Sony KDL-40bx421

[budm]

Re: Sony KDL-40bx421

Is your meter a TRUE R.M.S. meter?

[pop70458]

Re: Sony KDL-40bx421

Its not a true rms but i do have a fluke 334 also.

[budm]

Re: Sony KDL-40bx421

334 is the clamp on amp meter with other meter function it is not true RMS. Not really for electronics troubleshooting. But what is the meter you are using right now?
https://cdn.badcaps-static.com/pdfs/...ea2919f372.pdf

[pop70458]

Re: Sony KDL-40bx421

Its a craftsman 82140

[budm]

Re: Sony KDL-40bx421

OK, check the DCV at pin 4 (AC_RMS) and GND pin or the negative leg of the main filter cap C6330 (180uF 450vdc). The reading should show about 1.8VDC on pin 4.

[pop70458]

Re: Sony KDL-40bx421

I get 0.02v on pin 4.

[dick_barton]

Re: Sony KDL-40bx421

What DC voltage do you have across D6312

[pop70458]

Re: Sony KDL-40bx421

I get 9.8v on d6312.

[dick_barton]

Re: Sony KDL-40bx421

This is becoming quite confusing.

You appear to measure no appreciable voltage at AC_DETIN input which is needed to tell the CXA3810M that the mains supply is on and the IC should then output a voltage to AC_DETOUT.

Also the VCC supply for the CXA3810M appears to be too low for it to start running.

Page 57 of the CXA3810M data sheet shows a typical voltage for it to start running of 11.0V
It also shows a typical voltage for the CXA3810M to stop running of VCC typically 9.6V

VCC maximum for the IC is 24V and the zener diode D6313 across the VCC and Ground input of the CXA3810M is a 22V zener diode so I would be expecting more than 9.8V at VCC but less then 24V.

It would be worth checking the diodes D6317, D6312, D6313, D6320, D6314, D6105, D6104 & resistor R6106

[pop70458]

Re: Sony KDL-40bx421

i get these readings.

d6104----10.2v
d6312----9.8v
d6320----4.9v
d6313----i don't see it.
d6317----i don't see it.
d6314----0.02v
d6105----10.0v
r6106-----0v
r6106 I get 3.4 ohms with one leg lifted.

[dick_barton]

Re: Sony KDL-40bx421

So the circuit diagram is similar but not identical to your power supply.

What dc voltage do you have across D6304

[pop70458]

Re: Sony KDL-40bx421

d6304 is 0.02v.

[pop70458]

Re: Sony KDL-40bx421

I bought another power supply and it fixed the problem.

Thanks for the help.