Philips 20C937 (KT3) - can it be saved? - UK Vintage Radio Repair and Restoration Discussion Forum

anttails · 8th Jun 2021, 1:21 am

Greetings!
I have a nice Philips 20C937 PAL TV set from the 80s, that was from my grandparents. It was a nice set and I had it in working condition until recently...

But unfortunately, it no longer turns on. Here's what's happening: If I try to turn it on, I hear the screen trying to turn (the high pitch), but it immediately fails, tries again, fails and it's stuck on that loop.
Sometimes, for a split second, I can hear the speaker but that's it. It won't pass from this.
Last times it turned on, it would shut off randomly, getting back to work either by itself or a little poke on the side. That's not the case anymore...

Sadly in my area, people that are able to repair these TVs becoming very rare, and I'm no expert either (and I don't want to mess with something this delicate).
But I managed to locate someone that looked into the set and told me that the trouble may be on the "focus unit" part and sent me an photo that I'll attach.

I've tried to look up this part online, but so far to no luck. From what I've searched, it seems this set is built on the Philips KT3 chassis, but that's all I know.

Can this set be saved? I have no intention of getting rid of it, but I'd love to have it in working condition.
Thanks in advance and greetings from Portugal!

3CX15000A7 · 8th Jun 2021, 12:42 pm

Because you say "getting back to work either by itself or a little poke on the side" I would suspect dry solder joints as first.

Check/resolder, especially the PSU/linestage part!

it is possible something has blown by poking it too much . .

cmjones01 · 8th Jun 2021, 1:21 pm

When I was a teenager I fixed one of these with pretty much that exact same fault. Starting up repeatedly, accompanied by a sort of "footsteps" noise from the speaker. The problem was the tripler. I replaced it with one from a Philips G8 chassis which happened to be lying around, sealed the connections with proper EHT silicone goop, and the set lived a long and happy life afterwards.

Chris

slidertogrid · 8th Jun 2021, 1:46 pm

As the above posts state it could well be dry joints or tripler failure. Check on the panel where the line output transformer is soldered in, if there are any poor joints they may arc and cause the set to trip off. It may be a good idea to re-solder them anyway as sometimes a dry joint is not obvious until you put an iron on it and the solder falls away.

To check the tripler disconnect the wire that goes from the LOPT to the tripler. Unsolder the wire carefully from the tripler end it is easy to break the wire off the LOPT bobbin which will ruin the transformer. Ensure the wire is away from other parts and switch on, if the set stays on you may need a new tripler.
However the focus control could be the fault and disconnecting the tripler will also remove the voltage to the control so if it does work with the tripler disconnected it may not be guilty . I say this because triplers usually fail and don't respond to being tapped. the focus control however might...

The focus units can suffer from bad connections, the tags and the earth pin are soldered onto a thick film track and can break away. Again, any arcing will cause the set to trip.
The tags and or earth pin can be re-soldered back onto the thick film with care but once done you have to be careful refitting the spade terminals as the tags are easy to break off again. The tags need to be supported when pushing the spade terminals back on.
When the set trips see if you can hear any clicking in the focus control .

Hope this helps, good luck with it!

Rich.

8th Jun 2021, 1:21 am	#1
anttails Diode Join Date: Jun 2021 Location: Almada, Portugal. Posts: 1	Philips 20C937 (KT3) - can it be saved? Greetings! I have a nice Philips 20C937 PAL TV set from the 80s, that was from my grandparents. It was a nice set and I had it in working condition until recently... But unfortunately, it no longer turns on. Here's what's happening: If I try to turn it on, I hear the screen trying to turn (the high pitch), but it immediately fails, tries again, fails and it's stuck on that loop. Sometimes, for a split second, I can hear the speaker but that's it. It won't pass from this. Last times it turned on, it would shut off randomly, getting back to work either by itself or a little poke on the side. That's not the case anymore... Sadly in my area, people that are able to repair these TVs becoming very rare, and I'm no expert either (and I don't want to mess with something this delicate). But I managed to locate someone that looked into the set and told me that the trouble may be on the "focus unit" part and sent me an photo that I'll attach. I've tried to look up this part online, but so far to no luck. From what I've searched, it seems this set is built on the Philips KT3 chassis, but that's all I know. Can this set be saved? I have no intention of getting rid of it, but I'd love to have it in working condition. Thanks in advance and greetings from Portugal! Attached Thumbnails

8th Jun 2021, 12:42 pm	#2
3CX15000A7 Tetrode Join Date: Dec 2019 Location: Bergen op Zoom, Netherlands Posts: 65	Re: Philips 20C937 (KT3) - can it be saved? Because you say "getting back to work either by itself or a little poke on the side" I would suspect dry solder joints as first. Check/resolder, especially the PSU/linestage part! it is possible something has blown by poking it too much . .

8th Jun 2021, 1:21 pm	#3
cmjones01 Nonode Join Date: Oct 2008 Location: Warsaw, Poland and Cambridge, UK Posts: 2,677	Re: Philips 20C937 (KT3) - can it be saved? When I was a teenager I fixed one of these with pretty much that exact same fault. Starting up repeatedly, accompanied by a sort of "footsteps" noise from the speaker. The problem was the tripler. I replaced it with one from a Philips G8 chassis which happened to be lying around, sealed the connections with proper EHT silicone goop, and the set lived a long and happy life afterwards. Chris __________________ What's going on in the workshop? http://martin-jones.com/

8th Jun 2021, 1:46 pm	#4
slidertogrid Octode Join Date: Apr 2005 Location: Peterborough, Cambridgeshire, UK. Posts: 1,898	Re: Philips 20C937 (KT3) - can it be saved? As the above posts state it could well be dry joints or tripler failure. Check on the panel where the line output transformer is soldered in, if there are any poor joints they may arc and cause the set to trip off. It may be a good idea to re-solder them anyway as sometimes a dry joint is not obvious until you put an iron on it and the solder falls away. To check the tripler disconnect the wire that goes from the LOPT to the tripler. Unsolder the wire carefully from the tripler end it is easy to break the wire off the LOPT bobbin which will ruin the transformer. Ensure the wire is away from other parts and switch on, if the set stays on you may need a new tripler. However the focus control could be the fault and disconnecting the tripler will also remove the voltage to the control so if it does work with the tripler disconnected it may not be guilty . I say this because triplers usually fail and don't respond to being tapped. the focus control however might... The focus units can suffer from bad connections, the tags and the earth pin are soldered onto a thick film track and can break away. Again, any arcing will cause the set to trip. The tags and or earth pin can be re-soldered back onto the thick film with care but once done you have to be careful refitting the spade terminals as the tags are easy to break off again. The tags need to be supported when pushing the spade terminals back on. When the set trips see if you can hear any clicking in the focus control . Hope this helps, good luck with it! Rich.