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Old 10th May 2010, 8:40 pm   #521
oldticktock
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Default Re: Pye v4

R41 is 5.3M so within
R43/44 my meter cannot resolve
C37 not changed, only electrolytics changed so far, are C33 and C98

Edit is me or are the T/C grid lines now better since the C33 change see last pic in #503 and first pic in #519

Last edited by oldticktock; 10th May 2010 at 8:45 pm.
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Old 10th May 2010, 8:42 pm   #522
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Default Re: Pye v4

Quote:
Originally Posted by oldticktock View Post
R41 is 5.3M so within
R43/44 my meter cannot resolve
C37 not changed, only electrolytics changed so far, are C33 and C98
If you are using a DVM wait for a good few minutes beforereading R43/44 or snip one end off each resistor connection C37 may be o/c, that can cause cogging
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Old 10th May 2010, 8:44 pm   #523
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Default Re: Pye v4

Ok, DVM clipped and waiting on R43

Edit 1: well that can't be right tops out at 23.1K resistor is correct resistor has Y/V/O colour bands



Edit 2: C37 measures 42V as does pin 2 of V8 can I clip in a 15 uf, neg on chassis and pos on pin2/ would that help show if it is?

Last edited by oldticktock; 10th May 2010 at 9:10 pm.
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Old 10th May 2010, 9:28 pm   #524
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Default Re: Pye v4

Go for it! perhaps snip the resistors and check!
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Old 10th May 2010, 9:38 pm   #525
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Default Re: Pye v4

Cap made no difference
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Old 10th May 2010, 9:41 pm   #526
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Default Re: Pye v4

B*m, back to the drawing board but tomorrow for me I am afraid.
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Old 10th May 2010, 9:49 pm   #527
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Default Re: Pye v4

Chris, did the verticals improve with C33?

I would like to chase the video fault that is causing smearing. We could really do with some help from the experts though. Black to Grey produces a white band and Whilte to Grey produces a black band. In my simplistic mind this sounds like decoupling.

As you have not replaced the main HT caps and there seems to be no other decoupling I am thinking we might add some to see if it helps.

We need something like a 0.1uF 400V and you need to wire it in to the HT end of R31 and chassis.
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Old 10th May 2010, 9:56 pm   #528
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Default Re: Pye v4

Yes it got better after C33, just let me find R31
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Old 10th May 2010, 10:05 pm   #529
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Default Re: Pye v4

I think C33 was upsetting the video AGC so the signal presented to the sync seperator was too large. The V4 is very complex and all the bits interact.

A new C51 might improve the sync, and C45 might change the line frequency and linearity so probably ought to be changed.
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Old 10th May 2010, 10:05 pm   #530
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Default Re: Pye v4

ok found R31 one end is on L18 I take it the other end is HT. Just checking as it's late and i'm tired, another day at this beasty. If ok I will clip in a 0.1uF 400v on that point and the other end to chassis

Edit: C51 &45 for tomorrow then

Last edited by oldticktock; 10th May 2010 at 10:21 pm.
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Old 10th May 2010, 10:07 pm   #531
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Yes, you want the other end to L18
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Old 10th May 2010, 10:08 pm   #532
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ok thought so here we go.........
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Old 10th May 2010, 10:10 pm   #533
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Default Re: Pye v4

one quick observation is the picture filled more of the screen on start up
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Old 10th May 2010, 10:14 pm   #534
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Default Re: Pye v4

Well that cap should probably stay as it made the initial screen size a lot better, and the little bit it needed to grow to fill the screen, did not take long.

Still have the centre little blocks with smears
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Old 10th May 2010, 10:56 pm   #535
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Default Re: Pye v4

Sounds like the HT caps are a bit tired.

It's overshoot and not ringing. This is where a scope would come in handy. I think at this point I should leave it to someone who understands the likely causes.
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Old 10th May 2010, 11:24 pm   #536
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Quote:
Originally Posted by PJL View Post
A new C51 might improve the sync, and C45 might change the line frequency and linearity so probably ought to be changed.
Forget linearity, brain off line.
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Old 11th May 2010, 12:20 pm   #537
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Default Re: Pye v4

Jon Evans has kindly scanned the genuine Pye V4 and VT4 manuals. I discovered this from the other V4 thread. You can download them from http://www.thevalvepage.com/tvmanu/pye/body_pye.htm
Scroll to the bottom of the page.
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Old 11th May 2010, 12:27 pm   #538
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Default Re: Pye v4

Thanks Jeffrey and a HUGE! thanks to Jon (Duke_Nukem) for the V4 manual.

Having problems this morning with my solder station not getting to good temperature, pesky imports.

To circumvent this minor irritation I have been clipping in the electrolytics along side their originals and observing any changes, so far nothing.

I shall now have a read of the V4 manual.

Chris
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Old 11th May 2010, 9:32 pm   #539
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Default Re: Pye v4

Had a bit of a rest from diagnostics and spent the afternoon reading the PYE V4 manual and Spreadburys Vol2 on Video stage. Then decided to go over the work I had done thus far with the manifying lamp. I was particulary intersted in the contrast issue where turned anti-clockwise it gets to a point where the screen blanks, wind clockwise from that point and it seems to have little effect.

Reading about the APC, the contrast, the APC amp, and the smoothing circuit C45,R57 & C46, made me look at this area again. Checking the schematic I could see C46 I had replaced, R56 and R57 which had been checked, but I could not see C45. I started to think it was missing but got some tweezers in amonst the wires and low and behold buried under them was another little bad hunts, the missing C45 .002 sneaky little blighter.

I will replace that when I can get an Iron sorted out, not sure what effect it may have but it may help as it is part of the APC circuit.

Edit: what was I waiting for!! just snipped one leg of the old cap, clipped in a new and powered on. Did not notice much so whilst the set was powered on I removed one clip from the new cap and the picture went darker re connected and it went brighter, good this seeing the effects of caps in a live situation, makes it's effects more understandable.

Chris

Last edited by oldticktock; 11th May 2010 at 10:01 pm.
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Old 11th May 2010, 10:43 pm   #540
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Default Re: Pye v4

It's the capacitor that stores the pulse from the sample. This would have reduced the effectiveness of the APC but you are manually setting contrast anyway and your video source is very stable.

It's the smearing that needs sorting. Here are a couple of questions:
What happens if you turn contrast down and brightness up? Does the smearing reduce?
What happens if you add attenuation? Does the smearing reduce?
Can you try different valves for V8 EF80 and V9 ECC82.
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