Didn't have to adjust or fix anything to get the image shown here just plugged in an aerial and found a channel and turned the brightness up... not bad considering. Although as mentioned the crt is tired so will try and rejuvenate it to best as possible. Undergoing restoration currently.
EF183(6EH7) - 1ST VISION IF
EF184(6EJ7) - 2ND VISION IF
6AU6 (EF94) - SOUND IF
6GX6 - SOUND DETECTOR
ECL85(6GV8) - VERTICAL OUTPUT/OSCILLATOR
ECH200(6V9) - SYNC CLIP/SYNC SEPERATOR
ECL84(6DX8) - NOISE DETECTOR/VIDEO AMP
ECL86(6GW8) - AGC KEY/AUDIO OUTPUT
ECF802(6JW8) - HORIZONTAL OSC
EL36(6CM5) - HORIZONTAL OUTPUT
EY88(6AL3) - BOOST DIODE
DY87(1S2A) - EHT RECTIFIER
|Chassis hinged down|
I started by replacing all the resistors and capacitors in the video stage thinking it was something around there. The grid voltage on the ECL84 was fluctuating by about a volt or two when the fault appeared so I suspected something was acting up around there. Scoping this pin you could clearly see the video signal varying so I lifted the 330 ohm in series with the grid and the video signal became stable...So something was affecting it enough to upset the video signal levels. I also checked the waveforms coming from the LOPT they were all nice and stable.
Heating the board around this section would eventually make it go nuts, I even temporarily replaced the valve socket thinking it was that, but to no avail.
I then proceeded to look at the AGC circuit as the voltages there were also being affected and heating this area also made the fault really rear its ugly head really fast! I now had the area narrowed down, it was around the AGC pot and associated components. I replaced all resistors and a diode that tested dodgy, nope it was still there. The weird thing is that when I blasted a lot of freeze on all the components, the fault would stay the same. So I changed the pot, still no different! I was really clutching at straws here.
The AGC voltage was all over the place and I'd changed every capacitor in this area also, apart from one that had been changed in the past during one of its repairs. It was a modern looking yellow polyester type.....Hmm I wonder if this cap was faulty? So I took it out and checked it on my cap tester...It checked bang on at .047uf...What the hell!
I was getting ready to put a hammer through this as I'd run out of things to check...So I put in another cap in and would you believe it the fault vanished. That so called modern replacement capacitor was crook! I put the old cap back in and sure enough the fault returned.
Putting the old cap on the capacitance bridge and it seemed ok until I wound the voltage up and then all of a sudden the milliamp leakage meter started to flicker and jump around. So the cap was breaking down under load.
It just goes to show to never assume that a modern capacitor will be ok because its been replaced. And funny how freezing that cap never did anything in circuit, even out of circuit it would only break down when heated but the capacitance stayed the same. Capacitors are strange creatures. And this one looked used when I pulled it out so it was probably one the TV Tech had floating around in his tool kit that was taken out of another set.
At least now (Phew) that problem is gone and I can now continue on with this. Have been replacing more bits and the broken vertical output valve socket so its progressing along nicely. A few evenings have been spent trying to fix that problem... perseverance is the key, along with foul language soothed by cups of tea. You can see the criminal capacitor towards the bottom of the board in the third photo.
There is also a video of this TV now up on YouTube - here is the link http://www.youtube.com/user/glenz1975#p/u
8/10/2011 - Here is pretty much the final update on the Pye as it will pretty much conclude here but on a rather disappointing note. After replacing all the remaining components and power supply filter capacitors/diodes and replacing the broken valve socket on the ECL85, cleaning and adjusting everything up to give a best picture as possible on the weak CRT, I moved it into the rumpus room, set it up and used for about a week and then the picture tube decided to flash over internally and now I get virtually no picture, just a faint negative image.
I checked it on the CRT tester and it now has zero emission now with no cut off adjustment at all. Used the rejuvenate feature on the tester and that did nothing so I can now pronounce the CRT is being officially 'deceased'.
At least though there is some footage of it working on video.
So I guess its pretty much a static display until another CRT turns up an they are very hard to find here. The tube is a 25 inch where as most sets used 23 inch crt's so that makes it even more difficult to track down another. I only have one other Philips set which uses that exact same tube and that works fine and the CRT is excellent so I'm not about to go and sacrifice that for the Pye. I've added some extra photos of it too just to finish. Thanks for reading if you've gotten this far.
28/1/2012 (Photos Added) - I've had some good luck another one of these sets surfaced recently minus the chassis but all complete otherwise so I now have a donor picture tube to be fitted to the Pye and now have some extra parts for this model. Lets hope the donor CRT is ok.
20/7/2012 (Photos Added) - Well, here is the final ( I hope) update on this set it is rather belated and I actually did this back in Feb of this year, but, I fitted the donor CRT and and am happy to say that its works and gives a far better picture than the worn out original. Although the replacement is also a bit down on emissions as per the CRT tester results, it still gives a nice bright picture with plenty of contrast and is totally fine.
There was a bit of mucking around installing the replacement tube as I had to align it up the bezel as it was all off to one side when I first mounted so had to go and loosen all the bolts off and then slide it around to get it centred properly which wasn't that easy! I ended up propping set up at one end using cushions and using a torch pushed the tube around into the right posititon.
Once the set was powered up (fingers crossed that a picture would appear) it was just some yoke adjustments after it had warmed about 20 minutes or so and then the clamp was tightened.
So now I can sit back and use this one now rather than it just sitting there.
Had added some more photos of it running with the new picture tube and some shots of Dr Who from the 1960's. I think some overdue DVD's will be watched now!
|8/10/2011 - Chassis all finished|
|8/10/2011 - Underside view|
|8/10/2011 - The dead bits|
|8/10/2011 - All back together but alas now only a static display now until I can find a replacement CRT.|
|28/1/2012 - The donor set, the cabinet is pretty knocked around|
|Complete minus the chassis as I got it, lets hope that CRT is ok. I will strip this down for the extra parts.|
|Replacement picture all installed and ready to go.|