Amana HDC18 Microwave

[wolfman32]

I have one that is blowing fuses only when you try to cook. When you push a button to cook it will blow the fuse I have checked all I know. I am new to microwaves so any help would be GREAT!!

[H-Tech]

I'm not the best on it but sounds like microtron is shot.

[BigJon3475]

model number?

[cybercontadino]

Check your door switch assembly.The main fuse is designed to blow if "door interlock" switch or "monitor" switch is bad.

[wolfman32]

Thanks thats the only thing I've not checked.

[wolfman32]

Tried door switch assembl thats not it. It can get an amp draw reading it is pulling 82 amps. i called amana they didn't help any eaither thanks..

[cybercontadino]

If you haven't worked on microwaves before it's best to back away.The hi-voltage side produces extremely high voltages(4000V). Never put a test meter on any hi-volt component.

[Tiger93rsl]

sounds like a shorted magnatron, unplug your unit and discharge the capacitors then using your meter ohm out your magnatron to ground if you show any kind of a reading your shorted to ground. If you don't understand exactly what I'm talking about then find someone quallified to work on microwaves, they are extremely deadly if you don't know exactly what you are doing

[wolfman32]

I have checked everything to ground and nothing shows a ground. I understand about the high voltage. I treat all voltage as if it is deadly.

[Tiger93rsl]

try unpluging the magnatron then run the unit with the magnatron unpluged.

[wolfman32]

Did that also I unpluged them 1 at a time then both at the same time.
The samething.

[Tiger93rsl]

Wait a minute here I read the post a little closer it says fuses. If you are refering to the fuses on the board, then the problem more than likely is in the controll circuit, OR maybe the stirrer (fan) is shorted out, I was thinking it wast tripping the breaker one way to find out is unplug the light, stirrer and magnatron and hit start if it still blowes fuses than the problem is in the board, I would also suggest unmounting the board and examine it closely for any signs of damage.

[royc]

First of all you need to determine where the short is, the way to do that is to disconnect the HV transformer primary and start the unit. If it doesnt blow then you know your problem is in the HV side.

As someone else said, you do not use any meter on the HV side. It is also very helpfull to get a breaker the size the unit requires. Most 120v Micros use ABC20, havent worked on a lot of commercial stuff, so check what fuses are required. You dont want to stand there and keep putting fuses in finding where the short is.

If you blowing the fuse with primary off the transformer, then you need to start looking to see where the most likely problem is. The first thing is to check the Monitor switch, it checks to make sure that the door is closed, and if door open, or the striker doesnt engage it, or it is just plain bad, makes a direct short across your input line.

If you have determined that the short is in the HV side, then you need to start eliminating components. First remove both HV leads off the Mag tube, start the unit, if it sill blows go to the capacitor and remove connection. A common problem can be the Diode, but generaly if it has a short it will burn or have a burn mark on it, so it should be obvious, unless its included in capacitor.

As someone else mentioned, BE VEY CAREFULL with the HV side, make sure the capacitor is drained. I once worked on a commercial unit many years ago, discharged the capacitor and it didnt discharge completly, I crabbed the HV lead at the mag tube to remove wire, and got the hell shocked out of me, worst schock I have ever gotton in the over 40 years of being a tech, my heart almost didnt make it.

Also I can tell you that you can pretty much check HV problems with a plain screwdriver across capacitor, the HV crack can tell you if its got a short or open in the mag tube or Diode, but that comes with years of experience. Also very few shorted mag tubes will blow fuse instantly, the thing to listen for is the HV transformer hum, it will be very noticable if it has a short on the HV side.

If you suspect a control board problem, see if you can bypass it, and energize the unit without it, when doing so will tell you that at least the HV side is working, and you dont have a multible problem with hi side and low side.

Thats about all I can think of at the moment, and as I said before, BE CAREFULL with HV side, the motto is....if you work on the live hi voltage side...ON HAND IN YOU POCKET.....lol

Roy

[royc]

And btw, do something about your long location line, I hate scrolling across to read posts..lol

My old eyes are not what they used to be,,I still use 800X600..lol

Roy

[wolfman32]

I have unpluged the HV transformer and turned it and it will not blow a fuse. The HV trans. hums very loud. but nothing seems to be grounded. I have new spare parts and I have switched everything out but the mags. I guess I will try them but they check to be good. I have a book on this unit and I have tested everthing like the book says and everthing tests good.

[markwolf]

My vote is for an internally fused(melted/shorted)power diode at the capacitor.
Most standard meters will not have enough power to activate the diode to test it.
If you are going to be working on microwaves you will want a meter to test large power diodes.It is a common problem.

[leonmiller]

Remove the secondary leads from the transformer and try it again. If you have a megger, Amana recommends megging transformer first - if not, fire it up with secondary isolated. If it blows fuse, replace transformer. If you need parts help, post or email me. We are an Amama Commercial Service Depot. HDC-18's pretty bullet proof, don't see many any more - don't have manuals here at home, but can provide more assistance tomorrow when at office.

[leonmiller]

Got to my book, remove wires 4 thru 8 on transformer to open secondary and both filament circuits. Wire 4 is the HV wire, stay away when powered up!
If it still blows fuse replace transformer, give me your mfg. number off the serial plate and I'll give you a part number. - Good luck

[ndfrozen]

I have one that is blowing fuses only when you try to cook. When you push a button to cook it will blow the fuse I have checked all I know. I am new to microwaves so any help would be GREAT!!

You can isolate this unit in half, take off the triac
gate wire, its the single wire across from the pair of double wires on the triac. if it doesn't blow when you put in load, close door, and press number1, then problem is in mag. side of unit. if it blows problem in control side of unit.

If mag side -then check big transformer visually for burned up hv coil ( what i see the most, since drawing hi amps this is the main suspect, nothing else in this unit can handle that many amps more that a second or so), next is to visually check the mags at there hv connections, usually the white terminal shroud is burnt up or has a brown-blister on it. A dead give away that it is shot. next comes the caps - usually find grease or debris shorting out the terminals, then diodes for shorts to ground.
these are all visual checks, you can also use your meter to check them out, go to amana TS manual it will tell you how to, also get with amana's tech support pretty good folks.
to isolate mags you have to remove hv wire jumper from caps, leaving the hv wire on one cap. Run unit with small glass of COLD water if it heats up that mag circuit is good. next, move hv wire to other cap and do test.
NOTE: if hv transformer is bad usually at least one mag circuit will be bad also.

the control circuit consists of the op-panel, pcb, interlock switch, and wiring.these items are very close to other things we run into so I didn't cover them , but ask if you have any ?, .


NOW YOU MUST USE CAUTION WHEN WORKING ON THIS UNIT IT CAN PUT --you--- IN THE HOSPITAL OR WORST, IF YOU DON'T GIVE IT RESPECT. 4400 VOLTS WILL KILL YOU !!!!!!!!!!!!!!!!!!!!!!!!!

[Just In Time]

the door interlock switches make the fuse in the back blow