Pye dual standard CTV. No line drive.

[Steve_P]

Why do you want to remove it?

Anyway, a GY501 is a standard valve with a very will insulated base and top cap. Remove the top cap (pull) and lift out valve.

It won't be the problem though.

Cheers,

Steve P.

[MALC SCOTT]

Hi, the GY501 and the PD500 are fitted in the loptx enclosure and are not chassis mounted. There is a large plastic holder which the GY501 base and the PD500 top cap are mounted. I do not want to force it out. I was going to fit a new PD/GY to see if it made any difference. Cheers, Malc.

[Mike Phelan]

Malc
The PD & GY are always enclosed to avoid giving the user a lethal dose of X-rays.
If the GY anode is giving a 1" arc without earthing it, the overwind seems to be fine and you should get a raster, unless the GY is duff (pull anode cap off CRT to check GY s/c A-K and measure the GY heater for o/c) or something is passing excessive current through the PD (remove it to check).

There may be other (luminance etc) faults to prevent a raster, but the PL and PY should not be getting hot now if the LOP stage is sorted.

HTH

[MALC SCOTT]

Hi Mike, thanks for your reply. Do you know how to remove the GY501??
Cheers, Malc.

[Mikey405]

Hi Malc.

Congratulations on getting your set working this well so far.

I know it was the other Mike you were asking, but I hope he / you won't mind if I answer too.

To remove the GY501 is fairly easy. I haven't got a set in front of me down here in Devon, but I think I can remember. Maybe.

- Unplug the TV and fully discharge the tube EHT.
- Undo the two screws that hold the timebase / power supply chassis in to the set.
- Pull out the timebase / power supply enough to reveal the top of the smoke stack.
- Undo the screws (2 I think) that hold on the metal cover on the very top.
- Against spring pressure and the friction holding in the PD500, lift off the top cover and move it to one side.
- Unplug and remove the PD500.
- The ceramic / plastic combined top-cap / socket should now move about fairly easily.
- Discharge the tube (again).
- Pull off the combined top-cap / socket from the GY501 and move it to one side or lift it out if there is not enough room. (You may need to undo a couple of other screws to release the EHT cable.)
- Pull out the GY501 valve.

This is as I remember it, although I may have left out the odd detail here or there. Once you see how the odd springy-mechanism works, it's not too difficult to see how to remove the valves.

If you do replace the valve, it is always worth setting up the EHT regulation again (both valves can affect the setting, and component value drift means the setting is probably a little bit out anyway...) Some sets had a fixed value resistor you have to change, others have a fairly meaty pot underneath. (You should be able to reach both from the removable panel underneath the set.) Once you've set the TV up (give me a shout if you'd like any help), and if you have a good tube, you should have a fantastically good picture. They were always top-notch as far as picture quality was concerned, and are my favourite D/S set by far.

I hope this helps Malc.

Kind regards.

From Mike.

[Mike Phelan]

I know it was the other Mike you were asking, but I hope he / you won't mind if I answer too

No problem, Mike. Us Mikes must stick together.

Malc - from what I remember a few decades ago, it's not a problem removing these bottles as Mike explains. We will wait results with interest!

[MALC SCOTT]

Hi, very good news! I now have a perfect line drive waveform, both in frequency and amplitude. This was due to me not fitting a Suflex type cap in place of C217, 470pf.
I was then rewarded with narrow vertical raster. The EHT measured 26.5KV and the PL509 running at normal temperature. Then the EHT vanished but there is still a nice big arc off the loptx. It looks like the heater of the GY501 is not lighting. I do not have a spare to try. Any other ideas please? Cheers, Malc.

[Steve_P]

If there's a spark there, then it may well be the valve. Whip it out (procedure above!) and check the heaters. You can do this with an Ohmeter. Then, if you get a reading, clean the pins and the socket.

Order a GY501 or borrow one from another set, and try it.

The heater supply on a GY501 comes from a small winding on the LOPT. Is this OK?

Cheers,

Steve P.

[Mikey405]

Hi Malc.

I can send you a GY501 and PD500 if you need them. (I wouldn't look too closely at the GY501 to see if the heater is lit if you don't want a good dose of X-Rays...)