sanyo no back ligth

**selldoor** · 12-31-2012, 04:20 AM

Re: sanyo no back ligth

Off topic a bit - I have a question for Budm Or Tom66. On the bottom of the board (Pic post 70) Pan along the bottom edge t the midpoint hole then up slightly there are two points marked OVP 12v and OVP 5v - OVP means Over voltage protection? but are those actual components or what? Cant see anything to correspond on the top of the board.

**selldoor** · 12-31-2012, 04:47 AM

Re: sanyo no back ligth

Originally posted by budm

OK. please check the fusible resistor R322 that feed the B+ to the inverter transformer driving circuit.

You may as well check the other two fusible resistors at R332 .

I attach a datasheet for the transformer I am not sure what you can test on it
Start with the primaries - Power off - meter on 2000 ohms check and post result. Budm or Tom may be able to suggest further tests ( How to check the secondaries)

Attached Files

**ealequi** · 12-31-2012, 11:46 AM

Re: sanyo no back ligth

I am going to test the transformer to see if there is power going in and coming out

**ealequi** · 12-31-2012, 11:47 AM

Re: sanyo no back ligth

I am not easy to give-up

**selldoor** · 12-31-2012, 11:55 AM

Re: sanyo no back ligth

Dont do that - do resistance test only - did you read the datasheet
1500 Volts probably wont do your meter any good.

**ealequi** · 12-31-2012, 11:57 AM

Re: sanyo no back ligth

thank for the advise

**tom66** · 12-31-2012, 11:59 AM

Re: sanyo no back ligth

That datasheet for the transformer doesn't look like the correct part. It looks like a conventional 50/60 Hz transformer, not an SMPS one.

**selldoor** · 12-31-2012, 12:40 PM

Re: sanyo no back ligth

Originally posted by tom66

That datasheet for the transformer doesn't look like the correct part. It looks like a conventional 50/60 Hz transformer, not an SMPS one.

GOOD CATCH Tom - I am now fairly sure you are correct (again

)
I have checked and re googled under the part number PFT24-35 It is even available on Digikey cant think why anyone would save it on a pdf with the part number of this transformer MP-130B. I thought it was a bit easy to find and it did look the same shape/pins etc and the 1500Vrms threw me .
The one on the board is probably proprietory and unobtainable.

Ealequi - have you tested the fusible resistors?

**ealequi** · 12-31-2012, 01:05 PM

Re: sanyo no back ligth

which is that one? i still learning.

**tom66** · 12-31-2012, 01:15 PM

Re: sanyo no back ligth

Yes, he tested R322 which is the main fusible resistor in this instance.
The fault is probably on the IC which drives the MOSFETs.

**budm** · 12-31-2012, 01:47 PM

Re: sanyo no back ligth

So is R322 good or bad? I did not see the reply.
By the way the BL_ON at 1.7V is OK, I look at the circuit, it is fed by the 3.3V power supply for the switched transistor Q1805 of the main board. So you can splice the BL_ON wire back together and make sure to remove the 1K resistor from CN6.
The power supply board uses PFC Voltage booster, so he needs to check the voltage on th capacitor C821, it should have 170VDC when TV is off and about 380~390VDC when V is ON.

**ealequi** · 12-31-2012, 01:47 PM

Re: sanyo no back ligth

can you give me the location pls.?

**budm** · 12-31-2012, 01:52 PM

Re: sanyo no back ligth

Please take more pictures.

Attached Files

**budm** · 12-31-2012, 01:53 PM

Re: sanyo no back ligth

see post 140

**tom66** · 12-31-2012, 02:20 PM

Re: sanyo no back ligth

R322 was tested at 3 ohms. Given the lead resistance from a typical DMM, that seems like a good fusible resistor.

**selldoor** · 12-31-2012, 02:24 PM

Re: sanyo no back ligth

I wasnt sure about the soldering on that resistor - How about a voltage reading at both ends ?

**budm** · 12-31-2012, 03:26 PM

Re: sanyo no back ligth

I trace out the board, R322 is the main fusible resistor that feeds other fusible resistor for the 5V SMPS, and also the 12v SMPS circuits, so it must be OK.