On Saturday, July 17, 2021 at 3:57:08 PM UTC-5,
hon...@yahoo.com wrote:
I have a microwave from the mid 2000s that failed on me. It uses basic circuitry: transformer, diode, cap, magnetron....not an inverter type or anything fancy like that. One morning it seemed to mostly work, but the output rapidly dropped over a few
minutes. No bang, no smoke. Just stopped heating.
Everything tests ok, the transformer, diode, cap, even the magnetron resistance measurements are "good". I know there's about 10A to the filament with indirect testing, and I know the capacitor has near 2kV on it right after running the unit and
unplugging it. This was determined by knowing the cap has an internal bleeder and using the RC time constant to allow the voltage to drop to a safe value to measure.
Would this be indicative of a bad magnetron? Almost everything I read about magnetron troubleshooting leads me to believe there's nothing wrong with it, but then again the rest of the circuit also seems to be functioning correctly.
So.....magnetron seems to have failed again, not quite 1.5 years later. Microwave was running, then stopped heating. No bang, no smoke. I put my wattmeter on it, tried cooking again, saw around 1.2kW usage for a few seconds and thought it was ok, but
then dropped to around 300W. I haven't taken it apart yet but my bet is a bad mag.
This was a genuine OEM replacement part from a reputable supplier. So either 1. the part was defective and prone to early failure from the start or 2. something is making it fail early. But what? As I think about the other parts, the transformer, diode
and capacitor, I can't come up with a way for those parts to cause early mag failure. Transformers don't fail in a way that causes increased output voltage (not that I've seen), and a bad diode or cap doesn't seem to be capable of destroying the mag.
The original mag lasted 14 years and the usage has always been the same.
--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)