Riddled TV Repair Forum

JTS1957 · Joined: 21 Jan 2009 Posts: 1330 Location: Far, Far Away

Since you state you have raw B-Plus across C803, let's see if a couple of IC's are getting their B-Pluses. IC801S Pin 1 = Raw B-Plus; Pin 4 = 18 volts.
ICS803 Pin 1 is input, Pin 2 is switched output 5 volts.

Look near bottom of sub power schematic. You'll see a RY801S (above relay RL801S). Note that it has ground symbols on either end. The left side is the symbol for HOT (AC) GROUND - the other end shows the symbol for COLD ground. In general, if you're measuring on the primary (left) side of the power transformers and other isolation devices, you should reference HOT ground. If you're measuring on the secondary side of the power transformers, you should reference COLD ground.

It can't hurt to try taking measurements in standby (set plugged into wall - power button NOT touched) and run (set plugged in & power button has been pressed "once." IF the word "switched" is stated, usually the point will only have voltage when the "device" is switched on (ICS803 above, for example).

Also check the continuity of the various fuse devices like the following: FD801S; FD802S; FD803S; RS803; RS804 & FS801S. There may be more, I just grabbed half dozen.

Google

pensacol · Joined: 02 Jul 2009 Posts: 30

Checked all fusible devices, and they are good. FS801S was the one that was blown that I replaced earlier on. It has not blown since. IC801S has 160v on pin 1 and 20v on pin 4. ICS803 has 7v on pin 1 and 5v switched on pin 2.

JTS1957 · Joined: 21 Jan 2009 Posts: 1330 Location: Far, Far Away

Check C808 & C811. If both OK, most likely IC801S is bad. It has to be running for SMPS secondary voltages to be present.

I assume you get a relay click (otherwise no raw B-Plus). Also can't seem to locate a datasheet for IC801S.

pensacol · Joined: 02 Jul 2009 Posts: 30

Yeah I get a relay click. But only when power is first applied. Not when the set it turned on. Nothing happens when the power button is pressed but as soon as you plug it in the relay clicks and it sounds like it fires up the D-Coil. Of course the STR-x6757, IC801s is some special kind of switcher that is not available ANYWHERE! Just my luck.

JTS1957 · Joined: 21 Jan 2009 Posts: 1330 Location: Far, Far Away

Since the only fuse that failed leads to ICS801, let's check for pin 4 = 23 volts; pin 5 (or 6/or 7/or8) = near raw B-Plus.

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pensacol · Joined: 02 Jul 2009 Posts: 30

Correct. I do have 23v on pin 4, and 5,6,7,8 have 160v. I don't know if it helps or not, but the first thing I did to this was replaced the HOT. Replaced it and when switched on I got the same response that I do now with the exception of a buzzing coming out of it sounded like IC801S. I couldn't really tell where it was coming from but it was from that area. I pulled the board out and started checking and the first thing I found was that fusible link. I replaced that and haven't been able to replicate that buzzing since. I even tried removing the fusible link again and nothing. Don't know if it means anything or not. It wasn't a squealing like a fet shorting just a high frequency buzz like feedback or something.

JTS1957 · Joined: 21 Jan 2009 Posts: 1330 Location: Far, Far Away

The HOT that is in it now is? Type number? Tests?

pensacol · Joined: 02 Jul 2009 Posts: 30

I replaced it with a FJL6920TU. It was the same one that came out of it. The original was shorted. But the new one checks fine now. The damber diode off the collector of the HOT is fine also.