Re: help with wine cooler-something buzzing
In case you are still doing repairs on these types of PSU's. If the big transformer is buzzing, it could be the transistor attached to the black heatsink is bad. That's probably the one that drives the chiller and fans and sometimes it also supplies Vcc to the that 494 IC. If the transistor or IC is bad the PSU may go into "safety" mode which could cause the transformer to buzz. Without any load attached and without control panel, LED and NTC attached I think you should get 12Vdc on the middle pin of that transistor on the black...
glentz
Member
Last Activity: 04-13-2021, 08:18 PM
Joined: 07-17-2018
Location: chardon ohio
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Re: Magnavox 40me313v/f7 tv PSU
It works!!!Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Thanks to the help I received both in components to look at and theory, I think the board is repaired. Haven't reinstalled in TV yet but doesn't blow up and is producing same primary and secondary voltages as a known good board under the same conditions. After the last blow up discussed above, I decided to buy an ESR meter and one of those inexpensive transistor/diode/resistor identification and test meters. Both were useful with identifying some bad or suspect components that I missed at some point. Could have been after the initial failure in the...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
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Question about the oscillation. Without Q601 installed, will there be oscillation? I assume you mean the 160vdc will oscillate??? Is that something I can see happen with a multimeter or do I need a scope?
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Ok, thanks. I did find a 2% tolerance for one of them BUT it is only 0.35W power dissipation whereas the original ZD is 0.5watt. What do you think???
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Ok thanks for the additional information. I had originally checked D654/D652 but I'll check again.
Re: prior post about the two zener diodes, D605 and D623. Exact parts are not available, at least not in single piece quantities. It looks like the parts are 2% tolerance and the only parts I can find are 5% at best. Is 5% tolerance OK? If not, do you have a source for suitable replacements?
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Yes that thread is one of the ones I've looked at. I need to figure out why Q601 continues to fry itself, taking out components in the protection and switching control circuit. While voltages at the pads for Q601 seem within spec, it's possible the current isn't being limited properly or it's not oscillating which would point to something in the Q602 part of the circuit, possibly D605.
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
I've heard of the light bulb trick. What is the principle/theory behind that? Is the light bulb like a very low amperage fuse or what?
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Is there a way to isolate the hot side from the cold side? with the problems I'm having I'm hoping the cold side is still ok and would hate to cause more issues because of the problems I'm having on the hot side.
Greg LentzLeave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
P.S. I did check the secondary (cold side) diodes and found one bad one during my initial inspection. I've rechecked and all seem fine.
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Board number is BA3AT0F0102-2. Yes Q601 was replaced with same part, TK10A50D.
Greg...Leave a comment:
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Re: Magnavox 40me313v/f7 tv PSU
Thank you for the advice. Agreed that R611 and/or D608 were probably bad when I tried to repair first time. Agreed that I am only able to do standard diode check so even though zener D605/D623 do not appear to be shorted or open, they could be bad. I will replace those along with D608(again) and D607A(again). Is there any way to test IC601? Pins 1-2 showed readings indicating the "diode" was ok. I don't remember off hand what pins 3-4 showed but I know it wasn't a direct short. I do have replacement already in hand.
...Leave a comment:
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Magnavox 40me313v/f7 tv PSU
Need help. Have a Magnovox TV, 40me313v with a bad PSU, on the hot side I believe, and I can't figure out what's going on. I've read through prior threads covering repairs of basically identical PSU's such as [url]https://www.badcaps.net/forum/showthread.php?t=71919[/url] and threads referenced there.I have the service manual.
Originally the TV just stopped working. Initial examination showed the PSU fuse was fine but Q601 was shorted or otherwise not working and D653 on the cold side was bad. I replaced Q601 and D653 and that's when the problems really started. As soon as I powered... -
Re: New Members - please post your introductions here
Hi, I'm Greg Lentz. Electronics (electro mechanical to somewhat current) repair is a hobby for me.Leave a comment:
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