Microwave circuit board - what needs replacing? (see pic)

Thread Starter

Gmcelroy

Joined May 10, 2020
3
Hi, I’m trying to resurrect my unresponsive microwave from the dead and need some guidance from those smarter than I.

Here is info on the patient
Make: Audiovox
Model: ACM 1200
Issue: It’s completely dead. No display, no beeping, no nothin!

Here is what I’ve done to troubleshoot this far:

Tested power outlet with multimeter to confirm current is flowing.
Removed cover and tested internal fuse.
Tested thermal both thermal fuses.
Tested both interlock door switches.

The patient passed all of these initial tests. On to the circuit board. I removed the circuit board and found visual evidence of a blown...something:
7828F49A-CB42-4BFD-8FB9-0B7B44FAD710.jpeg
Any ideas on what happened here and how to go about diagnosing/fixing it?

Thanks for any help!!
Glenn
 

narkeleptk

Joined Mar 11, 2019
461
Can't really tell whats blown in your picture the zener diode (zd1) or the what I am guessing is a MOV (the green disc thingy)
I think both but hard to tell.
You'll need to supply better pictures. If you can capture any markings that is a plus.
 

Dodgydave

Joined Jun 22, 2012
9,168
Looks like a simple transformer and bridge rectifier psu with zeners and capacitors. Test the voltage from the transformer and output from the bridge rectifier across the capacitors.
 

Thread Starter

Gmcelroy

Joined May 10, 2020
3
So its definitely both VS1 and ZD1.
Its a tight fit you may be better off to remove them and inspect for any markings.
Thanks for that Narkeleptk! I Think I will test first to confirm those are the blown parts, but it certainly seems that way.

Looks like a simple transformer and bridge rectifier psu with zeners and capacitors. Test the voltage from the transformer and output from the bridge rectifier across the capacitors.
Thanks Dodgydave! I'm a newbie at this - could you provide any further guidance on what exactly to test? I have a multimeter but couldn't find the schematics of this circuit online since it's quite old. Happy to provide more pics if that would help. It would be awesome if I could just replace a couple of circuits and have this baby good as new!
 

Dodgydave

Joined Jun 22, 2012
9,168
Check on AC the mains on the Transformer primary side, and Secondary side.
If it's giving out voltages on the Secondary then check the input and output of the 5V regulator, if there's no Secondary voltages , unplug from the mains, and check on Ohms the mov, and the primary windings of the Transformer and any fuses.

20200512_150207.jpg
 
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