dead microwave

[james]

Frigidaire, Professional Series PLMV169DCD

When plugged in, no clock is displayed. Nothing. No response to any buttons.
No lights, no fan, no sound.
It failed gradually. Starting from a few buttons that didn't work, then
this.

It is a combo microwave/range hood. I opened up the panel/keyboard. There's
a layer of grease on the circult board, and some grease droplets dangling on
wires and connectors. Some greenish(!) grease drips out of connectors. Could
the grease cause the connectors to fail?

I found on the internet a parts and schematic PDF for this model.
Unfortunately, the schematic shows everything (relays, transformers, lights,
fuses, magnetron, motors) but the controller board. Yet the controller board
is where I want to start debugging since it houses the LCD display and hooks
up to the keypad. Does anyone know where to get the controller board's
schematic?

BTW, there's a note inside saying "this device should not be serviced by a
do-it-yourself repair person". I could understand if it says "this device
should be serviced only by a qualified person". But why get personal?

 

[Meat Plow]

Frigidaire, Professional Series PLMV169DCD

When plugged in, no clock is displayed. Nothing. No response to any
buttons. No lights, no fan, no sound.
It failed gradually. Starting from a few buttons that didn't work, then
this.

Uh Huh.

It is a combo microwave/range hood. I opened up the panel/keyboard.
There's a layer of grease on the circult board, and some grease droplets
dangling on wires and connectors. Some greenish(!) grease drips out of
connectors. Could the grease cause the connectors to fail?
Yep

I found on the internet a parts and schematic PDF for this model.
Unfortunately, the schematic shows everything (relays, transformers,
lights, fuses, magnetron, motors) but the controller board. Yet the
controller board is where I want to start debugging since it houses the
LCD display and hooks up to the keypad. Does anyone know where to get
the controller board's schematic?

Controllers are usually replaced not serviced.

BTW, there's a note inside saying "this device should not be serviced by
a do-it-yourself repair person". I could understand if it says "this
device should be serviced only by a qualified person". But why get
personal?

Because your health depends on you knowing what you are doing. What price
are you willing to see yourself and others possibly pay for a more
friendly message?

 

[William Sommerwerck]

BTW, there's a note inside saying "this device should not be

serviced by a do-it-yourself repair person". I could understand
if it says "this device should be serviced only by a qualified
person". But why get personal?

"I don't get no respect!"

Why not start by simply cleaning up everything? The only thing you might
have to worry about is electrostatic discharge damaging the controller or
other electronic components.

 

[William Sommerwerck]

Surely, the most fundamental first move is to take a meter to the power

supply, and see if there is at least some supply to the system control
micro etc ? The fact that it's covered in grease may well be neither here
nor there as far as the fault goes. Oils and greases are not known for
being particularly conductive or corrosive. Dead is a positive problem,
and one to which basic faultfinding techniques should be first applied,
before going off on an 'if-then-maybe' exercise ...

I'd normally agree, but the fact the unit /slowly/ declined suggests that
something other than a voltage loss is going on.

Of course, it takes just a few seconds to check the voltages. Couldn't hurt.

 

[William Sommerwerck]

I'd normally agree, but the fact the unit /slowly/ declined suggests

Well, not really. Analogue power supplies, such as the ones in
microwave ovens usually are, will die gracefully as a result of bad
electrolytics getting worse.

I've never seen this, but I sure don't know everything. Anyhow, what about
the fact that some buttons "failed" before others? (That's a rhetorical
question.)

 

[Meat Plow]

I've never seen this, but I sure don't know everything. Anyhow, what
about the fact that some buttons "failed" before others? (That's a
rhetorical question.)

The microwave as I understood was above a stove and was probably cleaned
frequently because of its location. I've seen many control panels
permanently damaged by cleaning fluids on not only microwaves but also
other home appliances and electronics. This fact can certainly account
for button failure.

 

[Meat Plow]

Agreed. I was just thinking of a scenario that would account for both
progressive failure of buttons, and then ultimately (apparent) total
failure of the unit to operate at all.

Arfa

Total failure as in front panel function could easily result from
cleaning fluids, corrosive cooking vapors, condensation etc..
I don't recall if the OP mentioned the interior light working when the
door was opened.

 

[William Sommerwerck]

If it has GE on the front, you'll be lucky to make it past the first year.

My GE over-the-cooktop microwave is 11 years old, gets near-daily use, and
is a-working still.

 

[Jeffrey Angus]

My GE over-the-cooktop microwave is 11 years old, gets near-daily use, and
is a-working still.

That's because it IS 11 years old.
The reference was for the new ones being sold at Wal=Mart.

Jeff

 

[William Sommerwerck]

If it has GE on the front, you'll be lucky to make it past

That's because it IS 11 years old.
The reference was for the new ones being sold at Wal-Mart.

I still have one of the last made-in-the US Littons, which I can pull out if
the GE fails.

Does anyone make a really good, reliable microwave?

PS: There's a classic MAD spoof showing an Appalachian family (is that
sufficiently PC) around their washing machine, which has been converted for
alcohol production: "Our Mayjag is 18 years old, and it's a-working still!"

 

[Meat Plow]

If it has GE on the front, you'll be lucky to make it past the first
year. ESPECIALLY if you bought it at Wal-Mart.

1100 watt GE here. Now 6 years old, works good as new.

 

[David]

Drivel: US DoE can't figure out how to measure microwave oven

power
output.
<http://www.federalregister.gov/arti...-test-procedure-for-microwave-ovens-repeal-of>
Sigh.

Jeff Liebermann [email protected]

Your tax dollars at work, Sigh^2.

David

 

[Meat Plow]

I was once asked to look at a heavily used microwave oven at a local
residential facility. The description was similar, but the problem was
obvious on first inspection. Long finger nails punching through the
elastometric contact keyboard. Once the protective membrane on the
front panel is punctured, all manner of liquids and gasses can cause
damage. I've seen this problem other times, where the customer doesn't
want to admit that they damaged the front panel, or somehow considers
such damage as normal. It also applies to TV/hi-fi remote controls,
printer control panels, calculators, where easily damaged flexible
membranes are used in place of hard plastic buttons.

While grease is usually non-conductive, having any grease in the various
connectors will produce lousy connections. I suspect a good cleaning,
and a low grease diet, might restore the oven to normal operation. The
green crud (copper sulfate) does not necessarily signal the demise of
the wiring, unless it's extensive. I would not replace any electronics
until the keyboard and controller cards are baptized in solvent. It
would also be interesting to determine how the grease entered the area.
Probably a mechanically mis-aligned exhaust duct.

I've seen the corruption of membrane switch panels from users spraying
things like window cleaners directly on them. Without any punctures.
While talking to the customer I try to ask how they cleaned their stuff
without trying to point blame. People don't like to readily admit to the
over zealous spraying of cleaners that can and do eventually seep into
membrane panels. I cringed in horror once watching my girlfriend cleaning
my then 2 year old GE oven, She sprayed the front with copious amounts of
window cleaner. I told her from now on she was to lightly spray it on a
clean cloth first then wipe the membrane. On everything. Not too many
realize this is a serious problem unfortunately.

 

[Fred McKenzie]

Drivel: US DoE can't figure out how to measure microwave oven power
output.

Jeff-

My impression is that the referenced article refers to efficiency, not
power output. It talks about such things as magnetron filament current
and warm-up time.

Somewhere on the web I found a procedure for measuring power. You heat
a liter of water for a certain amount of time, measuring temperature
before and after. Using a formula, temperature rise correlates to power
output.

I think such a procedure is basic, and don't see how it could be
challenged other than for "hot spots" in an oven. In my case, the oven
has a carousel to compensate.

My old 900 Watt Sharp microwave actually puts out 650 Watts according to
the procedure. I adjust cooking times meant for 1100 Watt units,
multiplying by 1100/650. The food appears to be getting the right
amount of heat.

An old Sharp "Half Pint" is rated for 450 Watts. The above procedure
agrees exactly.

Fred