Sony kv-9000ub Restoration - UK Vintage Radio Repair and Restoration Discussion Forum

TacoTuesday1839 · 22nd Jul 2025, 10:05 pm

Hi, I’m working on a Sony kv-9000ub with power but no picture. I have minimal experience working on crt’s but I have experience in audio equipment. I’m unsure where to begin testing although I have tried a replacement horizontal output transistor as it was getting hot but this has made no change. I can tune in a channel with clear audio, you can hear high voltage and the crt is glowing. The only brief life I got out of the screen was two lines that flashed on the screen when pressing the degauss button on the rear upon first power up.

ronbryan · 23rd Jul 2025, 8:45 am

For the HOT that is running hot, you could try changing C520 1uF 50V which decouples the collector supply to the horizontal driver transistor Q502 and associated horizontal driver transformer.

Ron

Welsh Anorak · 23rd Jul 2025, 10:14 am

Hello and welcome to the forum.

How hot is hot? Transistors in this position do run quite warm, certainly compared to ones you might be more familiar with. If it's unusually hot then of course Ron's advice is good - in fact changing this capacitor would be a good idea anyway.

You say you can hear the EHT and you get a brief display, so the HOT stage is working to some extent.
I'd have a look at the CRT base voltages to see if the cathodes are biased off or the G2 is missing or low. I'd expect between 100 and 140v on the cathodes, and 400-700v on the G2 pins.

A circuit diagram is invaluable here. If you don't have one you can download one from Elektrotanya.

Dr-Watts · 25th Jul 2025, 8:54 am

Sounds like a typical case of no frame to me and the set had gone into protection mode and blanked the picture to save screen burn

TacoTuesday1839 · 29th Jul 2025, 1:55 am

I have now replaced this capacitor, the horizontal transistor still seems to be acting the same and I have observed no change on screen, however in regards to the temperature it is too hot to touch for too long while powered up.

22nd Jul 2025, 10:05 pm	#1
TacoTuesday1839 Diode Join Date: Jul 2025 Location: Salford, Greater Manchester, UK. Posts: 2	Sony kv-9000ub Restoration Hi, I’m working on a Sony kv-9000ub with power but no picture. I have minimal experience working on crt’s but I have experience in audio equipment. I’m unsure where to begin testing although I have tried a replacement horizontal output transistor as it was getting hot but this has made no change. I can tune in a channel with clear audio, you can hear high voltage and the crt is glowing. The only brief life I got out of the screen was two lines that flashed on the screen when pressing the degauss button on the rear upon first power up.

23rd Jul 2025, 8:45 am	#2
ronbryan Nonode Join Date: Jan 2003 Location: Guildford, Surrey, UK. Posts: 2,011	Re: Sony kv-9000ub Restoration For the HOT that is running hot, you could try changing C520 1uF 50V which decouples the collector supply to the horizontal driver transistor Q502 and associated horizontal driver transformer. Ron

23rd Jul 2025, 10:14 am	#3
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 7,653	Re: Sony kv-9000ub Restoration Hello and welcome to the forum. How hot is hot? Transistors in this position do run quite warm, certainly compared to ones you might be more familiar with. If it's unusually hot then of course Ron's advice is good - in fact changing this capacitor would be a good idea anyway. You say you can hear the EHT and you get a brief display, so the HOT stage is working to some extent. I'd have a look at the CRT base voltages to see if the cathodes are biased off or the G2 is missing or low. I'd expect between 100 and 140v on the cathodes, and 400-700v on the G2 pins. A circuit diagram is invaluable here. If you don't have one you can download one from Elektrotanya. __________________ Glyn

25th Jul 2025, 8:54 am	#4
Dr-Watts Heptode Join Date: Dec 2006 Location: Milton Keynes, Buckinghamshire, UK. Posts: 718	Re: Sony kv-9000ub Restoration Sounds like a typical case of no frame to me and the set had gone into protection mode and blanked the picture to save screen burn __________________ Do you have the scope to be a TV repair man ?

29th Jul 2025, 1:55 am	#5
TacoTuesday1839 Diode Join Date: Jul 2025 Location: Salford, Greater Manchester, UK. Posts: 2	Re: Sony kv-9000ub Restoration I have now replaced this capacitor, the horizontal transistor still seems to be acting the same and I have observed no change on screen, however in regards to the temperature it is too hot to touch for too long while powered up.