Dynex DX-L40-10A Won't turn on.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Would a blow dryer be hot enough to heat it up? Then just take random readings from the caps?

[CapLeaker]

Re: Dynex DX-L40-10A Won't turn on.

Oh yes... it doesn't take much heat to lower the ESR on a cap. Blow drier is fine enough on low. You wouldn't want it to get baking hot.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Here's the results of the forced on state.

GND 0
GND 0
STB 2.8
5V S 4.84
5V S 4.84
12V slow drop to 0.01
12V slow drop to 0.01
GND 0
BR1 slow drop to 0.01
SW slow drop to 0.01
GND 0
GND 0
5V_M slow drop to 0.01
5V_M slow drop to 0.01

The 12v starts out around 7.9 and then drops. The 5v_m starts out around 4.8 and drops

This is the first time it's been powered on in days and this time plugging it in with the resistors in there were a lot of speaker pops which at the same time resulted in the readings for the dropping voltages to spike up and fall with each pop.
I wasn't able to reproduce this effect.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Should I even bother with trying to heat up the main board. It seems to me that the PS board has a bad cap in it or a bad coil?

[splitcrete]

Re: Dynex DX-L40-10A Won't turn on.

Lower left corner .

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Should I try this with the boards connected or not? Those las readings were with it unhooked.

[CapLeaker]

Re: Dynex DX-L40-10A Won't turn on.

Hook all the board together and heat the caps on the main board a bit, turn it on.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

So I've applied heat with a blowdryer to the area you pointed out. I tried pinpointing the flow to the different electrolyte caps in that area 4 or 5 times and got nothing. Then I decided to just hit the whole area circled and now I'm getting the spiking voltages.

Is it one of the blue capacitors or is it one of those short grey tower looking things?

I still can't pinpoint where the bad component is. Could it be a transistor?

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

I've been messing around with plugging/unplugging the set and taking readings. The last time I checked I was getting a clicking sound from the PS board and it's like I had heated up the main board.

There's a big resistor on the PS board that has over 15V on one side but 0V on the other. What's the wattage on that resistor?

Could that be the only issue with this set?

[CapLeaker]

Re: Dynex DX-L40-10A Won't turn on.

Do you have anything to check capacitance with? May be worth a try looking at that big blue cap C842. Resistors you can check with the power supply disconnected and your DMM in Ohm mode. If any thing gives you something weird, it is always wise to lift a leg or take the component out of circuit and check it with the DMM.
And we still need to see how much DC voltage is on the big black filter cap.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Is the big black filter cap the one that's bigger than a quarter and has the white label on it?

[CapLeaker]

Re: Dynex DX-L40-10A Won't turn on.

yep

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

That cap is flat against the board. That's going to have to be done with the board unscrewed.

[CapLeaker]

Re: Dynex DX-L40-10A Won't turn on.

just be really careful... there is lots of power in that cap.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Ok I unscrewed the PS board and propped it up with a book so I could get to those terminals. That big cap reads 416-417VDC.

What else should I be checking? I don't have a place where I can have this tv laid out and opened so everytime I get done checking something for you guys it wont be until the next day that I can get back to it.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

I checked the resistors on the PS board and the big 1k resistor in the lower right corner is bad for sure.
Does anyone know the wattage on that one? 5w? 10w?

[budm]

Re: Dynex DX-L40-10A Won't turn on.

Why do you think that 1K resistor is bad?

"That big cap reads 416-417VDC." Are you using new meter? That reading is on the high side.

[Funda]

Re: Dynex DX-L40-10A Won't turn on.

Why do you think that 1K resistor is bad?

"That big cap reads 416-417VDC." Are you using new meter? That reading is on the high side.

I know that resistor is bad because it read out to 0.02 when set to read 1k ohms.

My meter is fine because I gave it to one of our electricians to re-calibrate and I verified VDC and VAC were matching what his read.

I did graduate from ITT Technical Institute with an Associates degree in Electronic Engineering so I do know how to use a DMM. However I did graduate back in 2002 so my knowledge is a little old and I don't remember a lot of it.

What else should I be checking?

[budm]

Re: Dynex DX-L40-10A Won't turn on.

"I know that resistor is bad because it read out to 0.02 when set to read 1k ohms." You should read that resistance again with one leg of the resistor off the board, in my 40 Years I never seen MOX resistor goes shorted circuit. From 1000 Ohms to 0.02 Ohms?

[CapLeaker]

Re: Dynex DX-L40-10A Won't turn on.

what about a pic of the bottom side of the board?