Thorn 1500 - UK Vintage Radio Repair and Restoration Discussion Forum

bionicmerlin · 19th Feb 2016, 3:39 pm

Hi.
I have a Ferguson 3821 that I have been working on or should I say trying to work on.
When I first got the set it had frame collapse that was cured with a new valve, frame cramp found to be faulty condenser.
The things I am stuck on is poor sync. I can get the frame to hold maybe for 2 mins, maybe 5 mins maybe more if I'm lucky. Second problem is there is a very slow snaking of the picture, when I do I fact get a picture. I guess this is a mains hum. Third problem is not a problem as its OK how it is, but the focus appears not to function. Replaced 1 resister gone high but made no difference.

I have gone over and over again trying to find what's wrong. I have changed a few suspect condensers and one open circuit resistor and a few that's values gone high. I have been following advice on other threads but can't work it out.
I have found the pots on vertical / horizontal hold a bit iffy, so maybe they want replacing in the future as I don't have any replacements near the value.
This set has clearly not had much use compared to other 1500 sets I have, even the writing round the knobs is not worn off.
I only have limited knowledge but at the same time I can usually get by but not this time.
Any help would be appreciated, as I don't want to end up having to put it back in the loft unfixed after spending lots of time on it.
Thanks all, Andy

MALC SCOTT · 19th Feb 2016, 4:20 pm

Check the 47k resistor next to the sync seperator/osc valve for sync problems.

Welsh Anorak · 19th Feb 2016, 4:47 pm

Hi
Agree with Malc on the first problem - use a 1W replacement. It's easy to find right by the valve and fitted at an angle.
Second problem - mains electrolytic tired. It might reform itself otherwise a new can is needed. If you haven't already done it, replace the capacitor across the mains input with a proper class X2 type or else leave it out - they go bang!
Third problem - it's a 1500. The focus control can fail, but usually the CRT is to blame. Again lots of use will usually improve matters, though if it's really bad change the pot and the other resistors in the area - there are only a couple.
Keep on with it - they were good reliable sets with a fair picture.
Glyn

bionicmerlin · 20th Feb 2016, 3:19 am

Thanks for your help guys.
The 47k resistor was open circuit. Replaced with a 2W as that was all I had.
Replaced the condenser across the mains with an X2 as recommended.
Had the set running for about half hour, appears that has solved the sync problem and also the snaking problem.
I will try changing the resistors in the focus area at a later date. But will give the set a good bit of use first, after all I'm happy the way it is.
Thanks again, Andy

19th Feb 2016, 3:39 pm	#1
bionicmerlin Heptode Join Date: May 2010 Location: Warminster, Wiltshire, UK. Posts: 682	Thorn 1500 Hi. I have a Ferguson 3821 that I have been working on or should I say trying to work on. When I first got the set it had frame collapse that was cured with a new valve, frame cramp found to be faulty condenser. The things I am stuck on is poor sync. I can get the frame to hold maybe for 2 mins, maybe 5 mins maybe more if I'm lucky. Second problem is there is a very slow snaking of the picture, when I do I fact get a picture. I guess this is a mains hum. Third problem is not a problem as its OK how it is, but the focus appears not to function. Replaced 1 resister gone high but made no difference. I have gone over and over again trying to find what's wrong. I have changed a few suspect condensers and one open circuit resistor and a few that's values gone high. I have been following advice on other threads but can't work it out. I have found the pots on vertical / horizontal hold a bit iffy, so maybe they want replacing in the future as I don't have any replacements near the value. This set has clearly not had much use compared to other 1500 sets I have, even the writing round the knobs is not worn off. I only have limited knowledge but at the same time I can usually get by but not this time. Any help would be appreciated, as I don't want to end up having to put it back in the loft unfixed after spending lots of time on it. Thanks all, Andy

19th Feb 2016, 4:20 pm	#2
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	Re: Thorn 1500 Check the 47k resistor next to the sync seperator/osc valve for sync problems. __________________ Malc Scott

19th Feb 2016, 4:47 pm	#3
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,918	Re: Thorn 1500 Hi Agree with Malc on the first problem - use a 1W replacement. It's easy to find right by the valve and fitted at an angle. Second problem - mains electrolytic tired. It might reform itself otherwise a new can is needed. If you haven't already done it, replace the capacitor across the mains input with a proper class X2 type or else leave it out - they go bang! Third problem - it's a 1500. The focus control can fail, but usually the CRT is to blame. Again lots of use will usually improve matters, though if it's really bad change the pot and the other resistors in the area - there are only a couple. Keep on with it - they were good reliable sets with a fair picture. Glyn

20th Feb 2016, 3:19 am	#4
bionicmerlin Heptode Join Date: May 2010 Location: Warminster, Wiltshire, UK. Posts: 682	Re: Thorn 1500 Thanks for your help guys. The 47k resistor was open circuit. Replaced with a 2W as that was all I had. Replaced the condenser across the mains with an X2 as recommended. Had the set running for about half hour, appears that has solved the sync problem and also the snaking problem. I will try changing the resistors in the focus area at a later date. But will give the set a good bit of use first, after all I'm happy the way it is. Thanks again, Andy