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Old 30th Dec 2022, 8:00 pm   #1
Laurence Smith
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Default Pye CTL58VS TV.

This is one of the TVs that my dad had kept in the loft and I decided to have a proper go at restoring it over the holiday period. It gives a well-proportioned raster, but the video signal was not getting through to the CRT. It has a VHF radio with positions for Home, Third and Light included in the turret tuner.

I started by replacing the video demodulator diode (V5) which did not make any difference. Replacing C24 which is the coupling capacitor to the cathode of the CRT resulted in improved brightness with the raster staying focused with the brightness control fully advanced. Replacement of other suspect waxies and Hunts capacitors in the vision stages also did not solve the issue, but C32 which feeds the grid of V3 which is the first vision IF amp valve (EF80) had clearly failed and split open at some point in the past.

After this capacitor had been replaced, measuring voltages at V3 showed that cathode volts were too high at around 5.5 as opposed to the 1.8 specified in the manufacturer’s service data. The anode volts were also too high at 170v as opposed to 148v. Further investigation in this area showed that R6 which feeds the cathode had badly overheated in the past, resulting in it rising from 150R to in excess of 20M! The other resistor feeding the cathode looked okay but had decreased from 39 to 16 ohms, R4 in the HT feed to G2 was also showing signs of having cooked and had gone low from 150R to 50R and likewise with R7, which had decreased from 3.3 to 2.7k. All these were replaced, with a new R6 restoring the vision signal as per the final picture below. Voltages on V3 are now correct. The two 1000pf ceramic caps situated either side of R6 (see pic of PCB below) also appear heat damaged as there are small blobs of solder at their bases, so these will be replaced too. I’m thinking that the failure of C32 would have led to all this overheating and that was probably when the set got placed in loft…

The grid coupling cap to the audio output pentode section of the PCL82 was replaced, as sound was a bit distorted. Sound quality is now good on the VHF radio. The 0.5uf cap in the anode circuit of the boost diode has also been replaced with the result being that I now even have a faint image on the screen with the brightness control turned to minimum. The CRT seems to have plenty of emission which is promising.

There’s clearly quite a bit more to be done and I’ll be tackling the timebase panel next which has a variety of waxies and black Hunts caps needing replacement… It’s very difficult to achieve a stable image at the moment, and the frame timebase is running too slowly as there is visible flicker.
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Old 30th Dec 2022, 9:21 pm   #2
FERNSEH
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Default Re: Pye ctl58vs

Have you replaced the sync coupling capacitor between the video amplifier and sync separator valve? The capacitor is C75 in the circuit diagram in the 1958/59 Radio and Television book. The PCF80 sync separator valve is V21.
Does the CTL58VS employ a turret tuner?
No experience of this particular model. The Pye CTL58F was the model I used to service in the sixties.

DFWB.
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Old 31st Dec 2022, 3:55 pm   #3
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Default Re: Pye ctl58vs

C75 was one of the most grotty looking waxies in the set. I've replaced it today, and whilst the picture won't hold it has resulted in a dramatic improvement as per the photograph below.

This set employs a Cyldon turret tuner. I also have a CTL58F which was also in the loft along with this and my RGD The 17 set. The CTL58F is missing its speakers, speaker grilles and the back cover and the lopty is in a bad way as the raster fades out after a few minutes, even with a new EHT rectifier so I won't be attempting a restoration on that one.
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Old 31st Dec 2022, 5:26 pm   #4
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Default Re: Pye ctl58vs

No frame sync: check or replace C63 and C64. Frame sync integrator components should be OK, C78 and R98. Interlace diode is an M3, not a reliable device.

DFWB.
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Old 1st Jan 2023, 5:41 pm   #5
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Default Re: Pye ctl58vs

Thank you - replacement of C63 resulted in a stable image when the hold control R77 is fully advanced. I initially thought C63 hadn't made any difference, as I was only trying to lock the image with R77 around the mid-point where I get the bottom of the picture half-way up the screen, so I put two 1N4007s in series in place of the M3 diode as recommended on this forum. This worked, but I've since tried the M3 back in there and this works too.

There was a bit of foldover at the top of the picture, but replacement of C69 cured this. A new PCL82 frame oscillator/output valve has also extended the range of R83 (vertical amplitude) considerably.

At present I can't get the picture perfectly proportioned in terms of showing castellations at both the top and bottom - I can only get them at the bottom with a full scan or at both top and bottom by reducing the height considerably. I will continue replacing those old caps which should improve things.
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Old 1st Jan 2023, 8:52 pm   #6
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Default Re: Pye ctl58vs

Have you replaced the sawtooth forming capacitor C67 (0.1uF)?. Also, have you replaced C66 (0.25uF) the coupling capacitor between V12A and V19B?
V19B bias resistor R91 (270 ohms) often goes high value causing compression at the top of the raster. Output valve over biased.
Bypass capacitor is 200uF, 220uF is the preferred replacement value.
C67 is returned to the cathode of V19B to alter the shape of the sawtooth waveform. In a sense a form of pre-distortion of the waveform shape.
A parabolic waveform is developed across C73.

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Old 19th Jan 2023, 3:46 pm   #7
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Default Re: Pye ctl58vs

Update: Having continued replacing caps in the frame timebase and elsewhere, I have a much improved picture. C65 which is the grid coupling cap to frame oscillator measured 1.5MO leakage and appeared to have possibly overheated in the past. This was replaced resulting in the hold point being at the middle of the frame control rather than at the top.

I found that initially it was difficult to get the test card image centralized, as it was slightly off to the right. Adjusting the ion trap and picture centring magnet improved this, but once the main 200, 100 and 60 uF electrolytics had been replaced, reversing the ion trap and centring magnet adjustments resulted in a perfectly centred picture.

The replacement of these electrolytics did not improve the situation with the ‘breathing’ picture and neither did the replacement of the dual 16uF electrolytic which I noticed had been running rather warm. One of these is part of the power supply smoothing circuit and the other is in the G2 circuit of the frame output valve.

I then replaced C87 which is a 1uF electrolytic with a 2.2uF component as that is all I had to hand. This is situated on the HT rail to the frame oscillator and is also coupled to a tapping on the LOPTX. The replacement of this has pretty much cured the breathing issue and I’m now getting a very nice stable picture.

The EHT overwind is only just warm to the touch after 20 minutes or so operation, but as the set has not yet been used for any extended period of time I’m going to pass DC through the overwind for a day or so to make sure any moisture is expelled and then hopefully it won’t fail during soak testing.
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Old 19th Jan 2023, 5:55 pm   #8
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Default Re: Pye ctl58vs

That’s looking great Laurence, well done!


My only concern is the position of the ion trap. This must not be used to centre the raster. It should be adjusted for the brightest picture only, and should reside close to the CRT base.

I would recommend you re adjusting this for the brightest raster, irrespective of the picture position, then trying to centre the raster with the shift rings.

Cheers.

SimonT.
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Old 19th Jan 2023, 8:52 pm   #9
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Default Re: Pye ctl58vs

Hi Laurence.

Attached below is the guidance recommended by Mullard for the adjustment of ion trap magnets.

I hope you find it of help.


Cheers.

SimonT.
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Old 27th Jan 2023, 11:40 am   #10
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Default Re: Pye ctl58vs

Quote:
Originally Posted by thermionic View Post
Hi Laurence.

Attached below is the guidance recommended by Mullard for the adjustment of ion trap magnets.

I hope you find it of help.


Cheers.

SimonT.
Thanks for that Simon. I have re-checked the setup and since I replaced the main power supply electrolytics I've been able to get a properly centred picture with the ion trap set correctly.

I've been passing DC through the EHT overwind, although my DC power supply only goes up to 16.4v and the current passed at this voltage is only 0.28mA and the overwind doesn't get warm, so I don't think this is sufficient.

I have finished replacing the remaining Hunts caps now and I had it running for around two hours last night and the LOPTX was noticeably warm to touch afterwards, but not hot.
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Old 27th Jan 2023, 12:10 pm   #11
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Default Re: Pye ctl58vs

Correction: I meant 28mA not 0.28mA! I should also have said that some 'breathing' of the picture is still evident and I'm now not sure what might be causing this.
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Old 27th Jan 2023, 2:36 pm   #12
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Default Re: Pye ctl58vs

I should also have added that I'm having to adjust the line hold regularly during the first 15 minutes or so of viewing, as hold is lost every few minutes or so until it eventually settles down. The line oscillator is the triode section of V21 which is a PCF80, so I will try substituting a new valve to see if this makes any difference.
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Old 28th Jan 2023, 3:38 pm   #13
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Default Re: Pye ctl58vs

I was pleasantly surprised to find that replacing the PCF80 resulted in a stable picture from switch-on, requiring no subsequent adjustment of the line hold control at all. So the set now seems pretty much sorted and gives a good quality picture, with the only remaining issue being the breathing picture, which isn't that noticeable when watching a programme.
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Old 24th May 2023, 8:41 pm   #14
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Default Re: Pye ctl58vs

I have been continuing to work on this set over the last few weeks, as I had to replace a newly discovered hidden Hunts mouldseal feeding the grid of the triode AF amplifier and replaced the cathode bypass electrolytic for the same valve (PCL82). I purchased some electrolytics for the main power supply with a higher ripple current rating, as some of the ones I had put in originally were not sufficiently rated. Doing this has improved the situation with the breathing picture, although not completely eliminated it.

I have also recently been getting intermittent frame collapse which could be temporarily remedied by wiggling the PCL82 frame oscillator/output valve in its socket. Attempting to clean the base contacts with Deoxit did nothing to help, so I obtained and fitted a new ceramic base and operation is now stable and I’m having trouble free operation. I’ve had to spend quite a bit of time cleaning wax from the surface of the timebase panel from those old wax capacitors that had become warm and melted everywhere. I’ve also been listening to R4 on the inbuilt FM radio which seems to give very good sound quality.

All in all I’m very pleased with this set, which I will be using on a regular basis.
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Old 27th May 2023, 3:22 pm   #15
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Default Re: Pye ctl58vs

Whilst you state that the sound quality is good, this has the smallest speaker I've ever seen on any Pye TV.
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Old 28th May 2023, 9:15 am   #16
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Default Re: Pye CTL58VS TV.

Hi Edward,
It has two speakers, so a regular 6 1/2 inch one mounted on the side of the cabinet and a 3 inch tweeter on the front between the controls.
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