Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

[punkzter]

I picked up a Magnavox 37MF231D/37 Television (broken) last week. It wasn't powering on at all when I first got it. I took out the power supply board and replaced 4 caps (in the picture). When I plugged it in, there is a brief light that shines on the inverter board, and the green led under the on/off switch flashes. But that's it. The tv won't turn on.

Can anyone help me with the next step for this television? I Attached the flowchart from the service manual. The "No Work/LED is off" options seems to fit my situation the closest, but it's not exact, as the LED is not off, it blinks.

But I should take the measurements off of board 1089?

This television is very difficult to work on, since the motherboard/scaler board are shielded and rotated.

Can I take measurements on the power supply with the inverter boards disconnected? (Does what I'm asking make sense?)

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

For a quick test, with the set off, you could check all the diodes and zener diodes with your meter set to diode mode and check that none of them have gone short circuit.

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

Can those be tested in circuit? Or do I need to lift a leg of each diode out of the pcb?

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

There are two other threads that would be worth your while reading through carefully. Do a search for 37MF231D

Pinouts so you can check the voltages at the connectors
https://www.badcaps.net/forum/showpo...4&postcount=40

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

Can those be tested in circuit? Or do I need to lift a leg of each diode out of the pcb?

It is best to test out of circuit by lifting one leg but only if you have low readings when you check each way across the diodes. There could be low value resistors or transformer in parallel with them so lifting breaks the connection with other components.

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

When I test the diode, using my diode setting, what values should I see? And what is a low reading that would lead me to take it out of circuit?

Thanks!

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

When I test the diode, using my diode setting, what values should I see? And what is a low reading that would lead me to take it out of circuit?

Thanks!

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

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

Okay, thanks for that. Would it be best to check the voltages from the power supply board before looking into the diodes?

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

If you would like to check the voltages that should be a good start, however I would replace the bulged capacitors first.

[dskall]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

Would also help to get pictures of boards and connector at power supply.

[budm]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

+1 on the pictures of the boards.
Service manual for chassis TPE1.0U LA
http://elektrotanya.com/?q=showresul...oria=&kat2=all
There are many version of the boards used in the same model.

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

I will take pictures tonight and post them. I'll also attempt to take the voltage readings. I have worked on some other tvs, and this one is by far the most annoying. The power supply board and the main board are both hidden beneath (but screwed onto) this large metal shield.

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

I took some pictures, and will upload them soon. In the meantime, I discovered a diode that had shorted. It's diode 6079. The writing on it is: C9V1PH. Some research revealed that this is a 1N4739A diode. Would this work as a replacement:

http://www.mouser.com/ProductDetail/...lhIMTQtW2mo%3d

[budm]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

I took some pictures, and will upload them soon. In the meantime, I discovered a diode that had shorted. It's diode 6079. The writing on it is: C9V1PH. Some research revealed that this is a 1N4739A diode. Would this work as a replacement:

http://www.mouser.com/ProductDetail/...lhIMTQtW2mo%3d

The diode is tested off the board?

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

Yes, after the low reading, I pulled it and retested.

[budm]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

This looks to be your board:
Philips 313815864961 (3138 103 6294.2) Power Supply Unit.
http://www.shopjimmy.com/philips-313...wer-supply.htm
Pictures provided by shojimmy.

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

I took some pictures, and will upload them soon. In the meantime, I discovered a diode that had shorted. It's diode 6079. The writing on it is: C9V1PH. Some research revealed that this is a 1N4739A diode. Would this work as a replacement:

http://www.mouser.com/ProductDetail/...lhIMTQtW2mo%3d

BZX79-C9V1 from mouser

https://tinyurl.com/hfxjzf3

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

So that's a half watt diode instead of a 1 watt diode. That's the correct one?

[punkzter]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

I wanted to give an update. Replacing the diode fixed it. The tv now works! Thanks!

[dick_barton]

Re: Magnavox 37MF231D/37 Won't Turn On, Green Light Blinks

Did you use the 1W or 0.5W zener. Glad to hear it's working.