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Old 3rd Jan 2023, 5:17 pm   #21
alfatangowhisky
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Update (in a nutshell): We have glowing valves ! Also: audio output TX is poorly

Long version:

Not content with the audio output TX getting un-naturally warm, I changed C133 and this made no difference. I concluded therefore that due to the horizontal position of the transformer, the rain had a nice easy path into the windings / core whilst it was sitting out in the elements for however many years. I snipped the HT feed to the transformer and upon running up the chassis, HT was now over 100 volts whereas before with the bad transformer connected it was in the 60v range.

With that problem xsolvedx temporarily bypassed, I felt confident enough to crank up the input voltage a fair bit more, in steps of 5 vAC every minute until I got to 150 volts. By now the valves were getting a nice little glow going on and there was about 200mA on the heater circuit (with CRT bypassed). The PL500 (504) top cap was disconnected throughout.

Nothing exciting happened, which is good. Next I will dry out the LOPT overwind with some limited current DC.

Main picture shows the patient on the operating table with vital signs being monitored! (input volts AC, HT volts DC and heater circuit current mA).

It have also noticed that there have been a fair few replacement valves fitted from all sort of sources (Solus, etc) and the PL500 is now a (Mullard) PL504. So the set must have had a fair innings before the abandonment. Apart from the valves I haven't seen any evidence of other components replacements.
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Old 3rd Jan 2023, 10:37 pm   #22
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

The LOPT overwind is now getting warmed with 100mA of current overnight, surrounded by desiccant packs and next to a dehumidifier !

While that was being given a trial run I managed to get the volume / on-off / brightness / contrast control knobs off which then allowed me better access to the pots and power switch which are both grouped on a bracket. The power switch, which was not behaving properly (could hear one pole clicking then a half-second later the other one clicked) had another shot of Deoxit and several actions and eventually everything felt and sounded right. I haven't done any electrical checks on the switch since unmounting it and getting it to this state. Initial tests on Day 0 showed high resistance on the probably very tarnished contacts.

The tuner knobs were removed to allow the bracket holding them to be withdrawn to gain better access to their workings. Upon removing the VHF tuner cover all sorts of expired fauna and flora was discovered inside. This was all cleaned out (being very careful around the fine coil wires and not disturbing the position of the parts) and given a squirt of WD40 and the action was nice and clunky, with the fine tuner adjustment also working (although on the BBC setting it seems the 'carriage' does not end up in exactly the right place meaning the fine tuning linkage does not mesh correctly. It can still be turned but not as nicely as the other 4 stations).

The clutch that turns the outer channel indicator on the UHF tuner does not seem to be operating properly; turning the central dial does nothing until about half way round then it engages, moves the outer drum around and turns the shaft to the tuner. It should be turning the outer portion in unison with the central knob. Any suggestions on how to get these working correctly?

Also, I ask again if anybody can identify the exact model, noting the position of the tuners as they are not the same as in available literature (manufacturer's service manual for 10xx and 20xx series). Maybe this is a later model not covered by what I have, as the PCB is marked 'Radio and Allied Industries' rather than GEC (Radio & Television) Ltd
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Old 6th Jan 2023, 7:25 pm   #23
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Things are progressing nicely..

After 3 days of overwind drying (the last 2 days at 24v, drawing ~200mA getting nicely warm), I detached the deflection yoke from the CRT and plugged it into the chassis, started low with the variac and slowly wound up the mains.

At around 160v AC input there was the throbbing of the vertical output transformer and at around 170v after still hearing no line whistle I went to draw a spark from the PL504... and got one! The system switch was in 625 mode and my ears are now not able to hear what they once could.

Powering off and switching to 405 (I can hear that well enough) we got back to 170v, nice strong line whistle which could be adjusted with the relevant control, PL504 spark, and DY87 heater glowing. I then was able to draw a small clicky spark from the EHT connector!

All of this happened without incident, the only major issue so far being the duff audio TX.

Next, I will connect the CRT and try to get something up on it...
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Old 7th Jan 2023, 10:40 am   #24
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Excellent! It's always very satisfying to see the heater glowing in the EHT rectifier as it shows the line output stage is working OK. Fingers crossed that the LOPT holds up after it's been on for a while!

What state are your scancoils in? On both of my sets the plastic has turned to dust and just falls apart. Maybe they were aware of this problem and made some changes to the plastic in later production?

For a set that's spent a considerable time outside, the board looks very clean - presumably you've given it a good clean up?

Strange about the audio TX - I can't remember ever having a faulty one on any set I've ever played with. Will be interesting to see if it is to blame or if there is something else causing it to heat up.

Good progress so far!

Cheers
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Old 7th Jan 2023, 1:31 pm   #25
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

It really is incredible that you have got so far with this set in such a short time. I wonder why it was dumped, did it have a fault or was it just old and not wanted?
As far as the LOPT is concerned I would check the overwind temperature after a run to see if there is any signs of heating up. The speaker transformer can be easily checked either by testing the primary resistance and leakage with a meter or another way is to connect the primary to a 200/240v supply suitably fuse protected for a short time and measure the voltage on the secondary, around 6/7 volts should be present I think. Any signs of distress or excess current should show up quickly. If it is duff a replacement would be easy to find they are pretty standard.

I can't help with the model number I'm sorry to say, the foil label that would have once been on the back of my set is missing. I do have a service book somewhere I will dig it out and see what the model number options are.
I really like these sets, I have Three that are fitted with this chassis, A 23" "Blue front" GEC . a Grey front Sobell like your set and a 23" wood front GEC.

I watched Ojnoj's youtube video a couple of days ago of one of these sets brought back to life it didn't take a lot and the tube was excellent. It seems some sets just want to live!
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Old 7th Jan 2023, 6:10 pm   #26
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

I think you all should be sitting for this next update...

CRT plugged in, running at ~170v AC via variac but off 'limit', we have first light!

Contrast and brightness controls do nothing, and vertical hold won't reach far enough to get a more stable picture but the tube seems nice and strong (measuring only around 4.5 on the heater). I didn't get round to trying the tuner or switching to 625... a cup of tea was calling !

So next I feel I need to put the CRT back in its (cleaned) fascia and make some sort of stand to hold it so I can work on the board in a more service-like position.

This seems to quite a late set; I have discovered a date of Nov 68 on a capacitor. Really would like to find out the model number and the reason for the different arrangement of the tuners.


Nick; yes the plastic around the scan coils is fragile (I manage to chip a bit off) but it hasn't fully turned to 'dust', just very brittle but is holding everything together. I have some from other sets in better condition; I wonder if these would be suitable, if not at least for the plastics. Regarding the PCBs; I haven't really cleaned them apart from a going-over with a soft brush - no water, cleaners or solvents. I did everything gingerly so as to be careful around fine wires on some of the open IF coils etc.

slidertogrid; it would be hard to know if it did have a fault when dumped; there are some obvious faults but how many of them were caused by the 'storage conditions' I will never know. The audio TX for one looks no worse state than any of the other transformers or parts but the (short?) might have been its original death knell. If I get the rest of the set working I will certainly then focus on the audio TX - possibly even a re-wind if needed? Thanks for the diagnostics tips. I do have the general service manual covering many models via the Service Data DVD, with document reference PT1023/8/68 RE IP8/72 on the final page.

These must have been decent sets back in the day - I really am astounded how much abuse this one has taken. There have been grumbles about the fragile PCB traces but it seems the soldering is of excellent quality and the component choices also have proven to be top-notch.
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Old 7th Jan 2023, 7:53 pm   #27
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Hi,

I'm liking the look of this already. I think if you wind it up to full voltage you will get a better result. It is amazing how some sets just refuse to die! Hook up an RF source and see what you get.

As for the sound O/P TX, nearly anything will get a result. Even a small wall wort or transistor radio mains TX would do for now.

Great progress!
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Old 7th Jan 2023, 9:26 pm   #28
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Quote:
Originally Posted by alfatangowhisky View Post
These must have been decent sets back in the day - I really am astounded how much abuse this one has taken. There have been grumbles about the fragile PCB traces but it seems the soldering is of excellent quality and the component choices also have proven to be top-notch.
I must admit, I've not had any issues at all with the PCB tracks lifting. They seem very well made and sturdy. The component choices weren't quite so good on the earlier 1000 series. I think mine is about '64/65 and was full of red 'Hunts' plastic dipped caps. They looked very pretty, but were just as useless as any other Hunts capacitor Those caps that weren't Hunts were yellow TCC ones, which were also now just resistors. Talking of resistors, almost all of them had nearly doubled in value, so way outside of tolerance, but the set seemed to work fine in spite of that, so only a few critical ones got changed!

It will be very interesting to see whether the LOPT does get hot after an hour or so once you are on full mains and displaying a picture. Hopefully, your black overwind type is better than the earlier beige type.

It's a shame the model number sticker on the back always falls off, but I'm sure someone can come up with a full model number for it.

Good progress though - looking forward to seeing a picture on it once you have come up with a method of supporting the front and CRT.

Cheers
Nick
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Old 8th Jan 2023, 12:59 am   #29
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Well guys, two good news stories to share..

Tuner is alive as we have a version of the Hedghog test card (slanted look and banding is because of camera), and... the audio output TX has been given reprieve. I desoldered the wires and detached it from the chassis to get a better look and noticed something that should have been blinkin' obvious - a tag has been bent over meaning HT was shorting to ground via the TX case. We now have sound (albeit vision on sound) but at least the audio output section is now working.

Main focus is now on getting full height scan. I put in a new PCL85 and no improvement so it's probably going to go to component-level fault finding now.
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Old 8th Jan 2023, 2:12 pm   #30
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

From memory, a stock fault on these for low height was a resistor inside the line output screen, I think it was 2M2 but it's a while since I replaced one.
Great to see this rescued!
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Old 8th Jan 2023, 2:28 pm   #31
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Quote:
Originally Posted by Simon Gittins View Post
From memory, a stock fault on these for low height was a resistor inside the line output screen, I think it was 2M2 but it's a while since I replaced one.
Great to see this rescued!
Thanks Simon. I will check R140, R141 etc.
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Old 8th Jan 2023, 8:36 pm   #32
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Here's my 1014 which is still working:-

https://vintage-radio.net/forum/show....php?p=1356742

You have the later tuner. So may be a 1024 or 1034. The chassis had 19" and 23" tubes.
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Old 8th Jan 2023, 10:56 pm   #33
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Quote:
Originally Posted by Simon Gittins View Post
From memory, a stock fault on these for low height was a resistor inside the line output screen, I think it was 2M2 but it's a while since I replaced one.
Great to see this rescued!
Maybe the one you meant was R132 (1M2) which was measuring 3M so was replaced and got the height to around double what it was previously. Thanks for the suggestion!

Still maxed out the height control and now running on full 230 mains. Tried a new PCL805 but no more height.

So my next train of thought, apart from changing C147 and C150 (the TCCs), is that VDRs don't like 30? years outside in the rain. Both the height (maxed out on control but not getting to where it should be) and the brightness (cannot get it to go down from full-up) circuits have VDRs hanging off them (the green-tipped Mullard E298CD 'stick' on the height and the flat E299DD on the brightness)

BTW the on-screen picture is upside-down as to facilitate the best position for the tube I turned the scan coils through 180. And it seems I have a very similar yoke assembly, I think from a KB dual standard set and the plastic on that is in better condition.
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Old 9th Jan 2023, 8:00 am   #34
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Unbelievable result! Well done!

My bet would be the 2, yellow TCC’s first. Even though they seem ‘modern’, they are essentially a waxy in a yellow raincoat.

Keep up the good work, and fingers crossed the lopty holds out......


Cheers.

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Old 9th Jan 2023, 11:45 pm   #35
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Evicting those two TCCs (C147, C150) has resulted in much more height. Probably as much as I'll get running 100R instead of 70R on the dropper for the valves.

Next, change all cylindrical caps other than the mustards as this TCC sort have proven themselves not worthy to be on my dogs' dinner of a chassis!

Hopefully this will bring back some brightness control too!
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Old 9th Jan 2023, 11:58 pm   #36
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

What a fantastic result! It’s quite amazing that this decaying corpse of an old television has been coaxed back to life! I do enjoy a good basket case

Great work,
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Old 11th Jan 2023, 1:47 am   #37
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

What a fantastic resurrection story. I wonder how long it spent outside.
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Old 11th Jan 2023, 11:22 pm   #38
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Hello again

Thanks all for your encouragement.

I have now sorted out the brightness/contrast issue. Silly thing again; the controls take their ground from the mains neutral on the switch assembly, which is to chassis, but as I had the power control part of the on/off/volume control disconnected whist I sorted out the crusty switch, this meant that potentiometers had no ground and this were at max all the time. Should have spotted that one earlier!!

There is a bit more height with a fresh PCL805 (I fitted one while the bad capacitors were still present and it didn't seem to make a difference then), but still not enough. That is the only major outstanding electrical fix apart from tuning being a bit out (good vision at one end of fine tuning, good sound at the other but no nice mix anywhere in the middle).

Still haven't explored 625 much yet so don't know how the UHF tuner is doing but I thought I should get the bread-and-butter 405 right first.
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Old 12th Jan 2023, 10:47 am   #39
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

That looks remarkably good - well done!!

Whilst the fixed resistors will all have gone high in value, the presets, including the height & linearity controls will have radically reduced in value, usually by about half. So expect a 2.2M to now read about 1M!

This seems to be the case on all sets to a greater or lesser extent & before I was aware of the problem led to some real head scratching!

As finding replacement presets is often really hard and even NOS ones suffer the same problem, I've resorted to padding the value with extra resistors in cases where the reduced value causes problems.

Whether that will affect your height issue, I don't know, but it's worth bearing it in mind.

When photographing TV pictures, I find it works better to turn the brightness & contrast down to levels where the picture looks a bit sick and to reduce background lighting. This forces the camera to use a slower shutter speed and so you capture a complete frame without the black bands. It's still a bit trial & error though!

Cheers
Nick
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Old 12th Jan 2023, 2:03 pm   #40
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Default Re: Sobell D/S TV (1014 ?) on Facebook (Leven, Fife)

Quote:
Originally Posted by 1100 man View Post
That looks remarkably good - well done!!

Whilst the fixed resistors will all have gone high in value, the presets, including the height & linearity controls will have radically reduced in value, usually by about half. So expect a 2.2M to now read about 1M!

This seems to be the case on all sets to a greater or lesser extent & before I was aware of the problem led to some real head scratching!

As finding replacement presets is often really hard and even NOS ones suffer the same problem, I've resorted to padding the value with extra resistors in cases where the reduced value causes problems.

Whether that will affect your height issue, I don't know, but it's worth bearing it in mind.

When photographing TV pictures, I find it works better to turn the brightness & contrast down to levels where the picture looks a bit sick and to reduce background lighting. This forces the camera to use a slower shutter speed and so you capture a complete frame without the black bands. It's still a bit trial & error though!

Cheers
Nick
Yes, I'll have to go on a resistor measuring sesh. As for photographing the screen, my old phone had a better camera with pro features so I could adjust the aperture and more importantly the shutter speed to get the image clear and without banding. When I am on the home stretch I might capture it with my X-Pro to show the true quality of the tube, which is a real beauty.
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