Author Topic: Charred Magnetron Connector  (Read 1701 times)

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Charred Magnetron Connector
« on: May 13, 2013, 06:07:58 AM »
My Maytag Over the Oven Microwave Mdl# MMV4205BA works but makes a very loud buzzing/banging sound when the magnetron is energized.  Taking the cover off I noticed charred / burnt plastic on the wire plug at the magnetron.

I presume the magnetron is failing in some manner, can anyone explain what is happening to cause the banging/buzzing sound and why the connector is charring?

Offline niobrara

  • Technician
  • Member Since: Sep 2009
  • Posts: 1153
Re: Charred Magnetron Connector
« Reply #1 on: May 13, 2013, 08:47:24 AM »
Loose connection, try just repairing the connection with a tight new one and see if your noise stops.

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #2 on: May 13, 2013, 09:57:49 AM »
The connection was tight, I struggled to pull it off.  I have read numerous time to discharge the hi-voltage cap.  I connected jumper clips from a long plastic handle blade screw driver to the exposed chassis.   There wasn't any indication of a charge when I shorted the cap terminals to ground.  I expected at least a small spark but there was nothing.  Is it possible the cap is bad?  if so can the Magnetron work with a defective cap??

Offline niobrara

  • Technician
  • Member Since: Sep 2009
  • Posts: 1153
Re: Charred Magnetron Connector
« Reply #3 on: May 13, 2013, 10:13:36 AM »
Could be bad and no it cant. If you have a meter you can check the cap. All of them don't spark due to a bleed resistor. Does not matter if it was tight if the wire archs you have a bad connection. As long as you have it open repair the wire and start it and see if the noise is still there.

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #4 on: May 13, 2013, 12:36:11 PM »
Is all the microwave energy contained within the wave guide and oven cavity with the cabinet cover off?

Offline niobrara

  • Technician
  • Member Since: Sep 2009
  • Posts: 1153
Re: Charred Magnetron Connector
« Reply #5 on: May 13, 2013, 12:56:20 PM »
yes

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #6 on: May 14, 2013, 05:58:16 AM »
The wire connection at the magnetron is solid, the charring is slight and at the very top  of the clip.  The buzzing still continues.  It does not occur if the magnetron is disconnected.  Could it be the hi-voltage xfmr?  Is there a way to determine with part is the culprit?  I hate to buy an expensive magnetron and find the buzzing continues/

Offline tgoods

  • Technician
    Moderator
  • Member Since: Jul 2010
  • Posts: 1475
  • Country: us
    • Buy me a beer through paypal
Re: Charred Magnetron Connector
« Reply #7 on: May 14, 2013, 10:12:58 AM »
I hate giving microwave advice because they can kill you. Make sure the microwave is unplugged and the HV capacitor is discharged before doing any tests. Check the HV diode for continuity, if it's shorted, it will buzz.  Check the magnetron, there should be about 1 ohm between the terminals and infinite to ground. If it checks good, now comes the dangerous part.  Plug in the microwave, unplug the the mag, run the microwave, open the door and immediately discharge the HV capacitor. I use a U shaped insulated wire, held with insulated pliers, wearing rubber soled shoes with my left hand in my pocket. If you hear a loud snap, you know the rest of the high voltage circuit is working and it has to be a bad mag. A generic replacement for your mag is part number 10QBP0230.

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #8 on: May 14, 2013, 10:32:08 AM »
I appreciate your concern with respect to the danger, I used to work on large CRT displays, they too had large voltages. I have tried discharging the Hi-Voltage cap before, it doesn't seem to retain a charge.  Someone else commented that it might have a bleeder resistor. 

Just a quick review:  The unit heats everything well, with the magnetron disconnected there is no buzzing.  If the HV Diode was shorted would the buzzing continue with the magnetron disconnected?

I do not have any service literature, can you help me identify the HV Rectifier?  I presume it is connected to one of the leads from the HV Xfmr and one of the HV Cap leads.  Am I correct?

Thanks in advance


Offline niobrara

  • Technician
  • Member Since: Sep 2009
  • Posts: 1153
Re: Charred Magnetron Connector
« Reply #9 on: May 14, 2013, 10:36:04 AM »
MFG Number DE91-70063D

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #10 on: May 14, 2013, 10:42:00 AM »
Thanks for the link to the picture of the HV Diode.  I had seen a rather large two lead rectangular component that I assumed was the HV Diode.  This helps a lot.

Offline tgoods

  • Technician
    Moderator
  • Member Since: Jul 2010
  • Posts: 1475
  • Country: us
    • Buy me a beer through paypal
Re: Charred Magnetron Connector
« Reply #11 on: May 14, 2013, 02:45:00 PM »
Okay, I assumed it wasn't heating.  I don't think I've ever heard a microwave bang before.  It's got to be the magnetron or it's arcing in the waveguide. 

Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #12 on: May 14, 2013, 03:47:48 PM »
Banging might be too strong a word and send the wrong message.  Better to consider it as a very loud buzzing sound!  The oven heats well, I will try to isolate the failing component using an ohmmeter.

Offline shieldcracker

  • VIP Member
  • Member Since: Nov 2008
  • Posts: 86
Re: Charred Magnetron Connector
« Reply #13 on: July 23, 2013, 09:46:55 PM »
Your magnetron uW radiation is leaking past the RF gasket, or air is leaking in to the magnetron tube.
In any case the magnetron needs replacement.


Offline bushyiii

  • VIP Member
  • Member Since: May 2013
  • Posts: 8
Re: Charred Magnetron Connector
« Reply #14 on: July 24, 2013, 08:40:51 AM »
I replaced the magnetron, the buzzing continued unabated. 

We generally use the appliance for short periods, warm up items, coffee, tea, etc.  The buzzing is fairly loud during these events, recently I had the unit on for a longer period and the buzzing stopped.  I find that whenever the unit is on for longer than 3 minutes there is no buzzing. 

I am guessing the problem is really the xfmr, high current at 60 hz is probably shaking the darn thing, it probably heats up sufficiently by 3 minutes, expanding the wiring preventing the oscillation.  Anyhow, replacing the xfmr isn't a cost effective solution given the current price of a new unit.

Thanks to everyone for their suggestions and help.

donate
$1, $2, $5, $10, $20, $50
 

Video: GE Spacemaker Microwave Magnetron Tube Replacement

Started by AJ

Replies: 4
Views: 3022
Last post January 29, 2011, 11:47:39 PM
by JWWebster
Access to Connector: GE JGBC20WEW2WW Gas Range

Started by magician59

Replies: 4
Views: 1117
Last post September 22, 2011, 06:00:48 AM
by RegUS_PatOff
Newer Accuwave Microwave Hood Combo repeated magnetron failures & F7 codes

Started by whjeffs

Replies: 10
Views: 3521
Last post September 21, 2013, 01:13:06 AM
by appltech
Magnetron bad for 3rd time in Kitchenaid superba

Started by patpras

Replies: 4
Views: 1411
Last post February 29, 2012, 02:54:35 PM
by krazytech
magnetron for Whirlpool GMC305PDQ6

Started by evergreen appliance

Replies: 1
Views: 542
Last post April 23, 2013, 12:43:32 PM
by LowSL2