|
Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
|
Thread Tools |
29th Apr 2022, 12:51 pm | #21 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: Pye VT4.
You should be able to fit the V14 transformer with a little experimentation. The separate winding on the V4 transformer is for supplying line pulses for the flywheel sync and APC circuits.
I would connect it up in the V4 comparing connections with the V14 circuit with reference to scan coils etc. Test it to make sure you can obtain a reasonable line scan. An actual picture will be very difficult to obtain without the sync and APC pulses! If all looks promising I would wind a number of turns using VERY thin insulated wire around one limb of the LOPT Ferrite core making sure it does not come into contact with the EHT overwind. Wind on as many turns as can be accommodated neatly and test. Experiment with say 20 turns. You may have to reverse the connections to get the phase correct. A bit of a fiddle but if it works you will be very pleased with yourself! Hope this may help. Just checked the resistance of that sync winding. It is only .2ohm. It will probably only need maybe ten turns. Experiment! John. |
2nd May 2022, 5:40 pm | #22 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
|
Re: Pye VT4.
Both my V4 and VT4 have totally wrong LOPTs, one thing you may need to do is to rewire the line scan coils from series connected to parallel if you have lack of width. Youll only need around 5 turns of single core wire around the LOPT core for the flywheel sync feedback if you get no line lock or odd contrast control behaviour reverse the connections
Neither of my Frankenstein LOPT mods require the width or linearity coils. One is a Thorn 950 and the other one I don't know what it's from, the Thorn has a feedback winding fortunately. Cracking results on both.
__________________
Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member |
3rd May 2022, 12:33 am | #23 | |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Quote:
|
|
3rd May 2022, 1:05 am | #24 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Continuing on from my last post,as i said the test was a waste of time.Ah well put things back to normal on the v4 and check this is ok.The result is for some reason the V4 which was working perfectly before now does not!.At this juncture there was a lot of swearing as you can imagine.The situation at present is now low eht,no boost voltage no scan! I can only think i must have upset something in d/conn the scan coils and r/conn them.have checked these conns but can't find what is wrong,if only i hadn't done this!!I dont get what has gone wrong,the v4 chassis wasn't powered at all i was just borrowing the scan coils tube to test the vt4 . Graham.
|
3rd May 2022, 6:10 am | #25 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Hi,this is the scan i get on the v4 set that i messed up by borrowing the scan coils to test the vt4.not a good photo i haven't got a decent camera at the moment but it might give someone a clue as to what went wrong. Graham.
|
3rd May 2022, 8:10 am | #26 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: Pye VT4.
That is a crazy scan! Recheck your connections. I presume you did not disturb the scan coils themselves and simply swapped over the connecting wires on the tag strip? They become extremely delicate and prone to breakdown if disturbed shorting the line to the frame coils. The early coils were insulated with Cellophane that turns to brown dust with heat. The later coils are insulated with polythene.
Also check the screened lead to the scan coil tag strip. It can and often did become leaky or short. John. |
4th May 2022, 2:27 am | #27 | |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Quote:
|
|
4th May 2022, 2:52 am | #28 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
It was when i put the V4 back to normal that i found this was now no longer working.To say i am annoyed about this is a bit of an understatement.I now have the V4 using the small crt and that is what the crazy scan is shown on.I have used this in other tv's i have restored,it enables me to have the actual crt from the set out of the way while working on the chassis.There was a small crt made in the 1950s for this purpose i missed one on the well known auction site a few years ago.At the moment i have the crazy scan,low eht, no boost volts and i have used vocabulary that i couldn't repeat on here. Graham.
|
4th May 2022, 8:32 am | #29 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
|
Re: Pye VT4.
Perhaps try disconnecting either the frame or the line coils and get a horizontal or vertical line. Then with the coils oriented correctly reconnect the other scan. It might then become more understandable.
Peter |
4th May 2022, 8:49 am | #30 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: Pye VT4.
All part of servicing and restoring old TV receivers. Try doing it for the public for 40 odd years!
You did not mention if you disturbed the scan coils? What usually happens is the frame coils short to the line due to poor insulation. It looks like burnt sweet wrappers. It only requires removal of the coils from the neck to cause the breakdown. Dismantling the coils reveals quite a mess and I have never been able to repair them. I have encountered this many times. The same fault occurred on the slightly earlier FV2/4 series. I hope you discover another cause of the weird scan, you never know. John. |
5th May 2022, 1:20 am | #31 | |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Quote:
|
|
5th May 2022, 2:12 am | #32 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
I then thought I would eliminate the scan coils and tube by using the small CRT mentioned previously, this is what I did when I restored this set a number of years ago only connecting to the tube and scan coils once I got the set working well. The weird scan is still there so it must be something in the set which I have upset. One clue is that I did this test before, borrowing the scan coils etc and put it back to normal and checked the V4, it was OK apart from a few seconds after the warm up it made a high pitched noise only for a few seconds and then worked as normal, had it on for a while showing testcard c from the aurora and all seemed well. Just wish I hadn't repeated it. Graham.
|
5th May 2022, 9:07 am | #33 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: Pye VT4.
My thoughts are still with the scan coils.
The noise may have been the start of a short. If you have definitely got the connections correct I can't think what else would cause a distorted scan such as can be seen in your picture. This picture shows encircled the breakdown point of a V4 line coil insulated from the frame coils be cellophane that has become crisp, darkened and eventually broken down. Sorry to be such a bearer of bad news but later Pye scan coils can be modified to work but it needs a lot of patience to sort out connections, resistance and series parallel arrangements. If you do find a similar pair make sure they are insulated with flexible Polythene sheet. Failing this they will be a waste of time. When I was a young lad in the trade I used to talk to older engineers that had worked on all these old models. They used to say that if a V4 required a replacement tube they would warn the customer that the scan coils would likely fail soon after. They cost 35/- [£1.75] in 1964 and had to be costed in to the job. I hope you find something such as a broken wire, only hope. John. |
5th May 2022, 10:14 pm | #34 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
|
Re: Pye VT4.
Hi.
I know the V4 was prone to this on the earlier versions but I'm sure the VT4 was OK as they had the polythene insulators. There is a possibility I might have a good set of coils in the loft somewhere. I'll get a look over the weekend.
__________________
Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member |
6th May 2022, 1:28 am | #35 | |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Quote:
|
|
6th May 2022, 8:17 am | #36 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,145
|
Re: Pye VT4.
That would explain a lot. The GEC scan coils are probably a bad match for the V4. Do you know which model they came from and do the resistance of the windings match the V4 coils, within reason that is? The scan appears to show the line and frame coils connected together. I must admit I thought you were using Pye coils. John.
|
8th May 2022, 2:44 am | #37 | |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Quote:
|
|
23rd May 2022, 12:49 am | #38 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Hi, I have added a winding of 25 turns to the LOPT for the flywheel sync, I used 30SWG ECW .Not very good so tried reversing conns, it seemed to work better one way but could not get it to lock. Now thinking do I need more turns? Also does the gauge/type of wire matter? I have some thin insulated wire from Maplin but this is stranded not solid core, does it have to be solid core?
Graham. |
23rd May 2022, 2:21 pm | #39 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Hi, I tried 30 turns of the thin insulated wire from Maplin with the same results. I then thought to check the EF80 sync sep valve. On looking at this I discovered that it was an ECL80! and the EF80 was in the sound output stage. I must have mixed them up at some stage, swapped them over and it works .I then tried reducing the turns to 20 thinking 30 might be excessive. This still works OK but one side of the t/card circle is irregular and one side OK. I didn't see this with the 30 turns so might have to try adding them again? I felt a twit mixing the bottles up, the sound was still there but low volume and I thought I had just turned it down.
Graham. |
10th Jun 2022, 2:26 am | #40 |
Hexode
Join Date: Oct 2017
Location: Manchester, UK.
Posts: 361
|
Re: Pye VT4.
Hi all,have tried fitting the v14c lopt without success,eht is there and boost voltage but i cannot get any width.Although the lopt is for a V14c it differs as regards conns.The conns for line out valve and boost diode are the same but there is something different with the rest,i cannot find any circuit mods but have seen two chassis views of two different v14s one with same conns as mine and one with the different ones but cant tell from these the conns,it just shows that there are difference in the no of tags on the paxolin panel.I have decided to have a rest from this for now hoping that another transformer will turn up. Graham.
|