Sharp R959 Microwave

[hun]

The microwave part my Sharp R959 microwave is not heating things up. One of the things causing the problem could apparently be a faulty capacitor. Would be most grateful if some knowledgeable member could enlighten me on the following:

1. The high voltage capacitor, (manuf. Elcomtec), is rated 1.16uF 2100VAC. what would the ESR range of the capacitor be.

2. A replacement from Sharp costs an arm and a leg and there doesn't appear to be an exact replacement available on the web. The nearest equivalent I could find was either 1.10uF (2100VAC or 2500 VAC) or a 1.20uF 2500VAC. What would the effect be of replacing the capacitor with one of this?

Many thanks

[goontron]

Re: Sharp R959 Microwave

first the warning: DO NOT TOUCH THE HV WIRING UNTIL YOU HAVE DISCHARGED THE LARGE CAP AND BRINGED BOTH TERMINALS AND LEFT THE TERMINALS BRIDGED FOR THEY CAN STILL HOLD CHARGE FOR VERY LONG TIMES! HV IS VERY DANGEROUS AND CAN CAUSE BODILY HARM OR DEATH!

now the info:with high frequency radio wave generation, frequency tolerance is next to zero and microwaves are very high frequency so its easy to push too far, so i would say the 1.20 2500VAC cap would be the best bet on this one because of how close to the original uF it is and the higher voltage rating helps with transient surges and voltage variation from the microwave oven transformer.

legal stuff:neither i nor badcaps.net or any of its affiliates can be held liable for damages, injury, or death caused by your undertaking this project!
its 2Kv so had to include the legal stuff.

[larrymoencurly]

Re: Sharp R959 Microwave

http://www.repairFAQ.org has a guide to repairing microwave ovens and lists some parts distributors, like MCM Electronics, Premium Parts, and Dalbani.

I've had only 2 microwave ovens fail, and in both cases their magnatrons went out ( shorted feed-through capacitor for the power wires, cracked permanent magnet donut). The capacitors and high voltage diodes tested OK with an ohm meter. BTW even good high voltage diodes will probably test bad with a digital meter because they don't apply enough voltage. OTOH an analog meter's ohms function that applies 9V should work. But when I changed the magnatron I changed the diode, capacitor, and bimetal high temperature cutoff (mounted on magnatron) anyway because they didn't cost much extra.

Sharp magnatrons seem to be common and cheap from anyone but Sharp distributors. My replacements from MCM were a Goldstar and some generic. Be sure the mechanical fit matches, especially in the spacing of the bolts or studs and the orientation of the power connector (some are rotated 90 degrees). The magnatron's brass braid seal ring has to fit perfectly with the oven chassis.

I didn't dare check the high voltage, even with a neon bulb taped to a long wooden or plastic stick (hold next to wires; in dim light the bulb will glow if there's high voltage). I just tuned a TV to analog VHF ch. 2-4 and watched the interference (AM radio may also work).

[hun]

Re: Sharp R959 Microwave

Hi goontron - thanks for the health warnings and info. As advised, will use utmost caution on this repair. I'll give the 1.20uF a go after a final search on the web for a 1.16uf HV cap

Hi larrymoencurley - thanks for the link and great tips. Also good advice changing all those parts in one go. Unfortunately these things in the UK are so expansive - I worked out that the costs of replacing them comes to around 2/3 the price of a refurbished unit. If it's not the pleasure of finding out what the problem is, it would be simpler just to replace it.

[ben7]

Re: Sharp R959 Microwave

I worked out that the costs of replacing them comes to around 2/3 the price of a refurbished unit. If it's not the pleasure of finding out what the problem is, it would be simpler just to replace it.

Well, it's like that in the US too...