Restorer's dream part 2 the chassis.

[HamishBoxer]

Hi Dave (Boom),was going to say about positive/negative coefficients but was trying to keep it basic.
Mainly refering to surge protection.
David

[Retired]

Hi,

Thanks Chris; I thought it was just me that heard line whistle after leaving the workshop so I don't need treatment.

Many thanks for the information Jeffrey regarding the pot; by the time I had read it I had removed the pot cover as seen in the picture and sprayed the track with contact cleaner and also cleaned the pick ups; as this made no difference whatsoever I did as a friend suggested and bridged the two outer pot contacts with a resistor to see if this would indicate if the fault was in this area; I tried 2.2M; 1M and 500K resistors but it made no difference. The suggestion was good though because I could then forget the pot and it was a very easy check to make and one to remember.

I hope you had a good trip Dom and now that you've touched base once again you can get into the workshop. Thank you for your comments and I'm very interested in what you say about the set running at half speed as I remember Dave (Amraduk) also mentioned this and when I checked it was way back in post #173. I've now checked and replaced a couple of resistors in the frame hold area and am I correct that I now need to focus around T1 and V12 once again checking and replacing components as I have done around V13?

Is V12 and T1 the area which governs the speed?

Given the dreadful state of the original LOPT would this in any way affect the primary windings of T1. the reason I ask is that I once spent ages on a radio chassis checking just about every component possible only to eventually find open primary in the output transformer; the set was actually working but on very low volume. I could of course be way off mark but am thinking aloud.

I've also spotted a 2uF cap de-coupling what looks to me the screen grid of V12A but I haven't changed this; I thought I had changed all the big caps there is also an electrolytic that I haven't changed so just to be sure I'll have a go at these next if only to eliminate them. Would a class X2 2uF be OK to de-couple V12A with as I have some of these?

Changing the resistors and caps around V13 certainly brought up the test card and I think I've now been concentrating too much in this area because if the fault is as you both suspect down to running at half speed I need to resolve this?

I'm also happy to post a picture showing the area of the chassis I've been working in as suggested by PJL. V13 30PL1 is to the upper right. Many of the new components can be seen with the small coils soldered making for easy installation. I replaced the scorched resistor in the picture.

Every session in the workshop brings me that bit closer to success.

Kind regards, Col.

[Heatercathodeshort]

It's all in the caps Colin, don't worry about the resistors at this stage. 20% out will be acceptable. Concetrate on the frame output stage capaciors around the 30PL1 coded green on my circuit. Let's get the raster nicely shaped and what picture there is locked. The rest will be an easy job once the receiver is stabilized. Take care and sleep tight. Regards, John.

[PJL]

What's that fancy metal cased thing doing at the bottom of the picture? It looks like the 0.25 coupling capacitor and that definitely needs replacing.

[Retired]

Hi,

Thanks John; you went to so much trouble supplying the information and highlighted diagrams that I've been working from them and it's possible I've missed a cap so tomorrow I'll not only double check I'll count the highlighted caps and give each a number then log them off by double checking the chassis. This is slow work for me as it is so easy to make a silly mistake. I'll let you know when I'm positive every one has been changed.

Well spotted PJL; without checking I'm not sure which the big cap is at the bottom of the picture but as you can see I've already removed it by the new solder joint; I tested it on my Hunts Component tester and I'm sure this particular cap not only tested excellent for capacitance but also tested at 500V without trouble; to be on the safe side though I will replace it to see if it makes any difference.

Tomorrow is another day and I can spend more time on this chassis as we have nothing planned for the day.

Kind regards, Col.

[Heatercathodeshort]

They will all need replacing Colin. A 50meg leak in critical frame timebase capacitors will cause all sorts of linearity and frequency problems. Sometimes they read 100% but are still horribly faulty. Been caught out with that one many years ago! John.

[Amraduk]

Hello Colin,

Originally Posted by Retired

Is V12 and T1 the area which governs the speed?

No, its V13A and T1 which determine the speed, they and the associated components form the frame oscillator circuit. V12A is the sync separator which supplies signals to the frame and line timebases for synchronisation.

I've also spotted a 2uF cap de-coupling what looks to me the screen grid of V12A but I haven't changed this;... Would a class X2 2uF be OK to de-couple V12A with as I have some of these?

Yes, I think that would be suitable.

Changing the resistors and caps around V13 certainly brought up the test card and I think I've now been concentrating too much in this area because if the fault is as you both suspect down to running at half speed I need to resolve this?

As I said above, V13A is the frame oscillator (V13B is the frame O/P stage), so that's the area you need to work on to correct the speed!

Regards,

Dave.

[Retired]

Hi,

Thanks John; yes I've been well and truly caught out please see below.

Many thanks again Dave (Amraduk) for giving such a full explanation; I did find the 2uF cap and it turned out to be a non polarized electrolytic; it has electrolytic marked upon it but no indication as to pos and neg. It tested OK but again please see below.

The day started at 4am as I was wide awake in bed again thinking about what I needed to do today. I was in the workshop by 8.30 after doing the supermarket shopping (yes I'm rapid around both Aldi and Morrison's).

I had both John's and Jeffrey's excellent printed information with me to work from and one by one I checked every cap that John had highlighted ticking each off against a number I had given them so that I wouldn't miss any. It took ages but eventually all were accounted for and all were replaced by high voltage types so I just knew something was wrong somewhere.

I then followed up on PJL's suggestion regarding the 0.25uF coupling cap from T1. It was very easy to remove and I tested it once again on the Hunts component tester; capacitance was excellent but now it was leaking on the 300V/400V range. John I was caught out by relying on my tester as when I previously tested it the cap was fine up to 500V without showing any sign whatsoever of leaking. Drat it; this cost me a lot of frustration and time; I won't say the time or frustration was wasted; far from it because I'm learning all the time but I did inform the chassis yesterday to get a grip or it would end up in a a skip!! I replaced the offending cap with a 0.22uF 635V item testing it before installing.

What a powerful sense of well being I felt when I switched on; as soon as the screen lit up I knew at last all the frustration had been worth it; the scren was full height. I then switched on the Aurora and it took a lot of control fiddling but suddenly the test card appeared; having worked so hard on both the cabinet and chassis this was a truly moving moment for me and one which I'll always treasure; I can declare the set working at last; not perfectly but I've seen worse pictures when watching similar sets as a child; yes I'm over the moon.

A couple of weeks ago whilst looking at this wreck of a chassis I thought no way can I ever restore this into working order and would have truly struggled without all your first class expert help and guidance; I've taken note of every bit of information kindly supplied and would like to take this opportunity to give a special sincere thanks to both John and Jeffrey as both must have spent a lot of time and effort in putting together the information supplied and also thanks for supplying the valves; many thanks also to Mike for getting up close and personal with the chassis and getting the test card to flash up briefly; what a great bunch of guys you all are. Thank you all so much.

The picture shows the test card as it is now; on full screen but still requiring fine tuning as the picture is unstable; the test card displays as shown for a very short period of time then begins to roll so I presume this is a "hold" problem as the control is very; very sensitive; a slight tough will set the picture rolling in either direction. Once the picture is displayed correctly and stable then once again I'll require your expert guidance whilst I have a go at the audio stages. The light banding on the screen is due to the camera; in fact I took many pictures just to get this one as some had a very black band across.

I've put many hours work into the chassis over the last couple of weeks and confess it was rather disappointing yesterday to have put over ten hours work in with little progress. I would say to other novices whatever you do stick with it as too many sets get dumped to one side when things get tough and little progress is being made; I've felt at times what the heck am I doing spending so much time on a wreck of a TV but believe me to see the test card appear as it did this morning is worth every minute spent and all the frustration caused; my friend David who is watching the story only mentioned the other day that many sets become pushed under a bench to be worked on at a later date then eventually get dumped. I reckon I could get a picture out of a couple of caps and a resistor given the vast knowledge of the experts on this forum.

I've rambled enough but what a result; in a little over two weeks from a wreck into a working chassis; this hobby just does not get any better than this.

Kind regards, Col.

[Sean Williams]

Thats looking better - just needs a few more caps and I think perfection wont be far off

[IJK2008]

Well done Colin I think you are nearly there now. It will look fantastic when it's all back together in your restored/rebuilt cablinet.

You are also right to highlight the help we less experienced folk get from the 'old hands' as without them we wouldn't get there would we.

Ian

[ppppenguin]

The 2u cap is most unlikely to be non-polarised. Its the screen grid decoupler for V12A and will definitely have +ve on its top end. I don't really understand why this needs to be such a high value. Any 2u cap, electrolytic or otherwise, rated at 100V or more should be fine in that position.

As for the 0.25u cap, we really can't say it loud enough. All old paper caps, with the possible exception of metal cased hermetically sealed in oil types, are faulty. Even if they don't seem to be faulty, they almost certainly are. In some positions a little leakage won't matter, for example a screen grid decoupler. In others such as the 0.25u timing cap here, or an AGC line decoupler, even a minute leakage will cause trouble.

[Amraduk]

Hello Colin,

Great result! As everyone says, not far to go now! Good luck.

Regards,

Dave,

[HamishBoxer]

Excellent Colin! Great example of patience!

David

[Patrick Dixon]

Originally Posted by PJL

What's that fancy metal cased thing doing at the bottom of the picture? It looks like the 0.25 coupling capacitor and that definitely needs replacing.

Dat PJL - he very good!

[Billy T]

Originally Posted by Retired

I then followed up on PJL's suggestion regarding the 0.25uF coupling cap from T1. It was very easy to remove and I tested it once again on the Hunts component tester; capacitance was excellent but now it was leaking on the 300V/400V range. John I was caught out by relying on my tester as when I previously tested it the cap was fine up to 500V without showing any sign whatsoever of leaking.
Kind regards, Col.

I have missed some of this frame stage saga, but thinking back to my TV servicing days the bottom of the screen equates to peak current in the FOPT valve hence bottom cramp if the cathode resistor goes high or the bypass cap is o/c. The grid loosely corresponds to top of frame issues and from the photos it looks to me like the set was displaying extreme top foldover rather than a frequency-related problem.

It might not have been the case in this particular situation, or for this circuit, which is rather older than the oldest of UK sets I ever worked on, but it is a thought to keep in mind for the future.

Cheers

Billy

[Mike Phelan]

Well done, Col, not too far to go now.

[mark pirate]

I knew you would get there, you deserve to feel well chuffed with your efforts.
I am really looking forward to seeing the finished set, well done

Mark

[Retired]

Hi,

Thanks Sean, I'm still taking my time and changing caps; I changed another four Hunts 0.04 yesterday but these appear to be in the sound strip and didn't make any difference to the picture each time I switched on but it's another four out of the way.

Thanks Ian & Mike; hopefully it won't be long now before the set is completed and you will be able to see it when you pop over Mike.

Thanks for the information Jeffrey. Yesterday I removed the 2uF cap and had a very good look at it; the cap is a "Micropack" Electrolytic 2uF 200V WKG Type GE 32G. It doesn't have a +ve mark showing at all or any other indication of polarity; both end caps also look to be the same colour to me. The Ekco T311 circuit diagram also doesn't show this cap to be polarized unlike the other electrolytics which clearly are marked hence I asked the question. I've certainly now got the message loud and clear to change all paper caps.

Yes I totally agree Patrick.

Many thanks Billy; I'm not only reading with great interest all the posts but I intend to copy the entire restoration to disc for future reference and I'll also retain a copy of the disc inside the TV.

Its so easy to miss things as a novice and the simplest bit of information or advice can usually be interpreted a number of ways leading to silly mistakes. Take for example the sound advice to "CHANGE ALL PAPER CAPS". This to me meant all the waxy caps but the one that caused me the problem was metal cased and to be honest I had my hands full trying to absorb the masses of information already kindly afforded me without researching what kind of cap this one was. I've restored many vintage radios and always found my Hunts Component Tester to be a very good instrument for testing caps; if the cap tested OK then it would work on the radio but now I find I can no longer fully trust this instrument when it comes to TV work as it would appear a TV is very sensitive to the condition of it's caps. Upon the first test the cap in question passed test on the Hunts perfectly so was re-fitted much to my grief. But now I understand just how important caps are on TV work in future it will be a case of replace with new; I must say that I've always even tested new caps before fitting.

Other examples that trip me up are references to such items as "video amplifiers anode resistor" 12K going high. Check valve voltages; this I'm used to doing and I thought great I've seen a list of voltages so pulled it out and these covered the similar Ekco TCG316 chassis. As I was working on valve 30PL1 (T311 circuit diagram) I checked the sheet (TCG316) for voltages to find this valve not on the list. These might appear to be trivial things to more experienced members but they threw me at the time as did spending ages looking for a coupling cap that Ekco had decided was not needed.

I can get around these problems but it takes time; for example the 12K resistor; all I had to do was to study the circuit diagram and looking at the valves the anodes are dead easy to spot so all I have to do is find the valve with the 12K Anode resistor and check it. I still can't spot this resistor so as it is so important I check all anode resistors against the circuit diagram.

I'm used to cross referencing valves for radio work and have plenty of data but very little data for TV valves. Its taken me ages to compare one circuit diagram against the other as both show the valves with different numbers take for example 30PL1 V13 & 30P12 V14 this was when I intended to take voltage readings.

Even the 2uF cap was a teaser as I wanted to be perfectly sure that I was not making a mistake before moving on.

I am truly grateful for the immense help I've received and certainly don't wish to appear to be picky in any way whatsoever or to cause the slightest offence to anyone but I'm trying to let other novices know what I've been going through whilst working on this chassis; all the information kindly given to me has been spot on; the problem is me and my lack of experience.

It's taken fierce concentration over a couple of weeks to get this far but what a splendid result due to team work; you have all played your part and I've adhered to information and instructions given; the learning curve has been ballistic and I've lost a lot of beauty sleep; I still have some way to go but what a wonderful time I'm having.

Kind regards, Col.

[Heatercathodeshort]

Three verses of Rule Brittania and the National Anthem! WELL DONE COLIN!
Your picture appears to show the tuning a bit off. Does the fine tuner work? The tuning wand may have broken but is not required on the Ekco as the tuner is 100% stable. I can illustrate how to correctly set the tuning if required. It's a doodle!
Next replacement will be the 'fat' diode to obtain better frame sync. It is marked with a tiny diode symbol in red but if rubbed off you need to check the circuit to fit the replacement correctly. No sync will result if reversed but no damge will occur. The AGC circuits follow but that is something a little ahead but maybe time to check the vision detector diode but all in a methodical order and taken with a steady heart! It's fun Colin, lets keep it that way. Just got back with the lorries from the final show of the year. Fantastic weekend but must admit I had a feeling you would have a test card on that receiver when I returned. Test equipment is all very well but each item of equipment has to be 'learned'. You will find the act of warming an appararntly good capacitor while checking it for leakage interesting. The result might answer your frustration. Like the old advert for British Rail, 'We're getting there' The difference Colin is that you actually arrived.. Cheers, John.

[Retired]

Hi,

Many thanks Mark for your kind comments; once this set is fully restored I'll only take on something just as dumb again but it's great fun to leave my comfort zone.

John you are such a gem and thank you for your continued support and encouragement. This project came to an abrupt halt yesterday when I received a message asking if we would be in today as a lathe I've been expecting could be delivered at short notice. Yesterday afternoon I spent time finding a new home for my wood turning lathe and wiring it in to make bench space for the new lathe which arrived this afternoon in kit form; I mention this because up until now only two examples of my Myford MF36" lathe were known survivors making my lathe extremely rare now suddenly there are three and I own two of them so now I have plenty of winter projects stacked up.

Whilst awaiting the lathe I stepped back a bit and re-read all the information so far kindly given regarding this chassis and in particular John's which I had printed off just to check to see if I had missed anything. I still have things to check from the list.

The big fat Diode to obtain better frame sync you mention John is this the one coupled to V12A 30FL1 Anode via a 47K resistor? if it is I replaced it a while ago with a 1N4007 taking care to install it the correct way round? Its marked D3 on my T311 diagram.

Yes the fine tuner works and makes a lot of difference to the picture but the picture is very unstable both from side to side with heavy patterning and also it rolls very easily although I've become more used to the controls and can control the rolling more but the picture appears to have a mind of its own. I ran the set for half an hour today and managed to stop it rolling but without touching anything the test card would break up then correct itself; it was most interesting as if it was trying to repair itself.

The vision detector diode? I'm game for anything so please point me in the right direction as I'm not quitting until the job is done. I've been frustrated since taking this wreck on John and to me its all part of the fun; I find it fascinating and a challenge playing with electrical items that I know so little about but quickly learn with such excellent guidance. Yes please to setting the tuning as I want to learn the correct procedure. I'm pleased your weekend went so well and that I met your expectations upon your return.

I can now also confirm Jeffrey that the 2uF electrolytic cap is polarized; another forum member kindly visited and checked it for me; there are no markings to indicate pos and neg but my friend confirmed one end cap is red the other black but the colours had aged; drat this colour blindness but without my glasses I'm blind anyway; I stared at both ends of the cap but they looked the same to me; am I the only member to suffer from this because its a downright nuisance and why I was offered 12 home postings when I applied to join the RAF when I was single many years ago; I actually sat a Morse test and passed because one of the jobs offered was radio operator. As all the jobs were home postings I declined because the others were office jobs putting me behind a desk as a clerk because I could also spell.

Hopefully I can resume work on the chassis tomorrow afternoon and spend more time on it during the week; I'm a keen student.

Kind regards, Col.