• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

    Jake

Intermittent Power Interuption

kenquagliana

Premium Member
Joined
Dec 1, 2016
Messages
2
Location
Maryland
Model Number
R 5A51
Brand
Sharp
Age
More than 10 years
Hi Folks. This unit runs and heats normally for a few seconds to a few minutes then shuts down. It acts as if losing power; the display flashes slowly and reads all "8's". I can reset it. Then it will repeat.
I've checked all the door switches; Fuse and Hi Temp sensor (all good). Primary side of the HV Transformer reads a low ohm value and is good (I think).
I think the HV Can Cap is the issue. With the two terminals connected to my meter, the ohm values are dropping instead of rising (as I understand it should); The capacitor is a .88 uF / 2000V (not sure if it has the 10 ohm resistor - no indication on the capacitor). The Diode reads all zeros??? (not sure if its good - If I can replace the capacitor, I was going to replace it just to be sure). So far - no luck finding this capacitor.
Questions: Can I substitute an HV capacitor with a value of +/- 3% (.85 -.91)?. With or without the resistor??
Thanks in advance.
Ken Q
Baltimore
 

jeff1

Appliance Tech - Moderator
Staff member
Joined
Oct 10, 2004
Messages
23,923
Location
Ontario, Canada
Hi,

This unit runs and heats normally for a few seconds to a few minutes then shuts down. It acts as if losing power; the display flashes slowly and reads all "8's". I can reset it. Then it will repeat.
Main power cord, outlet plug, fuse holder, fuse, cabinet thermostat, loose wire, main pcboard.

I've checked all the door switches; Fuse and Hi Temp sensor (all good).
Ohming is a great tool, but often will not help with loose of power or intermittent issues.

I think the HV Can Cap is the issue
I doubt it, this is for cooking only.

With the two terminals connected to my meter, the ohm values are dropping instead of rising
LINK> Capacitor Testing | Appliance Aid

The Diode reads all zeros???
Unless you have a very high end meter, you can't check the diode.

jeff.
 

kenquagliana

Premium Member
Joined
Dec 1, 2016
Messages
2
Location
Maryland
Hi Jeff, Thanks for your prompt reply. Ok. I rechecked the can cap as described in your link (using my old analog meter) and it checks out good. When this machine runs for a few seconds it IS heating the cup of water normally.
All the other AC stuff checks out. I'm starting to think it's in the main PC board. When I first plug it in, it takes a while for the display to stabilize. Like it's charging up. Maybe it's a bad cap on the board?? But again, it acts like it's tripping a resettable breaker, or the relay isn't holding.
So, since PC board troubleshooting and repair is way out of my league, I'll try to find one before admitting defeat!!
Thanks in advance for any other ideas or suggestions. This is a well built unit. Hate to throw it away.
Ken
Baltimore
 
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