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 Apr 2019, 8:38 am   #41
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

Well disconnecting the other taps should make no difference. The TC via 47 ohms is disconnected as well as the feed from the horizontal linearity pin 6. so the EHT winding is disconnected. It was drawing 65mA at 30V all the power is going into the EHT winding. Last night I added an extra 12V it is now 42V at 85mA. I can just detect that it is slightly warm. Later I will completely remove the LOpT and try again. I would be amazed if the other connections were acting as a heat shunt!
Another thought is because it is in situ maybe the core which is connected to the chassis is keeping the windings cool?
Davewantsone is offline   Reply With Quote
Old 7th Apr 2019, 10:31 am   #42
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,678
Default Re: Pye V4

This should not be the case and it will not be necessary to remove or disconnect the LOPT.
The overwind may well be wound with Eureka resistance wire and will simply need a much higher voltage to warm it up.

I had a similar experience recently [Ferguson 984T] and ended up running it from the mains via a lamp limiter, meter and variac. It worked after two days. John.
Heatercathodeshort is offline   Reply With Quote
Old 7th Apr 2019, 1:13 pm   #43
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

I have now got it on 60V and it is drawing 110mA so almost 7W of heat. It feels slightly lukewarm. I did say earlier I think 10W of power will be needed to get it nice and warm. Like you said it does not have to be D.C.. maybe a pygmi bulb and a variac will put enough power in the windings to warm them up!
Davewantsone is offline   Reply With Quote
Old 7th Apr 2019, 2:17 pm   #44
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,316
Default Re: Pye V4

I agree that you can't go by the cold resistance reading of the winding and it should only be used as a 'clue' as to what might be expected. Feeding the transformer with DC won't have any effect on other circuitry connected to the primary, as it won't be acting as a 'transformer, so no need to disconnect it. Feeding it with AC will result in a voltage being produced at the primary, whether this voltage will matter will depend on examination of the surrounding circuitry to see what may or may not happen.

I guess you're using a meter in-line to measure the 'actual' current and not just relying on unreliable calculations that in reality are likely to be miles out?

If you leave a meter in-line, then ideally it wants to be an AVO type, and if left for long periods, the meter should be switched to the next higher amp range, as leaving it reading at a high scale reading on one current range for long periods will likely fry the shunt for that range. You can take the meter out of circuit once you've set the current, but take into account that without the added series resistance of the meter being in-line, that the actual current will rise by an amount that you'll need to allow for.
Techman is offline   Reply With Quote
Old 8th Apr 2019, 8:54 pm   #45
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

The only calculation was the initial which gave for a 455 ohm winding and a voltage of 30V was a current of 65mA, which was confirmed by the power supply output which measures output current and has a set current limit. This read 65mA. From the size of the winding I could tell 2 watts of power would not be enough to warm the LOpT. For the last 24 hours I have been applying 70V via a "Heath Robinson" collection of various power supplies and the current is now around 120mA. Which would mean the winding resistance due to it being warm has risen to around 580 ohms.The LOpT is now getting nearly 8 watts of power and is nicely warm to the touch. I will leave it for another 2 days and then report back on any progress.
Davewantsone is offline   Reply With Quote
Old 11th Apr 2019, 3:49 pm   #46
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

As promised feedback on my V4. For the past 3 days I have been giving the EHT winding 7 watts of power.
Time to power up again. To be honest not much difference. The width was probably slightly more but still around 3/4 inch narrow at both sides.
I then thought what about the scan coils?
What had happened is when I tried the chassis I had been given the scan coils were attached, so rather than unsolder the scan coils I removed mine and put the replacement ones on.
Now due to all the messing about and difficulty setting the coils up when I put my chassis back in I unsoldered the 5 cables going to the scan coils and resoldered my chassis cables to them. I knew my scan coils were good but I was not sure of the others. Anyway off came the replacement coils and back on went mine.
I was rewarded with a picture with the width about one inch too wide on either side! By moving the width control to half way the width was brought into satisfactory display.
Please find pictures below of results now obtained with a picture of T May to prove it is today! Also a photo of the duff scan coils!
Thanks for everyones help.
Attached Thumbnails
Click image for larger version

Name:	11APRa.jpg
Views:	141
Size:	72.9 KB
ID:	181225   Click image for larger version

Name:	11APRb.jpg
Views:	136
Size:	66.5 KB
ID:	181226   Click image for larger version

Name:	11APRc.jpg
Views:	140
Size:	118.0 KB
ID:	181227  
Davewantsone is offline   Reply With Quote
Old 11th Apr 2019, 6:57 pm   #47
Vintage Engr
Pentode
 
Join Date: Jan 2008
Location: Shrewsbury, Shropshire, UK.
Posts: 184
Default Re: Pye V4

I've just purchased a VT4 today, so everyone's hints & tips are most useful.The one I have looks as if it has had no previous repairs. The chassis has never been out, no rust, just a very thick 'carpet' of fluff.

I used to repair quite a few of these in the early '60's, but it's a long while ago now, so hearing from others in respect of possible problems is very useful.

I have recently had a couple of Philips 17TG100U LOPT's fail for similar reasons, i.e hygroscopic windings, so I shall be especially careful, as I need to get these two re-wound.

David.
Vintage Engr is offline   Reply With Quote
Old 11th Apr 2019, 6:59 pm   #48
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,316
Default Re: Pye V4

Excellent news! Very pleased for you.

It could be that both the transformer and the scan coils had dampness in them.

I think the lesson to be learned and the rule of thumb for anyone reading this, is to assume that ALL line transformers will be wet from standing, regardless of where they come from or what anyone tells you regarding their working state. As I said before, if an old TV has been in a dry loft and is retrieved at the latter end of a long hot summer, then having been in a baking hot loft for a few months you 'may' get away with not having to dry out the tranny. All other cases, other than those sets that have been stored in a warm room in a house for the years that they've been out of use, assume a wet LOPT and dry it out before a normally irreplaceable item is ruined. You were VERY lucky to get that transformer and I bet there are quite a few people who'd have loved to have been offered that tranny for their sets. As you've realised by now, the original one would have been OK if you'd dried it out in the first place. It's a shame no one mentioned it right at the start of the thread, but I think you had already got stuck into it at that stage and I suspect that most of us assume it's common knowledge, as the subject of drying out line transformers has been done to death, both on here and other forums.

Once again, well done and pleased to see it working - looking good!
Techman is offline   Reply With Quote
Old 11th Apr 2019, 7:15 pm   #49
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

Thanks for that. The original transformer fault was caused by a short circuit in the horizontal width coil. The insulation had deteriorated and two pins had gone s/c which saw off the line output transformer line scan winding.
Davewantsone is offline   Reply With Quote
Old 11th Apr 2019, 8:03 pm   #50
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

Quote:
Originally Posted by Vintage Engr View Post
I've just purchased a VT4 today, so everyone's hints & tips are most useful.The one I have looks as if it has had no previous repairs. The chassis has never been out, no rust, just a very thick 'carpet' of fluff.

I used to repair quite a few of these in the early '60's, but it's a long while ago now, so hearing from others in respect of possible problems is very useful.

I have recently had a couple of Philips 17TG100U LOPT's fail for similar reasons, i.e hygroscopic windings, so I shall be especially careful, as I need to get these two re-wound.

David.
I hope you will be successful.
The way I got mine going was to first of all replace every 3nF capacitors (most will be U/S) then the 0.001, 0.01 and 0.1uF capacitors.
Replace the v24 and v25 diodes with 1N414 diodes.
Check R126, R127 and R129 for correct values
Whilst doing this you may want to first remove the LOpT and connect to a DC power supplyand pump some power into the windings for at least 3 days.
If you could I would "ring" the transformer to see if it appears OK.
I would then reconnect the LOpT.
Remove fuse F3 and using a variac connect power to the set and slowly run it up to the mains potential and see if you get all the valves to light then maybe sound (with a suitable modulator on correct channel).
Now check pin 2 on PL81 and see if you get a negative voltage of around -27V.
Switch off then connect a ammeter across fuse F3. Turn variac up again and monitor current it should not exceed 150mA.
If you are lucky you may see EY51 light up and get some sort of picture!
Good luck.
Davewantsone is offline   Reply With Quote
Old 11th Apr 2019, 8:27 pm   #51
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 5,452
Default Re: Pye V4

Hi Dave, if it is the width winding that is damaged you may just be lucky and the LOPT can be rewound as it is on the lower voltage side of the transformer.
The EHT overwind is very difficult to rewind.

Ed
Ed_Dinning is online now   Reply With Quote
Old 11th Apr 2019, 8:30 pm   #52
Techman
Nonode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 2,316
Default Re: Pye V4

I was thinking that. If it really is just that winding you mentioned, then it's as Ed has said. However, I'm not hundred per cent convinced that a damp overwind didn't cause its demise. Worth looking into though.
Techman is offline   Reply With Quote
Old 11th Apr 2019, 8:41 pm   #53
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

Quote:
Originally Posted by Ed_Dinning View Post
Hi Dave, if it is the width winding that is damaged you may just be lucky and the LOPT can be rewound as it is on the lower voltage side of the transformer.
Yes the total resistance is only 12 ohms. It should be around 17 ohms.
The winding has two taps. so we have say pins 123and 4. The resistance to pins 1 and 2 is correct at 2 ohms and 3 and 4 is 2 ohms which is correct its the connection between 2 and 3 only 8 ohms should be around 13 ohms. so it looks like some windings are S/C.
Davewantsone is offline   Reply With Quote
Old 12th Apr 2019, 8:17 pm   #54
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 5,452
Default Re: Pye V4

Hi Dave, probably cooked and some turns are s/c.
A careful dismantling and strip down of the primary (after careful removal of the EHT overwind) should reveal this.

Ed
Ed_Dinning is online now   Reply With Quote
Old 12th Apr 2019, 8:28 pm   #55
Davewantsone
Pentode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 177
Default Re: Pye V4

Thanks for the info. If I get another Pye V4 or VT4. I may see about sorting this faulty LOpT out.
All that black tar stuff would need to be removed. Yuk!
Davewantsone is offline   Reply With Quote
Old 15th Apr 2019, 6:42 pm   #56
Vintage Engr
Pentode
 
Join Date: Jan 2008
Location: Shrewsbury, Shropshire, UK.
Posts: 184
Default Re: Pye V4

Quote:
Originally Posted by Davewantsone View Post
Quote:
Originally Posted by Vintage Engr View Post
I've just purchased a VT4 today, so everyone's hints & tips are most useful.The one I have looks as if it has had no previous repairs. The chassis has never been out, no rust, just a very thick 'carpet' of fluff.

I used to repair quite a few of these in the early '60's, but it's a long while ago now, so hearing from others in respect of possible problems is very useful.

I have recently had a couple of Philips 17TG100U LOPT's fail for similar reasons, i.e hygroscopic windings, so I shall be especially careful, as I need to get these two re-wound.

David.
I hope you will be successful.
The way I got mine going was to first of all replace every 3nF capacitors (most will be U/S) then the 0.001, 0.01 and 0.1uF capacitors.
Replace the v24 and v25 diodes with 1N414 diodes.
Check R126, R127 and R129 for correct values
Whilst doing this you may want to first remove the LOpT and connect to a DC power supplyand pump some power into the windings for at least 3 days.
If you could I would "ring" the transformer to see if it appears OK.
I would then reconnect the LOpT.
Remove fuse F3 and using a variac connect power to the set and slowly run it up to the mains potential and see if you get all the valves to light then maybe sound (with a suitable modulator on correct channel).
Now check pin 2 on PL81 and see if you get a negative voltage of around -27V.
Switch off then connect a ammeter across fuse F3. Turn variac up again and monitor current it should not exceed 150mA.
If you are lucky you may see EY51 light up and get some sort of picture!
Good luck.
Thanks for all the useful info, of course when I used to repair these in the early '60s they were not so old. However, one of the biggest problems with LOPT's & EHT circuitry, was the thick black sooty deposits from the smoke drawn in from coal fires. This was attracted by the High voltages & deposited just where one didn't want it.

It was the end of many Ekco LOPT's, both the cardboard & later plastic varieties.
I have actually seen a CRT that, due to this tarry deposit on the flare, arced over sufficiently to destroy the CRT! There was a groove melted into the flare, where the arc had progressed from the final anode connector, to the aquadag coating.

I shall take great care before applying any power. I nearly didn't get to purchase this TV, which came from a local junk-shop. The proprietor was most insistent that he wanted to plug it in & 'Test it" before selling it...

What did he think he would receive, even if it 'fired up'? (No pun intended).
Needless to say I put him right concerning both the safety & the possibility of destroying what could be a perfect working example, given the right expertise & TLC.

David.
Vintage Engr is offline   Reply With Quote
Old 16th Apr 2019, 8:24 am   #57
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,678
Default Re: Pye V4

Thick nicotine treacle like deposits were a very common cause of destroyed vacuum in CRTs especially the Thorn models such as the 3000/8500 that had the tube mounted upside down. The classic tracking line that Dave mentions from the EHT connector to the dag was always a bad sign. John.
Heatercathodeshort is offline   Reply With Quote
Old 16th Apr 2019, 9:34 am   #58
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 6,687
Default Re: Pye V4

I remember that, it used to cut through the glass.
__________________
G8JET BVWS Member and V.M.A.R.S
HamishBoxer is online now   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 8:45 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 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.