This looks close. Curious if this covers the speed oven/microwave.

http://www.searspartsdirect.com/partsdirect/user-manuals/HBL5751UC01-BOSCH-ELECTRIC+WALL+OVEN-manual

I would believe the glass 'lens' - screws out (just like an oven). Use a rubber glove - and turn the lens counter-clockwise.

Thanks guys, but that's for the Oven, not the microwave. The oven does have a clearly visible bulb with a cover in the back. Looking in the Bosch microwave now, it's unclear where the light source is (was.) Even looking thru the sub-assembly diagrams for the microwave on that searsdirect link (thanks), I don't see a light bulb mentioned at all in the microwave.

Put a hand mirror in the microwave, maybe need a flashlight - find out where the light source is. I would guess it is accessible from the front? If it is - open the door - at the top of the opening there may be a 'trim' or 'vent' strip held in with a couple of screws. Remove it - and you will probably find a little door over the bulb. I've had good luck with the Repair Parts Clinic .com

I looked at the parts diagram on searspartsdirect.com . It looks like there is an access door on the back of the unit for reaching the microwave light bulb. The light is in the top of the unit, I think toward the rear right-of-center as looking in from the front.

BTW: in most microwaves I've seen (without the upper heating element), the bulb is accessible from the inside by removing a plastic cover.

Weedmeister: "on the back", meaning the rear of a unit that is built into the wall? Let me know which diagram and part # your looking at so I can get my head around it. Thanks.

I've looked inside the unit with a mirror & flashlight like geoffrey_b suggested and afraid I just don't see any access panels or lenses to open from the inside. Near as I can guess, the light is coming from behind (above) some perforations (vent holes?) in the (metal) ceiling.

As stir_fryi said, its starting to seem like I might actually need to pay their field service tech $100 to come and disassemble the unit to change a $3 light bulb. So much for german engineering. This is probably by design to generate revenue.

How many 'Progressives' does it take to change a light bulb?

None - they prefer to be in the dark.

Sorry - just had to share that one.

upper cavity

It may actually be in the front.

I went to the store tonight and saw one up close. I think the light is behind a small mesh area in the front right. This probably means that either you have to take the oven out and there is a rear access door, or you slide the oven partially out and reach the bulb from above.

Lamp replacement for a Bosch HMT75M551B
Built-in Microwave.

All that is needed is a Phillips No. 2 screwdriver, wire
cutters and a replacement lamp. (1 x T170 25W
Microwave Oven Bulb with Base (Espares ES461903)

Isolate appliance from the power source.

Remove cap and screw (bottom central) holding
the built in outer stainless steel surround to the kitchen housing.

Remove the microwave from the housing.

Remove the three screws on each side and back (9
in all) from the top cover on the top of the microwave and set aside.

Remove five screws from the fan housing on top
of the microwave and set aside.

Remove the three screw at the bottom of the main
cover. (Two at the back and one on the right hand side). Pull the whole of the main casing
backwards to remove and set aside.

The lamp can be seen located towards the front
on the right hand side with three connecting wires. A red and brown at the front connection and a
yellow wire to the rear connection.

Disconnect the wire clips from the two old bulb terminals.

It will be necessary to brake the plastic base
cap to the bulb on the front side and unclip the base plate on the right to
remove it from the bulb mounting. I used a
pair of wire cutters to brake the bulb base plate to release the old lamp.

When the lamp has been successfully removed in
can be replaced by the new one and the wires reconnected as they were
previously configured.

Reassembly is the reverse of the disassembly.

The whole process can be done in under an hour.

The bulb has a cover beneath the unit Need to slide out of cabinet to do Oh well. Have fun!