NEC FS-6390 TV Problem PART 2

> I have repaired a few FS-6390 with this problem.

>> Most likely IC401 is crook, this is a LA7838 vertical output chip. >> >> Also check, >> R522 2.7ohm 2w fuseable. >> R523 2.2 ohm 1/2w fuseable. >> R427 100 ohm 1/4w fuseable. >> >> Replace:- >> C609 100uF 16v >> C533 2.2uF 160v >> C611 22uF 25v >> C411 100uF 35v >> C607 220uF 10v >> >> Russell Grifiths.

I have replaced these components and still no go. I also noticed that D401 (Fast recovery,Si.,General Purpose,3 Amps at 600V) was also dead. I replaced it, but still to no avail.

Could I have killed the new output chip by not diagnosing the crook diode before placing the chip??

Reply to
David
Loading thread data ...

Greetings David. I have just looked at the schematic and I don't think the shorted D401 would have caused IC401 to fail. But I can't be 100% sure about that.

Do you still have the horizontal white line across the middle of the screen?

Do you have around 27v at pins 8 and 13 of IC401

Below are the voltages on the schematic for IC401.

PIN Voltage

1 12v 2 7.3v 3 0v 4 6.1v 5 0v 6 5.9v 7 5.8v 8 27.2 9 2.3v 10 n.c. 11 0v 12 11.2v 13 27.7v

I have a FS-6390 on the bench at the moment. This one went out with a bang. A piece of IC601 (STRS6708) blew out of the chip, and several other parts failed nearby.

Just a little helpful advice. If you have more to add about a previous posting, continue the thread that has already been started.

Russell

Reply to
rg26ce1991

Hello Russell,

Yes, I still have the horizontal white line.

I have checked the voltage on pins 8 and 13, using pin 3 as the ground.

The voltages were as follows:

Pin 8: 0.8v Pin 13: 0.5v

It appears that these voltages are way too low.

Thanks for your advice on posting new threads, I'll take it on board for next time.

David

Reply to
David

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.