Microwave timer/clock 4 digit 7-segmnt display is out. Timer works fine.

(well, pin compatible on the segments, but it has a right-hand decimal point rather than the rare left-hand on the microwave oven, so not really 100% compatible...)

Best regards, Spehro Pefhany

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All well and good. But I need a typical driver circuit diagram to probe = voltages. It could be something as simple as a dropping resistor that's = opened up, or a local filter capacitor that is shorted... I need a pin = voltage map to find which voltage is missing.=20

=20 The brightness is plenty good for kitchens,=20

The decimal point is not used for microwave heating.

Ange

Akkk! If you keep running it empty, you might damage the magnetron.

I'm reminded of the opening of "The Outer Tsimmes"...

"There is nothing wrong with your television. But if we keep f***ing with it like this every week, pretty soon there will be."

voltages. It could be something as simple as a dropping resistor that's opened up, or a local filter capacitor that is shorted... I need a pin voltage map to find which voltage is missing.

If you look at this page:-

There are two gifs from an HP appnote. They shows suitable multiplexing circuits. It is possible that your circuit has stopped multiplexing so only single segments permanently on. May be missing a clock signal.

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Geo

solid

a

Can you view the board enough to count the pins on each of the non-display electronic chips?

Have to unscrew the bezel allen screws again. in a few days..

Ange

Seems to be near what I have.

I'm an old discrete component and vacuum tube guy.

I presume that "strobe" means hat there is only one driver, the SN7447 which is the only segment feeder, that the digit switched on at the moment by the strobe signal will take segment current and light up.

The current comes from the 7447, whatever of the 7 lines is to run to make the number of the instant.

In my uwave, only E segment is lit and the E of all 4 digits are on all the time. No other segments of all 4 digits ever light. Well, actually the

4 of digit 4 is lighting every time its turn comes in the countdown. Perhaps that digit is more sensitive.

One thing for me to look at is the health of the seven 47 ohm resistors.

Another is to check the + voltage supply. Do I expect 5 volts or some higher value? The two raw dc supplies are 10 or 20 volts (the filter capacitors gave away their location.)

Ange