Pye v4 - Page 21 - UK Vintage Radio Repair and Restoration Discussion Forum

oldticktock · 7th May 2010, 10:17 pm

Sorry PJL, can you clarify the proposal.
Replace C7 then test
then remove the Grid cap and test would that be C62?

PJL · 7th May 2010, 10:20 pm

Replace C7 and measure the voltage at C7 again.

oldticktock · 7th May 2010, 10:21 pm

ok will do, back shortly

oldticktock · 7th May 2010, 10:33 pm

113V now, more sounds coming from speaker now

oldticktock · 7th May 2010, 10:34 pm

There is another of those little caps on V1 I should probably change that at some point

oldticktock · 7th May 2010, 10:35 pm

I have test tone from Aurora......

oldticktock · 7th May 2010, 10:37 pm

something wants to come on screen but I cannot get it

PJL · 7th May 2010, 10:39 pm

The theory goes like this.

If the valve is not oscillating there is no signal on the grid of V2a and the grid is at 0V.

If the valve is oscillating there is a signal at the grid and this is rectified by the grid (the grid behaves like a diode and forward conducts during the +ve half cycles of the AC signal). This will put a -ve voltage on the grid.

As your meter is going to have a significant capacitance, trying to measure the grid directly will stop the oscillator. However, the -ve grid voltage will also reduce the anode current and this should result in a higher voltage on C7 if it is oscillating.

oldticktock · 7th May 2010, 10:40 pm

Test Card almost there by tweaking horizontal/vertical and contrast

PJL · 7th May 2010, 10:42 pm

Hoorah...I suggest you call it a night. The next stage would be to look at the video path. It looks like every ***** capacitor is going to need replacing before this baby lights up.

oldticktock · 7th May 2010, 10:45 pm

Some pics of the screen, the tone is loud and clear and every now and the I can get a glimmer of the test card.

Cheers PJL

oldticktock · 7th May 2010, 10:47 pm

Sorry Trevor did not want to upset you too.

murphyv310 · 7th May 2010, 10:48 pm

Line speed way off! try the hold.
I am leaving this to PJL now
Good Luck

PJL · 7th May 2010, 10:57 pm

Trevor, sorry for interfering again, just happened to be on-line when OTT posted and was following up your direction of thought.

You are far better qualified to finish this off as I know nothing about 405 line tellies...

cheers Peter

oldticktock · 7th May 2010, 10:59 pm

It won't resolve with the line. I have tried tweaks on sensitvity and line and vertical. It wants to but cannot.

Will pick this up tomorrow as suggested. And one hour short of going into the ninth day!!!

oldticktock · 7th May 2010, 11:01 pm

Peter, far too modest that's twice you pulled my sets from the brink. That's what this forum is about all pitching in to help and you certainly have.

oldticktock · 7th May 2010, 11:12 pm

latest

oldticktock · 7th May 2010, 11:28 pm

Quote:

Originally Posted by PJL

The next stage would be to look at the video path. It looks like every ***** capacitor is going to need replacing before this baby lights up.

Hope your around to advise tomorrow, time for some Zzzzzzzzzzzzzzzz

Chris

PJL · 7th May 2010, 11:40 pm

You are on the home straight now. It's just a case of working through the remaining caps starting at the line oscillator then line sync. Based on the state of them so far it's going to need the lot done. It would be a good idea to cross them off a list so you don't miss any. Tomorrow is not good.

ppppenguin · 8th May 2010, 9:24 am

Just look back at the start of this set and think how far you've come. As always the priority is to see something on the screen - your eyes, ears and sometimes nose are very powerful diagnostic tools. Well done!

Apart from the caps, I don't know if the semiconductor diodes suffer in these sets. There are 2 in the flywheel. Not sure what to use as modern replacements though I'd probably reach for the ubiquitous 1N914/1N4148 etc and see what happens. 1N4007 types are probably a bad choice as they are a bit slow for line frequency.

7th May 2010, 10:17 pm	#401
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 Sorry PJL, can you clarify the proposal. Replace C7 then test then remove the Grid cap and test would that be C62?

7th May 2010, 10:20 pm	#402
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Pye v4 Replace C7 and measure the voltage at C7 again.

7th May 2010, 10:21 pm	#403
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 ok will do, back shortly

7th May 2010, 10:33 pm	#404
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 113V now, more sounds coming from speaker now

7th May 2010, 10:34 pm	#405
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 There is another of those little caps on V1 I should probably change that at some point

7th May 2010, 10:35 pm	#406
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 I have test tone from Aurora......

7th May 2010, 10:37 pm	#407
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 something wants to come on screen but I cannot get it

7th May 2010, 10:39 pm	#408
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Pye v4 The theory goes like this. If the valve is not oscillating there is no signal on the grid of V2a and the grid is at 0V. If the valve is oscillating there is a signal at the grid and this is rectified by the grid (the grid behaves like a diode and forward conducts during the +ve half cycles of the AC signal). This will put a -ve voltage on the grid. As your meter is going to have a significant capacitance, trying to measure the grid directly will stop the oscillator. However, the -ve grid voltage will also reduce the anode current and this should result in a higher voltage on C7 if it is oscillating.

7th May 2010, 10:40 pm	#409
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 Test Card almost there by tweaking horizontal/vertical and contrast

7th May 2010, 10:42 pm	#410
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Pye v4 Hoorah...I suggest you call it a night. The next stage would be to look at the video path. It looks like every ***** capacitor is going to need replacing before this baby lights up.

7th May 2010, 10:45 pm	#411
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 Some pics of the screen, the tone is loud and clear and every now and the I can get a glimmer of the test card. Cheers PJL Attached Thumbnails

7th May 2010, 10:47 pm	#412
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 Sorry Trevor did not want to upset you too.

7th May 2010, 10:48 pm	#413
murphyv310 Dekatron Join Date: Sep 2006 Location: Kilmarnock, Ayrshire, UK. Posts: 5,422	Re: Pye v4 Line speed way off! try the hold. I am leaving this to PJL now Good Luck __________________ Cheers, Trevor. MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

7th May 2010, 10:57 pm	#414
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Pye v4 Trevor, sorry for interfering again, just happened to be on-line when OTT posted and was following up your direction of thought. You are far better qualified to finish this off as I know nothing about 405 line tellies... cheers Peter

7th May 2010, 10:59 pm	#415
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 It won't resolve with the line. I have tried tweaks on sensitvity and line and vertical. It wants to but cannot. Will pick this up tomorrow as suggested. And one hour short of going into the ninth day!!!

7th May 2010, 11:01 pm	#416
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 Peter, far too modest that's twice you pulled my sets from the brink. That's what this forum is about all pitching in to help and you certainly have.

7th May 2010, 11:12 pm	#417
oldticktock Retired Dormant Member Join Date: Nov 2009 Location: Weardale, UK. Posts: 1,981	Re: Pye v4 latest Attached Thumbnails

7th May 2010, 11:40 pm	#419
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Pye v4 You are on the home straight now. It's just a case of working through the remaining caps starting at the line oscillator then line sync. Based on the state of them so far it's going to need the lot done. It would be a good idea to cross them off a list so you don't miss any. Tomorrow is not good.

8th May 2010, 9:24 am	#420
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: Pye v4 Just look back at the start of this set and think how far you've come. As always the priority is to see something on the screen - your eyes, ears and sometimes nose are very powerful diagnostic tools. Well done! Apart from the caps, I don't know if the semiconductor diodes suffer in these sets. There are 2 in the flywheel. Not sure what to use as modern replacements though I'd probably reach for the ubiquitous 1N914/1N4148 etc and see what happens. 1N4007 types are probably a bad choice as they are a bit slow for line frequency.