Thread: Pye V4
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Old 11th Apr 2019, 8:03 pm   #50
Davewantsone
Hexode
 
Join Date: Dec 2011
Location: Wigan, Greater Manchester, UK.
Posts: 291
Default Re: Pye V4

Quote:
Originally Posted by Vintage Engr View Post
I've just purchased a VT4 today, so everyone's hints & tips are most useful.The one I have looks as if it has had no previous repairs. The chassis has never been out, no rust, just a very thick 'carpet' of fluff.

I used to repair quite a few of these in the early '60's, but it's a long while ago now, so hearing from others in respect of possible problems is very useful.

I have recently had a couple of Philips 17TG100U LOPT's fail for similar reasons, i.e hygroscopic windings, so I shall be especially careful, as I need to get these two re-wound.

David.
I hope you will be successful.
The way I got mine going was to first of all replace every 3nF capacitors (most will be U/S) then the 0.001, 0.01 and 0.1uF capacitors.
Replace the v24 and v25 diodes with 1N414 diodes.
Check R126, R127 and R129 for correct values
Whilst doing this you may want to first remove the LOpT and connect to a DC power supplyand pump some power into the windings for at least 3 days.
If you could I would "ring" the transformer to see if it appears OK.
I would then reconnect the LOpT.
Remove fuse F3 and using a variac connect power to the set and slowly run it up to the mains potential and see if you get all the valves to light then maybe sound (with a suitable modulator on correct channel).
Now check pin 2 on PL81 and see if you get a negative voltage of around -27V.
Switch off then connect a ammeter across fuse F3. Turn variac up again and monitor current it should not exceed 150mA.
If you are lucky you may see EY51 light up and get some sort of picture!
Good luck.
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