Stella ST1093A.. (Philips 150 chassis.)

I got this set by a circuitous route. Initially it belonged to another collector but he couldn't quite get it to work, so he brought it down to Cottered for me to have a look at. The problem was a fairly simple one and I thought it would be simple to sort out. Nothing on 625 lines. Signals on 405 looked OK as far as he could tell.

So back off, give it some power and a signal and see what transpired. There was nothing on 625 and what looked like inverse video on 405. The IF board has a large system switch in the middle and every time I tapped it or the board, we would get hum on sound and flashes on the screen. So it all pointed to the system switch, which I told him to take apart and clean. Simple job I thought, and I left him to do it because I only have one hand and he has two.

He then spent an evening redoing the system switch and also he had previously put the vision signal diode in wrong too he said. So he then reassembled it, put an aerial in the back of it and tuned around for signals on 625.

Still nothing. I said something rude about it at this end and said I would take another look at the next Rusty Radios meet.

The next meet came and he moved it into my car for it's permanent journey to Bush House. On the kitchen table it went and I started from scratch. 405 went through OK but 625 did nothing. So I was back to the troublesome IF board, which worked great on 405 but didn't want to know on 625. Has this set been round the houses, I thought. At least the system switch was OK now, I thought.

Actually, 625 wasn't completely dead. On Channel 39, which my UHF modulator is on, I found that in one place I could hear the sound, very faintly. So I looked around the IF board again and heaved a sigh as I went for the signal generator.

Then I stopped and thought. Most things had probably been tried, so I resorted to cunning and a touch of my famous cowboy trickery. The IF for the most part was OK, so we were looking at 625 sections only. With two screwdrivers, a metal and a non metal one, I looked at the cans again, and when I pushed the metallic screwdriver into one of the cans, the sound became louder. I removed the cover of the can and looked inside it. I tried moving the IFT's inside about with my bare hands and suddenly the 625 line section burst into life. When the IFT was moved to the left, it worked. Let go and it stopped.

This particular can as the one to the left of the system switch and it had L228, L227 and L226 inside it, as well as the vision detector diode and a few capacitors. Close inspection revealed a break in one of the coils. The system switch later on actually chose one of two paths our of here and the break in L227 was enough to stop the signal going down the 625 path.

So the IF board came out and went to a mate of mine to be resoldered. IFT's are ticklish and I only have one hand, so it was best left to somebody with two!

It came back a couple of days later and I refitted it to the set. Then I fitted it right and it started to work on both standards. I changed the valves in the UHF tuner and the sync separator valve as they were all past their best. We now had good pictures on all standards, which aren't that clear below because of my digital camera.

Then I was off with the polish to make the set look reasonable apart from the three knobs on the front. There was one complete and two others, and they looked a mess. I didn't have any of the original knobs, but I did have a set of knobs from a Philips 170 series set. These quickly went on the front of the set and although not original, they look OK.

So this set finally worked. Sometimes, test equipment doesn't work as well as cunning and luck. Let me give you a tip from being in a workshop for years. Sometimes, the simplest of faults can be very confusing. Stop, put the meter down and think. Don't dive in.

Cheers,

Steve P.