i get this model in today and will take a look on it for a friend of mine,, its from 1987 and actually works, but the brightness on the screen seems to be weak, i have tried to adjust the G2 potmetre (number 3472, 4.7Mohm) but only the black areas in the pictures getting more bright, i dont think the fault is around G2, but where?
im sorry i cant upload any picture, the uploader is making troubles and show up some warnings about my pictures are to big in size 🙁
Hi Frank, i get a try later again about the pictures 🙂
And here they are
I wrote a service article on these for Television magazine back in 1993 (link below) and just scanned through it to see if there was anything there that might help. Unfortunately this wasn't one of the few stock faults. I would suggest you check voltages around the CRT base and scope the video waveform. I'm suspicious that dried out electrolytics may be the cause so it would be a good idea to check any decouplers on the supply rails.
https://americanradiohistory.com/Archive-Practical/Television/90s/Television-1993-02.pdf
thanks you, i will take a look on it tomorrow, there is few points i want to measure
Had many calls to these sets due to back up battery u/s. Contrast, brill on min.
now i have time to check the schematic, and the issues could be the tda4580 (video control combination circuit) chip or SAB3035 (citac circuit) chip,the last converted the signals from the ic2 bus to a voltage signal and feed the TDA4580 chip, i noticed colour and contrast ajustment dosent work,
Before you start changing chips, disconnect the back-up battery. I know this might make it lose any memory it has but I have had occasions where it has caused a lock-out effect. The set will work without the battery but of course it won't remember anything.
you got the point i remove the backup battery and now i can adjust contrast and colour and brightness, but the picturetube needs to be regenerated, it´s indeed weak and unsharp, except in the middle
Ahh yes glad that solved part of the problem. Not surprising the CRT is low. Don't know if it will boost but worth a try. Gentle at first and see how it responds.
hmm was the philips picture tubes bad from that time? i know it´s a thinn neck tube, and they are not god, i will make a try, my friend only want to see some movies in the bedroom before sleep, so it wont be used 8 hours a day 🙂
I've never seen the 2B chassis in the wild but can see the obvious similarity with the 2A whose PSU I've had many a tussle with. Strange that they crop up very rarely compared with the G11 and KT3/K30 on Ebay.
John.
We never saw that many either, even less of the 3A ? , they both must have been comparatively rare in the NE
hmm was the philips picture tubes bad from that time?
They didn't seem to be as good as those fitted in the 2A.
I don't think that is necessarily true Rich, didn't that just apply to FST (FSQ in Philips parlance) tubes in general ? The later 2A had FSQ tubes as well, and they didn't seem to last as long as the 2A pre-FSQ/FST models.
The FST tube IMO never lasted as well as the earlier 30AX etc., which were more fragile than their predecessors and so on...., each newer generation while having better pictures than the last never seemed as robust or as long lived as their immediate forerunner in general, oh well I guess we couldn't have it all ?
Ps. the FST Thorn sets never seemed to last as long as their predecessors in general either. ?
It's so long ago now I don't really remember. It just seems that the flatter tubes were pretty rubbish in terms of life expectancy. It's all academic now really since they are all way out of their normal lifespans.
True! ?
good point about the flatter tube is like more rubbish, i remember whhen i was the yungest mann at the electronic workshop, we get mange 16:9 telleys in for repair, same fault every time, red/blu or the green gun was dropping out, if we knocked on the neck it changed colour :-(, most of the tubes was from philips, 2 maximum 3 years old, but philips shipped new for free 🙂
