our game can give me any thoughts or ideas or happen to have a replacement hidden away?!

Here's some pics. The first is from 5 years ago when I had frame scan, the two others are from today. The offending transformer is shown. Quite a tiny one.

Cheers!
Matt
Attached Thumbnails
Click image for larger version

Name:	PYE 3.jpg
Views:	223
Size:	84.3 KB
ID:	146526   Click image for larger version

Name:	pye.jpg
Views:	204
Size:	48.6 KB
ID:	146527   Click image for larger version

Name:	pye1.jpg
Views:	201
Size:	24.1 KB
ID:	146528  
matspar is offline   Reply With Quote
Old 21st Jul 2017, 6:28 pm   #56
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle on Tyne, Tyne & Wear, UK.
Posts: 4,506
Default Re: The Pye VT2 revisited!

Hi Matt, yes frame blocking osc transformers often give up the ghost due to the fine wire with which they are wound.
The common one is fitted to the Bush TV22 of which I've rewound many, bit I'm not sure if it would work in your Pye. It should be possible to reverse engineer yours.

Ed
Ed_Dinning is offline   Reply With Quote
Old 21st Jul 2017, 9:00 pm   #57
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: The Pye VT2 revisited!

Thanks Ed will let you know if I end up needing your expert help. I've had a couple of other kind offers which I'm following up now. It'll be nice to get back to where I was 5 years ago with this wretched Pye!

Matt
matspar is offline   Reply With Quote
Old 24th Jul 2017, 8:07 pm   #58
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: The Pye VT2 revisited!

The transformer has gone off for a rewind so the VT2 saga is on hold for a short while!

Frame scan should resume in due course and I'll report back when the time comes, and maybe fire off a few questions about the next obstacle no doubt!

Matt
matspar is offline   Reply With Quote
Old 30th Jul 2017, 9:14 pm   #59
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: The Pye VT2 revisited!

Good news. The frame blocking transformer has been expertly rewound by Jerry Walker who did a fantastic job with a fast turnaround. The secondary winding had gone o/c since the chassis was stored away 5 years ago.

It has been reinstated in the set and frame scan has been restored! now just need to get a picture. There is a lack of line and frame hold which is frustrating me.

The frame speed looked like it was too fast and it was giving me a 'twice normal speed' image. I'm in the process of going through all the resistors and found a 47k (V7 anode load resistor) had shot up to over 1m. Replacing this looks like it has cured this as the picture information now looks correct but the frame now rolls. I can slow it down but the pot reaches the end of its track and it won't lock.

The VT2 is quite a fiddle to work on, as the chassis is fixed to a timber base which makes access to anything impossible when assembled. I've removed the base and strapped the chassis to the cabinet support bars using cable ties. Has worked a treat but just means I have to work on it upside down.

Here's a few pics of my progress. These were taken before I found that bad resistor and the image has since improved (a bit)
This is supposed to be test card c!

Matt
Attached Thumbnails
Click image for larger version

Name:	DSCF4130.jpg
Views:	146
Size:	67.2 KB
ID:	147104   Click image for larger version

Name:	DSCF4131.jpg
Views:	151
Size:	65.9 KB
ID:	147105   Click image for larger version

Name:	DSCF4133.jpg
Views:	132
Size:	82.9 KB
ID:	147106  

Last edited by matspar; 30th Jul 2017 at 9:20 pm.
matspar is offline   Reply With Quote
Old 4th Aug 2017, 4:51 pm   #60
matspar
Pentode
 
matspar's Avatar
 
Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 111
Default Re: Pye VT2 EHT problems

I've spent most of today working on the Pye and its beaten me yet again.

Thought I'd solved it as I discovered a 2.2k resistor which should be a 2.2m. (R27 on trader sheet) I'd replaced this in the past and must have read the value wrong. Replacing this with the correct 2.2m has locked the frame scan but the picture information is all wrong again. Here's a pic to give you an idea - I'm getting a double image vertically and loads of flyback lines so am I right in thinking the frame frequency is wrong?
The line hold appears to be locked ok. I have been through all the resistors, all the caps are new and I've ran out of things to try. Can anyone advise me please? what area do I need to concentrate on.
Would the fault be in the frame output or the sync separator? I am totally stuck with this set!!!!

Matt
Attached Thumbnails
Click image for larger version

Name:	DSCF4154.jpg
Views:	83
Size:	71.0 KB
ID:	147374   Click image for larger version

Name:	DSCF4155.jpg
Views:	75
Size:	76.6 KB
ID:	147375  
matspar is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 10:51 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright ©2002 - 2017, Paul Stenning.