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Sony KV-35V45 CRT tube short, trying to figure out and clear it !!!

Hi. I have a problem with a Sony KV-35V45 tv. For some reason i was unable to find out how to create a new product on the fixya's site. Oh well. First tv was intermittent. Green background instead of black, and pink instead of whites. Tapping on the crt got it back to life, i have a short there. It went ok for a while, and then bad again. Here's my question now; i'm checking to find the short on the CRT. And, possibly blow it off. Which pins of the CRT should have continuity ? I'm trying to understand but i'm having a hard time. I see pins labeled as : 1 - EC 4 - E-SPG 5 - G2 6 - G1 7 - H1 8 - H2 9 - G1-2 10 - KB 11 - KG 12 - KR 13 - G1-3 I see that CV, E-SPG, G1, H1, G1-2 and G1-3 are all connected together on the pc board connected on the CRT. On the CRT tube pins, i see continuity between G1-2, G1-3 and G2. Is this normal ? I also see continuity between G1 and H1, and G2 and H2. I have checked the PCB off the CRT tube and i see 209V on each of the 3 colors KR KB KG, but when connected to the CRT, i see 209V on KR and KB, but KG fluctuates from 109V to 209V (that's what i see on my meter). I'm trying to understand how this thing works here, i don't know how it works at all. H1 and H2 are the heater, on which i can pump 10V to clear it out ? I don't understand where my short is, how to find out and how to clear it. If anyone got light me up on this case i would really appreciate it. I understand that buying a new tv is the best choice, but environmentally wise i don't think it is. I don't wanna trash this TV whatever time it takes me.

Posted by Anonymous on

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  • Anonymous Aug 09, 2007

    Oh god. Thanks for that nice reply, Mike.

    I already did a huge mistake before reading this. Some local guy told me i should use 12V on the heater for 5-10 minutes. I did.. but 12VDC :( Didn't know it was High Frequency AC.. uh.

    Now the tv is in even worst condition. At least, i had a flashing image before with a pinkish tint and some green on the blacks, but now i can't get image to come on anymore.

    If i pump the voltage on the back of the neck of the crt board there's a pot there, if i go all the way i get a purple screen with some 'retrace lines' whatever that means.

    I wonder if i killed something now. I also wonder, if i should buy the CR-XA adapter for the B&K Precision model 467 i have here to blow the short, or use the capacitor method still ?

    The adapter runs for 75$ usd + ship. I'm wondering if it worths it at this point, since i did a mistake on the heater.

    The continuity is still there on the heater pins, i get about 4 ohms there which is ok according to the service manual.

    The G2 is isolated. No continuity to the other pins, my bad. Just double checked that.

    I'd appreciate your input at this point just to make sure what best option i should use.

    Thanks a bunch, Vincent.

  • Anonymous Aug 22, 2007

    Hi Mike. Are you still around ? I've tried what you said with a 200V 47UF Cap. When i connect the cap, the screen goes black and i can barely see 'video 1' on the screen. It seems that it didn't clear out the short.

    I'm wondering if i could 'isolate' the heater using those ways described in the forums, using some wire and some turns around the flyback ? If you got any other ideas don't hesitate to post. Thanks a lot, Vincent.

  • Anonymous Aug 22, 2007

    I've tried another thing now. Put the CRT glass down, and tap on the neck with crt pcb removed. Put crt back to original position, and power set on.

    Now i got 209V stable on the 3 cathodes. No more green raster screen, just standby led flashing and no image :|

    I've tried adjusting G2 (goes from 233V to 275V, what does that need to be set to ?)

    If anyone feels like helping it'd be really nice. Thanks, Vincent.

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On the CRT itself, without the socket connected, you should have continuity (0 ohms) between G1, G1-2 and G1-3. Those 3 pins are Grid 1 and are tied together inside the neck. You should also have continuity (maybe 5 ohms or so) from H1 to H2. Those 2 are connected to the 3 heaters (in parallel). When the set is on there will be 6.3 volts of high-frequency AC power at those pins, and you should NEVER try to pump more voltage to the H pins. If you clear out the continuity between the 2 H pins then you blow open all 3 filaments and the set is garbage. There should NOT be continuity of any kind between G2 and any other pin. If there is then the tube is bad and cannot be fixed. There should also be no continuity at all between any other pins. The good news is that from the voltages you posted, you have a heater-to-cathode short that developes in the green gun when the tube is warm. To remove this short, take a 22uF 250V capacitor and put an alligator clip from the negative lead to ground. Connect the positive lead of the capacitor to the 200 volt boost source and turn the set on, which charges the capacitor. Tap lightly on the neck of the CTR and when the voltage drops on the KG pin, the screen will go quite green and that is when you should take the positive lead of the charged cap and touch it to the KG pin on the tube socket. This should remove the heater-to-cathode short. A 22uF cap has enough charge to clear the short but usually not enough to blow open the filament itself. Using a capacitor larger than 22uF runs the risk of blowing the filament open and you do not want that. It is tricky to get it right because you have to have a charged cap and the tube must short out and you have to get the charge from the cap into the tube before the set shuts itself down. Try that and post your results.

Posted on Aug 09, 2007

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