Riddled TV Repair Forum

pensacol · Joined: 02 Jul 2009 Posts: 30

Got this tv from somebody, and it wouldn't turn on. Power light just blinked. They said they had an estimate done on it and they said it was the HOT and a couple resistors. They cut the leads on the hot which had been replaced before because it's not the original. Does anybody know where I could find a service manual for this set (chassis model K60A)? Or are there and updates to this board or common problems? It's a really nice tv and I would love to see if I could get it fixed.

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pensacol · Joined: 02 Jul 2009 Posts: 30

Update: Found a cracked solder joint on the flyback, the pin connected to the collector of the HOT. HOT was shorted I'm guessing cause of the cracked joint. Set still will not turn on. Only get 3 blinks on the power light. No power to the main board at all. Figuring something in the power supply. I get 160vdc across the main filtering cap off the rectifier, but if I go from positive to ground on the board I only get 88vdc. I have checked every diode on the board thinking one was leaking to ground but they are all good. Here are a couple pictures, and I have marked where I checked the voltages. I have also included the power supply schematic. Could somebody please take a look at it and see what I might be able to check. Also. You will see the jumper that I soldered across 2 pins on the board. That was a 4 amp pico fuse that was blown. The jumper was there for testing so don't worry I put a 4 amp fuse across it before I applied power the first time Very Happy

Thanks guys. Hopefully somebody can help me.

Top Of Board
Bottom of Board
Schematic

kuhurdler · Joined: 28 Dec 2006 Posts: 2879 Location: Overland Park, KS

Which gnd are you using. If its earth ground 1/2 of your b+ makes sense. Usually earth ground is in the middle of the bridge rectifier.

pensacol · Joined: 02 Jul 2009 Posts: 30

Straight across the main filter cap off the rectifier I get 160v, to any other gnd I get 88v, tried heatsing gnd, the one on the bottom left of the "bottom of board" picture, and the soldered trace lines right to the right of that gnd.

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

What about secondary SMPS (reference TUNER ground) voltages?

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pensacol · Joined: 02 Jul 2009 Posts: 30

If you look at the diagram for the sub power board (above link) this is what i get off the SMPS to reference ground:

Pins 18,17,16,15,14,13,12,10 off the secondary to reference = 0v
positive probe Pin 1 to negative probe pin 18 = 89v
positive probe Pin 1 to negative probe pin 2, 3, or 4 = 160v

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

Now let's try that again, taking the DC voltage readings across these capacitors:
C801 / C802 / C814 & C823

T801S Pins 12 & 15 are secondary (cold / tuner) grounds.

pensacol · Joined: 02 Jul 2009 Posts: 30

0v across all of those. One more thing. Do you want me to take those readings with the set on or off? Let me know and if I need to I'll check them again with it on. Power supply had power but unit was not officially on. But of course it won't turn on either.

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

Try it both ways.

pensacol · Joined: 02 Jul 2009 Posts: 30

Yeah, I got 0 volts on all those caps with the set on or off. I put the clips on the see if it would move at the moment it was turned on and nothing. So I guess I'm not getting any secondary voltages? I'm still learning switch mode supplies, but insent there an occisilator or something that drives the transformer to produce the secondary voltages? I'm not quite sure but from what I've read it seems like that's how it happens. What can I check? I really appreciate all of ya'lls help. This is the best tv repair forum I have found yet.