GE Microwave,no heat?

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • RCA2000
    Senior Member
    • Sep 2014
    • 111
    • USA

    #21
    Re: GE Microwave,no heat?

    But Kaboom...did you ever see THIS::

    An early 80's IIRC Kenmore MWV. Came in with a blwo n fuse. Replaced. closed door...no shorts on HV area.. Lit off...worked FINE.,..cooked well... UNTIL...I shut it OFF..or opened the door. THEN..there would be a loud "rumbling noise" from the HV tranny...and the fuse blew again.

    at first...figured a weird door sw. problem or such.. SO I unhooked the primary of the HV tranny...and replaced the fuse...and opened and closed the door MANY times..NO problem.

    Unlike most--if not ALL..modern MWV"s...this one used a TRIIAC..instead of a relay to break the primary line the the HV tranny. At FIRST...I thought "maybe it has a bad triac..which is SOMEHOW not "conducting right"..and somehow "chopping" the power to the tranny...which it would NOT like. BUt this did N OT help...powered up...worked great..until stopped or door opened AGAIN..SAME rumble from tranny and blown fuse.

    I was not sure where to look next. THEN..I recalled a tv set which used a triac for control...and it ALSO did something similar. That turned out to be a bad OPTOCOUPLER.. which drove the gate of the triac. Somehow it was NOT conducting fully or such...and chopped the power to the VRT tranny (this was a Zenith CC-II set)...which then tripped the breaker after some seconds.

    Turned out it was the SAME case HERE. The control board DID have an optocoupler--and evidently it WAS acting that way. After I located another opto (this was NOT a "modern opto" it was a LOT larger--as was the one in that tv set..) and installed it on the board ALL was GOOD..

    I think I saw that..TWICE On an MWV and mabye 3 times on a tranny-powered tv set...

    Comment

    • goontron
      5000!
      • Dec 2011
      • 4108
      • US

      #22
      Re: GE Microwave,no heat?

      Originally posted by RCA2000
      But Kaboom...did you ever see THIS::

      An early 80's IIRC Kenmore MWV. Came in with a blwo n fuse. Replaced. closed door...no shorts on HV area.. Lit off...worked FINE.,..cooked well... UNTIL...I shut it OFF..or opened the door. THEN..there would be a loud "rumbling noise" from the HV tranny...and the fuse blew again.

      at first...figured a weird door sw. problem or such.. SO I unhooked the primary of the HV tranny...and replaced the fuse...and opened and closed the door MANY times..NO problem.

      Unlike most--if not ALL..modern MWV"s...this one used a TRIIAC..instead of a relay to break the primary line the the HV tranny. At FIRST...I thought "maybe it has a bad triac..which is SOMEHOW not "conducting right"..and somehow "chopping" the power to the tranny...which it would NOT like. BUt this did N OT help...powered up...worked great..until stopped or door opened AGAIN..SAME rumble from tranny and blown fuse.

      I was not sure where to look next. THEN..I recalled a tv set which used a triac for control...and it ALSO did something similar. That turned out to be a bad OPTOCOUPLER.. which drove the gate of the triac. Somehow it was NOT conducting fully or such...and chopped the power to the VRT tranny (this was a Zenith CC-II set)...which then tripped the breaker after some seconds.

      Turned out it was the SAME case HERE. The control board DID have an optocoupler--and evidently it WAS acting that way. After I located another opto (this was NOT a "modern opto" it was a LOT larger--as was the one in that tv set..) and installed it on the board ALL was GOOD..

      I think I saw that..TWICE On an MWV and mabye 3 times on a tranny-powered tv set...
      Rather common in SMPSs actually.... Im fixing a server PSU right now and the optoiso wont cut out. It blows switchers.
      Things I've fixed: anything from semis to crappy Chinese $2 radios, and now an IoT Dildo....

      "Dude, this is Wyoming, i hopped on and sent 'er. No fucking around." -- Me

      Excuse me while i do something dangerous


      You must have a sad, sad boring life if you hate on people harmlessly enjoying life with an animal costume.

      Sometimes you need to break shit to fix it.... Thats why my lawnmower doesn't have a deadman switch or engine brake anymore

      Follow the white rabbit.

      Comment

      • kaboom
        "Oh, Grouchy!"
        • Jan 2011
        • 2507
        • USA

        #23
        Re: GE Microwave,no heat?

        Originally posted by RCA2000
        But Kaboom...did you ever see THIS::

        An early 80's IIRC Kenmore MWV. Came in with a blwo n fuse. Replaced. closed door...no shorts on HV area.. Lit off...worked FINE.,..cooked well... UNTIL...I shut it OFF..or opened the door. THEN..there would be a loud "rumbling noise" from the HV tranny...and the fuse blew again.
        Weren't those the Sanyos? Sears didn't switch to Goldstar for their MWOs til the late 80's AFAIK... Even when working properly, those triacs still needed their little heatsink. But they often half-shorted- light dimmers did this after those spectacular lamp failures/arcs. Since the arc in a blown/blowing lamp is assymetrical, one half-wave of current can greatly exceed the other; that peak which is beyond the triac's capabilities destroys that side of the device. The result was the bulb(s) would be stuck on, at about half nominal wattage, even with the control all the way down!

        Now imagine a large transformer with low DCR- that MOT for example. If the triac's half shorted, the fuse blows upon plug-in; if improperly/assymetrically driven, the "net" result is the same- net DC thru that transformer- saturation and blown fuse.

        Originally posted by RCA2000
        at first...figured a weird door sw. problem or such.. SO I unhooked the primary of the HV tranny...and replaced the fuse...and opened and closed the door MANY times..NO problem.

        Unlike most--if not ALL..modern MWV"s...this one used a TRIIAC..instead of a relay to break the primary line the the HV tranny. At FIRST...I thought "maybe it has a bad triac..which is SOMEHOW not "conducting right"..and somehow "chopping" the power to the tranny...which it would NOT like. BUt this did N OT help...powered up...worked great..until stopped or door opened AGAIN..SAME rumble from tranny and blown fuse.
        If they used an odd (at the time) photo-triac optoisolator, the little triac inside the opto could also have one side go bad. Or leakage. Or both. Hence the "randomness" of the noise; you mentioned rumbling.

        An internal diagram of that optocoupler would've been interesting...

        Originally posted by RCA2000
        I was not sure where to look next. THEN..I recalled a tv set which used a triac for control...and it ALSO did something similar. That turned out to be a bad OPTOCOUPLER.. which drove the gate of the triac. Somehow it was NOT conducting fully or such...and chopped the power to the VRT tranny (this was a Zenith CC-II set)...which then tripped the breaker after some seconds.

        Turned out it was the SAME case HERE. The control board DID have an optocoupler--and evidently it WAS acting that way. After I located another opto (this was NOT a "modern opto" it was a LOT larger--as was the one in that tv set..) and installed it on the board ALL was GOOD..

        I think I saw that..TWICE On an MWV and mabye 3 times on a tranny-powered tv set...
        Again, almost sounds like a hybrid module- like a "mini STK."
        "pokemon go... to hell!"

        EOL it...
        Originally posted by shango066
        All style and no substance.
        Originally posted by smashstuff30
        guilty,guilty,guilty,guilty!
        guilty of being cheap-made!

        Comment

        • RCA2000
          Senior Member
          • Sep 2014
          • 111
          • USA

          #24
          Re: GE Microwave,no heat?

          But NOT so common..on a 60HZ line powered supply. I agree optos TODAY..are VERY often at fault--when an SMPS will not run, runs away or latches and blows the switching device. And it is NOT easy to check them other than by subbing...

          I STILL WONDER...just how much FUN it was..back in '72,'73..for TV techs...when they encountered a Motorola Quasar with the JA SMPS power supply. These techs were used to 60HZ power trannies or HOT chassis sets. The JA was a combinatin of BOTH.. (HOT primary side and COLD output side) .and a WHOLE LOT like a modern SMPS ckty-wise. . But for the "old timers"...I can just IMAGINE...them finding a shorted switching transistor, putting a new one in and as SOON as power is applied BAM !! OUT it goes INSTANTLY--and THEN..not having ANY idea..where to look next !!

          My guess is they usually just SUBBED the WHOLE JA module" and "let the factory sweat it out"..

          Comment

          • RCA2000
            Senior Member
            • Sep 2014
            • 111
            • USA

            #25
            Re: GE Microwave,no heat?

            That was over 20 years ago...when I saw that Kenmore with that problem. There was NO internal diagram of the Opto..or for THAT matter control board. Nealry ALL techs would just "replace the board"...but I have LONG tried my BEST to REPAIR boards..then and NOW...when it is possible.

            Actually..on the MWV...IIRC..it was a black, epoxy-encased device like today...BUT a LOT bigger and NOT with a standard DIP layout. ON the TV.(this was the late 1980's IIRC) I THINK..it was a "blob" of some sort--all wrapped in fiber tape--with a pair of wires on each end. Pretty sure THAT one showed a LAMP and a PHOTOCELL..inside on the schematic.

            Comment

            • michael dranfield
              Badcaps Veteran
              • Jan 2016
              • 232
              • England

              #26
              Re: GE Microwave,no heat?

              Originally posted by clearchris
              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.
              Its a very common fault having a poor connection at the magnatrons filament terminals , the magnatrons filament can draw upwards of 10 amps so any resistance here becomes critical .

              Comment

              Related Topics

              Collapse

              • Document Archive
                Mounting and Handling Guidelines for TO220 TO220F TO247 Cases / Packages
                by Document Archive
                Mounting and Handling Guidelines for TO220 TO220F TO247 Cases / Packages

                The TO220, TO220F and TO247 are the popular packages for power devices because of their versatility and ability to dissipate moderate amounts of heat. This application note describes the basic guidelines for handling power MOSFETs in TO220, TO220 and TO247 packages shown in Figure 1. Please note that only mechanical and soldering guidelines are covered here. Additional precautions are required for isolating high voltage rated devices to meet safety regulations.

                Securing a good thermal interface between...
                10-07-2024, 04:35 AM
              • harp
                detecting heat with IR LED receiver
                by harp
                detecting heat with IR LED receiver

                I have some dark IR led, and want to know if it is be situable to detect pure heat (not visable glow ir radiation) in well lighted desk?

                So, if I put hand over it in near distance like few centimeters, that detect rising heat, not covering it from light.
                Something like termal camera, but in one spot, any simple circuit?...
                09-06-2023, 06:03 PM
              • ludovik
                Moto G84 short after heat
                by ludovik
                Hello everyone,
                i was reballing the power manger of a moto g84, after applying heat i tried to power on and it wouldn’t.
                i injected 1.5v to some capacitor that seem in short because both side beep if tested.
                when i inject i feel the cpu burning;
                since the cpu is exactly on the other side of the board, is that possible that the heat from the reballing damaged the cpu? do you know where i can find schematics or what can i do?
                i know this is not enough to explain the situation so if you need any other info ask me please!
                Thank you very much in advance
                11-08-2024, 02:13 PM
              • jm1234
                Solder joints on heat sinks matter?
                by jm1234
                Hi,
                solder joints on heat sinks - how much do they matter? Could poor joints on heat sink cause issues if they are not properly joining to hot ground?
                I'm looking at power source module of Panasonic plasma TV and I see many of these having visually poor quality, but could they matter? In general I would guess no, but I saw a video where someone was stressing out the importance of tightening the screws when fastening the power source board specifically for the ground to be connected properly.
                Thanks
                04-28-2024, 04:38 AM
              • myth77
                direct heat stencil,where do you get it? and how to prevent warping?
                by myth77
                So, lately i found that for smaller chips like pch it is very difficult to reball with nondirect heat stencil. So i decided to try direct heat stencils...and while i am waithing some stencils to arrive i have a few questions:

                1. From who do you buy a quality direct heat stencils? i am reading that they can vary in quality and make a big difference...Any trusted sellers?

                2. I am reading also the problem of warping (curving) direct heat stencils...Is it because of quality of the stencils? or/and because some preheating is also required? and help and advice here?
                01-17-2022, 05:06 AM
              • Loading...
              • No more items.
              Working...