Philips FL1.17 chassis - what should I have done?

[Studio263]

This set had a shorted chopper transistor that had blown the fuse. It was an ON4827 which I don't have so I fitted a BUT12A instead.

After a bit of a solder-up I powered it up via the variac and it worked well. After a bit of a run i tried it directly on the mains, again good results were obtained. At this stage I let it go, it's a big bulky thing to have cluttering up the workshop and it seemed to be behaving perfectly, the tube was even still pretty good.

However, I'm sure these sets were a real trial when we had them all those years ago, and you had to buy a huge repair kit (which even had a small printed circuit in it!) to get them going again. Will I be seeing this set again in the (very) near future do you all think?

[Sideband]

maybe, maybe not!! I've done loads of these in the past and they were not bad at all. Chances are that if the set works OK now, it may have just been dry joints that saw off the chopper. A BUT12AF is OK in this position but it may give startup problems. Sometimes these sets refused to start properly but once running, they would go all day. The gain of the BUT12 is quite critical and should be above 16 for reliable operation. Most new ones are OK in this respect but I think it was changed to the ON4827 because the gain was usually 20 - 25. Generally these were used in the larger sets and widescreen versions.

You're right about the repair kit but it wasn't really huge in component terms...PCB control panel, four diodes for bridge rec, the transistor and a couple of chip components and I think the 5 volt regulator was changed to a different type.


Rich.

[Welsh Anorak]

Hi
I think when the PCB control module was faulty it tended to kill everything else at switch-on! I do think there was a small electrolytic on it though that can cause problems - however I think it's best to keep your fingers crossed!
Glyn
PS Is that REALLY a vintage TV? Must be getting old...!!

[Studio263]

Originally Posted by Welsh Anorak

PS Is that REALLY a vintage TV? Must be getting old...!!

I know what you mean, it made me feel old too, they were a new model when I was working in the shop. I was very surprised to find that this one however was 15 years old, that must explain why there always seems to be one at the rubbish dump whenever I go.

Think about it, that's like having a Decca Bradford in 1990...

[Studio263]

The answer is something else obviously, it's back with me now. This time it's ruined two of the rectifier diodes as well. After changing these and the transistor (again) it works but obviously confidence is zero. As the set runs and the HT line is correct simple meter checks are useless as everything is fine. Normally I'd suspect either electrolytic capacitors or high value resistors on the SMPS primary side but this design has neither, so I'm down to:
1)BUT12AF not man enough
2)Poor contact on the plugs that hold the power supply sub-panel (it seems a bad idea to run the base drive current through a plug and socket needlessly)
3)Optocoupler (wasn't this a 2A thing, when the chopper goes change the optocoupler? I never beleived it by the way)
4)snubber capactior across the chopper - well, it's a blue disc-type one and we know what a nuisance they can be in Philips sets...
Anything else I've missed?

[Welsh Anorak]

Hi
Oh dear! I assume the Philips kit is NLA - though it was a bit pricey, as I remember. I'd replace all four HT diodes with Philips types (BYW95, I think) and that blue disc. It's fair to assume the base drive is being spiked, so check the sub-PCB carefully. Replace the degaussing thermistor and solder the transformer again.

Then emigrate.

Glyn

[MALC SCOTT]

Hi, i may have a good psu control pcb for this chassis. I will check tomorrow. Malc.

[MALC SCOTT]

Hi, i have a NOS psu control pcb. I have just tested it in a working set and it is ok. Yours for the cost of postage