Polaroid FLM-2601 - Power Supply keeps blowing fuse

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Great! It is 15V, 1/2 Watt will be enough, is it surface mounted? At first thought, I was thinking that your new MOSFET has gone out again.
You can use through hole if you have room.
Oh, I forgot, there is also Resistor-Diode connected in series and then in parallel with the 220 Ohms resistor, might as well check that also.

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Well resistor checks out now. I took out the zener and it passes current both ways. So what else should I look for when replacing these other than the power rating?

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

That makes sense why you are getting about 200 Ohms reading at pin5, so it can be either shorted out Zener Diode or shorted out Gate to Source on the MOSFET. Take your choice, remove the Diode or the MOSFET to find out where the short is. Getting close!

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

It is only coming up at .2-1 ohms nonetheless no where near 4.7k

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

So the short is external to the IC, if you measure that 4.7K resistor which is in parallel with the Diode D910 (15V Zener), what do you get (do not solder pin 5 back in yet), I expect to see 4.7K Ohms (use Ohm mode to check the resistance).

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

It measures 3.23 MOhms

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Just lift just pin 5 and put the meter on pin 5 of the IC and ground to check the resistance. I think pin 5 is shorted out inside the IC.

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

I think thats R939 (for resistor in parallel with that zener). Ok, I'll take D910 and the IC out and check it.

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Pin5 (output drive) does not read right (I expect at least 4700 Ohms) since it has (R932) 220 Ohm resistor which is connected to Zener Diode D910 to Ground, it also has (R930?) 4700 Ohms resistor in parallel with this Zener Diode. So something must be shorted to Ground at the right side of R932 like shorted out D910. Otherwise it may have internal short. You may have to lift up the IC NCP1207 () pin 5 from the board and take the measurement again. It may have been damaged when the MOSFET went out.

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Ok here are the resistances
P1: 16.38 kOhms
p2: 86.5 kOhms
p3: 220 ohms
p5: 221 ohms
p6: 5 MOhms (then steadily drops)
p7: OL
p8: 8.4 MOhms (then steadily increases)

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Since youi will be working in the AC Primary side circuits, the circuit Ground for that section will be the Negative leg of that Large Main DC filter cap, not the safety ground.
Be real carefull not to touch the priamary section with your body, you should have this TV/Board plugged into the GFI outlet. You check the resistance on the pin of the IC with ref to the same ground as above without power to the board, you should let the big cap discharge down to 0 volt.

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Sorry I haven't gotten to this, been busy.
But do have some results. I have not tested the cap or resistance of all the pins yet but here are the voltages and resistances.

I had to test the board out of the tv so where the ground is connected to chassis is just hooked to an outlet screw.
I tested from the ground pin of the IC (and the main ground which yielded very different results)
The results from the ground pin are:
Pin 6: 6-8v
Pin 8: 365-380v
(The voltages would cycle through those numbers)
S->ground and G->ground were .3 ohms (from pin 4)

[tibimakai]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Ha ha, I have just picked up one of these right now and it's completely dead, haven't opened it yet.
Here is a video one Youtube:
http://www.youtube.com/watch?v=OqZG1F_h1CA
I may just keep it as a monitor for my workbench.

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

OK, we need to check the resistance of V907 (the 24V MOSFET) between S pin and Ground, G pin and Ground.
Then check the Dc voltage of HV (start up) pin8, Vcc pin 6 (You should see the voltage jumps up if there is any activity).
You will also want to check that 47uF/25V running cap that is attached to the Vcc pin 6. I would replace it anyway.
Then also, with the TV is off for 1/2 Hour, check the resistance reading of all to pin of the 24V SMPS IC with ref to ground.

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

I replaced V906 and V907. The V907 is the one after the SMPS IC and I replaced it with a 80C instead of 60C.

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

OK , we now need to look at the SMPS IC and MOFET, but can you tell me which MOSFET you replaced as shown in the Diagram?

[drpj23]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Ok, the voltage on the cap remains constant but I have no 24vdc at all.

And wow, I feel like I know nothing after reading that lol.

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Please see the attachment explaining how it works.

[tom66]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

It looks like the standby supply generates the power for the PFC when it is started up. Does the 386V remain reasonably constant or does it drop off? The Vcc for the controller is derived separately.

[budm]

Re: Polaroid FLM-2601 - Power Supply keeps blowing fuse

Yes, jump 1 and 2 will force the power supply to stay on. The diagram makes it so much easier to troubleshoot. But just to be sure you should trace out the connections on the connector to make sure it matches the diagram, just in case.