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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
Trinitron (kv-27ts20) appears to have lost it's green because I can see only
purple, pale pictures. The problem occurred during a hot scorching day when it became intermittent then permanent. Is it the tube or the circuit board? I like to use a test jig tube to find out. I have two 17" Trinitron in the basement and I'm trying to hook them as a test jig. The problems are simple. Can this be done if the subject tube does not appear to be an exact connection match? If so, how many wires jump from one tube to the other? Four? (Red, Green, Blue and Ground.) Or do I just plug em all in to the other tube as close to on the labeling as possible. What are possible side effects? Example: Tube one (kv-27ts20) contains about nine pins. Tube two (kv-xxxx) contains about seven pins. Tube three (kv-xxx) contains about seven pins. |
#2
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
Forget trying to swap tubes with a different model - unless you want to see
how much equipment you can wreck in one day. You didn't give enough information for a diagnosis. It could be something as simple as a purity error due to a magnetic field from something like a speaker, or if you relocated the set. It could be an electronic fault in the colour decoding or display circuitry, or a tuner fault. Also, if it's an older set, the high value resistors on the tube base PCBs of Sony TVs tend to drift off value and cause lousy pictures - replace them with metal film ones instead of carbon. Let's hear more about the fault and the diagnostic tests done thus far. "Wdyorchid" wrote in message ... Trinitron (kv-27ts20) appears to have lost it's green because I can see only purple, pale pictures. The problem occurred during a hot scorching day when it became intermittent then permanent. Is it the tube or the circuit board? I like to use a test jig tube to find out. I have two 17" Trinitron in the basement and I'm trying to hook them as a test jig. The problems are simple. Can this be done if the subject tube does not appear to be an exact connection match? If so, how many wires jump from one tube to the other? Four? (Red, Green, Blue and Ground.) Or do I just plug em all in to the other tube as close to on the labeling as possible. What are possible side effects? Example: Tube one (kv-27ts20) contains about nine pins. Tube two (kv-xxxx) contains about seven pins. Tube three (kv-xxx) contains about seven pins. |
#3
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
When I was working in warranty service for Sony, this is one of the
models we were handling. On the back of the CRT socket there are marked R G and B cathodes if I remember correctly. Use a DVM and measure the voltages. I cannot remember the exact voltage range, but they should be within about 15% of each other. The voltages are okay, then this is a very strong indication of the tube being defective. If the tube is shorted, it can also bring down some voltages. Disconnect the socket of the tube, and take the readings on these points again. If the are within specs, the tube is shorted. Component failure on this board is very rare unless the tube when short, and did some damage. In your case, I strongly believe the tube went defective on the green section inside of it. This is common on these sets, after many hours of tube use, and considering the age of the set. You cannot jumper in the wrong tube. The electron-gun configuration, voltage drives, and video drives must match exactly. The same goes for the HV specs. If you mess with this, you are doing something that is considered very dangerous for your safety, and also for the components in the set! -- Greetings, Jerry Greenberg GLG Technologies GLG ============================================== WebPage http://www.zoom-one.com Electronics http://www.zoom-one.com/electron.htm Instruments http://www.zoom-one.com/glgtech.htm ============================================== "Wdyorchid" wrote in message ... Trinitron (kv-27ts20) appears to have lost it's green because I can see only purple, pale pictures. The problem occurred during a hot scorching day when it became intermittent then permanent. Is it the tube or the circuit board? I like to use a test jig tube to find out. I have two 17" Trinitron in the basement and I'm trying to hook them as a test jig. The problems are simple. Can this be done if the subject tube does not appear to be an exact connection match? If so, how many wires jump from one tube to the other? Four? (Red, Green, Blue and Ground.) Or do I just plug em all in to the other tube as close to on the labeling as possible. What are possible side effects? Example: Tube one (kv-27ts20) contains about nine pins. Tube two (kv-xxxx) contains about seven pins. Tube three (kv-xxx) contains about seven pins. |
#4
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
I'm sorry to dissapoint you but their were no diagnostic done so far except a
bang here and there on the components with a wooden spatula. The TV weren't transported before the failure. I'd decided not to buy a service manual. I'd also felt the temperature on each heat sink and they appear to run warm as normal. The Tv has been repaired twice by a friend and probably replaced the tube and the resistor(s) you pointed out. My idea of the test jig is probably a bad one. -Wd Forget trying to swap tubes with a different model - unless you want to see how much equipment you can wreck in one day. You didn't give enough information for a diagnosis. It could be something as simple as a purity error due to a magnetic field from something like a speaker, or if you relocated the set. It could be an electronic fault in the colour decoding or display circuitry, or a tuner fault. Also, if it's an older set, the high value resistors on the tube base PCBs of Sony TVs tend to drift off value and cause lousy pictures - replace them with metal film ones instead of carbon. Let's hear more about the fault and the diagnostic tests done thus far. |
#5
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
I think you have a very creative idea. Something I can do in a day. I'd never
thought of this. Had been tying to determine wether the tube has passed thru all the good time for weeks and needed to find a way out. I'd been eyeing a new 27" Trinitron on the market for $700. Anything below this price seem to have un-crystal clear pictures. I use it to watch PBS or documentaries, wich requires a TV as clear as Plasma TVs. Thanks for your and everyon'e else's advices. Especially yours. -Wdy When I was working in warranty service for Sony, this is one of the models we were handling. On the back of the CRT socket there are marked R G and B cathodes if I remember correctly. Use a DVM and measure the voltages. I cannot remember the exact voltage range, but they should be within about 15% of each other. The voltages are okay, then this is a very strong indication of the tube being defective. If the tube is shorted, it can also bring down some voltages. Disconnect the socket of the tube, and take the readings on these points again. If the are within specs, the tube is shorted. Component failure on this board is very rare unless the tube when short, and did some damage. In your case, I strongly believe the tube went defective on the green section inside of it. This is common on these sets, after many hours of tube use, and considering the age of the set. You cannot jumper in the wrong tube. The electron-gun configuration, voltage drives, and video drives must match exactly. The same goes for the HV specs. If you mess with this, you are doing something that is considered very dangerous for your safety, and also for the components in the set! -- Greetings, Jerry Greenberg |
#6
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
I'd just completed the test in 5 minutes and here are the results:
Blue: 195 volt Green: 194 volts Red: 200 volts The city charge ten dollars to throw away TVs here. |
#7
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Sony Trinitron lost green & a homemade CRT test jig. (kv-27ts20)
These are the parts you need to check/replace:
replace open r587& shorted d518 on "A" board replace leaky C508 0.047MFD |
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