GE Microwave,no heat?

[ivtec]

Hi guys; i have here a Ge microwaves that turns on normally all functions are running including fan but doesn't heat anything,i tried another HV diode and still no heat,i know that more likely to be the Magnetron, which costs too much money it's not worth it, but before i through it out,could it be the big Cap?
thanks.

[diif]

Re: GE Microwave,no heat?

I would think that if it's powering up then the big cap is working.

[stj]

Re: GE Microwave,no heat?

did you check the magnetron?

dont they have a heater - heater open? getting power?

[ivtec]

Re: GE Microwave,no heat?

did you check the magnetron?

dont they have a heater - heater open? getting power?

Thanks stj; i found the issue, it was Temperature Control Switch Thermostat,believe it or not, all info available pointed to Magnetron,or HV Diode,or HV cap,or switch, well i started by changing the HV cap,then checked cap which was good,so luckily i had some Temperature Control Switch Thermostat in my scrap and it started to heat,almost went to land fill if i did not have those Temperature Control Switch Thermostat,since everything pointed to Magnetron which costs 100 bucks,
this is a GE microwaves it's almost new,i really needed one, mine was a GE but small and old,the door did not open easy,so one more out of land fill.

http://www.ajmadison.com/cgi-bin/ajmadison/PEB2060.html

[stj]

Re: GE Microwave,no heat?

not bad, the only thing lacking is an infrared heater for grilling / browning

[ivtec]

Re: GE Microwave,no heat?

not bad, the only thing lacking is an infrared heater for grilling / browning

For me that's a luxury that i never had, so what does this one does is more than luxury for what i'm used to have.

[clearchris]

Re: GE Microwave,no heat?

Two microwaves I have fixed both just had a loose connection at the magnetron. I suspect the magnetron vibrates and weakens the connections. If either one breaks that way again, I'm soldering the spade plugs on.

The other two I fixed were worn door switches.

I don't think the magnetron, diode and caps go out as often as people online make it out to be.

[RCA2000]

Re: GE Microwave,no heat?

FYI...to ALL..

I have had to work on a few COMMERCIAL MWV's lately.. ALL of them needed a Mag tube, and most a tranny too. (They use these things HARD.) NEW parts for these ran WELL over $200---which would have KILLED the repairs. BUT...I was able to find NOS(out of damaged ovens) mags for $30 or UNDER..and trannies for about that much...on EBAY. I was able to save the repairs and STILL make decent money by doing it this way..ALL of them worked WELL..

The mag used--2M248J--1KW power on these Amana--made ovens..Avg cost to ME..about $30..

[RCA2000]

Re: GE Microwave,no heat?

Two microwaves I have fixed both just had a loose connection at the magnetron. I suspect the magnetron vibrates and weakens the connections. If either one breaks that way again, I'm soldering the spade plugs on.

The other two I fixed were worn door switches.

I don't think the magnetron, diode and caps go out as often as people online make it out to be.

Keep in mind...there is ONLY about 3V. AC on the fil pins of the tube. PLUS a 4-5 KV DC voltage too. BUT the fil is LOW voltage and HIGH current....OVER 10A. ANY SLIGHT bit of bad connections and it will NOT usually heat. I have seen that a LOT on MWV"s..

[stj]

Re: GE Microwave,no heat?

i dont know why more company's dont use a switching psu like panasonic, it would probably be cheaper and make variable power simpler.

if your replacing both the magnetron and transformer then one probably killed the other.

[RCA2000]

Re: GE Microwave,no heat?

Mag's were ALL shorted...likely they ran them TOO LONG..just "hoping" they would just "start working again".

ON two of them..the HV sec. was arcing to the tranny frame. one was just shorted on the HV sec. NO bad HV diodes or caps in ANY of them.

I believe the reason more companies do NOT use an SMPS on their HV supply for MWV"S...is that while they DO work well...when they FAIL...they ten to SELF_DESTRUCT...and then you WILL need a new SMPS (inverter) board. They are virtually IMPOSSIBLE to successfully repair and TEST..(due to the HUGE DANGER..in doing so)

[stj]

Re: GE Microwave,no heat?

not so different from a transformer then, just lighter

[goontron]

Re: GE Microwave,no heat?

(due to the HUGE DANGER..in doing so)

That depends on who you're talking to.

The problem in testing and repairing is driving the bastards!

[RCA2000]

Re: GE Microwave,no heat?

Just remember (EVERYONE)...than a Microwave oven...is at least a HUNDRED TIMES MORE DEADLY.. HV wise...than ANY tv EVER MADE...including those "brute force" Pre-war sets !!

Not sure there is such a thing as a "safe shock" from an energized HV supply...from a MWV !! The cap hurts bad ENOUGH !!

I would say in order to successfully repair an inverter-type MWS PS... one would at the VERY LEAST...need to replace the IGBT's--(1 or 2--depends on the board) and ANY low-level stuff driving them. But you probably would NOT be able to "free run" (run it with the HV unloaded) one safely... likely--it likely would INSTANTLY vaporize the IGBT and driver chip and such. ANd I cannot IMAGINE..a safe "dummy load" for the HV winding of the SMPS tranny output on one..

A standard 60HZ tranny on a mwv CAN be 'free run (VERY carefully).. at least for a short time...with NO ill effects...have done so...MANY times successfully...with NO issues.

[goontron]

Re: GE Microwave,no heat?

Just remember (EVERYONE)...than a Microwave oven...is at least a HUNDRED TIMES MORE DEADLY.. HV wise...than ANY tv EVER MADE...including those "brute force" Pre-war sets !!

Not sure there is such a thing as a "safe shock" from an energized HV supply...from a MWV !! The cap hurts bad ENOUGH !!

I would say in order to successfully repair an inverter-type MWS PS... one would at the VERY LEAST...need to replace the IGBT's--(1 or 2--depends on the board) and ANY low-level stuff driving them. But you probably would NOT be able to "free run" (run it with the HV unloaded) one safely... likely--it likely would INSTANTLY vaporize the IGBT and driver chip and such. ANd I cannot IMAGINE..a safe "dummy load" for the HV winding of the SMPS tranny output on one..

A standard 60HZ tranny on a mwv CAN be 'free run (VERY carefully).. at least for a short time...with NO ill effects...have done so...MANY times successfully...with NO issues.

I've worked on transmitters that use > 10kv at 5 or more amps. MW ovens run at around 2kv and 1200 watts (going off my panny MW) that's 0.6Amps. The training received for the transmitter would apply to the MW, no?

Dummy loads.... Those would be a problem...... For most.

As for free running trafos, moot point. 120kv 200ma dental x ray machine transformer, it doesn't free run for long. Once the air ionizes anyway. But it free runs. More than likely to run into open circuit protection on switchmode stuff. I know Xenon sign trafos have it.

Those points aside, You don't sound seasoned.... How "new" to the HV game are you? This is not a game for the uninitiated.

[RCA2000]

Re: GE Microwave,no heat?

But that X ray supply is likely a standard iron tranny type...they usually CAN handle it.

But a hi-freq SMPS producing 4-5KV at over 200MA.into an OPEN ckt? not sure just HOW the feedback ckt would like that. might not be pretty.

BTW MWV"s IRON trannies produce about 2-2.5KV...BUT it is DOUBLED..by the diode, cap AND the magnetron itself...so the EFFECTIVE voltage the tube sees is MORE than 4KV.

And of COURSE..ANYONE who has worked on X_ray equip or transmitters KNOWS very well...how to safely service a MWV supply.

Is nearly 30 YEARS...into the "HV game" long enough for your taste !!

[goontron]

Re: GE Microwave,no heat?

Is nearly 30 YEARS...into the "HV game" long enough for your taste !!

Fair enough... Why so twitchy about it then? (all the warnings.) IIRC Somewhere in the forums EULA it says that one's stupidity is one's own fault, we can't be held liable for one's stupidity.

[RCA2000]

Re: GE Microwave,no heat?

For those who may NOT be as seasoned... In case they do NOT realize just how DANGEROUS a MWV can be.. MUCH...MORE dangerous than even a 35KV projo tv set !!

EVERYONE has heard about the 'radiation" problem of a MWV...which is NOT really a problem at ALL...unless a door is messed up or a seal compromised or such. and it is NOT "residual"..after the power is OFF...there is NO microwaves produced at all..so no real danger there...

I just wonder how many people are aware of the MAJOR HV DANGER..from them..even the SMALLEST one?

This does NOT mean they are not safe to work on. I have repaired more MWV's than I can count.Especially over 20 years ago...when they cost a LOT more than today. But it is important to KNOW what NOT to do. A general rule is...DO NOT--EVER..make a HV measurement on one..while under power. Now I HAVE done so before...with a KNOWN good and SAFE HV probe that was SECURELY grounded--and hooked to a fluke DMM. But for most others who are not "seasoned"..FOLLOW this rule !! And ALWAYS discharge that cap !!

I realize this seems basic...but maybe not to EVERYONE here.

[kaboom]

Re: GE Microwave,no heat?

Keep in mind...there is ONLY about 3V. AC on the fil pins of the tube. PLUS a 4-5 KV DC voltage too. BUT the fil is LOW voltage and HIGH current....OVER 10A. ANY SLIGHT bit of bad connections and it will NOT usually heat. I have seen that a LOT on MWV"s..

And it's got ~4.3KV in common mode to the chassis or any other ground!

You know as well as I that many have blown their meters up "assuming" there's "only" three volts present.

There's 3V across the fil leads; not "on" the fil leads as you've stated. The voltage "on" the fil leads, taken together, is enough to obliterate a poorly insulated meter when someone checks "just" the fil supply.

The MWO transformer and doubler is the most dangerous electrical device found in the home.

Oh, "radiation?" It's not even ultra-long IR, much less ionizing. Chicken-littles started that scare in the 80's; snopes-ers and "megamouth-Joneses" continue it today- Drop it already!

The magnetron doesn't even begin conducting til the voltage across it exceeds a "threshold." It does not behave as an ordinary diode! Had a bad Panasonic inverter whose diodes went leaky after mag shorted. Subbed good one for testing- no output, no current spike as fil heated. Subbed smaller mag- now got output/current after fil heated longer than 30 seconds. The smaller tube had a 3.8kV threshold vs the 4.2kV of the original. Some of the individual diodes in the "stacked rectifiers" (just like a FBT) must've shorted, lowering the PIV of each unit (there are two in a Panasonic inverter), limiting the absolute output voltage to where the bigger mag didn't conduct. Primary side current limiting kicked in and also lowered fil voltage as the leaky diodes heated up and their effective PIV/Vf dropped.

Replaced the whole mess with a 60Hz TX diode and cap- it's one of my personal micros...

If fil voltage must be measured under load (almost never, since poor connections are obvious and that 10+A winding is pretty tough), set the meter on a power line insulator, in/over the cable groove. Use a pin type:


Keep the leads away from any/everything, since they'll be live. Consider their insufficient insulation to be no insulation at all.

I've only done this twice with troublesome Panasonic MWO "inverters" and twice with regular iron-core transformers during "testing" purposes.

To others reading: Horizontal outputs and CRT anodes are nothing compared to this.

[RCA2000]

Re: GE Microwave,no heat?

And it's got ~4.3KV in common mode to the chassis or any other ground!

You know as well as I that many have blown their meters up "assuming" there's "only" three volts present.

There's 3V across the fil leads; not "on" the fil leads as you've stated. The voltage "on" the fil leads, taken together, is enough to obliterate a poorly insulated meter when someone checks "just" the fil supply.

The MWO transformer and doubler is the most dangerous electrical device found in the home.

Oh, "radiation?" It's not even ultra-long IR, much less ionizing. Chicken-littles started that scare in the 80's; snopes-ers and "megamouth-Joneses" continue it today- Drop it already!

Hence all of my "warnings" here..

BUT IF one is working on a NORMAL MWV--with an Iron-type of HV supply.. (ONLY..this does NOT apply to an inverter PS)..one CAN CAREFULLY unload the HV terminal on the tranny and THEN..one CAN measure the filament voltage..