Anyone With Philips K12 Experience?

[jayceebee]

I was wondering if it might be OK to ask for knowledge/assistance from the TV folk here, for my friend Chris over on VRAT. If the mods think this is inappropriate, then feel free to delete.

Chris has recently acquired a 1979 26" PYE 66K1826/15P K12 Chassis for his museum, and it has a very strange fault, which he is struggling to resolve.
The Philips circuit diagram, as you might expect, is very confusing. Coupled with that, none of the members over there have very much if any experience with the K12, myself included. I'm aware that quite a few members here have seen this set and certainly a few of our European members are quite familiar with the K12. To us in the UK this appears to be a high end chassis with some strange features such as the way the CRT is driven, is it colour difference drive like the K11? There "appears" to me to be no luminance drive to the cathodes it looks to me to be grid modulated with the cathodes being used for black level and beam limiting? the lack of an English circuit description doesn't help.

The link below will take you to the thread, and there is a link within that to a YouTube video of the fault (ignore the sound, that was interference picked up from his workshop).

Link here.


If anyone has any advice to help him, please post here and I will pass it on, I know he would be most appreciative as both our communities share the same goal, preservation of vintage Radio & Television.

Thanks for taking the time to read.

John.

[Maarten]

It seems to be a Swedish made set (I would be interested in a picture of the type plate on the back), so please look out for RIFA capacitors in the mains filter, in the front panel and/or on an aux supply pcb.

One of those took out a nice Swedish K11, not only with smoke but by actually setting it on fire, owned by fellow collector Marcel van Grinsven (marcelstvmuseum).

In general, problems after transporting a K12, can be caused by the sockets of the large modules (not the smaller or ceramic modules).

[ben]

I had a few K12s pass though my hands here in Spain. I recall one where the actual slider controls gave problems - led me a bit of a dance. If the contrast is all over the shop, I suppose there might be a broken contact there.

I still have one almost identical to this in my stores. Must dig it out one day.

[Red to black]

Has he tried cleaning the PCB spark gaps yet? I had one totally drop the green gun and cause the same symptoms due to dirt contamination, I used a fibre pen to repair that one.

[jayceebee]

Thanks for the comments, that’s a smart looking set Ben.

Hi Maarten, I’ve attached a couple of labels from the set which may give you the information you want.

Hi R2B I have mentioned it and presume he has done so.

John.

[hans]

These were good sets. It is a long time since i worked on these, but I remember that the thick film modules on the crt board could be troublesome. If they made the contrast low I can't remember.

Another thing that should be checked that was a big problem, but not related to picture are the contacts on the modules in the line and powersupply stages. The tinned edge connetors especially on the EW module gets bad and that would blow up stuff.

[jayceebee]

The problem has now been resolved and ended up being caused by a broken connector on the red thick film drive module holder. The broken connection was the feedback resistor on the module from the red cathode to the cutoff feedback network on the RGB matrix module U410.

Chris sends his thanks to the UKVRRR members who contributed and the mods for allowing this thread.

John