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Old 15th May 2007, 12:24 am   #1
Tazman1966
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Smile Pye CT205 various faults - a success story!

Against the odds another Pye Hybrid lives on into the new millennium! Hereís the story so far.

I picked this set up from Mikey405 (cheers once again) after he had put all the screws back into the chassis after the previous owner had left them all out!? I was surprised that amongst its troubles that this poor Pye didnít have lung disease it was so caked in nicotine . Even the mains lead is gooey. (Yuk Ė and I smoke as well!)

When I got the set home after a quick superficial check that everything was where it should be, I crossed my fingers and with one hand firmly on the off switch on the socket, I switched on, gulp!

The sound burst into life in its normal tinny Pye Hybrid way , just white noise at the moment and the valve heaters started to glow. I twiddled one of the tuner buttons and got BBC1 sound but it kept drifting? Hmm, something to worry about later perhaps. My ageing ears started to pick up a faint line whistle but there didnít seem to be any sign of the line output stage breathing some life. Whilst gingerly having a bit of a closer look a plume of smoke started rising from deep in the bowels of the LTB board. Time to switch off and investigate properly which bring me to this evenings activities!

First of all I decided to replace the tripler as it was filthy, gungey and thus suspect and I had a NOS one courtesy of Glyn (Welsh Anorak). Should I try power again I thought? Hmm, better clean the EHT connector on the tube first as it was filthy and covered in sticky goo and showed sign of having been arcing. So out with the surgical spirit and soon the connector, cable and cavity were clean and shiny. Power up again and it was the same as before with smoke rising from place(s) unknown.

I swung the panel down and had a closer look. I noticed that R203 (47k) was burnt out. A-ha the source of the smoke maybe! I replaced it and while I was at it replaced R303 in the heater chain which was the wrong value (50 instead of 22) and was wired sloppily on the print side, with one from my cannibalised ITT CVC8. Power was applied yet again and still no line o/p activity. A quick check with my (well my mate Bruceís) Ďscope showed that all was okay at pin 8 of the PL509. The valve itself looked like it had led a very hard life so I nicked one out of my Dynatron for now and bingo, up rustled the EHT. All that was on the tube however was a very off centre line across the screen and I still couldnít get station to stay tuned. Just then, I saw another plume of smoke and after seeing that it emanated from the frame timebase panel I switched off again.

R258 & R259 were both badly charred and much lower in value than they shouldíve been. The electrolytic (C256) that connects to the junction of the two resistors was leaky, a black bodied ďCallinsĒ, now thereís a surprise! With those components replaced and the AC128 driver transistor re-soldered properly, I though that would be it in that dept.

While the soldering iron was hot I thought Iíd do the usual CDA panel mods and changed the PCL84 grid leak resistors R380/1/2 from 2.2M to 1M (I know the official mod is 680k but that's all I had and surely it's better than nowt?) It was then that I spotted that R361 in the blanking circuit had snapped off. Next was to tidy up the 12k resistor from the anode of the green amp which had been made up of a very wobbly 8.2k 10W wirewound in series with a 4.7k 3W wirewound. I replaced it with a 12k 7W. Ahh, much tidier!

Here we go again and on with the power. I left the plug to the frame timebase out and checked the voltages; -30V, +30V and +15V. Not quite right but not bad. The HT line was a bit high at 305V but as the line timebase got going, it fell to the correct figure of 285V and stayed spot on. There didnít seem to be any signs of distress so I switched off and reconnected the FTB plug. On switching on again I rechecked the voltages in the FTB and they were much closer to what they should be at -24V, +24V and +15V. The EHT rustled up and so did a raster, hurrah! I plugged in the aerial, twiddled a button and up came a snowy colour picture. Ah well itís a start. The heightís a bit on the low side on the max setting and the blue greyscale is very peculiar at the moment but so far so good.

Iíll update the story as soon as I investigate these remaining faults and post some pictures for the other couple of mad Pye Hybrid fans!

All the best,

Tas

PS Sorry itís so wordy but itís been my first restoration thatís had loads to do.

PPS Does anyone know why the tuning was drifting away from the stations at first? Itís rock solid now. Was it the supply to the varicap tuner?
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Old 15th May 2007, 8:22 am   #2
Mike Phelan
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Default Re: Pye CT205 - a partial success story!

Quote:
I noticed that R203 (47k) was burnt out.
Common fault - any carbon resistor that handles line pulses is suspect; this one is for the flywheel sync.
Quote:
(I know the official mod is 680k but that's all I had and surely it's better than nowt?)
Should be fine, Tas. It's not really an official mod, AFAIK, just one of mine, but I would be very surprised if others hadn't reached the same conclusion.
Quote:
PPS Does anyone know why the tuning was drifting away from the stations at first? Itís rock solid now. Was it the supply to the varicap tuner?
Try freezing the TAA550 2-pin regulator (may have been replaced with a ZTK33B). They used to fail quite frequently. Rarely it is the tuner itself.

HTH
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Old 15th May 2007, 4:11 pm   #3
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Default Re: Pye CT205 - a partial success story!

I'm sure I once had a no signal condition due to me forgetting to connect a plug to the CDA panel. I seem to remember the tuning voltage is derived via the CDA one, or am I mistaken?

I once had low gain due to the tuner, but not actual drifting. As Mike says the TAA550 is suspect should the condition re-occurr.

Well done on the work so far Tas.

Cheers,
Brian
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Old 15th May 2007, 5:36 pm   #4
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Default Re: Pye CT205 - a partial success story!

Hi Mike and Brian.

Thanks for the help guys. I've got a couple of busy work and social days so I won't be able to tackle the Pye for a few days but I will post an update if anyone's interested.

By the way would a dodgy PL509 have killed R203?

The odd blue greyscale fault looks a bit like blue lateral mis-convergence but it isn't and of course having colour difference drive to the CRT means that there won't be flareing which could be mistaken for mis-convergence. When I post the pictures you'll (hopefully) be able to see what I mean.

All the best for now,

Tas
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Old 15th May 2007, 6:38 pm   #5
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Default Re: Pye CT205 - a partial success story!

Can we have some pictures please ?

Dave W
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Old 15th May 2007, 8:05 pm   #6
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Default Re: Pye CT205 - a partial success story!

Hi Dr Watts and all!

Happy to oblige with the pics. As you can see from the strange blue to the right of stuff it's a bit of a puzzle to me. If you turn the contrast down the picture takes on a yellow tint as well but with a more correct section across the middle third of the screen perhaps linked to the brightness of certain parts A fault in the B-Y clamp area maybe?

As well as changing the PL509 I also changed the PY500 again nicked from the Dynatron. I tried putting the original PY back in the Pye but it then took ages to come on and the width was much reduced and just very gradually getting wider but at best there was a good three inch gap either side so in went a brand new one that I got today and full width again.

The solution to the tuner drift is an easy one. Buttons 1 and 2 are f d. What was happening was when you pressed them in hard the contacts were obviously making but then breaking as soon as you let go with the AFC attempting to hold on to the station for a short time, cunning eh?! Shortness of time means I cannot strip the push button unit down at the moment but I'm sure I'll find one end of the springy contact snapped. They can be soldered but don't last long (Invicta experience again!)

As for the very snowy picture that was easy as well. The first station I came across was Channel Five which through our communal aerial on our area of St Albans gives very poor reception

The cabinet looks worse than it is! The top and sides are great and the funny plastic that is hanging off the front by the buttons is the original plastic packing film that never got peeled off from new. The control facia is imaculate underneath. As you can see I've already cleaned up the On-Off, Brightness etc controls. They were well brown. As for the missing veneer I have a solution for that.

Right, must go as we're gonna be late.

Tas
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Old 16th May 2007, 12:33 am   #7
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Default Re: Pye CT205 - a partial success story!

First thing you must do is do the convergence from Scratch. Have you got the Manual by the way?

Leave the set on for 10 Minutes, Then turn the colour off and link it to your signal generator. Switch to Red Raster, and make sure it is all red. Similarly blue and green. If not, degauss and realign.

Now, go to crosshatch. On the tube neck, there will be 4 adjustments, one for each gun and blue lateral. Use the three magnets on the tube neck and the blue lateral to converge the center of the screen.

Then, and only then, go to the convergence pots. Blue gun off, converge the remaining guns (Red and Green) to give a yellow pictures. Then blue gun on and converge for white.

Then go back to the test card and see what it looks like.

Cheers,

Steve P
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Old 16th May 2007, 8:41 am   #8
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Default Re: Pye CT205 - a partial success story!

The pictures don't explain the symptoms properly. Sure enough the blue field convergence is out - one of the pots doesn't do anything but it's the apparent blue lateral that's out but it's not that it is more colour output based (I think). When I get home I'll see if I can take some better pictures.

Tas

PS I've got the manual for the 693 chassis. The only downside is that although the curcuit's the same the layout for the LTB/Power panel is different of course having the PCB rather than the square box!
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Old 16th May 2007, 9:31 am   #9
Mike Phelan
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Default Re: Pye CT205 - a partial success story!

Tas
Quote:
Originally Posted by Tazman1966 View Post
By the way would a dodgy PL509 have killed R203?
No - if the LOP stage is not running, there will be no current through it.
It is a stock fault - despite the fact that it seems not to need 2 watts, the line pulses cook it. Sometimes takes the two flywheel diodes as well.
Other suspect resistors while you are here are the 1K5 (?) across the line lin control and the one (100K?) in series with the line hold control.

Quote:
The odd blue greyscale fault looks a bit like blue lateral mis-convergence but it isn't and of course having colour difference drive to the CRT means that there won't be flareing which could be mistaken for mis-convergence.
Don't know what you mean by that - CDA drive simply means that the luminance (Y) component is subtracted by the CRT instead of earlier on.

Steve's advice is good; as we used to say, "get it right in black and white" before looking for a colour fault.

If the blue seems smeary (poor HF response) turn the colour and red and green guns off and use a crosshatch.
It is probable that the fault is not before the CDA panel - if you pull the two leads out from the chroma signal that will prove it.
I have had the capacitors go O/C between the two anodes of the PCL84 with similar results.
Swap the CRT leads to see if the fault is on the CDA.

HTH
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Old 16th May 2007, 10:06 am   #10
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Default Re: Pye CT205 - a partial success story!

Steve and Mike.

YEAH! That's what I mean "blue is smeary" and in my tongue tied way couldn't explain. I seem to remember I couldn't explain in words a similar fault on the G8 a couple of months backThanks for that! I'll try it tonight.

Best wishes and many thanks,

Tas
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Old 16th May 2007, 12:01 pm   #11
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Default Re: Pye CT205 - a partial success story!

Hi
Much banging of head, but I still can't remember what caused this fault, though I've definitely had it before, and I'm sure it's on the CDA panel. As far as I remember the black and white picture was OK (ish). As Mike says, swap the leads from the decoder and see how the blue looks then - I think the lack of blue (where there should be blue) is the giveaway.
I think taking the board out and scowling at it for a while helps (i.e. look at the print, especailly earthing) then make a few resistance readings comparing channels, then put the board back and compare voltages in the red and blue channels (green can be misleading).
This was always quite a rare fault - and you get TWO different sets with the same symptom? Is that just bad luck?
And that looks a very smart tripler you've got in there....

Glyn
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Old 16th May 2007, 12:33 pm   #12
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Default Re: Pye CT205 - a partial success story!

It certainly is Glyn. Given the smokey environment that the set obviously came from I don't think the tripler would've stayed that clean and white

Thanks again,

Tas
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Old 16th May 2007, 2:47 pm   #13
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Default Re: Pye CT205 - a partial success story!

Good convergence can be obtained using Test Card "F" in black and white if crosshatch generators etc are not to hand. Obviously for optimum results a crosshatch is needed. There's a DVD out, titled "Test Patterns" that was advertised in "Television" a few years ago which includes crosshatch etc.

A strange fault, co-incidentally on a Pye hybrid set(!) was trapezium distortion on the blue gun only. A wire from the scan coils was found to have broken off at the connector to the main PCB!

Excellent pictures allowing for the convergence errors! Well done!

Brian
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Old 16th May 2007, 10:52 pm   #14
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Default Re: Pye CT205 - a partial success story!

Hello Brian.

I have got the DVD with the crosshatch pattern on it already. I used it when I did the convergence on the Philips and the Dynatron - very useful.

Hi Mike.

I did what you said and confirmed that the fault is on the CDA panel. The fault is most noticable when the blue output is driving the green. I also tried the red lead into the blue but it is not as noticable. Anyway pictures attached. The named capacitor would be C370 at 680pF I assume.

'Fraid I've got no further so far...way too busy

All the best folks,

Tas


Pic 1 is the blue feeding green, pic 2 is the blue feeding red and pic 3 is as it should be connected. I've noticed that having uploaded the pictures it's still not as clear to see as in real life, oh well.
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Old 16th May 2007, 11:00 pm   #15
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Default Re: Pye CT205 - a partial success story!

I remember uploading the layout of the PCB LTB/PSU panel in another thread, (can moderators please help with a link? Think it concerned a Dynatron).

That's the beauty of having two identical sets, one can confirm diagnosis by swapping over panels (eg: the CDA one!).

Not a fault I've personally experienced, but would be interested to hear of the outcome! However on a closer look It's possible the blue laterial magnet is out of adjustment. Does it have any effect?

PS: You've struck lucky with this set! The tube in my 205 was awful!

Cheers,
Brian

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Old 17th May 2007, 12:44 am   #16
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Default Re: Pye CT205 - a partial success story!

Can't find my original scans so I hope no one minds me uploading them again!
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Old 17th May 2007, 2:18 pm   #17
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Default Re: Pye CT205 - a partial success story!

Hi Tas
Agreed - check C370, R396 - and R392 can go - these are in the clamp. It's possible there's an amplifier fault - I'd check C359 (25uF), C363 and C366. Luckily there aren't too many components, and you can always swap parts!
I wouldn't suspect a convergence problem for this fault.

Glyn
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Old 17th May 2007, 5:13 pm   #18
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Default Re: Pye CT205 - a partial success story!

Tas
The fact that the fault is the same on the same CDA socket but changes with the gun used completely exonerates anything to do with the CRT or convergence.

Definitely on the B-Y CDA channel - output or clamp. Switch the red and green guns (A1s) off to see what is happening more clearly. Follow Glyn's advice; prime suspect is C370 O/C or physically broken.
It is more of a "ring" than a "smear" - poor LF not HF response.

We are waiting with bated breath!
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Old 19th May 2007, 2:54 pm   #19
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Default Re: Pye CT205 - a partial success story!

Hello all, sorry about the delay in replying just too busy!

Brian.

The blue lateral convergence magnet works fine and if you adjust it you actually get blue fringes on both sides of the verticals. I'm positive that it's not a convergence problem now. Yes I know the blue horizontals are curved but I'll have a go at that later. Thanks for the diagram of the LTB/PSU board so much easier than trying to trace the components and read in the semi darkness the component reference numbers.

I tried swapping the CDA panels over from the Dynatron and although the blue ringing fault had gone there appeared to be no black level clamp and very high brightness. Maybe I left something unplugged. I did note that on the Dynatron there is a lead connected to PL30 which there isn't on the Pye and there is also a red three pin plug connected near to R393 on the Dynatron - maybe something to do with the Tint and Picture Sharpness controls? Does that mean that they're not compatible?

Glyn and Mike:

I popped down to my local Maplins and picked up the capacitors to change as I didn't have those values which I did and no difference It was also difficult to fit them as they're so much smaller than in the olden days. I also changed R396 (8.2M) but R392 tested fine.

I have taken some more pictures to try and illustrate the fault better first with all guns on then blue only and then green only to try to show that's clean. I has a crosshatch pattern up at first but it looked like misconvergence so TCF it was, but I was not able to turn off the A1's as the switches are knackered so the best that I could do was turn the A1 pots right up or down depending on what I wanted to see.

I'll keep trying to do a bit of a component check this afternoon.

If/when that finally gets fixed I've still got the to find out why RV29 the blue amplitude control on the convergence panel doesn't do anything - the cause of the curved blue horizontals I would assume, sort out the very noticable Hanover Bars, the broken tuner button contacts, and the cabinet too! Lots to keep me busy

I'll keep you updated.

All the best and thanks to you all.

Tas

PS How much would you expect to pay for a NOS PL509 or PL519?
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Old 19th May 2007, 2:59 pm   #20
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Default Re: Pye CT205 - a partial success story!

Me again.

Having just had a look at my own pictures again I'm begining to wonder if there is a decoder fault and this fault is turning up much earlier on on the line as you can't quite turn the colour off completely. Is it okay to simply unplug all the leads to the decoder to check and there should be an okay mono picture. I seem to remember Mikey Bennett's article on the Pye Hybrids stating so.

I'll try again!

Tas

PS Time to watch the footie now though!
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