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Old 25th May 2010, 4:51 pm   #641
oldticktock
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Default Re: Pye v4

That is going to take me forever as there is not one original cap left in circuit except the electrolytics (actually 2 of those were changed as well), 17 resistors changed and 4 diodes.

Scan coil tags ok
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Old 25th May 2010, 5:07 pm   #642
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Default Re: Pye v4

You dont need to check everything, the problem is in the line stage, and no doubt to do with the heat, so forget frame, audio and other parts.
Now look at the circuit, you will see the PY81 the anode takes its HT from F1 as you know the current in a diode flows from the anode to cathode so you should check the voltage on the anode then the cathode, use a meter with a pointer here as if the line stage should work you may blow your DVM. there should be a volts drop between the anode and cathode but only a few volts if its a big drop that would mean the valve is conducting hard, strange though that F1 hasnt blown, after this check the volts on the PL81 top cap and see if this any different to the volts on the top cap of the PY81, if this voltage is low too take the top cap off the PL81 and measure the volts on the PY81 top cap again, if it goes up something is loading up the line stage, could be shorted turns or an external component.
Did you know you can test a lopt with a scope (the best tool you will have you know)
Lets know your results!
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Old 25th May 2010, 5:16 pm   #643
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Default Re: Pye v4

Trevor, do you really mean putting a meter probe on the top caps of the LOP and bost diode? If things are working there's several kV of pulses which most meters really won't like.
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Old 25th May 2010, 5:22 pm   #644
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Default Re: Pye v4

Hi, Jeffrey, did it for years, Avo's are ok but wouldn't dream of it with a DMM,
In honesty these old sets dont have a lot of pulse on the PL/PY top caps, try drawing a spark on the V4 top caps you will be lucky to see a spark even on a good one.
One thing you will notice on these is how bad the EHT regulation is there's not a lot of current available.
I am just trying to find out where the fault is, OTT I think is way over his head here and as from the start feel he needs someone sitting beside him!
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Old 25th May 2010, 5:27 pm   #645
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Default Re: Pye v4

Thanks for the explanation. I suppose I first came to TVs in the 110 degree single standard era where there was always a decent spark to be had from the top caps.
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Old 25th May 2010, 5:47 pm   #646
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Default Re: Pye v4

I thought the Bench DMM being good for 1000V, would be ok? anyway.

Using AVO 7 set to 400V

Anode of PY81 rose to about 160V then dropped off quickly down to 100V I switched off as PY81 get's very red and hot.

Tried again for cathode (TC) hardly registers. Tried again on anode this time rose to about 100V then drops off 50V

Is the second attempt poor due to the heat generated and I need to wait for cool off?

Edit1: tested volts on PY81 TC (anode)..... 15V
Edit2: tested volts on PL81 TC......nothing
Edit3: removed PL81 TC and then test TC of PY81, get about 15V

Last edited by oldticktock; 25th May 2010 at 6:03 pm.
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Old 25th May 2010, 6:19 pm   #647
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Default Re: Pye v4

Just a thought. The top cap of the PY81 is the cathode, not the anode. If it glows red [anode] there is heavy current flowing. Does the line output stage liven up a bit with the top cap removed? [small spark on anode of EY51?] Also check for S/C boost cap C106 .5uf and C106 .1uf. Lack of line drive will result in the anode of the PL81 glowing a dull red but this usually does not cause overheating in the PY81. Bit of a mystery. J.
P.S. I would use the AVO with this receiver. Digital meters can give misleading results and confuse the situation. They are also much tougher if modestly overloaded.
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Old 25th May 2010, 6:38 pm   #648
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Default Re: Pye v4

Hi John,

On my way to your predicted 126 pages......

With the Top cap connection removed from the PY81, the cherry red core does not happen, I measured 210V on the topcap of the PY81 valve, PL81 reads 0V

210V on one side of C57 (boost cap) 0V on the other

Last edited by oldticktock; 25th May 2010 at 6:48 pm.
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Old 25th May 2010, 7:51 pm   #649
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Default Re: Pye v4

With top cap leads removed

PL81
TC1(a) -9V
pin9(k) 1.2mV

PY81
TC1(k) 216v
pin9(a) 216v
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Old 25th May 2010, 8:26 pm   #650
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Default Re: Pye v4

With the top cap of the PY81 removed there is nowhere for the current to go! Hence the same readings on both anode and cathode (a valve is very nearly a perfect diode with no load). The PL81 then will only draw current thro the Screen grid (G2) a far from ideal situation I may add, and will quickly shorten the valve's life. I see that the anode is a minus voltage which would make me think there is line drive on the control grid G1.
So there is something that is really pulling current from the PY81, I would assume (hopefully) that you have checked the LOPTx per-se and this is not the problem so either C57 is short or breaking down under load or the LOPTx is also breaking down under load.
I feel now that I must now advise you to take the set to someone to give you a second opinion, it's really hard to this here, in all honesty I feel I must now stop. Feel free to take the set to David Boynes who if he has time would look at the set or he can bring it up to the Scottish meet and we can do the repair here and log it on this thread at the time with photos and text of what we are doing, but right now I personally would draw a line.
I am still in a lot of pain and am struggling with the PC.
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Old 25th May 2010, 8:43 pm   #651
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Default Re: Pye v4

Yes Trevor, you have been more than helpful and I would not expect you to continue with this remote assistance especially in your condition.

Thanks to all others who contributed and those who came along for the ride, I almost got there, I was that close to completing it, the picture was starting to look good, this just turned into an unexpected road crash.

As I said in a pm, I need to put this to one side and have a go at one of my other Bush sets, I'm in danger of loosing any confidnce that I had built up on the previous 2 sets, so I will tackle either the TV53 or TV22.


Chris
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Old 26th May 2010, 12:05 am   #652
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Default Re: Pye v4

Quote:
Originally Posted by murphyv310 View Post
Hi, Jeffrey, did it for years, Avo's are ok but wouldn't dream of it with a DMM
A bit OT but I wish someone had told me this before I fried an almost new DMM doing just that. It wasn't a cheap meter either. That mistake cost me almost 50 euros
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Old 27th May 2010, 10:10 pm   #653
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Quote:
Originally Posted by oldticktock View Post
Ok Trevor did exactly as you said, all removed from lopt except TC for PL81 & PY81 & EHT

This has now stopped the PY81 centre core form looking like it's going to go critcal mass on me.
I think this test may have disconnected the cathode connection to the PY which is through the linearity coil.

Trevor suggested it might be a lack of line drive. Remove F3 the line output fuse and measure the grid of the PL, it should be negative.
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Old 28th May 2010, 8:41 am   #654
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Default Re: Pye v4

Hi PJL,

Had a break from the PYE for a few days infact from TV's totally.

Not had chance to try your test yet.

One thing I did do yesterday morning was replace the PY82's with NOS and powered up If you remember I had to set the voltage tap to 220V due to the Dropper lash up failing but the original centre section is ok, which allows 220V to function. I noticed that there was white sparking going on at the bottom of the new valves and switched off straight away. I Put the old ones back and they don't do this, but i'm not sure but they don't seem to be that bright when they are up and running. I Will remove and connect the heaters to my bench PSU and observe then I will know if that's relevant

Think I need to do some checking later on when time permits (car MOT today )but I wonder if the dropper lash up failing caused something else to fail when I was on 240, Both the 10R and 20R that I added are O/C. I think the above is either a red herring or signifcant.

Chris
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Old 29th May 2010, 12:22 am   #655
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Default Re: Pye v4

While searching through Television for something else I came across this vintage TV article.

Keith
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File Type: pdf Pye V4.PDF (306.1 KB, 865 views)
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Old 29th May 2010, 4:34 pm   #656
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Default Re: Pye v4

An update,

After bashing my head against the PYE V4 for a few days it started to leave a dent in my forehead so I contacted Teleman, who lives just down in the next village.

The V4 lives again and looks like the hairdrier treament worked on the LOPT boost stays at around 455V and any residual moisture will hopefully burn off with use.

Now you are probably wondering what was the fault, it was the scan coil screen lead!!! the hairdrier treatment must have shorted it out. Teleman went straight to this first test There was me looking at everything else but that nice fat black screened lead.

Teleman did witness this V4's bad attitude though, so he can vouch that it is a very moody set as after replacing the lead it decided to not work at all, this was overcome and it was left running. Teleman also verfied my bad contrast pot and replaced that.

I get it home and switch on .....dead as doormouse.... the 500ma fuse had blown, replaced and it's now running, see what i mean attitude or what!

So what's left to do, the dropper needs sorting out and a better CRT, the dropper will get done the other will have to wait for one to turn up. Just glad that this is finally sorted I can continue now with a clean sheet with nothing bugging me. I felt like I could not move on to the next set without this nagging uncomfortable feeling of something not completed.
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Last edited by oldticktock; 29th May 2010 at 4:57 pm.
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Old 29th May 2010, 5:48 pm   #657
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Default Re: Pye v4

Hi Chris , You have done a great job on the restoration of this set , as i remaked the neatness of your work is very good . I think with a good crt & a bit of tlc this set will make a fine example of a PYE V4. Keep up the good work, any problems you know where i am , Chris..
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Old 29th May 2010, 6:00 pm   #658
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Default Re: Pye v4

Quote:
Originally Posted by oldticktock View Post
An update,

Now you are probably wondering what was the fault, it was the scan coil screen lead!!! the hairdrier treatment must have shorted it out. Teleman went straight to this first test There was me looking at everything else but that nice fat black screened lead.

.
Hi OTT
One thing I said to check in post 640! (pvc wiring)
Can you please return the spare LOPTx that I sent you, I somehow dont think you will need it!
Glad you have a result now.
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Old 29th May 2010, 6:03 pm   #659
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Default Re: Pye v4

I know....... I'm a numpty........ no problem Trevor PM me your address and It will be returned.
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