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Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Found the LOPT (just traced the HT lead back from the tube), insulation looks a bit cracked.....
I'll post again once I've delved a bit further. I'm hoping to be able to run this from the original driver circuit, as well as other drivers, so I'm trying not to damage anything, and taking my time.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I see from these data sheets that your CRT anode voltage is 12 kV - 16 kV, Replacing the LOPT will be the least of your problems in restoring the tele to full working order.
You may find this page on making a 405-line test card generator helpful:
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Proud Mary wrote ...
I see from these data sheets that your CRT anode voltage is 12 kV - 16 kV, Replacing the LOPT will be the least of your problems in restoring the tele to full working order.
You may find this page on making a 405-line test card generator helpful:
Those are very interesting links, PM.
I have too many projects underway at the moment to build the 405 picture generator in the last link in the near future, but I can see that you could adapt that circuit to produce 405 line video.
If anyone else wants to take on this project, please see my post in 'Sale and Trade'.
If there are no takers, I'll probably get around to 'disecting' the LOPT at some point.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
The pitch insulation in antique valve electroncs almost always has those shrinkage cracks. Over years of use, the considerable heat inside valve equipment drives off the more volatile fractions of the pitch, resulting in this kind of destructive shrinking and embrittlement. Age alone does not seem to have this effect, as replacement NOS LOPTs of the period can usually be installed straight from the box in restoration jobs.
LOPT failure was perhaps the most common of the major faults in televisions of the period.
EY51 was the first miniature EHT rectifier to really catch on with post-War TV designers, and its small size also allowed it to be used in HV test equipment probes.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Proud Mary wrote ...
The pitch insulation in antique valve electroncs almost always has those shrinkage cracks. Over years of use, the considerable heat inside valve equipment drives off the more volatile fractions of the pitch, resulting in this kind of destructive shrinking and embrittlement. Age alone does not seem to have this effect, as replacement NOS LOPTs of the period can usually be installed straight from the box in restoration jobs.
LOPT failure was perhaps the most common of the major faults in televisions of the period.
EY51 was the first miniature EHT rectifier to really catch on with post-War TV designers, and its small size also allowed it to be used in HV test equipment probes.
I imagine the insulation is similar to 'Jeffreys Marine Glue', which is used for sealing decks on traditional wooden boats. It is a mixture of bitumen, linseed oil and turps. I could probably 're-juvenate' the insulation by heating with some linseed oil and a drop of white spirit, and then re-applying it. Whether this would be sufficient is questionable, though, as the secondary may be damaged due to the failure of the insulation.
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1957 RGD 'Deep 17' model 'A' (405 line b/w TV)
