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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details. |
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25th May 2017, 12:01 am | #41 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
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Re: Ancient microwave oven - repairable?
Proper commercial microwaves are still expensive and complex things, with several magnetrons to penetrate the food evenly. Domestic models just heat the outer half inch or so of the food and steam the rest. That's all you need to heat up a mug of soup or tin of baked beans of course.
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25th May 2017, 12:26 am | #42 | |
Octode
Join Date: May 2010
Location: Worcestershire, UK.
Posts: 1,880
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Re: Ancient microwave oven - repairable?
Quote:
Not an effective method for shorter cooking times. The newer inverter types do have proper proportional power control.
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25th May 2017, 7:50 am | #43 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
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Re: Ancient microwave oven - repairable?
Leaving the tin outside, of course!
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25th May 2017, 9:08 am | #44 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
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Re: Ancient microwave oven - repairable?
Due to the way magnetrons work it is impossible to put a grid in one to control the power. They work by spiralling electrons in a magnetic field until they hit a resonant cavity and the RF is extracted from a cavity by means of an aerial.
The way to reduce or control power is to change the pulse rate at which they are fired or to alter the HT voltage on them. The best history and description of a magnetron is here http://www.johnhearfield.com/Radar/Magnetron.htm Malcolm |
25th May 2017, 11:55 am | #45 |
Pentode
Join Date: Nov 2006
Location: East Yorkshire, UK.
Posts: 131
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Re: Ancient microwave oven - repairable?
Ages ago i completed the RETRA microwave course, thirst thing we were taught was the 3 "D"s,
Disconnect (unplug it) Door (open it just in case some idiot plugs it back in again) Discharge ( short out the high voltage cap with a well insulated screwdriver) Most faults on the H/V side can be diagnosed with a multimeter set on ohms range with no need to apply power. When working on the mains side of the transformer i always disconnected the spade terminal feeding mains to the transformer and tucked it out of the way that way no H/V to worry about, Many faults were caused by dodgy door interlock switches, these can be opened up to check for pitting on the contacts or the lamp failing and blowing the fuse (easy money) Steve |
9th Jun 2017, 4:16 pm | #46 |
Heptode
Join Date: Jul 2010
Location: Wellington, New Zealand.
Posts: 653
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Re: Ancient microwave oven - repairable?
In the course of trying to repair my microwave, I made up a discharging lead - two probes connected by wires and a 1k ww 5watt resistor - all well insulated by heatshrink. After turning off unplugging and opening the door you'd shove the probes down the cap terminal boots - go and have a cup of tea - then come back and check all was earthed/charge gone. Turned out eht rec was shot and it was cheaper to buy a new oven. Still have the old oven somewhere and it will become a small paint spray cabinet soon - thanks to the turntable.
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