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Old 18th Jan 2022, 3:26 pm   #21
Sideband
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

I think the serial number indicates 15 week of 1984....KR00 415 981711.

Confusion over the number of chips in the decoder. Teletext sets had an additional switching chip fitted so the TDA 3560 was the decoder and the other chip (number escapes me) did the switching between text and TV. As far as I'm aware, the very early two-chip decoders (as fitted to early KT3 and K30MkI) didn't have teletext. It was a very long time ago so happy to be corrected (even though I repaired hundreds of these in various versions....)!

Note: You can't interchange decoders...two chip for one chip or vice versa!!
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Old 18th Jan 2022, 3:58 pm   #22
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

Hi Rich,
Chris over on VRAT very clearly posted a diagram of the K35 chassis which definitely showed the earlier two chip decoder (part of his G6 project at the time), as I say this was something I hadn't seen before,
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Old 18th Jan 2022, 4:03 pm   #23
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

Meaning of the date code (last line) of Philips ICs (1970-2000):
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Old 18th Jan 2022, 4:28 pm   #24
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

I've had a look at pins 3,11 and 18 on the RGB module, my book indicates 19v should be there, but there is only 16v.

I can't see R1455 by the LOPT, but I assume this is marked R455 on mine and measures fine, as do R456 and R583 (fusibles).

Interesting that the set is a year younger than I thought, I'll have to wait a while longer to celebrate its 40th birthday, fingers crossed!

Many thanks, Neil.
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Old 19th Jan 2022, 1:53 am   #25
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

Indeed made in week 15 of 1984. The orange 8404 label is typical of German production and points to april 1984, so it corresponds to the type label.

I'm quite surprised Krefeld TV production lasted that long. They might have run the K35 production line a bit longer than other factories because (as far as I know) they never switched production to the K40 chassis.
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Old 19th Jan 2022, 1:13 pm   #26
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

Bear in mind I'm working from a K30/II manual so there will be differences as you've found already. Philips often left the first digit reference off the PCB so you have the correct components.
Right - I think we should have a look at the blanking circuit. This is centred around T (1)535 which is situated just below left of the CRT cut-out.
Also it would be a good idea to check the brightness and contrast voltages on pins 18 and 19 respectively on the decoder pin outs. Both should swing between around 1 and 3 volts.Diodes D1420, 1422 and 1423 live nearby and could be holding the IC down.
Keep trying - we'll get there!
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Old 19th Jan 2022, 3:43 pm   #27
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

Thanks Glyn - much appreciated!

Firstly, I checked the brightness / contrast voltages on the decoder and they are normal enough - brightness 0.5 - 3.1v on pin 18 & contrast 2.3-3.2 on pin 19.

Then I looked at TS535, and the voltages are a bit off here:
Again according to the diagram, I should have 12.3v on the base, but have 16.9v.
At pins 5 & 9 on the decoder connector, (which goes to pin 8 on the TDA3560) I should have 1.1v but have 5.4v.

I've checked the resistors surrounding TS535 (R535, R534, R529 & R540) all are ok.

I wonder if the overly high voltages are a symptom or a cause of the problem?

Neil.
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Old 20th Jan 2022, 10:56 am   #28
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

Looks like T535 isn't conducting. This is the flyback blanking transistor, so might well be holding the IC off. We know the decoder board and IC are OK, so I'd change the transistor to start with and see what happens. It's a BC558 which is a pretty normal PNP transistor. Have you got a 'scope?
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Old 20th Jan 2022, 1:01 pm   #29
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

I've just tried a replacement BC558, which has had no effect, unfortunately - I was very optimistic, but sadly it wasn't to be!

I'm afraid I no longer have a scope, having had a mains transformer burn out on my old one and as I mainly restore record players and the occasional radio, I haven't bothered getting another one yet.

Thanks! Neil.
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Old 20th Jan 2022, 3:00 pm   #30
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Default Re: Pye StudioCOLOUR (K35 chassis) No picture / sound

ISTR having a problem with the line oscillator module causing this but I have no idea why - or whether I'm completely wrong. Back to the drawing board...
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