Where is the power fuse

Possibly a bad door switch behind the holes where the latch hooks go into. Usually with the bad switch the timer counts down but nothing runs. It all depends on which switch is bad. Usually 3 switches inside.

There are door switches and one of them is evidently out of adjustment or the little actuator arm on it is.

A 1974 Microwave Oven is probably not putting out more than 600 watts. You need to do a power test to determine it's actual power output. Place a 2 cup glass measuring cup with exactly 500 mL of cold water. Record the starting temperature of the water. Run the microwave on 100% power for 18 seconds, using a watch or timer, not the timer on the unit. Take the water out and stir it to make sure that there are no hot or cold spots in the measuring cup. Record the new temperature. Example: 78.4-64.1= 14.3.
Multiply 14.3 X 38.75= 554.125. The power output is 554 watts IEC. If the recipe is set for a 1200 watt unit, and your is almost 600 watts, obviously, you would double the cook time. Since this is rough, you need to experiment a bit. If the cook time is 10 minutes, check your product at 8 minutes. Be sure to push the stop button before you open the door when it is in cook mode. This will save wear and tear on door switches and leave the remaining cook time on the timer. Let me know how this works out for you..

If the timer counts down and nothing else happens, the secondary interlock switch is bad. This switch completes the cook circuit and this is why it doesn't run. You need an ohm meter to diagnose and find the right switch. Switch failure is caused by opening the door when it is in cook mode. Push the stop button first before opening the door and this failure will cease to occur. BE CAREFUL !!

The main fuse in the microwave oven has blown, this is often caused by one or two door switches going bad usually the result of food partical build up and must be replaced to fix the problem.

try resetting the clock. If it is digital, push the clock button and then the number buttons untill you have the proper time displayed...then push the clock button again. If your clock and timer are manual, try pushing in the clock lever and turning it 1/4 turn. If this works it would indicate that your timer has a start and finish time and that the oven is not working because the clock has rotated around to the finish time.

I have exactly the same problem; always after 59 secs, it stops.

It's posible that since it was running empty, the magnetron overheated and a thermal cutout or thermostat located on the magnetron opened.

Magnetrons may be protected by a thermostat, which will reset when it cools, or a thermal fuse, which is a one-time use device. It is also possible that in some cases, a thermostat will fail when opened.

In the worst case the magnetron may be damaged due to running empty.

I hope this will solve your issue.

Good Luck.

If my solution proves useful please accept it.

Regards
Arjun

Try to unplug your microwave then leave it for 1 hour the purpose is to reset and drain stored current after 1 hour plug it again ,if still notworking there something wrong inside. Usually, when your microwave oven doesn't work it all, the internal fuse (thermal fuse) is blown. This fuse protects both you and the oven. When it blows,you need to replaced it or you need to have a qualified appliance repair technician replace it.

Hope it may help you;

Regards
VOTIT

It is possible that the magnatron is bad but hard to say on a no heat problem without checking all components. A lot of model give 5-7 yr warranty on that part.