I would first point out that this is not a job if you are not aware of the risks of working with high voltages and high power RF transmitter systems. There is a risk of electric shock, and if the case is not properly re-assembled, and/or if there is Magnetron damage, there is a risk of dangerous levels of RF leakage.
This is what worked for me (so far) ... First making sure I had disconnected from the mains power - I removed the 4 fixings on the rear of outer case, and the one on the side. I needed to remove two 'Security Torx' type screws. The other fixings were cross-head self-tapping type screws. I found that I had to wrestle with the case (pulling toward the rear) to disengage the metal spring clips inside at the front on the outer case. Once free at the front, I could lift the case clear. I then carefully checked that the HV 1uF capacitor pack had no residual charge on it, with a (working!) multimeter fitted with high voltage probes. The cap was marked as rated at ~2kV, and appears to have an internal discharge resistor, but as there was no guaranteed this was still working, I didnt want to risk a very nasty electric shock. The bulb holder is upside down at the top nearer the front, and I could lift this out by popping the clips. The old bulb was a screw fit. I replaced this one (marked '240V 20W G1') with a 15W SES Cooker bulb. This is rated to 300degC so I reckoned it would survive better than a fridge or household type. I then re-assembled in reverse order, with a similar wrestle to re-engage the spring clips, and re-checked the bulb worked with one screw fitted before re-fitting the rest. I used a bowl of water as a dummy load when running the magnetron.
Once again - this is not a job for the unwary due to the risk of shock and RF exposure - and it may just be easier to use it without a functioning bulb.
Anony Mouse, June 2011
