Pye VT4

[Terry]

Plenty of drive to the PL81, at the correct frequency though not locked.

Why would you expect it to be locked, Jeffrey?

It's a phase locked loop and, from your description, there is no line output, so there is a break in the loop!

[ppppenguin]

Exactly. I wouldn't expect it to be locked until the LOP stage is working to some extent. There might be some very weak signs of locking as I bring the hold control to the correct frequency but at present there are none.

Actually I was deluding myself about the LOP drive and need to sort that out. I was using an old scope probe (my nice probes don't usually get used in valve TVs) and it turned out to have a dodgy x10/x1 switch. It was switched to x1 I never normally use x1 probes so always allow for the x10 factor. With some posh probes the scale factor readout is switched automatically to allow for x10 probes.

Incidentally, a Tek 2465B isn't the most obvious scope to use for fixing TVs. However it's the one that's always on my bench and ready for use. I don't even have a simple scope of the sort typically used for TV servicing. I suppose the digital Tek TD210 is about the nearest I get.

[Murphyv310]

I left my V4 on over few hours some years ago on one of the hottest summer days we had at the time. I seem to remember the shed at 33c. The lopt was fried and I cobbled in a Ferguson jobbie. It's still in and gives a far more stable EHT at high brightness. It may eventually get a jellypot so I can refit the screening can.