Pye CT205 various faults - a success story!

[Mikey405]

Hi Taz.

All you need to do is disconnect the 2 little leads (Red and Blue) from the decoder to the CDA panel to rule out the decoder.

I think a scope would be an invaluable aid to sorting out this problem Taz. I can send you a disc with a cross-hatch pattern on if you would like, and then you can get the scope on the CDA panel and start comparing the blue with the other signals. I'm sure you'd be able to find the fault pretty quickly then. If you get stuck, I can always send you another CDA panel, but it may have a worse fault than this one, or you are welcome to bring the set up to Solihull, but it is a bit of a journey for you down in London.

It's interesting that the effect is present to a slight degree on the Green too. The G-Y being generated partly by the B-Y of course. This may point you in the direction of checking on the low-voltage side of the CDA panel too. Perhaps C359, R370, R373 or R364? Maybe even VT31 itself...

Thanks Taz.

Kind regards.

From Mike.
PS. I have dozens of NOS PL509s if you want one.
PPS. Do you have a picture of the red output on its own?

[Tazman1966]

Hi Mikey.

I've given up on the football yawn! I'll get back on to the set now and try to disconnect the leads to confirm that there's no fault on the decoder (well none that would cause those symptoms.

I'd love a NOS PL509 if that's okay I'll swap it for some fluorescent fittings for your loft!!!

By the way the strange coating that appeared to be on the front control panel is nothing other than the original packing that was still left on there and never pealed off. It is still like new underneath

Thanks Mike and all the best,

Tas

[Mike Phelan]

Tas
You do have a decoder problem, witness the Hannover blinds, but the smearing / ringing is definitely in the CDA panel, as you will have proved by swapping the panel and disconnecting the inputs from the decoder.

The colour not turning right down is not too much of a problem; if you really want to kill the colour, taking out the two aforementioned leads does just that.

The blinds are a problem around the PAL delay line or chroma demodulator cct, but you need to get the blue sorted first.

[Tazman1966]

Hello Chaps.

WOW! Some progress. As I suspected having a real close up look at the photographs I had a feeling that the colour signal was really messy (remember I said that you couldn't quite turn off the colour control) and sure enough on disconnecting the little blue lead and the little red lead and a great monochrome picture is the result. So despite all of our initial thoughts the fault is on the decoder panel.

Time to get Bruce's scope out and see what is causing the blue signal to be so "messy" (well I knew I'd have to work on the decoder sooner or later with those dreaded Hanover Bars)

All the best for now,

Tas

[Steve_P]

On the colour control, front panel, is a Largish Electrolytic Cap. I've not looked any further, but what if it was Open Circuit.

Cheers,

Steve P

[Tazman1966]

Hi Mike P.

Now I'm really confused.

As I said a bit earlier (I think we were typing at the same time!) disconnecting the inputs to the CDA panel from the decoder panel gives a good clean monochrome picture.

Get this though! Even more weird is that if you disconnect the blue lead on its own there is a pretty good picture without B-Y of course but without ringing/smearing. If you disconnect the red lead and re-connect the blue lead you get a pretty good picture without R-Y and NO RINGING. Connect both leads and the ringing comes back.How could that be? Is something happening whn the two inputs are mixed to get the green?

Confused? I sure am.

Tas

[Focus Diode]

I would imagine there's two seperate faults ie: ringing on the CDA, proven by swapping the panel and hanover bars on the decoder. I would deal with one fault at a time to avoid confusion. You certainly raised an interesting point about incompatability between the Pye and Dynatron panels. usually lack of black level clamp (with flyback lines) is due to the BC108 transistor close to the PL802 on the CDA panel, but if all is ok on the Dynatron it seems there are extras on this panel that make it incompatible with the Pye one!

Cheers,
Brian

[Steve_P]

Right, well here goes with my thoughts:

CDA Panel. Swap the valves out - you never know. If this doesn't cure it, don't muck about - Swap VT29, VT30, VT31. There's 3 electrolytic caps - Two go to deck and the third one links Green to the other two. Again, swap all three.

Decoder Panel : This from Mikey's site...

'Extremely bad hanover blinds with incorrect colours (Yellow jaundice flesh tones): (D/S and S/S) This is caused by the PAL bistable not reversing the phase of the R-Y signal on alternate lines. Check D26, D27, VT22, VT23 on the PAL decoder board.'

Does this help.

Cheers,

Steve P

[Tazman1966]

Hello Guys!

R E S U L T!!!

Whilst trying to see what the fault looked like when swapping the little blue and little red leads over i.e. the inputs from the decoder I had the telly switched on and happened to catch a glimpse of the screen as I had my hands on the leads and pulling them about and noticed that the fault started to vary wildly and got even worse. I found that by moving the clump of leads around I could make the fault almost vanish?!! When the leads from SK17, SK18 and SK19, the outputs from the CDA panel to the tube grids, were lifted up as high as possible the fault vanished.

Glancing at the Dynatron I noticed that these leads were in a sticky yellow tape sheath thing all equally spaced from each other along with the leads from PL13 and the whole thing was suspended from the shield of the CRT by a plastic band. Now I understood what was happening. The yellow tape thing had long since lost its stick and was in fact sitting on the bottom of the cabinet when I first opened it up. It ended up in the bin unfortunately. These leads were therefore allowed to be draped on the panel and the red output lead was actually threaded under the little blue input lead from the decoder and the others were nearby as well. What I assume was happening was some sort of feedback or interference of some sort between the inputs and the outputs of the CDA panel. Who could've guessed that it could be as simple as that?

The pictures show what I mean. The first is of me trying to point to the offending lead dressing. The second is the rather snazzy made up tape thing for which I used parcel tape. The third and fourth pictures show the resulting improvement in the picture.

I tried to take some close ups of the fault on the screen when varying the dressing of the wires but they didn't really come out.

As you can see, the Hanover Bars are not too bad now as I adjusted RV12(PAL balance) on the decoder and got a much improved result.

Some bits are still to be done(convergence panel fault, tuner buttons 1 and 2 etc) and it has developed another fault If you flex the boards or wiggle the wiring loom you lose field sync and the colours turn into rainbows. More dry joints or loose connections I suppose.

Here's the pictures at this stage. Hope you Pye fans like 'em

All the best and thanks chaps,

Tas

[Hybrid tellies]

Even some non Pye fans like it. Great news and congratulations on finding this fault.
Memory is a wonderful thing especially when it's jogged. The company I use to work for was a Dynatron dealer in Bath so we use to see an awful lot of the Pye 691/697 chassis, and yes now I can remember getting all sorts of strange faults caused by those leads not being correctly positioned, especially after changing crt.

[Focus Diode]

Should've remembered that too Simon! Well done on getting the set running to a very high standard! Looks superb!

Despite their problems I do like these sets as long as the poor EHT regulation can be tolerated and the set not used for VHS playback which is abysmal, and modifications introduced, although helpful, do not completely eliminate problems. Thankfully with DVD this is not a problem!

Well done again Tas!

Cheers,
Brian

[Mike Phelan]

Bingo!

As I said a bit earlier (I think we were typing at the same time!) disconnecting the inputs to the CDA panel from the decoder panel gives a good clean monochrome picture.

I think we were! It seemed even weirder when I saw that the ringing fault went when you dissed the decoder output. That did not make sense, and when this happens, it is inevitable due to something obvious or silly.

I guess someone had twizzed the PAL balance pot in a vain attempt to cure the fault (!)

So, the fault was after the CDA and before the tube. I should have remembered spraying switch cleaner on my hands to remove the sticky yellow mess on my fingers when I serviced these.

I'll archive this thread in due course ...

[Tazman1966]

Morning and thanks guys for all your input. When I've finished the remaining faults and sorted the cabinet out I'll put up some nice pictures of this Pye on it's stand too.

All the best for now.

Tas

PS I'm sure I'll be on the cadge for help again soon!!!

[Focus Diode]

Hi!,

Here's a couple of Pye set scans! The first is from the later CT205/2 black and white cabinet version. This is dated 10 FEB 1975! I used this set domestically for over two years with just one breakdown (after 9months).

The second is a 305 in poor shape, dreadful tube!

Cheers,
Brian

[Hybrid tellies]

Great pictures, on the first picture, looking at that test card, is there a little bit to much height?

[Tazman1966]

Hi Simon.

Nice to see Brian's pics and another Pye Hybrid in working order. The comment about height may be right but if you remember with these sets the regulation wasn't all that and so the brighter the picture the more height and less width there was so if you set the height right for a very bright picture such as the test card when you get a darkish picture the height is underscanned and given the twinkling teletext lines at the very top the underscan becomes very noticable hence the need to overscan on bright scenes.

I really must practice at not being so wordy

Tas

[Focus Diode]

Indeed the height was high Simon, it was set for deliberate over-scan to avoid the gap at the top and bottom of off-air pictures. This wouldn't be neccesarry nowadays of course with Freeview!

On the 205/2 you can just see the slight purity error on the left. The original speaker failed so I fitted another (with feed resistors to get the ohms right), this dramatically improved the overall sound quality although the purity error was introduced!

The Pye's and 26" Invicta are safely stored at System A's place at the moment, I'm off in June so I'm tempted to bring them here!

Cheers,
Brian

[Hybrid tellies]

Hi Brian & Tas
I did notice the purity errors but not sure if that was the photo or not. It's funny these sets were the bane of our lives at times but you could not help but have a soft spot for them.
Ref the poor EHT regulation, one morning the boss pointed out to me the slight lack of height on a recently repaired Dynatron in the workshop, I cleared the fault by reaching out to casually turn the brightness up. I did not say a word but all the other engineers in the workshop just roared with laughter.

[Tazman1966]

Hello Folks.

Well my work on the Pye is complete

The final bits and bobs that I did are described here.

First the annoying blue line convergence. What was happening were that the blue horizontals were bowed and could not be adjusted with RV29 the Blue Amplitude pot. You could get a sort of compromise effort by adjusting RV28 the Blue tilt and L51 Blue Parabola but then after a few minutes it would gradually drift out again and there seemed to be a bit too much heat around the wirewound in series with RV28 (which seemed to be very scratchy). Out came the meter and I found that RV29 was stuck at 20R so as I hadn't got a replacement, I took the pot apart and cleaned and bent the wiper up to make a better contact. I put it back together and tried again...still no adjustment. Then I did what I should have done in the first place and checked the little 10R wirewound in series with it and found that it was open circuit. The overheating around RV28 should've given me that clue as the two systems are in parallel with each other. I replaced it with a 7W one - the only one to hand and a bit on the large size but I just managed to make it fit! Now the control worked and with the aid of my trusty crosshatch DVD did the convergence from start to finish and I'm very pleased with the result. I must say that even at 7W the new resistor gets quite hot too.

Next was the push button unit. I suspected that the springy contacts on buttons 1 and 2 may have been snapped at one end although I seem to remember that unless they snapped off completely the whole unit jammed up. Sure enough the contacts had snapped of completely and were nowhere to be seen so no repair to that However with the buttons out it gave me the chance to give them a really good scrub and boy did they need it. All of the grooves were caked in brown gunge. You can see the clean result in the picture.

As for the dry joint causing the intermittent rainbows...who knows? I could not get it to do it anymore

Time to do a real good clean on the cabinet. The soapy water was filthy and yellowy brown afterwards but the top and sides are in remarkably good condition. Maybe the nicoteen preserved them.Next what to do about the chipped and missing bits of veneer on the front surround. Well I said I had an easy fix for that. I stripped the remaining pieces off and then sanded down the chipboard until smooth and then using some matt black insulation tape stuck it to the smooth clean edges and then trimmed the excess with a Stanley knife. I hope you agree it complements the black control panel etc.

Finally a polish up, a set up (inc reducing the EHT for added reliability) and a soak test in the garage it was time to transfer the set to the house and give it pride of place on the sideboard like the Philips and the Dynatron before it.

Here are some pictures. I'll have to split them between two posts. Hope you like them and soon the Pye and Dynatron will be side by side in my little collection alcove in the back bedroom but more on that another time!

All the best,

[Tazman1966]

...and here are the other pictures with one picture especially for Mikey405 without whom I would not have had the set - a massive thank you matey!

By the way if anyone has a scrapper with a decent push button unit that would be great so I could have all six buttons working.

Cheers and thanks to one and all for your help and encouragement.

Watch this space for the next restoration - you'll like this one Dr Watts!

Cheers

PS: Sometimes there are line on the photos which are not in real life. I notice you can get rid of them if you make the pictures bigger when viewing them.