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 24th Sep 2020, 11:55 am   #21
G6ONEDave
Hexode
 
Join Date: Dec 2019
Location: Owston Ferry, North Lincolnshire, UK.
Posts: 350
Default Re: My first foray into Old model TV repairs.

I can either send you a scan of the schedule A + B service manual or send an original one via post, if that helps. There are also some service bulletins for this set. The manual covers models 990T, 991T, 993T, 995T and 997T.
Dave
G6ONEDave is offline   Reply With Quote
Old 24th Sep 2020, 1:36 pm   #22
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Dave I would be very pleased to have the scans of the service manual, I will pm you my email address. Thank you.

I have attached a picture from the underside of the frame with the screen removed, it seems to match the trader sheet.

Click image for larger version

Name:	myferg10.jpg
Views:	100
Size:	82.9 KB
ID:	216322

I have also measured the resistances of the windings. I have removed the Width link so that it isolates the scan coils on the tube and between the Max width point C and the Anode of the PL81 there is 27 Ohms, 25 Ohms to the Min width setting.

If I measure between the Anode of the PL81 to the Anode of the EY51 gives me 12.3K Ohm. So going off Graham's previous post on resistances it would seem to be duff. If anyone has access to a 991T and could take similar measurements it would be appreciated.

Looking at the data sheet for the CRT the max lg3 current is in the order of 0.5 mA so the winding is only carrying a low average current and wonder if this 12K is OK?

The TV is no inside the house where I have the opportunity to take resistance readings of various parts. I have used some plastic sheet to protect the CRT next from the Ion trap magnet.

It will be a while before any form of mains is applied I would think. I have no mains variac so may need to use the series light build method of limiting things. Need a few valves first.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 24th Sep 2020, 3:43 pm   #23
rambo1152
Nonode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 2,169
Default Re: My first foray into Old model TV repairs.

Quote:
Originally Posted by AdrianH View Post


If I measure between the Anode of the PL81 to the Anode of the EY51 gives me 12.3K Ohm.
I thought that looked bad then I RTFM

The figure is on the trader sheet just above the circuit
Transformers T1 f-g 15,000.0 (Ohms)

I'm almost as relieved as you must be

40v would drive 25 - 30mA taking in your measurement and the trader sheet's figure
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 24th Sep 2020, 4:45 pm   #24
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 7,612
Default Re: My first foray into Old model TV repairs.

just a warning about the tuning control. It consists of a common plate moved by the tuning control sliding three iron dust cores into the aerial input, bandpass and oscillator coils.
Now here is where the problem lies. The iron dust cores rust and get stuck in the Paxolin coil formers. If you move the tuner setting the cores being stuck break up from their brass threaded adjusters leaving the cores stuck in the formers.
It is a fiddle to repair and I have done quite a number the first being a Ferguson 998T in an article I uploaded to the Forum many years ago.
It is a lot easier if you can obtain some similar adjusters from a scrap push button radio.
It might be possible to glue the bits back together but it might be an effort too far!
Check which channel the tuner is set to. It is marked on a little vertical scale just under the tuning knob/wheel. It would be easier to set you signal source to that channel rather than risk the damage mentioned.
Get the power supply and line output stages working first. The line oscillator is complicated. There are two .01uf capacitors inside the discriminator transformer and the oscillator will not run if these are faulty and they usually are! They look like resistors with the same colour band markings and usually go O/C . This all sounds a bit of a journey but if you tackle it in the right order and find the strength to prevent yourself from carrying out a damaging chassis clean [half inch paint brush and vacuum cleaner only] you may be surprised at what you can achieve. Take plenty of notes and pictures. Good luck with it.
PS. You have the octal plug fitted for a Type A Band 3 tuner therefore it must be a final production run. John.
Heatercathodeshort is offline   Reply With Quote
Old 24th Sep 2020, 5:23 pm   #25
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Thanks for that Graham, Why I did not see the resistance values I do not know? A case of RTFM at this end.

I have basically just been spending time looking things over, checking a few resistances, the mains switch was bad, but has cleaned up with some solvent and contact cleaner, went from 90 Ohms to 0, so that is good.

I cut out the 0.1uF cap across the mains it was in an horrible state, looks like the wax coating had all soaked off the thing and solidified over the chassis and the bottom of the cap. So a couple of Panasonic X2 rated ones will bought for this.

I just placed two PY82 valves in the PL81 and PY81 valve positions to check out the heater continuity and all seems to be fine, the christmas tree dropper is giving me the correct values.

OK John on the tuning control, it is free to turn OK from 1 to 5 so that looks OK the ferrite formers are moving freely.

I did get confused over the fact the V2b cathode has a TV co-axial socket connected to it, but assume that would be from a tuner IF output.

I have an idea. I am still getting hold of the PL81 PY81 valves for the OPT stage so they will be several days to arrive. From what I have read many will bring up the sets on a variac leaving them at low settings for some hours to give capacitors chance to reform, before stepping up a bit etc.

So I was thinking of using one of my 12 Volt Buck power supplies and sticking it across the HT line and starting off at 50 Volts taking it slowly up over hours to 200 Volts. As the heaters are not on and I am missing the LOPT valves there should be no appreciable current draw, but it may give me a chance to check a bit more out before I finally start applying mains power.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 24th Sep 2020, 7:19 pm   #26
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 7,612
Default Re: My first foray into Old model TV repairs.

The co-ax socket is for the type A tuner. It has an octal plug and the I.F. output co-ax plug. Very simple to install. You just cut the heater link on the chassis and plug it in! These models usually have a Bakelite blanking plate on the side of the cabinet.
just make sure it is the actual cores that are moving and not just the brass bits! It can be very baffling when you first encounter this.
The 991T also sports push pull sound using a pair of ECL80s. Top receiver of it's day. John.
Heatercathodeshort is offline   Reply With Quote
Old 24th Sep 2020, 8:13 pm   #27
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 7,612
Default Re: My first foray into Old model TV repairs.

Don't worry too much about LOPT resistance readings. The manufacturers changed the spec of their transformers during production. It's not uncommon to discover transformers that read around 10k on the overwind but state maybe 500 ohms in the manual.
Eureka resistance wire was often used to reduce capacity and 'ringing'.
It's not so easy to get a connection on the EY51 anode. It sits in it's own Bakelite coffin complete with lid and the LOPT has to be removed to get to it! J.
Heatercathodeshort is offline   Reply With Quote
Old 26th Sep 2020, 1:34 pm   #28
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Well I have three valves turn up today PL81, PY801 (I hope this will work instead of the PY81) and an EY51. I am still in the rocess of building up the HT only volts on the sets without all the valves in place using a buck converter, this is just me trying to ensure that the two main Electrolitics do not go bang when I connect to mains.

I went through the circuits and service sheets several times (Thanks very much to G6ONEDAVE). and worked out what the DC resistance should be without heaters lit, and worked it out to be 15.19K Ohm with the SCH D build of the TV.

So I started with 50 Volts, which should give me 3.3 mA draw, the best it would go down to was 4.4 mA. I then started to slowly work my way up in voltage steps to be at 200 Volts as I am today, if all goes well I shall take it to 250 Volts tomorrow and also apply some low DC through the LOPT now the set has been inside for a few days.

I am struggling to find a two hole mains plug to use for the back of the set, if anyone knows the correct term to use in search that would be nice. What I did notice reading the service sheets was they went from the big pin being live to being chassis part way through production, bet that was fun.

Still trying to generate a 405 Line Video signal, I have ordered a HH2, but still hope to generate something from the PC at some point.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 27th Sep 2020, 4:51 pm   #29
petertheorgan
Hexode
 
petertheorgan's Avatar
 
Join Date: Dec 2006
Location: Bromley, Kent, UK.
Posts: 308
Default Re: My first foray into Old model TV repairs.

Hi There,
the correct connector for the mains lead has been unavailable for years but the option that I use is to take one of the brass sockets out of a 2 amp female socket and use it to replace one of the sockets in a 5 amp female connector ( you may have to fatten it out with a bit of heat shrink to make it sit firmly in the plastic socket , I have a couple in the junk box , pvt me your address and I will stick the brass bit in the post
Peter
petertheorgan is offline   Reply With Quote
Old 27th Sep 2020, 8:19 pm   #30
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Thanks for the offer Peter, hang on for a while, I need to figure if I can get the set working and then take it from there. I also do not have any 5 or 2 amp free sockets so would probably be better seeing what modern day connectors I can change the two pins for. They would probably have been found if we still had the meetings happening.

I have the TV at 250 Volts from the buck converter now, the leaking current is starting to get down to numbers I would be happy plugging the unit in and the main smoothing caps then going bang. So tomorrow I wil have some current going through the LOPT to ensure it is dry althoiugh being inside in the house now for a few days should help.

I have ordered a HH2 which should be with me possibly towards the end of the coming week, but I have also found a way to generate 405 lines with software using my Hackrf-one being displayed OK on my Sony 9-90UB. I still wish to find a way of generating signals from my PC video card although this seems to be highly dependent on the cards in the PC, no success to date.

So this coming week when the wife is at work I shall play more.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 28th Sep 2020, 3:31 pm   #31
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

OK to day has been a bit more prep work such as re glueing the CRT base back on the next,. Managed to remove the base completely clean out the old adhesive and use rapid epoxy to glue it back on and finally re-solder the wires.

Last check of the underside of the unit and found two Hunts caps that had cracks in the plastic so replaced them.
Click image for larger version

Name:	myferg11.jpg
Views:	39
Size:	30.5 KB
ID:	216579

Finally put the PL81 and PY801 in the sockets and power the unit up! No bangs or clouds of smoke but not really any life either, the HT is getting up to around 185 Volts, I am hearing what could be some frame osc and something that sounds like it is gasping for air and then the HT drops to 150 Volts at this stage the set is unplugged. I have no speaker plugged in as I was hoping to hear the time base, but nothing. So I will connect a speaker to the unit and see if the audio stage is making any noise, then I will try the two caps as mentioned in the the horizontal time base. If I have it correct these would be C61 and C63 in the service manual or C35 and C36 on the trader sheet.

I believe this will necessitate complete removal of the coil pack and can L25/26/27 (trader sheet).

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 28th Sep 2020, 4:42 pm   #32
rambo1152
Nonode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 2,169
Default Re: My first foray into Old model TV repairs.

Quote:
Originally Posted by AdrianH View Post
I still wish to find a way of generating signals from my PC video card although this seems to be highly dependent on the cards in the PC, no success to date.

Adrian
HackRF, PC, and HH, you are certainly "hedging" your bets

If your PC has a PCIe slot you just need an old ATi Radeon HD2400XT card which will cost you about 6

These cards have the unusual DMS-59 connector, so you also need a DMS-59 to 2X VGA splitter cable which will cost you an extra 4 or so if not included with the card.
__________________
--
Graham.
G3ZVT
rambo1152 is offline   Reply With Quote
Old 28th Sep 2020, 7:37 pm   #33
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,226
Default Re: My first foray into Old model TV repairs.

Hi Adrian, do not run with the speaker disconnected as you can damage the opt. Use a 3R resistor instead.

Ed
Ed_Dinning is offline   Reply With Quote
Old 28th Sep 2020, 7:39 pm   #34
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Well replacement of the two caps made no difference, there nothing else for it but to get the meter out and start probing for voltages. I do not have a suitable isolation transformer yet to allow for use of my scope.

The set does tune, if I stick a wire into the antenna socket and tune through I can pick up recovered audio through the speaker together with mains hum. So that is one good thing.

Thinking head on.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 28th Sep 2020, 7:40 pm   #35
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

OK Ed I have a 4 Ohm resistor I will stick that on.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 28th Sep 2020, 10:45 pm   #36
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Had enough for tonight, I was measuring around the valves before the line driver stage V10 and V11 (trader sheet) and caught one of the hunts capacitors which then shed half the plastic coating.

So replaced the brown Hunts tabular capacitors, a couple of 0.01 and 0.001 values, not that I think it made any difference, but I have a batch at 400 Volt working. I can draw a very week spark from the anode cap of the PL81, but no signs of any final HT either with or without being connected to the CRT.

Tomorrow I will remove one side of the line scan coils from the LOPT, I believe I can do this by removing a wire from either side of the Line Linearity coil. That seems to the easiest way, not sure what it proves though apart from the scan coils are not dead short. It appears the PL81 is not drawing a lot of current as there is no red glowing anode but have not measured current.

I will also check out the 500pF cap across the LOPT, but being Silver mica I would not really suspect that.

I could try a few EF80 Valves in the driver stage, I have some pulls may even have a boxed one, but even with a low emission driver I would have expected a better spark.

I suspect reading some of this you now realise TV are something I have no knowledge of at all and I am fumbling around somewhat. But it is one way to learn.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 28th Sep 2020, 11:39 pm   #37
Oliver35
Pentode
 
Oliver35's Avatar
 
Join Date: Apr 2016
Location: Halesworth, Suffolk, UK.
Posts: 185
Default Re: My first foray into Old model TV repairs.

I’m certainly no expert on TVs, I’ve only restored the one- a Ferguson 988T, a little older than yours. It certainly is a way to learn, and a very satisfying one- eventually!
If I were you, I’d try and focus on one area at a time. If you’ve got a spark at the o/p valve cap, there’s something going on, but having just read through the thread again, it looks like you’ve still got a problem with low HT? If that’s still the case, I’d take a good square look at that problem on its own first, as that will have an effect on the performance of the other stages. It must be being dragged down by something.
Possibly a stupid question on my part, but you mention using a ‘buck converter’ to power the set- what sort of unit is that? Could it be that it lacks sufficient power to drive the set, and is itself being dragged down by the load?

If you need any B9G valves, I have a few old TV valves here which I don’t really use, just spares for the Fergie. Some are pulls and some are NOS, I can have a look if you’re missing anything.

Oliver
Oliver35 is offline   Reply With Quote
Old 29th Sep 2020, 1:08 am   #38
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

Hello Oliver;

The buck converter was a simple 40 Watt 12 Volt to HT unit I put across the rectified HT points whilst there was the odd missing valve, there fore no heaters. The idea was to ensure the two main smoothing caps did not go bang on mains power, so I started at 50 Volts and went up in 50 Volt stages to 250 Volts with about a day at each level. This was simply because sometime when testing old caps I had some just go short on application of HT.

Now the TV is powered by the mains, new PL81 and PY801 fitted 3 amp fuse in the plug and the 1 amp slow blow fuse on the chassis.

If I get the set going it will have caps replaced, but the initial idea is to try and get some HT running to ensure the LOPT is not duff or I have a bad CRT. The HT is low, but do not know why as yet, I guess I should test the two PY82's for the HT rectifiers and a few valves in the process.

The only other time I have worked on TV's would be some 40 plus years ago with the Decca Bradford, but at that point I was getting old rental sets going for a quick buck to earn some cash. That was just done with replacement of panels and a polish. This will be the first time working on a TV set which is all valve and I need to fault find with fingers crossed the LOPT and CRT is fine.

But today is another day, well after sleep it is.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Old 29th Sep 2020, 9:41 am   #39
Heatercathodeshort
Dekatron
 
Heatercathodeshort's Avatar
 
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 7,612
Default Re: My first foray into Old model TV repairs.

Hello Adrian, I don't want to crash into your thread so I will just post these two pictures of the results of my 991T chassis overhaul carried out over the last few days.

A couple of months ago I was presented with just the chassis from a 991T by another Forum member. The cabinet had been carried away by woodworm and was nothing more than powder.

On examination it was very much original and was tuned to channel 5 [Wenvoe] At the time I put it aside but your acquisition of another 991T stimulated me to put it on the workbench and see what it had to offer.

I won't go into the details but after a couple of days in the workshop I have the results seen in the pictures. There were a number of head twisters.

It may be useful to compare notes as you progress with yours.

I would only say that it is important to follow a plan. Power supply, Line timebase, frame timebase, signals, sync separation and finally sound.

The chassis is a high gain fringe model employing flywheel sync but it does not enjoy and form of vision AGC hence the sensitivity control on the back.

The line oscillator will not run if the 2X.01uf capacitors, [in my version they looked like resistors] inside the discriminator transformer are faulty and they will be if they are original as mine were. It's a delicate winding and care has to be taken when removing the can from the chassis. Take notes and pictures.

When the line oscillator is running a negative voltage of around 20V will be recordable at pin 2 of the PL81 line output valve. The .01uf coupling capacitor is an early must for replacement.

DVM's will give significantly high readings in sensitive parts of the circuit compared to those in the manual. No problem if you are aware of this but you can't beat a workable AVO 8 when working with these old receivers.

Components have a 20% tolerance so for goodness sake don't go on a mad resistor change if they are just outside this. They have to be well out of tolerance to actually stop the chassis working, well out.

I agree a safe scope connection would be a help but I didn't use mine during the restoration of this one.

Good luck with it and I hope you succeed! Regards, John.
Attached Thumbnails
Click image for larger version

Name:	Ferguson 991T Chassis. (1).jpg
Views:	80
Size:	41.8 KB
ID:	216642   Click image for larger version

Name:	Ferguson 991T Chassis. (2).jpg
Views:	98
Size:	65.1 KB
ID:	216643  
Heatercathodeshort is offline   Reply With Quote
Old 29th Sep 2020, 11:00 am   #40
AdrianH
Hexode
 
Join Date: Mar 2020
Location: Blackburn with Darwen, Lancashire, UK.
Posts: 429
Default Re: My first foray into Old model TV repairs.

John I do not have a problem with anyone putting any comments/pictures or words of wisdom in the thread, in fact as a beginner and somewhat nervous person around HT (past experience) I welcome peoples thoughts and hope it will lead me to ask some not so dum questions.

I will use component values from the [BTrader sheet[/B] as more people will have them rather than the service manual and bulletins as passed to me by G6ONEDave.

The two caps in the can (C35, C36) have been replaced these done with 400 Volt Film type radial caps. I will get some silver mica for them at a later stage. The old ones were measured and actually measured high such as 0.025 and 0.035uF.

Yes I am using a DVM at present but have been mainly dealing with the HT line so not an issue, must get my Avo 8 working again.

The other caps I have replaced have all been the small cylindrical brown Hunts caps as shown in the picture previously, that is only because some were cracked open and the other that are in the line stage one when I caught it with the probe shed it's coating, I doubt they were faulty in value but the replacement caps are pennies.

OK on the 20% value of resistors, I was measuring R44 the 4K7 in the LOPT enclosure at 5K3. I left it alone as around 12% error.

I would ask if you can show me a picture of where the ion trap magnet is. Reading the service manual it says the arrow should point towards the screen, which would place it below the tube, the Phillips service sheet for the tube says the arrow should be pointing away from the screen which would put it above.

Lastly it does look like it was one of the later sets with the mods for the Tuner type B bulletin 15, and also with a Vision AGC mod bulletin 12.

I was hoping as other posts have suggested just trying to get a bit of a raster before embarking on a cap changing exercise, but if low HT is the issue I may have to, the two resistors on the anodes of the PY82's are OK at 40 and 43 Ohms, so they are still within spec.

I will also see if my DVM can measure the line frequency to see what it is running at.

I will plod on with it, and measure pin 2 of the PL81, pity I can not have a member looking over the shoulder giving pointers.

Adrian
__________________
Ask questions and learn, or try to!
AdrianH is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 3:37 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 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.