Trinitron KD-32FS170: No Power - Videokarma.org TV - Video

YamahaFreak · #1 04-07-2015, 04:16 AM

This TV is a few firsts for me: first KD-series (digital) Trinitron, and the first I've worked on from this era that doesn't do ANYTHING when plugged in. Neither the front panel button nor the remote control activates the set. I don't even get any standby LED blinks!

Nothing looks compromised on the mainboard. The TV makes no noises at all...just as if it was never plugged in. I don't even know where to start on this one, oh dear. Thanks again you guys, for putting up with my constant service requests.

CoogarXR · #2 04-07-2015, 07:15 AM

When all else fails, I would trace the 110v in and see if you lose it somewhere, like an MOV or an open transformer or something.

zeno · #3 04-07-2015, 07:25 AM

Dont think I ever worked on one & I know I wont
have a manual. Start by finding the STBY ( standby )
power supply. Should be a small one that gives +5 V & 12 V.
Some are on a separate board & some keep all running
& turn the hoz osc on/off for on/off. Sonys are well marked
so you can usually find the micro marked at VCC, RST etc
to see if its getting 5V.
May also use the same as the wide screens with the
2 IC's, one is STBY & other 130 V.
BTW if the main fuse is blown violently it may be a
lightning hit. If so probably a total loss.

73 Zeno

YamahaFreak · #4 04-07-2015, 04:53 PM

The AC fuse is intact, so I can only assume power is getting past it. There are only three boards in this set - Mainboard/power supply, CRT board, and the digital tuner board.

Electronic M · #5 04-07-2015, 05:16 PM

The line should feed a diode bridge and a large cap (something like XXXuF @ 200V) check for ~170Vdc on the cap...That should feed a switch mode power supply which likely uses a transformer to create smaller DC supply voltages....Probe around and see if those supply voltages look sane.

ChrisW6ATV · #6 04-08-2015, 12:55 AM

I have worked on Sony monitors that would go totally dead from one bad electrolytic capacitor in the power supply. If you have an ESR meter, check all of the ones in the power supply standby circuits. The one I remember was something like a 220uF/50v capacitor. It will NOT "look bad" (such as the top being bloated).

rca2000 · #7 04-08-2015, 01:06 AM

Does this set use a relay for power switching? If so...is that clicking.

If it is NOT---and you have your standby voltages ok....there is something called the "ZCD" ckt., (Zero cross detection) that may be at fault. WHat is is SUPPOSED to do...is limit the current through the relay, in a way that it is turned on ONLY at the "zero cross" point of the AC line. In THEORY anyway...this is supposed to be easier on the relay contacts. In REALITY this little ckt caused headaches--as it will NOT allow the set to come on at ALL---NO relay click--if it is defective. Usually--it is a bad or maybe a couple--of SMD diodes in this ckt. I am NOT sure how to bypass this--as the set MUST see this pulse from this ckt--before it will allow power up.

Geoff Bourquin · #8 04-10-2015, 06:43 PM

I think ZCD failure gives a blink code. Also, IIRC you can turn the TV on with ZCD failure by entering service mode. That happens with the TV off, then use the remote and press "display" "5" "volume down" and "power" in that sequence. If ZCD is bad it'll turn on and display the error counts on the screen.
ZCD always seemed like an uneccessarily complex solution for a simple problem.