Sony KDL-55EX620, no stand-by volts from one bad resistor?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Voltage comes up to 4.44V with CN6101 detached from PSU

4.44V on the 444th post. You have to be kidding me!

[R_J]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Well something on the main is killing the ac_off_det line unless thats normal operation but it does'nt seem likely

That line connects to ic9000 via RB9031 (100Ω)

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

That makes sense. So there's really nothing to short out on that circuit on the main board but the X-REALITY processor?

EDIT: Just saw your addition to last post, will check schematic

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Well something on the main is killing the ac_off_det line unless thats normal operation but it does'nt seem likely

That line connects to ic9000 via RB9031 (100Ω)

While tracing down circuits near that resistor array I checked all 4 of them, I believe the reading in diode mode was .120

So I guess that confirms a short in the X-REALITY processor, IC9000?

[R_J]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

When checking resistors use ohm setting, not diode test, in this case the resistors are each 100Ω. If you check from ground to the one that is connected to the ac_off_det line it is likely close to 0Ω to ground
If that line is LOW the ic believes there is a problem with the power supply so it won't allow it to be turned on

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

At what ground point should I measure, and on what side of the resistor?

[R_J]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

You would use chassis ground or pin 1 of cn6002, You can find out which resistor it is by puting a probe on CN6002 pin 9 and check to each of the 4 resistors of RB9031. the point that is 0Ω is pin8, now check the other side (pin7) of the resistor to ground, that will check the input point (AE5) of the ic9000

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Voltage comes up to 4.44V with CN6101 detached from PSU

4.44V on the 444th post. You have to be kidding me!

STBY power supply is only 3.3V so I cannot see how you can have 4.44V at the collector of the Transistor which has resistor R6403 (8K2) between STBY3.3V supply and the Collector.. you better recheck your test.
AC_OFF_DET also feed connector CN6102 pin 7, anything connected to CN6102?
What did you use for GND ref. for the meter?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Sorry about the lengthly delay is replying. I wanted to check and re-check before posting more bad info.

Well R_J, it appears you are correct about one of those resistors being shorted to ground, Please see the attached picture, annotated with the ground point I used and findings at the resistors.

Can you tell me if I was grounded in the right spot? If I was I think the results are conclusive.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

STBY power supply is only 3.3V so I cannot see how you can have 4.44V at the collector of the Transistor which has resistor R6403 (8K2) between STBY3.3V supply and the Collector.. you better recheck your test.
AC_OFF_DET also feed connector CN6102 pin 7, anything connected to CN6102?

I will check and report back.

That is the AC_OFF_DET pin voltage at pin 7, CN6101 after unhooking the connector from the PSU

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

That is correct, just think about it, you have 3.3V power supply Voltage to run tha detection circuit and some how you are getting 4.44V (Collector) on the Transistors, how can that be?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

That is correct, just think about it, you have 3.3V power supply Voltage to run tha detection circuit and some how you are getting 4.44V (Collector) on the Transistors, how can that be?

No load from the mainboard?

Transistor shorted?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

What did you use for GND ref. for the meter?

When testing at CN6101 pin 7? Chassis

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

No load from the mainboard?

Transistor shorted?

Well, look that circuit:
1) Where would 4.44V be coming from?
2) If Q6402 is shorted between E and C then how can you have 4.44V at the Collector with ref. to GND?
3) What Voltage do you get if you measure between C and E pin of that Q6402?
4) What Voltage do you get between CN6101 GND pin 9 and STBY3.3V pin 10? 4.44V? if it is then that is why you are getting that 4.44V reading.
5) The STBY3.3V is generated by IC6251 (NJM2884), the feeding Voltage is 4.67V Typ. as shown in the schematic, so with light load the STBY3.3V can be higher than 3.3V depend on how that IC6251 functions.

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

So if you connect the main board back in place and then check the resistance between Pin 7 (AC_OFF_DET) of CN6101 and the GND pin 9, what resistance do you get? This test will tell you what the load is being put on the AC_OFF_DET line.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Well, look that circuit:
1) Where would 4.44V be coming from?
2) If Q6402 is shorted between E and C then how can you have 4.44V at the Collector with ref. to GND?
3) What Voltage do you get if you measure between C and E pin of that Q6402?
4) What Voltage do you get between CN6101 GND pin 9 and STBY3.3V pin 10? 4.44V? if it is then that is why you are getting that 4.44V reading.
5) The STBY3.3V is generated by IC6251 (NJM2884), the feeding Voltage is 4.67V Typ. as shown in the schematic, so with light load the STBY3.3V can be higher than 3.3V depend on how that IC6251 functions.

So if 3.3VSB comes from IC6251 and the feed voltage is 4.67typical then it seems to me IC6251 must have a short, passing all the input voltage instead of reducing it and sending it on?

So if you connect the main board back in place and then check the resistance between Pin 7 (AC_OFF_DET) of CN6101 and the GND pin 9, what resistance do you get?

Infinity

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Infinity with main board connected back in place?
If AE5 pin of IC9000 is shorted to GND then it should show about 100 Ohms.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Infinity with main board connected back in place?

Yes

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Infinity is not going to load that AC_OFF_DET line to be <1V.
See picture on post 117.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

So then IC6251 is short?