1969/70 Pye CT72

At least it will have the 691 chassis and the CDA board hopefully will be in good condition unlike the later versions.

Another CT72 on the forum !  Well done The Teleman 

Crikey, it is nearly a year since I last used mine, I had better get her out for a run.

Here it is on the old forum from March last year...(about half-way down the page).

http://www.forum.radios-tv.co.uk/viewtopic.php?f=5&t=11553&start=100

If you need any measurements for reference, pictures etc, just let me know.

I have a rare Ekco version of this set, the CT107. My parents bought it secondhand in 1972.

Hi pye625 , many thanks for the offer of help , I saw your set when you first put it on this forum , it's in fantastic condition , if my set turns out to be half as good as yours I'll be pleased

Hi Malc , I've only ever seen pictures of the Ekco version , nice looking set 

cant wait to get this set working 

ps sorry for all the spelling & typos I put it down to being tired working night shift 

The_Teleman said
 I saw your set when you first put it on this forum , it's in fantastic condition , if my set turns out to be half as good as yours I'll be pleased

With some TLC, I'm sure it will be a great set. The tube is good on your set too, so that is a good start. 

Have you got the legs for yours? 

It would be possible to make some with the exact measurements from mine if needed.

Hi Andrew , unfortunately the legs are missing so I will be on the lookout for something to fit in place . 

I see you can buy hard wood from eBay so I would appreciate it very much if you could let me have the measurement 

I've been thinking about how to go about repairing this set , I have a good working Pye CT205 / 697 chassis & I understand all the panels are interchangeable so I was going to repair each panel in turn using the 697 as a test rig then return them to the 691 

i would appreciate your thoughts on this 

many thanks 

Chris 

I would test the set first after the usually cap reforming etc, you may be pleasantly surprised and not a lot needs doing to it. Use the good CT 205 as a test bed as a last resort. Disturbing a working set may mean two faulty TV's, joints and connections get brittle with age, may be making work for yourself.

There are differences between the two sets, the only PCB's that are the same are CDA, Decoder and Frame. Not sure if the IF strip has modifications for the varicap tuner and the Power/Line Module is very different in design, again I would be surprised if it was plug compatible, the mains power is definitely different. Fixed a lot of both type 40 odd years ago but only PCB's I swapped around were the  first ones I mentioned.

Hi Chris,

I think Frank has some good advice there 

Each leg is 32cm long, the top portion is 4cm square and after 6cm from the top it starts to taper inwards to 2cm square at the base. The outer corner, however, remains straight all the way down to the base.

Hi guys , advice noted , I do remember years ago putting a 697 pcb timebase in a 691 after a fire in the lopt & that worked ok but not sure about the other way round 

thanks for the leg measrments Andrew .

chris 

The_Teleman said
...I do remember years ago putting a 697 pcb timebase in a 691 after a fire in the lopt & that worked ok but not sure about the other way round...

 They ARE interchangeable BUT the edge connectors on the 697 are slightly tighter for the thinner PCB type unit so the 691 type is hard to get the edge connectors on if transplanted into a 697.

I couldn't wait to start on this set , the timebase is the second version with the 2 PCB's on the underside .

on inspection it looks to have had a hard life & most if not all the electrolytics need replacing, in fact the only ones that seem OK are the smoothing capacitors .

there are signs of previous repairs around the line osc some caps are fitted to the print side 

a nice bodge /repair can be seen where the mains lead has been solders directly to the back of the two pins of the mains input & no insulation of the pins sticking out of the back cover 

I'm going to start by replacing all the out of spec caps first & Check any high value resistors along the way .

The 1.5k resistor across the line lin coil looks original, probably fall to pieces when you touch it. The 330pf, I think that is the value, cap in the line osc circuit, if it's polystyrene it will be suspect, intermittent stops the line osc. The mains transformer looks original, shorted low voltage bridge rectifier will burn out the transformer if left on. The mains fuse blows much too late. Later transformers had a replaceable fuse. If the transformer is good I would fit fuses in the feed to the bridge rectifier, it was a mod I did on any of these sets that didn't have the Pye fusible link in the TX. May sound like a bodge but it saved many transformers. The 180pf cap, again from memory, on the LOPTX tuning cap goes s/c, at least the burn is easy to spot.

Will be following with much interest but may not have many posts, childminding duties for the next few weeks so usually not fit for much after a day with them. Where do they get their energy from?  Definitely  at the end of the day.

Hi Frank , Thanks for the advice on the mains transformer mod i didn't know about that one , I believe the cap in this line osc you refur to is the 820pf suflex type cap , we used to replace both suflex caps in the line osc for improved reliability .i know the line refused to start at times , the red glow of the PL509 was a dead give away .

this thread could take a while as I'm fitting it in between work & sleep after a night shift that really messes with your head at times ( as if I need that ) 

but im hoping this will be fun to do as I always liked these PYE sets 

chris 

Well I had an hour or so on the PYE set today & managed to replace a handful of capacitors, interestingly the only one within spec is the badly burned one in the centre of the photo which is the cathode bias of the PL509 according to the service manual this should be 80uf but someone had fitted a 220 uf maybe that's all they had to get the set working at the time .

the suflex capacitors are from the line osc circuit the 820pf is reading 11pf & the 2200pf is totally o/c I remember an  engineer when I was an Aprentice saying never trust a suflex & so far I've found his words of wisdom to be true . 

The_Teleman said
I remember an  engineer when I was an Aprentice saying never trust a suflex & so far I've found his words of wisdom to be true .   

Well I never!  I always thought them reliable and solid as rocks, but it just goes to show.

There was a discussion on another forum about polystyrene caps. There was a comment that Suflex were unhappy with the reputation that they believed was due to other makes of polystyrene caps being inferior. Theirs they believed did not suffer from the problems.

No idea if it's correct.

One property they do have is good stability for oscillators and tuned circuits. Whether they were Suflex or other makes, if you had an intermittent fault  polystyrene caps were first suspect.

Maybe  I should of said suflex type caps as there is no manufacturers mark on them 

I do remember servicing Gec 2040 series sets back in the 70's where we replaced all the suflex type / polystyrene caps in the reference osc circuit because of reliability issues .

if suflex as a brand is more reliable why did manufacturers fit inferior quality substitute surely it can't be just a cost issue 

this is probably where the Japanese manufacturers came into favour by using better quality components giving rise to better reliability.

chris 

The_Teleman said

if suflex as a brand is more reliable why did manufacturers fit inferior quality substitute surely it can't be just a cost issue 

chris   

Afraid it was a cost issue, I understand that costs need to be kept under control but it was like now very competitive on price of the finished item. 

Watching one of the videos on the forum about Japanese sets being subsidised for export, that would not have made things easier for UK manufacturers, but they had financial problems long before that .

Pye/Ekco brought a BW set out around 1967, the spec and looks were not that good. The area sales manager said, paraphrased ' we have to make a saving of £2 a set on parts compared to last years models', may not sound much today but then for parts it was a lot.

Difficult days for Pye.

Frank

Well at long last I got to finish replacing all,those out of spec components in the linetimbase/ power unit 

doing the rest of the set should be a walk in the park , yeah right ! 

I took the easy option & replaces the electrolytics on the I/f unit first as there was only 3 

I decided not to touch the decoder at the moment 

the CDA was next , again all 8  electrolytics are out of spec 

same went for the frame pcb . I was hoping not to have to do a blanket change of caps but as they all seem to be out of spec it looks like the only way to go .

the convergence panel had 2 electrolytics 1 of them was a bipolar type & a callin type too .

now this is where I had a bit of a dilemma the sound output , should I check the caps or leave well alone ?      I went for it & it was a good job I did 1 was actually s/c the 220uf  , while I had the control panel out 2 more on there had to be replaced.

while I was doing all this today I had the power supply hooked up to reform the main smoother as this was about the only electrolytic I hadn't had to replace ! 

Now finaly I was ready to power up ,so slowly wound up the variac , the sound hissed & so did the EHT but not for long the EHT died this was quickly traced to a dodgy pin on the PL509 valve base, the CRT showed a very dim light with the brighnes having no variation on the screen , now is it just me or is there something about the smell of a set when it's been out of action for some time ?  Anyway , the tripler failednow where am I going to get one of those from ? As a quick fix I borrowed one from a working 697 , well it's not working anymore ! This restored once again the EHT bit I still had a dim screen, checking around the CRT base I noticed the slide switch that collapses the frame for setting up the grey scale moving this made a difference to the brightness , a quick clean sorted that . This is one thing after another , now I have a bright uncontrollable raster , no HT on the CDA panel this was traced to a edge connection on the  timebase not making contact.

thats it for now time for a break more tomorrow all being well .