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Old 9th Oct 2020, 2:51 pm   #121
AdrianH
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Default Re: My first foray into Old model TV repairs.

HA!
The TV came out of the cabinet again today. After pouring over the circuit and reading an old Practical Television article, found R103 on the frame circuit had gone from 150K Ohm to 205K ohm so as over it's 20% changed it and now have better frame linearity and the adjustment pot is near mid range.

The mains plug from eBay arrived, not sure on using it, It is quite loose on the smaller of the two mains pins, and despite one hole being slightly smaller then the other, the plug will go on both ways.

I am going to try and fit a paxolin washer inside to reduce the opening so that it could only ever fit one way round. I could also fit some heat-shrink to make the fitment a bit tighter. Wonder if anyone can confirm it this is the type for the Ferguson or another make of TV, I suspect a PYE plug?
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It was a gamble on being the correct type so not trying to knock an Ebay seller.

Adrian
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Old 9th Oct 2020, 7:44 pm   #122
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Default Re: My first foray into Old model TV repairs.

I think the mains connector you have is from a Pye set, both sockets will be the same size. I have been looking for a long while without success as my Ferguson 998T also came without one.

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Old 9th Oct 2020, 7:47 pm   #123
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Default Re: My first foray into Old model TV repairs.

That is not the correct mains connector. That appears to be a PYE type used from model V4 through to the CTL58 series. both sockets have the same large diameter but the smaller one appears to be the same as the large one but squeezed up. It will work but not correct. John. Pics to follow.
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Old 9th Oct 2020, 8:11 pm   #124
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Default Re: My first foray into Old model TV repairs.

The answer to your mains connector problem as suggested by Petertheorgan earlier in this thread is an excellent one. A single socket taken from an old 2amp 2pin wall socket replaces one of the 5amp ones in the standard flex connector and makes a perfect fit for the smaller diameter one used in the original 991T connector.

Failing this a piece of 30amp choc block makes a good and solid replacement but looks naff.

The original Bakelite socket is also shown for the extensive Ferguson series. The later versions are light brown in colour and moulded onto the mains lead.

A Bulgin version was also manufactured for EKCO but these are very rare. John.
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Old 9th Oct 2020, 8:29 pm   #125
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Default Re: My first foray into Old model TV repairs.

I am using some 30Amp Choc block as it is as I have none of the old style connectors here.

The Pin spacing seems to be correct on this Pye one just wrong diameters. and it is more a two pronged connector rather than cylindrical.

I will continue to to look for various connectors to make something better.

Cheers

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Old 17th Oct 2020, 11:45 am   #126
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I have a question on the screen image, there is something that does not look right, but I am not sure if down to bandwidth, ringing or just a poor tube?

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Looking at these two images, where the horizontal lines are OK there can be two or multiple vertical lines on the screen, this has the general effect of making the image look blurry, unfocused etc.

So any clues as to where I should I be looking ? If it is down to bandwidth, then I may well need assistance from someone on the matter.

The only references I can see in the service manual is to :-
De-focussed vertical line a) Line deflector coils SC. b) Line to Line deflector coils OC.

I tend to think this fault refers to a single white vertical line, which is obviously not the case but do wonder if it may be a symptom of some shorted turns?

Anyway I pass to you experts for advice.

Adrian
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Old 17th Oct 2020, 12:08 pm   #127
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

looks more like slight IF alignment is needed
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Old 17th Oct 2020, 2:05 pm   #128
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

Agree. I did mention earlier that it is a fringe model designed to give a picture under very poor conditions such as operation in a very low signal area or a location where excessive interference [motor car ignition or heavy industry] would probably unlock the timebases under severe conditions. It has probably been aligned for gain rather than definition. reducing the bandwidth can eliminate the majority of fine grain [noise] a common feature of fringe area viewing. J.

Realignment is dodgy unless you have a very accurate signal generator paired with a frequency counter. I would be tempted to leave it alone unless you have the equipment.
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Old 17th Oct 2020, 2:22 pm   #129
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I have the gear, not designed for TV but the IFR Com120B which has a sweep generator and analyser built in, but what should I expect, books tend to show it as a flat topped response between Vision carrier and a couple of MHz higher, with the lower sideband dropping off to nothing. And at what levels. Reading through the manual and service items suggests there are a few components to short out, or dampen if doing the static method.

Would you have a picture showing the response curve as that is what I would imaging it really to be a curve!

I quick look around the underside shows that the V1 anode resistor R8 has been off in the past as the wire no longer goes through the valve pins and is just soldered on top. So I would think at some point it has been 'tuned'.

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Old 17th Oct 2020, 2:41 pm   #130
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I would start by checking resistances of around the valves in the section first before doing alignment. There are youtube videos showing alignment procedures. In my opinion your better doing the alignment using the equipment of the time rather than a SA
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Old 18th Oct 2020, 12:01 am   #131
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

Well I had another look at the TV, checking resistors as suggested first, I did find a 1K that was actually out f the 20% at 1K3 so changed that, all others found to be reasonable, I had changed several over the general repair process.

I also hooked up the TV to the test set and had a tune. AGC disabled and signals keep low to make sure not to go into limiting. Looking at the video circuit it was easy to notch out the sound carrier at 19.5 MHz and adjacent sound carrier at 14.5 MHz they were quite noticeable.

Tuning on a spot frequency of 17.75MHz as suggested in the manual was more difficult as some of the tuning screws have been rounded off somewhat and the indicated increases hard to notice, but with a low signal input small peaks on 17.75 were generally found. From that point I opened up the scan rate over a few MHz and did a sweep of the IF video pass band, it was not as expected, But it really made very little difference to the picture on the screen.

Here are a few screen images captured on a hand held camera.
The centre of the span is 17.75MHz in all pictures.
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The marker here is at 14.5 MHz which would be the adjacent channel sound channel, so there is a notch at this point.

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On this one the marker is at 19.5 MHz where there are several notches of the sound carrier.

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On this one the marker is at 18.4MHz which with a 16 MHz video carrier would indicate a max pass of 2.4MHz, well it does to me anyway!

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The screen view, I noticed in this pic that I have a bit of line linearity to sort out, as I normally view from the right had side of the TV when setting it up, I had not noticed this, a job for the flat blade screwdriver in the line linearity magnet some time.

Think I will leave the set for a while and get my audio amp finished so I can at least listen to some loudish music upstairs when I have the chance.

Adrian
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Old 18th Oct 2020, 8:46 am   #132
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I think you haven't been telling us the full story Adrian and you've actually got a colour TV there with a convergence error and your screen shot was taken with a B&W camera.

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Old 18th Oct 2020, 9:23 am   #133
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

Hmm Colour TV, I wonder if I should get one. No, I remember the size definitely no more TV's.
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Old 18th Oct 2020, 10:48 am   #134
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

Joking aside, I think you have done a very good job.
The 991T is a rather special receiver designed to give the very maximum performance from distorted and weak signals. A stable picture of entertainment quality was the goal and as can be seen by the pictures I posted of an excessively attenuated signal, locked solid, proves the point.
Don't be too critical with your excellent result! Regards, John.
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Old 18th Oct 2020, 11:21 am   #135
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I've been dipping in and out of this thread and I must congratulate you on you determination and logical approach to this first television restoration. Obviously, excellent input from our fellow forum members too.
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Old 18th Oct 2020, 12:37 pm   #136
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I agree with John (HKS) and Taz. You have worked wonders with the Ferguson and as stated in earlier posts the test card problem is the IF alignment. Your step response has ringing and in my experience after setting the correct stagger tuning of the stages you just need to make very small changes whilst looking at the test card bars and check which direction of change reduces the ringing without adversely reducing your bandwidth. Go round each of the cores iteratively making tiny changes towards a more controlled step response. You may need quite a few iterations.

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Old 18th Oct 2020, 2:16 pm   #137
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

I appreciate the comments and the assistance provided, it has been an interesting and occupying time.

I just replaced the EY51, not that it really needed it as the HT seemed to be holding up well in the first place, but as I got one when I got the PL81 and PY801 it was sat on my bench from that point on. So out came the LOPT a bit of a clean and new valve fitted.

On the retuning, I think that will await for a major boredom period. L18/19 is the coil can that is very close to the screen and that is the one with most problems to the cores being worn out adjusters and stiff to move. Not sure if the crimp on caps are meant to come off the tubes but I tend to think that is what I would need to do to free off the cores and tidy up the ends. So that would have to wait some.

Perhaps at some point I will come across a part TV with decent tube that can be used, but for a TV that initially came in at 20 it will do for now.

The main thing about these projects for me is learning and trying to understand the various sections in how they work, I find it fascinating that one valve can be a mixer, oscillator and amplify as well. Reading Scroggie's Foundations of Wireless helps a lot.

Perhaps I will try something with my failing 'radar project' box and a 405 line picture may appear on a small 3 inch green DG7-5 at some point.

Cheers

Adrian
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Old 18th Oct 2020, 2:29 pm   #138
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

With IF transformers there are often two ferrite cores. If the are stiff try release oil. If one is particularly stiff you can sometimes have more luck with the other end and then having removed one using a long trimmer attack the sticky one from the other end. Once you've got them out you can get a fresh trimmer slot by turning them end for end. The clips on the cans should not get in the way. They are only there to clamp the cans to the chassis.

Peter

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Old 18th Oct 2020, 3:00 pm   #139
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

Hi Peter it is this type of IF can.
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I tend to think the metal parts got damp at some point making them rust a bit, possibly with some rust clogging up the works on the inside, perhaps with gentle use of jewellers screwdrivers I can lever the crimps out of the tube and pull them off, with the tube in place it does become a bit of a task, which is why I think it will await some time.

Adrian
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Old 18th Oct 2020, 4:13 pm   #140
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Default Re: My first foray into Old model TV repairs. Ferguson 991T.

Yes, very similar to the tuning front end. In normal service life they never got 'twiddled' as Ferguson I.F. strips were drift free but I suspect yours may have been due to bad reception conditions. I think you said a couple had been 'rounded off' in the past.
You may find the cores have become detached with damp and age. John.
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