Panasonic TC-32LX85 Dead

[budm]

Re: Panasonic TC-32LX85 Dead

You can apply the external 5VDC to that filter cap (470uF 25v) for the standby power supply, just lift up one end of the cathode side of the rectifier that feed that filter cap, see post 35 where I circled the diode. You will have the TV plugged in then turn on your external power supply.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

I lifted cathode of D7015, attached the 5V to C7015 and as you can see by the glow the TV is up and running!

So now we know it's the PS thanks!

So what does that say about why the 5V is going low, the other voltages would be OK so something for sure in the standby section?

[budm]

Re: Panasonic TC-32LX85 Dead

Great, now I will have to look at the diagram of that 5V power supply to see which component/s is causing the problem. BTW, so the circuit draws about 560mA.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Sorry here is the correct SM, the others were for other chassis, I'm not sure if you had it. Pgs 30-31

[budm]

Re: Panasonic TC-32LX85 Dead

OK, try lifting one end of the Zener D7014. BTW, is D7006 also installed? It looks like both diodes are connected in parallel. If it is installed, then lift its leg also.
Power up and see if it will work using load that draw 600mA.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

OK looks like those 2 diodes are on the bottom of the board too, will do it tomorrow. So I'd be reinstalling D7015 and not using the external PS, correct???

[budm]

Re: Panasonic TC-32LX85 Dead

That is correct.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

OK Bud, lifted cathode of D7006 and removed tiny SMD D7014 and TV comes on!

Both of these diodes seem to test good.

Something of interest:
Checked voltage at FB/OLP pin 4 (using pin 3 as ground) of IC7000 (1.4V) and TV exhibits same relay clicking behavior and not turning on, until I remove the probe.

[budm]

Re: Panasonic TC-32LX85 Dead

OK, put d7006 back in place, I do not knw why they have two Zener in parallel unless the diagram is not correct. Are they really connected in parallel?
Is cap c7013 installed?
I would like to know the P/N of this IC also.
BTW, what dc voltage do you get at VCC pin. Q7000 sure has strange biasing circuit for it also.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

IC7000 is A6159

https://cdn.badcaps-static.com/pdfs/...cd00f00320.pdf

Yes diodes D7006 and D7014 are in parallel.

C7013 is there and not shorted.

BTW what did we just do by removing those diodes, bypass the FB/OLP in IC7000??

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Reinstalled D7006 but not D7014 and TV is still powering on OK.

[budm]

Re: Panasonic TC-32LX85 Dead

Those Zeners are for clamping, I have a feeling the D7014 has leakage.
Use the TV for awhile to see if it will come on every time.
So what DC Voltage do you get at the VCC pin?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Today when I went to turn on TV it was dead. I did not put D7014 back in. STB5V is around 3.5V, and I get about 10.6V to the VCC pin of IC7000 that you asked about. Does that seem low? I didn't get a chance to check that when it was working.

[budm]

Re: Panasonic TC-32LX85 Dead

Operation Start Voltage VCC(ON) 17.5V
Operation Stop Voltage VCC(OFF) 10
So it is low, close to the stop working voltage point of 10V.
Try putting a 4.7uF 50V cap at the VCC pin and ground.

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

Is that what C7011 is supposed to be for? I replaced that cap with one I had from another TV, could that be it?

[budm]

Re: Panasonic TC-32LX85 Dead

It only has 0.1uF (C7009) for the VCC pin instead of the typical 22~47uF used on the VCC pin, the filter cap used on the AUX winding for running the IC is also very small, only 4.7uF (C7011).

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

OK I ordered a few new Panasonic 4.7uF 50V, I will replace C7011, and then try what you said. You mean 4.7 and not 47uF right?

[budm]

Re: Panasonic TC-32LX85 Dead

From the spec sheet:
VCC Pin Peripheral Circuit
The value of C2 in Figure 10-1 is generally
recommended to be 10μ to 47μF (refer to Section 9.1,
because the startup time is determined by the value of
C2). In actual power supply circuits, there are cases in
which the VCC pin voltage fluctuates in proportion to
the output current, IOUT (see Figure 10-2), and the
Overvoltage Protection function (OVP) on the VCC
pin may be activated. This happens because C2 is
charged to a peak voltage on the auxiliary winding D,
which is caused by the transient surge voltage coupled
from the primary winding when the power MOSFET
turns off. For alleviating C2 peak charging, it is
effective to add some value R2, of several tenths of
ohms to several ohms, in series with D2 (see Figure
10-1). The optimal value of R2 should be determined
using a transformer matching what will be used in the
actual application, because the variation of the
auxiliary winding voltage is affected by the
transformer structural design.

 FB/OLP Pin Peripheral Circuit
Figure 10-1 performs high frequency noise rejection
and phase compensation, and should be connected
close to these pins. The value of C3 is recommended
to be about 2200p to 0.01μF.
In order to make the value of C3 low and make the
output response fast, DZ1 and C4 are connected.
DZ1 prevents C4 charging in normal operation. The
zener voltage of DZ1, VZ should be set higher than
FB/OLP pin voltage in normal operation. Usually, the
value of VZ is about 4.7 V to 5.6 V.
C4 is for OLP delay time, tDLY setting. If C4 is too
small, the power supply may not start due to OLP
operation (see Section 9.8). The value of C4 is about
4.7 μF to 22 μF.
C3, C4 and DZ1 should be selected based on actual
operation in the application.

It does not seem that PANASONIC is following the IC manufacturer recommendation.
See page 22, 23 for circuit example and parts.
This is the diagram for 5V 1A power supply.

[budm]

Re: Panasonic TC-32LX85 Dead

OK I ordered a few new Panasonic 4.7uF 50V, I will replace C7011, and then try what you said. You mean 4.7 and not 47uF right?

What do you have in small value caps?

[kevinm34232]

Re: Panasonic TC-32LX85 Dead

I just want to be sure, above you said use a 4.7uF 50V on the VCC pin?