Miss Humble Pye.

[MickMcmichael]

Where on earth do I start with this old beauty! A lovely old PYE CT70.

This set and its history have been described on here before. Basically it was found in pieces in a loft somewhere near Scarborough about 5 years ago. Tube and shield were in the loft. The decoder, tuner, smokestack, cabinet and peripherals were strewn around the house. Each were rooted out and our host for the day explained that her dad had dismantled the set back in 1996. Presumably for a reason but no one knew.

Anyway, Rich (Slidertogrid) was salivating over it more than I was and I think he was actually dribbling when negotiating a price with our hosts; so he took it while I picked up a couple of V2000 VCR's instead. It had already been a good day for Tellypickers and our long wheelbase Transit was struggling and creaking by the time we got home to Peterborough.

Rich reassembled the set but didn't plug it up. It looked the biz amongst his collection and I started to wish I'd caused a hullaballoo and grabbed it for myself!

Three weeks ago I got the call I'd been waiting for. The old Pye was seeking a new home and its preference was to come to me. Whoopee-Doo!

A deal was done quickly and here she is. We've seen Mr Rusty-Pye and Mr Tatty Pye previously from Mike and Taz. Well this one is female and in very nice almost untouched condition - till I got my hands on her!

Just plugging the set up was a real time consuming job. A vast amount of wiring loom is hard wired into the large timebase panel and the rest of it goes everywhere. There are so many three pin black and red plugs you need a service manual just to work out where everything goes!

Eventually I reached the point where the set was ready to be plugged in after initial basic work such as replacing the VA1104 thermistor etc.

Slowly on the variac and smoke puthered out of the timebase panel at around 160v - but where from? Could have been anywhere. LOPT, X-Ray Spex dept', power supply. Anywhere!

I lifted the springy sprung device that the PD500 and GY501 sit in and disconnected these valves from the overwind. Now I could run the set to see if the smoke was from the stack or underneath.

After about 2 minutes of running the set the PL509 started glowing like a 15 watt bulb...oops...then smoke from underneath. Tried a new PL509 and the PY500 glowed (probably because the new PL was cold and everything else you could fry an egg on!). It was obviously time to investigate the line oscillator which turned out to be another quite big job.

I disconnected both the screen and control grids from the PL509 so as I was able to monitor the line oscillator with a scope without any overheating.

The 129 volts was missing from pin 6 of the PCF802 (anode). The 33k from the HT which feeds it was open circuit. Gotta work now..

Nope. Nowt. Not a sausage.

I remembered my days fixing thousands of PYE 205's and those little suflex capacitors in the line oscillator along with the 4uf and 1uf which always must be changed when line problems are suspected. I replaced them all, connected the scope again and switched on again. Good line drive this time with no ringing or any problems.

Re-connect the control and screen grids and see if I can draw a spark big enough to light a fag on from the PL509. Yes!

Fit a new EHT lead as the old one was crusty and stiff, then re-connect the PD and GY assembly and re-fit the metal can roughly so as to protect the bits of me that need protecting!

I was rewarded with this semblence of a raster. Just a bit of a square over to the left (pic taken in the mirror). I've no idea whether the set is swithced to 405 or 625 as all the bowden cables are missing. But at least the LOPT seems to be ok .... Phew!

There should be lots more to come on this one and although very busy with other things, I hope to update every few days or so.

Miss Humble Pye is on her way back!

Cheers all,

Mick.

[slidertogrid]

Hi Mick.

Well you have got further with the Pye in a few days than I did in years! I really didn't want to part with the set but it was taking up a lot of space and to be honest I couldn't see me ever getting it going.

I wouldn't have let it go if it hadn't been you! Taking that lovely Sobell mono in part exchange helped! Just like back when the set was new it had an old mono traded in against it!

Anyway, I shall be watching this thread with interest! If I hear a distant boom and see a mushroom cloud go up on the horizon I will be sure to switch my phone off!

Rich

[Dave Moll]

Originally Posted by MickMcmichael

I've no idea whether the set is swithced to 405 or 625 as all the bowden cables are missing. But at least the LOPT seems to be ok .... Phew!

The line whistle, if audible, should give a clue. In my case, if I can hear a set's line whistle, it must be 405 - as these days I'm deaf to 16KHz.

[Welsh Anorak]

Well, you don't get a raster like that every day! Still, you have some frame scan which is always a bonus on these and it looks like the CRT is possibly OK. Is it possible the wiring to the convergence board is wrong - I know there are very many similar plugs on these. Also isn't it a CT71?

[MickMcmichael]

Hi Glyn.

It's definitely a CT70 - it says so on the tin (tube shield). I think the CT71 was possibly 19" but not too sure.

You could be right about the convergence. I have yet to work out which positions of the various 405/625 switches are which. There's two on the IF board, then one each on the convergence and the timebase. I need to know that they're all in the correct positions before further fault finding continues.

At this stage just some sort of raster is a godsend because I bet there aren't any Lopty's about!

Hope to do more before the FA cup, assuming I don't nod off after lunch!

[Nuvistor]

We sold the Ekco version, slight cabinet differences but that’s about all. I went to a lecture by Len Briggs at Bell Vue in Manchester so many years ago about this chassis.

[MickMcmichael]

Well the last couple of weeks have been interesting to say the least.

That postage stamp raster on the left hand side was proving a little elusive and was only cured after a big flash and a bang from the timebase panel.

I switched on one morning and the raster was at full width (not the frame, though ) and touching the wiring loom reduced the size once more. This went on a little while as I was trying to establish which wires were intermittently making contact. I fumbled a little harder and suddenly the PCF802 lit up like a 40w bulb, there was a bang and everything faded out slowly.

H'mm... removed the PCF and check continuity on heater pins 4 & 5. Nowt!

Replaced PCF802 and still no heaters but all valves had continuity. It was when checking the PCL84's on the CDA board I saw what had happened. There are two separate heater plugs on the CDA board; one in and one out. It was the plug next to the PL802 had come adrift from its socket and shorted against one of the big 5 watt resistors carrying 285v HT on the CDA.

Plugged it back in and heaters and set came back on.

Silly, stupid clumsy old fool!

Full width raster back. Then gone again.

Something inside the cabinet had been catching my eye for several days without really 'connecting' and was just being sort of dismissed... it was a braid of wire with a spade terminal at one end (connected to nothing) and it was connected at the other end to the chassis which housed the decoder, CDA and frame boards.

"Aha!" I thought, "Bet that is supposed to earth the front panel"

I lashed up some crocodile leads from the spade terminal to the front panel and the raster came up permanently. All of the convergence circuitry is over there and it was all trying to work with a floating ground connection.

Now the low frame. Voltage checks around the chassis proved that there was no -20v lines coming from the power supply. They were all sitting at 4.5v positive! All +20v lines were ok.

Huh? Surely the BY122 low voltage bridge is ok then?

Actually, no. The little red coloured low voltage bridge had a black burn mark on its underside. I replaced it with a BY164 and all lines came up. Hoo-naffin'-ray!

Frame collapse! Really? Yes!

Remove frame panel and check BD124's. All ok. Then half of a 560 ohm 2 watt resistor fell onto the bench leaving the other half in the board. Replace 560 ohm and frame returns.

Next I plug in a 625 signal from the output of a freeview box. Tune in as best I can and get sound but it was accompanied by a very detuned picture that I could do nothing with. The contrast control worked and I could tell (just from experience really) when I had actually 'hit' the exact tuning spot. The contrast level went right down with just a blank raster showing and no snow on screen.

It looked very AGC-ish and the -20v goes to this stage, of course.

The two diodes in the AGC circuit (OA47's - D5 & D6) both measured completely different to each other and were therefore hoisted out and replaced with nice new ones from CPC. I also replaced the two transistors VT7 (AGC rec) and VT8 (AGC amp) as I assumed that when the bridge rec originally blew its load it could have done all sorts to the poor old components connected to it!

This proved to be the case and I was rewarded with the pictures attached. Believe it or not there is colour there. That poor old decoder seems to have survived all the trials and tribulations of this set's history!

Frame sync very poor... have to look into that but for now I'm pretty pleased with the progress.

Better converge it a bit I suppose. Tomorrow, maybe.

More to follow...

[slidertogrid]

It's nice to see a picture on the old set after all these years! You have done very well there mate! It couldn't have gone to a better home.
I'm pleased all the major parts are functional. I'm sure you will soon have the picture looking good.
I noticed the LT transformer looked new when I had the set I bet the bridge went short and burned it out I remember it happened on the s/s "metal timebase" sets. That's probably why it was finally retired.
Excellent write up
Rich

[MickMcmichael]

Thanks Rich.

Yes it's definitely a new transformer in there. It sticks out like a sore thumb not being covered in cack!

Looking at the set overall it's not had much done to it in the past. The 405/625 switching on the IF board has been soldered into the 625 position on the back of the board and they left the switch alone - thankfully. The soldering is really old and it's difficult to tell the difference between that and the original soldering.

Next job now is to give it a bit of a set up convergence and geometry wise just to see where I am with it overall.

[Andrew2]

Oh what memories this dredges up from my days as a young TV engineer. In those days we'd stick anything out on rent and we had quite a few sets with this chassis lurking inside. The sets were big and heavy and for some reason these tellies were favoured by people living in pokey upstairs flats.
Looking at those photos, it brings home just how crude they were.
I'll sit here and enjoy from a safe distance!

[1100 man]

Hi Mick,
Another entertaining restoration saga! Great stuff- looking forward to the next instalment.

Will be interesting to see what it looks like after a good setting up session!

Cheers
Nick

[Tazman1966]

Originally Posted by MickMcmichael

...Frame sync very poor... have to look into that but for now I'm pretty pleased with the progress...

And pleased you should be! Nice progress so far

As for the weak frame sync, I've found on many occasions that the 4.7M resistor that feeds the sync separator transistor (a BC107, I think) from the HT line over on the IF panel, rises massively in value. It's odd that the line sync is still pretty strong in these cases but frame sync is almost non existent. Sorry for the lack of circuit reference numbers but I'm working from memory here.

[Welsh Anorak]

Agreed - I've been fooled by rock solid line sync with poor frame and it's still the 4.7M (half way down on the right of the IF panel) that's playing tricks.

[MickMcmichael]

Thanks for that Tas & Glyn. I remember reading something about it in TV mag once, a long time ago. You've jolted my memory!

I'd rarely worked on these IF's until recently. All of the "205's" in my day were British Relay versions which were quite different at the front end.

Hope to get back on it later today as I shall need to sort that synch' before I can start setting it up.

Cheers,

Mick.

[slidertogrid]

Originally Posted by MickMcmichael

I'd rarely worked on these IF's until recently. All of the "205's" in my day were British Relay versions which were quite different at the front end.

Mick.

Yes very different, the "front end" was in Chapel street ! The Tellies just had a switch? No IF faults on the relay version!
I remember buying loads of the solid state GECs Ex relay the IF board was bare with the exception of the audio amp module...

I am eagerly waiting for the next episode of "Miss Humble!"

Rich

[MickMcmichael]

A bit more progress and a few more other faults become evident!

Finally got the frame sync sorted. Firstly I replaced the 4.7m (to base of sync sep transistor from HT). It had risen to 7meg but a replacement made no difference. The collector load resistor (82k) from the same HT line had gone up to around 135k and again there was no difference when replaced. Then a similar thing happened to when I discovered the fault causing the postage stamp picture a few days ago.

All of a sudden the frame locked after I'd had the hair dryer spraying some hot stuff around the sync separator. Trouble was it was random and wasn't actually a component fault. Moving the leads around on the IF made the frame sync come and go. I narrowed it down to plug PL5 adjacent to the luma delay line.

Investigation revealed both a dry joint on the back of the plug on the IF board AND an intermittent break in the leads to the plug, probably at the point where they're crimped.

Sorted all that out and the picture is solidly locked.

I did a very quick set up. Have to stand on a damned orange box to do this as my little old legs aren't long enough for me to see the mirror over the great big cabinet! Hands around the scan coils and that fearsome timebase whirring away next to me and my "crucial bits" are not very far away from it at all. At least the covers are on...

Well it was only a quick set up to get the statics in. The colour is turned down as it's rather intermittent at the moment and I set up the blue scale as best I could for a quick twiddle. ( I hope to achieve a good grey scale eventually! )

Purity rather poor - there's a broken VDR on the tube shield de-gauss connections and I'm not sure if I've got one.

Also, I have to have the sound turned up to maximum at the moment! As I decrease the volume control, there is an extremely loud frame buzzing through the speaker ( 50Hz I presume ) and it drives me mad! This is probably more earthing problems which I'll need to sort out sometime soon. There's earths everywhere on this set and I assume they all have to go in the right places.

Still plenty to do...

Cheers

Mick.

[slidertogrid]

I bet the old boy who ( it seems reluctantly) dismantled the set never expected that the set would be reassembled and restored to working order! The fact that all the parts were kept and labelled seems to suggest he hoped it would live again. and thankfully he didn't remove the front of the set from the cabinet .
Well done Mick!

[dazzlevision]

“Purity rather poor - there's a broken VDR on the tube shield de-gauss connections and I'm not sure if I've got one.”

That’s a Mullard/Philips VA8650 PTC thermistor.

[MickMcmichael]

Well today has been more of a good housekeeping day rather than fault finding.

There's been a load of small jobs building up since day one and I decided to get all of these done in one go.

The CDA board really needed tidying up around the PCL84's. The three anode loads (8.2m) needed replacing (R394/5/6). The two in the red & green channels were up to 13meg and the one in the blue channel read 21meg!

Also, the three 2.2m in the grids were high - all at around 5meg (R380/81/82).

My purity problems from last night (did I say VDR in the de-gauss? Well maybe it looks like one, should have known better) were vastly reduced by sorting all the earths on the CDA. It's a very well known issue on these sets for coloured shading across the picture and needs to be done properly. This made a huge difference as you can see. I still need a new de-gauss thermistor and I'm told there's one on the bay so I'd better grab it.

Next tidy up the frame panel and put back in the chassis.

Last job for today was to replace the preset AGC pot on the IF board. It's been intermittent (cheapo little pot) and a replacement has meant that I can now set it up and see a picture without intermittent cogging verticals!

Still got to trace the awful frame buzz through the sound channel.

Focus a bit one ended. It's just like you want to give it another quarter turn but nowhere to go. Line shift also at one end.

Have still only set up the static convergence and haven't touched the dynamic as yet. Hopefully it's going to set up nicely, eventually.

Sorry about the backwards test card - it's still a mirror shot until I can turn the set round.

Very pleased so far. Chips tonight!

Cheers for now,

Mick.