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Old 2nd Sep 2017, 2:51 pm   #1
6.3volts
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Default Sony KV-9000UB

Can I please ask you colour experts for some input on this one.
This lovely set seems perfectly able to tune in a signal and the sound is perfect.
The vague remants of a picture can just be seen but is very poor and looks to have no white or grey scale content.
The tube has 120v on all 3 cathodes to G1
530v on G2 and about 2.1kv on G2.
Final anode is looking like 19kv or so.
All three colour adjusters on the back seem to work ok.
the 3 photos are showing the results from my pattern gen. RG&B give good horizontals with poor verticals and blue verticals are too faint to show.
Brightness and colour are on max.
On the top circuit board all marked voltages are close to correct.
Can any one advise from this information if it's a bad tube or a circuit problem. The set is too nice to break.
Any advice and/or some service info would be very welcome.
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Old 2nd Sep 2017, 3:35 pm   #2
ronbryan
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Default Re: Sony KV-9000UB

The Y drive pnp transistor is Q305, 2SA773, on the bottom board. It drives all the emitters of the RGB output transistors. The manual says 4.6V on Q305 base, 5.2V on the emitter and 0.58V on the collector. Can you check this? The collector load for Q305 is R353 39 ohms.

Q305 is near delay line DL302 and is close to connector A-3 on the edge of the pcb.

Ron
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Old 2nd Sep 2017, 7:08 pm   #3
6.3volts
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Default Re: Sony KV-9000UB

Ron thank you for you reply.
Q305 has the following voltages.
Without signal B=6.7
E=7.4
C=7.4
With signal B=7.04
E=7.75
C=7.75
Looks like an E-C dead short.
Most of the stated voltages printed on the board a high in this general area but are more or less right further out into the rest of the board.
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Old 2nd Sep 2017, 8:04 pm   #4
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Default Re: Sony KV-9000UB

Ron update to earlier reply. R353 is reading 3.6k so will investigate Q305 and nearby components tomorrow.
Can you please advise how I obtain the service info as I could then hopefully be able to check my way through the circuit voltages etc. Nothing seems to come up on google.
Regards Jonathan.
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Old 2nd Sep 2017, 8:53 pm   #5
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Default Re: Sony KV-9000UB

Jonathan

I have a Sony KV9000 manual if you want it. It has voltages printed in red, which makes photocopying difficult.

I've photographed a useful section of the circuit diagram, which may help you meanwhile. Send me a pm if you find it unreadable and I'll email the higher resolution version.

R353 is shown as a fusible component, so it looks as if it has tried to do its duty and expired, if it reads 3k6 instead of 39R.

Ron
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Old 3rd Sep 2017, 11:14 am   #6
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Default Re: Sony KV-9000UB

So far Q305 (which looks to be replacement) is testing ok.
I've tested the three RGB o/put transistors and they look good so at the moment the only problem seems to be the R353 which has acted out its fuse role.
It's tempting to replace it and press go but I'll wait now for the manual to arrive (thank you Ron). Or maybe I won't. Must be a reason for the failure of R353.
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Old 3rd Sep 2017, 7:06 pm   #7
Lloyd 1985
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Default Re: Sony KV-9000UB

I think I had the same problem with my one of these, the resistor was duff so I replaced it (didn't know at the time it was a fusible one!) and the set has worked fine since.

I'd have to open the set again to be sure what the component number was, the symptoms you describe sound identical though.

Regards,
Lloyd
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Old 3rd Sep 2017, 7:40 pm   #8
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Default Re: Sony KV-9000UB

Just opened up my set and it was R353 that had gone. No idea why it died, but the replacement didn't go out in a cloud of smoke, and the set is still working! I've had fusible resistors on a few Sony things go for no apparent reason.

Regards,
Lloyd
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Old 4th Sep 2017, 7:55 am   #9
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Default Re: Sony KV-9000UB

Thanks Lloyd, this gives me the idea to replace R353 and hit 'go'. It may be that time degrades it slightly leading to slow decline. I'm always worried about transistor circuits as they are easily damaged compared to valves.
Regards Jonathan
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Old 5th Sep 2017, 6:18 pm   #10
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Default Re: Sony KV-9000UB

Latest update.
I replaced the faulty resistor and was rewarded with a picture.
I set what I think is a white balance and now have a watchable picture.
There are slight geometry concerns in the form of side to side pincushion effect being narrower in the centre and a slight lack of height at the top. Also there is an area of colour distortion at the lower left of the screen which changes depending on the colour in that part of the picture.
I'm reluctant to disturb the various elements on the neck of the tube but I'm hoping the colour distortion can be corrected as it spoils an otherwise acceptable set.
A service manual is on its way but does anyone have any ideas what to do about the lower left colour fault? This is outside my knowledge atm.

Jonathan
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Old 5th Sep 2017, 7:01 pm   #11
ronbryan
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Default Re: Sony KV-9000UB

Have you tried the manual de-gauss button? It's on the back panel.

Ron
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Old 6th Sep 2017, 7:06 am   #12
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Default Re: Sony KV-9000UB

Yes Ron. but I haven't checked if the circuit is working yet.
I just noticed that the picture is rotated slightly clockwise on the screen.
Hopefully the manual will arrive today.
Jonathan
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Old 6th Sep 2017, 8:06 pm   #13
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Default Re: Sony KV-9000UB

A purity fault combined with rotated picture, if there is a common cause, can essentially be one of two things:

1) the deflection yoke has slid back a bit (Sony sometimes used tape between the neck and the yoke, in that case the tape slid back). Adjust the yoke for optimal rotation, purity and dynamic convergence.

2) a stray magnetic field (non-functioning degaussing circuit or external influence)
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Old 7th Sep 2017, 10:52 am   #14
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Default Re: Sony KV-9000UB

Thanks for your advice. Now that I have a service manual I am more confident to have a go.
The rotation was easily cured by (eventually) managing to release the yolk from the neck. I was expecting this to mess up the other settings but I still have a very watchable picture. The yolk is hard up against its spacers. The vertical lines were always dead on with the horizontal lines sloping down slightly to the right. My 1980s home Sony tv had exactly the same problem from new. I'm assuming this to originate from yolk geometry.
I also adjusted the height and pincushion and most of the colour shadow has gone from the screen. I note that the lower left of the screen is the only corner not to have a small magnet stuck to it-would this be a possible cause?
Interestingly if I run the set upside down the colours are all over the place.
I'm at a very early stage with colour so any advice would be very welcome.

Jonathan
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