Rca led50b45rq

[budm]

Re: Rca led50b45rq

Your tracing appears correct. I checked resistance between the resistor 000 and pin 12, from 000 to both sides of C4, and also from the incoming side of 000 to both ends of C4 and to pin 12. I get a reading of 1 with all of them, however a couple of times i had it bounce all around from 70.0 and below when checking the incoming side of 000 to the outgoing side of C4.

"from 000 to both sides of C4" what kind of resistance it showing on the meter 0 Ohms to both side of C4?
We need to know if the resistance is in OHM, K OHM , or M OHM.
Since you have 12V at BOTH end of that '000' OHMS resistor and it has connection to pin 12 of the IC then it is impossible to get 0.28V as you report earlier. You have to think logically at this point when it does not make sense based on your DATA, or error in your measurement. Point 'A' has 12V and is connected DIRECTLY to point 'B' so it is impposible not to have 12v at point 'B'.

[x_orange90_x]

Re: Rca led50b45rq

I checked with the lowest resistance setting on my multimeter 200 (see attached picture). All that displayed was a 1 all the way to the left of the display.

[vinceroger69]

Re: Rca led50b45rq

as some of these readings do seem a little odd maybe put a new battery in your multi meter as maybe a little low also test a brand new battery and check it reads the correct dc votage on your meter as in the past we have seen multi meters give odd/false readings.

[budm]

Re: Rca led50b45rq

I checked with the lowest resistance setting on my multimeter 200 (see attached picture). All that displayed was a 1 all the way to the left of the display.

That means it is more than 200 Ohms, your meter is showing over range.
Just touch the two probes together and see what you get and that is what you should get when you measure the resistance from 000 resistor to pin 12 of the IC.

[dick_barton]

Re: Rca led50b45rq

I checked with the lowest resistance setting on my multimeter 200 (see attached picture). All that displayed was a 1 all the way to the left of the display.

This should help you.

https://www.youtube.com/watch?v=nPdECcBU1Vc

[x_orange90_x]

Re: Rca led50b45rq

I just checked again using the 2000k setting. I got the same 1 reading that fluctuates for a couple seconds and drops to 000. That is from either side of the 000 resistor to the out-going side of C4 (the side just before pin 12). Once i got the same result directly to pin 12, but following attempts left me with the 1 to the left.

[budm]

Re: Rca led50b45rq

Stay with 200 Ohm scale, we need to see <1 Ohms or so resistance when tracing the direct connection between point 'A' and point 'B'.
We need to find out what that end of 000 resistor is connected to.
That VCC pin 12 of that IC should have direct connection to Emitter/or Collector of the switched transistor some where on the board, just a matter of finding it.

[x_orange90_x]

Re: Rca led50b45rq

We need to find out what that end of 000 resistor is connected to. That VCC pin 12 of that IC should have direct connection to Emitter/or Collector of the switched transistor some where on the board, just a matter of finding it.

Check out the attached pictures and let me know what you think.

[budm]

Re: Rca led50b45rq

https://www.badcaps.net/forum/attach...0&d=1491216069
So pin 12 goes to the EMITTER of Q13? That section is for the current sensing of the for the Power MOSFET that drives the transformer.
I think you need to find out which pin of the IC is connected to the 0 Ohms resistor, I can only see the trace going the IC but cannot tell unless you Ohm it out..
BTW, are you sure about the P/N of that IC?

[x_orange90_x]

Re: Rca led50b45rq

I shared that picture and tracing with you because it *looked* as though it may go that route. I can clearly see a trace going under C4 and over to Q13.. But i don't really know what I'm looking at. That's why i wanted to share it with you. The P/N is L6599AD. I downloaded the Spec sheet for it in order to get the Pin-out.

[budm]

Re: Rca led50b45rq

At this point I would put one probe on the 000 resistor and another probe on each pin of the IC to see which pin will show <1 Ohm resistance, meter in 200 Ohm scale.

[x_orange90_x]

Re: Rca led50b45rq

I will check them all tonight. I suppose it's possible that I've got the diagram backwards, but unlikely because of the orientation of the text. This chip doesn't have a little dot indicating pin 1. Instead it has a little triangle logo. However, i read that if there are no clear markings for pin 1, then with the text right side up Pin 1 would be the lower left pin.

So what reading should i expect to find in the correct situation?

[dick_barton]

Re: Rca led50b45rq

Post a photo of the IC to help identify pin 1

[x_orange90_x]

Re: Rca led50b45rq

Post a photo of the IC to help identify pin 1

If you google an image of this chip, some of them do have an indicator hole located in that bottom left corner.

[dick_barton]

Re: Rca led50b45rq

Is there a chamfer down the left hand side of the IC looking at the photo you've just posted?

[x_orange90_x]

Re: Rca led50b45rq

The attached picture is from the other side of the chip.. No chamfer

[dick_barton]

Re: Rca led50b45rq

Is there a chamfer down the left hand side of the IC looking at the photo you've just posted if not then it looks like as you have already numbered.

http://wb5rvz.org/common/locatingPin1

[vinceroger69]

Re: Rca led50b45rq

i have fitted one of these ics a while ago and fitted it thinking bottom left was pin 1 the psu worked fine so must of been correct

[budm]

Re: Rca led50b45rq

If I am correct one of that IC pin should have direct connection between the two points. That switched Voltage source has to used for something.

[x_orange90_x]

Re: Rca led50b45rq

If I am correct one of that IC pin should have direct connection between the two points. That switched Voltage source has to used for something.

OK.. I think I've finally got what you're looking for. Between PIN 12 (yes, the one we've referred to the entire time) and that point you marked (which i believe is C5 capacitor on the other side), i got 1.4-13 on the 200 scale. ALSO, this time between the out going side of resistor 000 and PIN 12, i got 5.7-195 on the 200 scale.