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  #1  
Old 09-09-2018, 11:58 PM
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Need help on Sony KV-8000 with troubleshooting.

I havenít had much success with a sony kv-8000 with no video and has sound. I have traced video with my scope and used my DVM and tonight I got out the B/K 1077B to inject signals. I have no brightness of any kind on the jug. I can put a SMPTE pattern and see color if I play with the intensity control and I see a shift in color bar if I adjust hue. Where Iím stumped is figuring why I have a video signal albeit not the recommended peak to peak level but itís there. Canít get video to show up if I inject at cathodes. I have heaters on crt glowing. R,G,B drives arenít even warm to the touch after being on for awhile. Iím really stumped. I donít understand how ABL circuit works. Wondering if I got some kind of blanking problem. I tried jumpering coupling caps in video circuit. Any veteran techs that had a lot of Sony experience that might be able to shed some light on my problem? By the way for those that donít know ABL means automatic brightness limiter.
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File Type: jpg 295E27A0-399B-40C4-BF68-8E7BB38E996C.jpg (62.6 KB, 24 views)
File Type: jpg 8A5C49F2-63B0-4C43-9D74-2A6BB379D161.jpg (95.1 KB, 45 views)
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  #2  
Old 09-10-2018, 10:03 AM
zeno zeno is offline
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IIRC there was a 'lytic coupling cap in the video that
caused weak & streaky video.
Check the CRT voltages on cathodes. Should be apx 130V on most
sets. If near 200V you get no raster if everything else OK.
You can force a gun on by grounding a cathode through an
apx 18K resistor. Use the same value as the collector resistors
for the R,G, & B outputs.
Last look for open resistor in G-2. Usually carbon & high value.

73 Zeno
LFOD !
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  #3  
Old 09-10-2018, 11:50 PM
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Tried grounding the cathodes at CRT pins used a 22K resistor to ground. Schematic uses an 18K and 22K was the closest to it I had. It functioned though for the test. I see individual color with no video. Left DVM in car will try measuring them tomorrow. At least I know I have good HV and deflection. Zeno, any memories as to what cap might be failing?
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File Type: jpg B8847DC8-248F-4EDE-8759-2EF175B400B6.jpg (67.5 KB, 18 views)
File Type: jpg 73B88FAA-6153-4E3C-9EAA-601EF44506E7.jpg (61.5 KB, 17 views)
File Type: jpg 4C629C12-0F25-4F16-BB07-3CA0185FFA17.jpg (66.8 KB, 18 views)
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Sony Trinitron is my favorite brand.
My wish list:
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Last edited by Popester; 09-10-2018 at 11:55 PM. Reason: Added more information.
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  #4  
Old 09-12-2018, 03:57 PM
zeno zeno is offline
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OK I pulled the SAMS & its newer than the set I was thinking about.
C442 is probably the same part in yours.

ABL If I am wrong someone please correct me, its been YEARS !
Samples the low end of the HV winding. If the HV draws too much
current the ABL will pull down the video drive to prevent blooming etc.
Failure may cause low or no video or blooming, retrace etc.
BUT in 40 yrs I dont remember any problems there. Thats MANY thousands
of TV's !

For now keep in mind from Q401 on its direct coupled all the way to the CRT
so anything throwing off the DC voltages will be reflected down the line.
If it were me I would check transistors for leakage & voltages then
shot gun all the little 'lytics. Its a high parts count area so may be quite a challenge.

Good Luck
Zeno
LFOD !
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  #5  
Old 09-18-2018, 11:46 PM
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Iíve been back at it. I replaced 6 lytic caps in the video drive. Still very very faint luminance. I thought I would test the jug and see what kind of shape itís in and check for shorts. I pulled out the B/K 467 and that manual and the B/K 490 donít list the socket adapter. The Sony parts number is 8-737-701-05 and the description is 230BWB22. Anyone know what the socket number Iím suppose to use is? I havenít made a universal adapter and donít have hardware to make one yet. Any ideas?
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  #6  
Old 09-19-2018, 09:53 AM
zeno zeno is offline
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Looking at the pixs of the force on your CRT is at least
good if not better.
The color is probably OK & you are just seeing that but no video.
Take back what I said about cathode voltages. This uses less.
Keep in mind as the cathode V goes higher the pix will darken
so I bet all 3 are up to 120 VDC.
Measure the DCV along the video chain & trace with scope & see
where the video drops out or the DC voltage is off.

73 Zeno
LFOD !
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  #7  
Old 09-23-2018, 12:16 AM
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So, checking all three R,G,B drive transistors Q701,Q702,Q703 I seem to have 4.5V video signal P-P on my scope at the base of the transistors. I'm suppose to have according to the Sony schematic 6.3V P-P. I've included pics of the schematic so I hope you can follow along. The collector of all three of these is reading source voltage which is 126Vdc. The collectors should be at around 100 Vdc. It's like the transistors are biased off. All three emitters are about 4.63Vdc and should be about 5.4Vdc. The base voltages are low too they are reading 3.05Vdc and should be 5.0Vdc. I replace the following lytics in the video circuit to no avail. C441,C442,C404,C405,C406 and C301. I've checked transistors tonight in circuit and injected video which didn't help from the B/K analyst. I didn't see video. I have very very faint color bars on the screen. It's basically color without luminance. When I'm on the color bars if I vary brightness, and picture controls I see slight changes. If I vary color and hue I notice intensity from no color to very slight color. And hue I see a shift in my bars changing phase. I wish I could just figure out what is effecting my bias turning these outputs off. I hope the pics are helpful to someone out there. Attachment 197700
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File Type: jpg image.jpg (111.8 KB, 14 views)
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Sony Trinitron is my favorite brand.
My wish list:
Sony 8-301W
Sony KV-5000
Sony KV-7010U
Sony KV-1210U

Last edited by Popester; 09-23-2018 at 12:22 AM. Reason: Spelling
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  #8  
Old 09-23-2018, 12:18 AM
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Second image.
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Sony Trinitron is my favorite brand.
My wish list:
Sony 8-301W
Sony KV-5000
Sony KV-7010U
Sony KV-1210U
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  #9  
Old 09-23-2018, 09:51 AM
zeno zeno is offline
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This is what I meant by challenging.
SAMS gives 12V P-P B of Q402 & 6.8V P-P on the C
Also check around Q507 & Q407
Thats about it as far as DX repairs. Its to the point of having to be there.

73 Zeno
LFOD !
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  #10  
Old 09-23-2018, 10:37 PM
mrjukebox160 mrjukebox160 is offline
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I would check around Q409 ABL and Q402.
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  #11  
Old 09-26-2018, 11:11 PM
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Making some headway, but puzzled. Okay, I have video now, but don’t understand why. The base resistor of Q402 in circuit read low. So I had to remove it to test it. It broke installing back in the circuit. R414 a 51K resistor is now open because it’s broken in half. So I have video, but if I jumper in a new resistor my video goes away again. Any ideas Sony experts? Have to wonder if ABL circuit is shut off with the resistor being open in the circuit
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File Type: jpg 6513474B-629B-49E6-B6DC-2F498AFEF5D2.jpg (51.3 KB, 20 views)
File Type: jpg 47D038DF-43F7-441B-8D37-201746817CB4.jpg (104.3 KB, 11 views)
__________________
Sony Trinitron is my favorite brand.
My wish list:
Sony 8-301W
Sony KV-5000
Sony KV-7010U
Sony KV-1210U

Last edited by Popester; 09-27-2018 at 03:00 AM. Reason: Spelling
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  #12  
Old 09-27-2018, 01:25 AM
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I wonder if C404 or C405 is leaking and causing the DC bias current to shift.
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  #13  
Old 09-27-2018, 02:46 AM
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Those lytics were changed along with 4 others in the video chain. I am wondering about that ABL transistor though. Sony does some strange engineering. I watched the set with the back off tonight about an hour and a half and intermittently the brightness/contrast would fluctuate. At least I know the video circuitry is functioning. Got to get a 51K resistor and go from there. Kind of odd. I'm trying to figure out the ABL part of the circuit. That battle continues (another day).
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Sony Trinitron is my favorite brand.
My wish list:
Sony 8-301W
Sony KV-5000
Sony KV-7010U
Sony KV-1210U
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  #14  
Old 11-05-2018, 12:51 AM
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More puzzled than before. See photo. Is this transistor a 2SC1363? I have an original Sony schematic (it is Canadian and not US schematic) that calls for an 2SC634A. I ordered a couple off of eBay and they aren’t the same size. I wouldn’t think the Canadian schematic would be any different from the US model as far as semiconductors go. The ABL transistor Q409 calls for an 2SC634A. But the photo is what I removed from circuit board. This is all original. Just curious what is going on.
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File Type: jpg 72DAA002-B99F-45EC-B833-037C74CB719F.jpg (70.7 KB, 14 views)
File Type: jpg EAA4C9B2-C683-45A4-BC09-F5639E807436.jpg (83.7 KB, 12 views)
__________________
Sony Trinitron is my favorite brand.
My wish list:
Sony 8-301W
Sony KV-5000
Sony KV-7010U
Sony KV-1210U

Last edited by Popester; 11-05-2018 at 12:53 AM. Reason: Spelling
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  #15  
Old 11-05-2018, 10:48 AM
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Sometimes they substitute equivalent parts on the production line, and sometimes they make changes that might not be in your service manual.

If it's original, and doesn't test bad, I wouldn't replace it. You don't want to create more problems by shotgunning easy to test parts. If it is bad, then you can probably safely use either part.
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