Sony Trinitron Wega problem - UK Vintage Radio Repair and Restoration Discussion Forum

Rossc1985 · 18th Nov 2015, 1:31 pm

Hi all, the problem we are having with the Sony TV is you turn it on and sometimes you get sound and no picture. I have checked the scart leads. This is not all the time, and if you turn it off and leave it a while its then fine. We use old TVs as that's the way we roll. I've never had a new TV, this one came from freecycle about 3 weeks ago. The picture is fine. I haven't had this fault before any ideas please, thank you .

MALC SCOTT · 18th Nov 2015, 1:52 pm

Could be low emission crt. Adjust A1 volts when no pic is there, Malc.

toshiba tony · 18th Nov 2015, 4:22 pm

Some of these sets used auto grey scale correction and this could cause problems. As was mentioned in the post before mine though a tired thermionic device is favourite. Or to give it it's friendly name, the tube.

Rossc1985 · 18th Nov 2015, 4:28 pm

hi thanks for replys the picture is great when working is this a expensive item and easy to fit ?

Welsh Anorak · 18th Nov 2015, 7:10 pm

Hi there.
First things first - is there anything on the screen when there's no picture such as a menu? If there is then there's a fault with the connections or early in the signal stages. If not then the above is likely. Unfortunately I suspect you may not have too much experience of TVs - no offence intended! It could just be the A1 voltage needs adjusting. You'll need to give us the model number of the TV and we can point you in the direction of the control you need to adjust.
Usual disclaimers - there are lots of volts in there so be careful!
Glyn

ben · 19th Nov 2015, 2:58 am

Cracked solder joints are extremely common in Sony gear. But check the other things mentioned first.

Rossc1985 · 19th Nov 2015, 1:20 pm

Hi thanks for all your replys their is nothing on the screen a very tiny line across top of the screen the set says trinetron 100hz and wega.i no that tvs hold their charge so usely leave them turned off for 24hours correct I do no have a a great nolage of tvs just had lots of cheapies freebies over the years sort of get to no common faults and that noboby wanted to help repair them usely just used them till they totally died before sourceing another .the picture is great when it works also the power light goses red green red geen not all the time we haven't had set very long at all thank you all so much for your help with this and my video is a great site thanks Ross

Clydeuk · 19th Nov 2015, 3:35 pm

From your description of the problem I would say the tube seems most likely. I got out of TV repair around the time these made an appearance, but have encountered a few since.

The auto grey scale circuit I believe samples the 3 guns at switch on, which is what the thin line you see at the top of the screen is, it attempts to get the right balance and compensates for differing gun emission between the 3 guns. Until it achieves good balance the picture remains cut off, and if it fails within a time limit the front panel LED's will flash the fault code, I think the flashing LED's on the front are giving you the fault code for this failure mode.

Auto grey scale is very good at hiding failing emission in a CRT, but once it gets to a certain point (like yours) it can't achieve a satisfactory balance any more. The fact that you can get a good picture just means it's probably borderline and occasionally it is managing to get satisfactory balance.

I found on a few sets that if you touch the probe of a test meter on any of the CRT cathode connections the picture will appear.

The only place you are likely to get another CRT is from a scrapper, and chances are that will have the same problem, I believe it is very common on these sets.

Welsh Anorak · 19th Nov 2015, 5:44 pm

Hi
That's quite likely - though do check the transistors on the CRT base for dry-joints. I remember a dodge was to fit resistors to the collectors of the RGB transistors and return them to a common point to fool the auto greyscale.
Otherwise it's back to Freecycle!

Rossc1985 · 20th Nov 2015, 11:26 am

ok thank you all for all your help Ross

Maarten · 22nd Nov 2015, 6:30 pm

Keep in mind that Sony used the Wega trademark on many different sets which may or may not exhibit different stock faults and symptoms. Please always give a full model number (KV-xxxx found on the back) for the best and most detailed advice.

Anyway, try adjusting the A1 (G2) tension up a little bit, if it is indeed an emission problem this might help. If there is no difference, look for dry joints especially on hte CRT board.

18th Nov 2015, 1:31 pm	#1
Rossc1985 Retired Dormant Member Join Date: Oct 2015 Location: Torquay, Devonshire, UK. Posts: 25	Sony Trinitron Wega problem Hi all, the problem we are having with the Sony TV is you turn it on and sometimes you get sound and no picture. I have checked the scart leads. This is not all the time, and if you turn it off and leave it a while its then fine. We use old TVs as that's the way we roll. I've never had a new TV, this one came from freecycle about 3 weeks ago. The picture is fine. I haven't had this fault before any ideas please, thank you .

18th Nov 2015, 1:52 pm	#2
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	Re: Sony Trinitron Wega problem Could be low emission crt. Adjust A1 volts when no pic is there, Malc. __________________ Malc Scott

18th Nov 2015, 4:22 pm	#3
toshiba tony Heptode Join Date: May 2006 Location: Accrington, Lancashire, UK. Posts: 978	Re: Sony Trinitron Wega problem Some of these sets used auto grey scale correction and this could cause problems. As was mentioned in the post before mine though a tired thermionic device is favourite. Or to give it it's friendly name, the tube.

18th Nov 2015, 4:28 pm	#4
Rossc1985 Retired Dormant Member Join Date: Oct 2015 Location: Torquay, Devonshire, UK. Posts: 25	Re: Sony Trinitron Wega problem hi thanks for replys the picture is great when working is this a expensive item and easy to fit ?

18th Nov 2015, 7:10 pm	#5
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,918	Re: Sony Trinitron Wega problem Hi there. First things first - is there anything on the screen when there's no picture such as a menu? If there is then there's a fault with the connections or early in the signal stages. If not then the above is likely. Unfortunately I suspect you may not have too much experience of TVs - no offence intended! It could just be the A1 voltage needs adjusting. You'll need to give us the model number of the TV and we can point you in the direction of the control you need to adjust. Usual disclaimers - there are lots of volts in there so be careful! Glyn

19th Nov 2015, 2:58 am	#6
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Sony Trinitron Wega problem Cracked solder joints are extremely common in Sony gear. But check the other things mentioned first. __________________ Regards, Ben.

19th Nov 2015, 1:20 pm	#7
Rossc1985 Retired Dormant Member Join Date: Oct 2015 Location: Torquay, Devonshire, UK. Posts: 25	Re: Sony Trinitron Wega problem Hi thanks for all your replys their is nothing on the screen a very tiny line across top of the screen the set says trinetron 100hz and wega.i no that tvs hold their charge so usely leave them turned off for 24hours correct I do no have a a great nolage of tvs just had lots of cheapies freebies over the years sort of get to no common faults and that noboby wanted to help repair them usely just used them till they totally died before sourceing another .the picture is great when it works also the power light goses red green red geen not all the time we haven't had set very long at all thank you all so much for your help with this and my video is a great site thanks Ross

19th Nov 2015, 3:35 pm	#8
Clydeuk Hexode Join Date: Mar 2012 Location: Liverpool, Merseyside, UK. Posts: 453	Re: Sony Trinitron Wega problem From your description of the problem I would say the tube seems most likely. I got out of TV repair around the time these made an appearance, but have encountered a few since. The auto grey scale circuit I believe samples the 3 guns at switch on, which is what the thin line you see at the top of the screen is, it attempts to get the right balance and compensates for differing gun emission between the 3 guns. Until it achieves good balance the picture remains cut off, and if it fails within a time limit the front panel LED's will flash the fault code, I think the flashing LED's on the front are giving you the fault code for this failure mode. Auto grey scale is very good at hiding failing emission in a CRT, but once it gets to a certain point (like yours) it can't achieve a satisfactory balance any more. The fact that you can get a good picture just means it's probably borderline and occasionally it is managing to get satisfactory balance. I found on a few sets that if you touch the probe of a test meter on any of the CRT cathode connections the picture will appear. The only place you are likely to get another CRT is from a scrapper, and chances are that will have the same problem, I believe it is very common on these sets.

19th Nov 2015, 5:44 pm	#9
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,918	Re: Sony Trinitron Wega problem Hi That's quite likely - though do check the transistors on the CRT base for dry-joints. I remember a dodge was to fit resistors to the collectors of the RGB transistors and return them to a common point to fool the auto greyscale. Otherwise it's back to Freecycle!

20th Nov 2015, 11:26 am	#10
Rossc1985 Retired Dormant Member Join Date: Oct 2015 Location: Torquay, Devonshire, UK. Posts: 25	Re: Sony Trinitron Wega problem ok thank you all for all your help Ross

22nd Nov 2015, 6:30 pm	#11
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: Sony Trinitron Wega problem Keep in mind that Sony used the Wega trademark on many different sets which may or may not exhibit different stock faults and symptoms. Please always give a full model number (KV-xxxx found on the back) for the best and most detailed advice. Anyway, try adjusting the A1 (G2) tension up a little bit, if it is indeed an emission problem this might help. If there is no difference, look for dry joints especially on hte CRT board.