GE Spacemaker Microwave dead

[marlin100]

I have an older microwave that is dead at the panel, nothing, nada.  No noises just dead.

Model JVM1860CD 001

Checked main fuse, all the thermostats/thermal fuses, the door switches and the monitor interlock

Nothing inside looks burned or damaged.

I think I've done the most obvious things.  Ideas appreciated!

[moish]

Check your circuit braker. (sometimes partly tripped enough to cease power to circuit) 

[marlin100]

I did.  The outlet is fine.

[electro_doc]

have you checked for power.  You say you checked continuity on all points but did you check to see if power is getting to any points in the circuit? I'd try to follow power from where it enters to where it should go to power the board. Start with the basics

 

Doc

[marlin100]

I did. I traced the power cable black thru the bottom NC thermal fuse to the PCB.  There was 120V at that post on Conn 2.

I don't know how to check the transformer on the board or the LVT in the unit.

I'm wondering if there's some test I am missing (and a procedure) that comes up frequently as an issue in fault diagnosis when there's nothing displaying on the control panel, some component failure.

[MoTeD]

if you have power to the board but no display then the board is dead and needs replaced.

 

[3brothers]

Always start from the source

Breaker, outlet, plug and so fourth. It will show the problem

[marlin100]

are there any test procedures for the board before I decide to purchase one ?

[marlin100]

I took the board out and examined it a little more closely.  Turns out there's a resistor that looked burnt, R51.  I happened to remember seeing a webthread somewhere about a resistor on my same board and luckily I stumbled back across it.

https://www.physicsforums.com/threads/help-identifying-a-burnt-resistor-wb27x10438.760219/

Fantastic.  I removed the resistor and it is burnt, open circuit.  Getting another one.  Wish me luck and if this works there's another troubleshooting step, examine the board...

[marlin100]

The resistor replacement got the display to work.  

I've only done a couple of things with the unit, not back together yet.  I started the vent fan and it works but get a buzzing noise, from the control area.  Same thing if I open the door.

Ideas ?

[marlin100]

There a capacitor on the board 220uF that has a nice bulge on top.  I am going to replace that now...

[marlin100]

FIXED!  Like new.  This model circuit board obviously have a defective design or defective parts since so many have reported the exact same problem.

 

[Budget Appliance Repair]

I don't think so much a defective design as just the nature of the beast with electrolytic capacitors wearing out.

Pretty common to see on any circuit board that is 10 plus years old and some even much newer.

As in the Wikipedia entry: https://en.wikipedia.org/wiki/Electrolytic_capacitor, a pretty well know problem with capacitors manufactured 2000 to 2005

Quote

A stolen recipe for such a water-based electrolyte, in which important stabilizing substances[44][45] were absent,[46] led in the years 2000 to 2005 to the problem of mass-bursting capacitors in computers and power supplies, which became known under the term "capacitor plague". In these e-caps the water reacts quite aggressively and even violently with aluminum, accompanied by strong heat and gas development in the capacitor, and often led to the explosion of the capacitor.

 

[marlin100]

Good to know thanks.