Pye StudioCOLOUR (K35 chassis) No picture / sound

[harvestgold]

I have owned my Pye StudioColour TV since 2005, and it was still giving an excellent picture, until Saturday, that is! It is a model 56 KS 3400 /05 T and uses the Philips K35 chassis with basic push button controls. It had a problem with the brightness pulsing with changes in the picture a few years ago, which I found had resolved itself after I replaced it with another set for a few months - I think it got scared after being threatened with going to the tip!

For a while, there has been the odd flicker of red on the screen particularly when cold.
I had a go at solving the red flickers on Saturday and discovered plenty of dry joints on the ‘motherboard’, which I re-soldered, and it worked fine, for a very short time, whereupon the picture disappeared!

The symptoms are now as follows:
No picture, but a very dim plain raster with horizontal lines, only noticeable in fully darkened room.
No sound is getting through either, although the audio section is working, i.e. background noise gets louder with volume slider and quiet pop when changing channel.
When switching off, the momentary coloured ‘bloom’ on the screen is much brighter than normal.

I have double checked my work and also looked for more dry joints on the main board and slot in pcbs. I’ve also cleaned the contacts on the edge connectors and sockets and checked all other plugs / sockets. I can’t see any bulging capacitors or heat damage or anything like that.

Does anyone have any advice where to look before I drag in the multimeter and service info? My level of skill in TV repairs is rather limited, but I am aware this uses a live chassis and the dangers involved in messing with it, I’ll be bringing in the isolation transformer and taking care!

Many thanks for any help, Neil.

[Welsh Anorak]

If the TDA 3560 is socketed, it's worth removing and cleaning the pins. This is what usually causes intermittent colour variations - it's possible it's decided to give this new fault as well. Start here, and possibly replace the IC if you've one to hand. I've probably got one if you're stuck. Then it's time to dust off the meter and check for the +12v on the decoder PCB.
Do the brightness and contrast controls do anything? Certainly sounds like it's in the decoder/RGB area, so do double check your work again just in case.

[harvestgold]

Thank you very much for that, Glyn. The TDA 3560 is socketed, so I've checked the pins and socket and they look fine, but I've given them a quick clean, without any effect.

I've re-checked over the boards for dry joints and re-examined the ones I soldered and all looks okay. There is a 13v test point near the Luma / Chroma and RGB boards, which measures a bit low at 12.3v - I'm not sure whether that could be an issue.

The brightness / contrast controls have no effect on the screen.

Thanks again! Neil.

[Welsh Anorak]

12.3v is fine.
I have the K30 manuals but not the K35 supplement. Is it a remote control model? That makes a difference.
I take it you don't have a TDA? I know it's lazy, but that's where we would have started as it's easy to change! I have a K35 here with severe leaking battery damage so you'd be welcome to borrow the chip or board.

[harvestgold]

Unfortunately, I don't have a TDA 3560 to try in it, so the offer of a loan of yours to try would be most welcome!

The set is a basic, non remote model without any batteries to leak, thankfully!

I don't have the full K35 manual either, but it is covered in the 1983-84 'Red book'.

I'll send a PM with my details.

Many thanks again, Neil.

[harvestgold]

Thanks very much to Glyn, I have tried a replacement TDA3560 and also substituted the RGB and Luma/Chroma boards, the only difference being an increase in blue in the picture, but still only a dim blank raster with flyback lines and also no audio getting through. The brightness and contrast controls have no effect.

I’ve checked the marked test points on the main PCB and most are reasonably close to what is marked apart from:

Point by D583 should be 155v is 197v
Point on pin 10 of the connector to the RGB module, should be 155v is 195v
Point on C460, should be 285v is 314v

A couple of the 13v points seem a bit low; Pin 9 of the connector to the IF/ detector/AGC board, and R455 are 11.98v.

Any further thoughts would be most welcome.
Neil.

[Welsh Anorak]

The 195v is due to there being no work done by the RGB panel which I'd expect from your symptoms.. I'll get the manual out tomorrow and study it. Off the top of my head, I'd expect a fusible resitor has failed.

[harvestgold]

Thank you for that, it's very kind of you to continue to help me get it going!
Neil.

[Sideband]

Can we please confirm the model number before getting too involved? The K35 is VERY similar to the K30 but I don't think there was ever a non-remote K35. One of the big differences was in the RGB area. I know the K30 MkI and MkII had TDA 3560 fitted and later versions had 3561. I'm not sure the K35 ever had a TDA3560 fitted since they were all teletext models. It was a long time ago so I stand to be corrected. I do know that there was confusion with some over the K30/35 chassis as to actual type.

[marceljack]

If there is no sound nor picture and the audio amp works, I would assume the problem lies in the reception area (IF / demodulation): probably no video nor sound at the outputs of the demodulators.

[Welsh Anorak]

I do remember a set that looked very like a K35 but was a non-remote version with a slider volume control. Possibly I just assumed it was a K35 as it looked like one??
Philips did continue to make large-screen non-remote TVs right up to and including the CP90NRC to satisfy the demands of rental companies.

[harvestgold]

This is very interesting and I apologise for any confusion. I was told it was the K35 chassis by a forum member, when I posted about it back in 2005 (the post has since been deleted), so I assumed that was what it is.

I'm looking at the K35 service info now and it certainly looks like the set I have - the RGB module is the same, but the Chroma module in the K35 info (T78) is different in so much as it has additional parts at the top for teletext connection. However both my set and the K35 info have a TDA3560 as IC35 on that board.

There are some photos of the TV in this thread (post 18)
https://www.vintage-radio.net/forum/...d.php?t=107738

Neil.

[Maarten]

The model number 56KS3400/05T would indeed point to a K35 chassis. The Philips equivalent is probably 22CS3040 which would be just about the most basic K35 model ever.

In the other topic, you mention it was made in Germany in 1983 which is very interesting since that would make it one of the last sets made there. Do you by any chance have a picture of the type label?

[Welsh Anorak]

As I mentioned esrlier, Philips did supply the British market, mainly rental, with basic non-remote sets of which this is one.
There was also a 22" 2A non-remote chassis version with an odd rubber front mounted 'keyboard' and a large volume knob. I suspect all these would have sold in very small numbers outside the UK. The ones I saw (and often bought) were usually ex-rental sets. I imaginw the 21" CP90NRC was the last large-screen non-remote TV Philips sold.

[Nickthedentist]

There was also a non-remote 20” CTX-E which looked very similar to this. I had one, found in a skip outside a very posh house in SW19, not the kind of place which would stoop to having an ex-rental!

[Red to black]

What I didn't expect was that there was a version of the K35 chassis with the older two chip decoder, I had always assumed that the K35 chassis was a progression of the later single chip (TDA3560/1) MKII KT3 /K30 chassis with all mods.
Not so according to Chris at VRAT as he posted a diagram with the earlier two chip decoder plus a chip for the text interface belonging to the K35! this I hadn't seen before!

Anyway wasn't there a 160V cap that gave the dark picture symptom on a KT3/K30 chassis? I will look it up

[Welsh Anorak]

Yes, there was a 4.7uF capacitor that was increased if I remember. However this is an odd one because the brightness and contrast do nothing and the sound is not there, though that might be a red herring. Time to get the manual out...

Never seen a two-chip decoder in a K35 - in fact there weren't many in the K30s either. Possibly supply issues - or else they found a big box of decoders they'd forgotten about!

[Welsh Anorak]

Right. I have a note on the diagram that R1455 (560R) can go O/C. This supplies 23v to pins 3,11 and 18 of the RGB module. Might be worth checking this voltage is present. The resistor is just to the left of the LOPT where R1456 (100R, fusible) and R1583 (2R2, fusiuble) live. These are in the same area and might cause problems.
If we're on the wrong track then we'll have a look at the blanking circuit centered around T1535.

[Maarten]

Regarding the decoder, it could have had something to do with the german origins, probably low production numbers and clearing out old stock indeed. If harvestgold feels like it, maybe he could also take a picture of the decoders with labels and date codes on the ICs visible. That would answer the backstory.

[harvestgold]

Thank you clearing up the K30 vs. K35 question. I have taken a few photos, as requested. It looks like original owner got the date when he bought it wrong, as I assume the orange label on the board indicates a 1984 date of manufacture not 1983. Still, it's only a few months out!

I'll go and fetch the meter in and investigate further, as suggested!

Thanks! Neil.