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I used to repair a lot of Microwaves years ago but have got a bit rusty on them. Got a Panasonic NN series with a no heat fault, Circuit through mag and not down to earth,Diode and cap OK and 230 to tranny. The clamp meter only read 2.3 amps and I remember that the load should be about 6 amps when running, Any idea as to the fault Mag or Tranny? Old customer would go with either but not both components. Its a built in model in brown and customer cant find a suitable replacement.
GooseRe: Microwave Question
Hi: A lot of the transformers have a built in non replaceable fuse in the filament winding to the Magnetron, with the TX disconnected you should get the following resistance readings:
Primary: 2 – 5 ohms
Filament: Less than 1 ohm
H.V: 20 – 120 ohms
From any connection to TX casing using a Digital meter with a min 40 meg resistance range should be o/c.
HTH
Andy. 8)Re: Microwave Question
Got back to the job today and all the measurements are withing range, So other than a faulty mag I’m a bit stumped. I had a bit of a problem testing the diode as AFIR you need a tester or meter with a 12v battery and as mine was only 6v I rigged up a test lamp with one from a 12v car alarm fob.
Re: Microwave Question
Hi: Don’t forget you can’t check the diode, cap or circuit protector with a Digi. Any Analogue meter with a 6v or higher battery should be able to test the diode, Cap & circuit protector. What happened when you tested the diode with the lamp ? Also have you checked that you actually have 240v to the transformer primary? Have you checked the thermal cutouts for continuity? If all the above are o.k then it seems that the Magnetron is the only thing left.
Re: Microwave Question
Years ago I used to use a Steinal Combi check which being 12v was fine for checking diodes. Using the 12 battery and lamp the diode was off one way and lit the other. I might chance a mag from AWI as the customer is desperate to get it repaired.
Goose
Re: Microwave Question
AWI used to be pretty knowledgable about repairs & only too glad to give advice, worth a call in case there’s anything wev’e overlooked.
Can u post & let me know how it turns out in the end.
Thanks: Andy. 8)Re: Microwave Question
to be honest i would do it the dangerous way
this will only work on old transformered units not invertor types
diconnect mag turn on for about 5 secs
turn off and unplug (for safety and to remove earth return)
short cap to earth and see if you get a big spark (using a well insulated screwdriver )
if you do all hv ok just mag down
you have to be careful but no more dangerous than opening an unknown microwave and having to discharge for safety
hope this helpsDave
Re: Microwave Question
I always short the cap before doing any work and I did get a spark, So again it looks like the HT sides OK. Have ordered a mag from AWI will let you know the outcome.
Goose
Re: Microwave Question
if it says “inverter system” on the door… give it a miss… panasonic reccomend u change both parts on inverter system… mag and trans.. and the price is ridiculous
Re: Microwave Question
Called back today and the new Mag did the trick! One very happy customer. Got a £10 tip as well 🙂
Thanks all for the advise
GooseRe: Microwave Question
No problem mate, glad it worked out for you.
If your considering going back into Microwave servicing, there’s a good little Analogue meter available. it’s made by pros-kit has a 9v battery & is just the right size to fit in your toolkit goes up to 20 meg resistance so useful for more than just Microwaves, about £15.00 from places such as CPC etc.Andy 🙂
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