Frustrating day with RGD telly !! - UK Vintage Radio Repair and Restoration Discussion Forum

high_vacuum_house · 16th Nov 2023, 8:33 pm

Sometimes you wander why you start on a telly that doesn't want to go! Had all of this today on a 405 line transportable RGD set and still more work to do.

Lead from LOPT to EHT rectifier anode had broken away from overwind. Repaired and EHT now ok.

EHT now not OK. Screen grid resistor to PL81 gone O/C. Replaced. Now EHT is back.

Frame timebase was working ok. Now off the end of the control. Series resistor value shot up in value. Replaced, now working ok.

Set has lost virtually all signal. After a lot of messing about, the standards converter to aerial socket has gone O/C. Found another and now back in business, though now there is complete frame collapse.

Frame oscillator anode load resistor now O/C. Had to make up one with various values in series. Frame timebase now running ok, but now no sound or video coming through. After more fruitless playing, the tuner valves must be well past it as the variac had been knocked to 225V. back up to 240V and all is well. Looks like 2 new tuner valves needed now.

Video now good but no sound. Wire had come adrift from speaker. Now we have both sound and vision for nearly 20 minutes so far!!

More fun tomorrow I am sure.

Christopher Capener

high_vacuum_house · 17th Nov 2023, 5:26 pm

Well, It has been behaving ok so far and have put it back in the cabinet.
The picture is much better than it looks on the photo, I should have turned the workshop light off as it is very bright with it on, though there is a peculiarity that the horizontal lines on the test card seem to split on the left hand side, though watching a programme, this is not visible at all. I don't think it is a focus problem. The contrast looks washed out but this is an artefact of the room lighting and the camera.

Maybe if it behaves this evening, I will put the back on in the dark, so it doesn't notice!!

Christopher Capener

peter_scott · 17th Nov 2023, 5:35 pm

I hesitate to suggest anything in the presence of so many more experienced TV engineers but perhaps HT ripple at the line output??

Peter

Nuvistor · 17th Nov 2023, 7:25 pm

Didn’t KB/RGD have problems with scan coils causing poor interlace about the time this set was made? Seem to remember it was cross talk between the line and frame coils. You could adjust the coils in some way to help or the usual way was a fresh set from KB/RGD.

16th Nov 2023, 8:33 pm	#1
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,836	Frustrating day with RGD telly !! Sometimes you wander why you start on a telly that doesn't want to go! Had all of this today on a 405 line transportable RGD set and still more work to do. Lead from LOPT to EHT rectifier anode had broken away from overwind. Repaired and EHT now ok. EHT now not OK. Screen grid resistor to PL81 gone O/C. Replaced. Now EHT is back. Frame timebase was working ok. Now off the end of the control. Series resistor value shot up in value. Replaced, now working ok. Set has lost virtually all signal. After a lot of messing about, the standards converter to aerial socket has gone O/C. Found another and now back in business, though now there is complete frame collapse. Frame oscillator anode load resistor now O/C. Had to make up one with various values in series. Frame timebase now running ok, but now no sound or video coming through. After more fruitless playing, the tuner valves must be well past it as the variac had been knocked to 225V. back up to 240V and all is well. Looks like 2 new tuner valves needed now. Video now good but no sound. Wire had come adrift from speaker. Now we have both sound and vision for nearly 20 minutes so far!! More fun tomorrow I am sure. Christopher Capener __________________ A proper radio is one that needs to be moved with a wheelbarrow !!

17th Nov 2023, 5:26 pm	#2
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,836	Re: Frustrating day with RGD telly !! Well, It has been behaving ok so far and have put it back in the cabinet. The picture is much better than it looks on the photo, I should have turned the workshop light off as it is very bright with it on, though there is a peculiarity that the horizontal lines on the test card seem to split on the left hand side, though watching a programme, this is not visible at all. I don't think it is a focus problem. The contrast looks washed out but this is an artefact of the room lighting and the camera. Maybe if it behaves this evening, I will put the back on in the dark, so it doesn't notice!! Christopher Capener Attached Thumbnails __________________ A proper radio is one that needs to be moved with a wheelbarrow !!

17th Nov 2023, 5:35 pm	#3
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,259	Re: Frustrating day with RGD telly !! I hesitate to suggest anything in the presence of so many more experienced TV engineers but perhaps HT ripple at the line output?? Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

17th Nov 2023, 7:25 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,379	Re: Frustrating day with RGD telly !! Didn’t KB/RGD have problems with scan coils causing poor interlace about the time this set was made? Seem to remember it was cross talk between the line and frame coils. You could adjust the coils in some way to help or the usual way was a fresh set from KB/RGD. __________________ Frank