Question about clamp meters.

[digge]

Hi

I have Uni-T UT203 clamp meter i use for troubleshooting things like heating elements and stuff at work. Now a microwave was dropped in my lap and i need to troubleshoot it.

My question is, would it be safe as in not damage the clamp meter if i used the clamp on the High Voltage side after the transformers in the microwave? Not sure what voltage is supposed to be there but quite a lot more then mains voltage. Don't have any meters that would handle that kind of voltage directly but thought it would be a quite good quick check if the clamp meter could tell me if its the upper or lower magnetron that's not outputting enough. Ofc i can measure on the input side but am just curious as what would happen, like will it just display out of range or something or just simply die?

[budm]

Re: Question about clamp meters.

That high voltage for the Magnetron is more than 2000V, the current will be less than 1A depends on the power spec of the Micro wave, I would not put the Clamp on to it. So does it have two high voltage transformers for each Magnetron?

[Kiriakos GR]

Re: Question about clamp meters.

What you actually need is one HV probe (resistor diviner) for multimeter.
And also one very good quality multimeter with very good accuracy at the mV range.
Your clamp meter is unable to display such high volts and also it is very possible the poor isolation of the test leads to set your life in a great danger.

Every repair is an opportunity for earning some cash, but if you do not have the proper tools it is wise to skip this one.

[redwire]

Re: Question about clamp meters.

Live testing a microwave oven is pretty dangerous, and the UT203 has only a Cat. II 600V rating. At 2,000VAC any cracks/bare spots in the clamp-jaws would be trouble.
Another (safer) approach is just to check the HV rectifier diode and doubler-capacitor - the high failure rate parts. If they are okay and primary current is off then I would suspect the magnetron.

[digge]

Re: Question about clamp meters.

Thanks for replies. It was more a curiosity question more then anything else. If you dont ask you dont learn anything

Ill take the components apart and measure them the old fashioned way i guess. Atm its outputing around 800W-1000W inside the microwave, wich is about half of what its rated for so im guessing that either a cap or diode failed.

budm: It has one beefy transformer for each magnetron (2 of them, upper and lower) with one cap on each for boosting the voltage.

[momaka]

Re: Question about clamp meters.

Is this an "old-school" microwave with a big transformer inside or one of those newer inverter microwaves?
If the latter, check settings on the microwave first (i.e. which power it is set on). Just to make sure it's not something simple first, you know .

[kaboom]

Re: Question about clamp meters.

Thanks for replies. It was more a curiosity question more then anything else. If you dont ask you dont learn anything

Ill take the components apart and measure them the old fashioned way i guess. Atm its outputing around 800W-1000W inside the microwave, wich is about half of what its rated for so im guessing that either a cap or diode failed.

budm: It has one beefy transformer for each magnetron (2 of them, upper and lower) with one cap and diode on each for boosting the voltage.

Added by me.

Check magnetron(s) for cracked magnets. If they lose their magnetic field, they're nothing but vacuum diodes.



http://repairfaq.org/sam/micfaq.htm

[digge]

Re: Question about clamp meters.

Is this an "old-school" microwave with a big transformer inside or one of those newer inverter microwaves?
If the latter, check settings on the microwave first (i.e. which power it is set on). Just to make sure it's not something simple first, you know .

Its an oldschool one with two transformers.

Added by me.

Check magnetron(s) for cracked magnets. If they lose their magnetic field, they're nothing but vacuum diodes.

http://repairfaq.org/sam/micfaq.htm

Have checked the magnetrons with ohm meter, the cans are a *insert curse word of choice* to open so i wont bother with opening them.

Found that the diodes are busted so will swap those out. The caps seems fine and the magnetrons are fine (ohm wise). If the magnetrons are busted i will probably just toss it, probably way to expensive considering the age of the microwave.

[ben7]

Re: Question about clamp meters.

Found that the diodes are busted so will swap those out. The caps seems fine and the magnetrons are fine (ohm wise). If the magnetrons are busted i will probably just toss it, probably way to expensive considering the age of the microwave.

Check the primary and secondary of each transformer too, just in case the busted diodes caused one to overheat and go open circuit.