Re: the kitchen stove
- From: m kinsler <kinsler33@xxxxxxxxxxx>
- Date: Sat, 16 Jun 2007 05:39:21 -0000
On Jun 13, 11:16 pm, m kinsler <kinsle...@xxxxxxxxxxx> wrote:
Well, hi once again. It's been about eight years since my last post
to this group. The old mail browser I'd been using got overloaded,
and I got wound up with real life, sort of. But it was only
temporary, and now I have a problem of my own.
We took a lightning hit to somewhere along our power line tonight. I
have a whole-house lightning protector, but there was a nice crackle
from the power supply of the computer I was working on. That wasn't
the problem, though. In the kitchen, the stove--Amana model AGS761W,
a gas stove probably made in 1994, was beeping, showing 'F5' on its
display. Unplugged it, tried all sorts of resetting techniques,
nothing: it runs for thirty seconds and then beeps and displays F5.
The part in question is called an ERC, electronic range control, part
number probably is 343461 but at this point I'm not sure, and all the
parts houses tell me that it's no longer being made and unavailable.
I have inquiries into Amana and repairclinic.com. eBay doesn't seem
to have that control, though there are a couple of electronic control
modules for other stoves, so I know I was doing a thorough search.
My guess is that 'F5' means 'bad module' or something helpful like
that. Without the oven, I have an exceptionally unhappy Natalie, and
she'd like me to get it figured out already. I cannot fathom being
able to come up with a workaround for this unit: it incorporates the
oven thermostat, the oven timer, and the self-cleaning oven stuff.
My strategy is to start at the power supply, which would have taken
the initial hit from a power-line overvoltage, and then test each
component in turn. Trouble is, the power supply is fine, because the
various clock functions work, right up until the unit fails some sort
of a self-test procedure about twenty seconds after you plug it in.
Then we see 'F5.'
If anyone has any experience in this sort of thing, please let me
know.
Mark Kinsler http://www.mkinsler.com, if it still works.
Well, I may have fixed it. 'F5' is indeed the code for a bad
electronic module, and there is indeed no replacement. And so,
inspired by other posts here, I went a-hunting. There was a
complementary pair of transistors on the board, 2n2222 and 2n3906, but
an in-circuit ohmmeter test showed that those were probably okay.
There was a gigantic microprocessor-sized chip beneath the fluorescent
clock readout, an EEPROM, what looked like a processor peripheral made
by Robertshaw, a Darlington amplifier array, and a discrete Darlington
transistor pair.
Turning a necessity into virtue, I noted that since the module
functioned properly, even turning on certain functions, for a couple
of seconds. Then a self-check would fail, and shut the thing down.
This made me think that the EEPROM was okay, and that the two
processor-like chips probably were too. And if they weren't, I
couldn't have replaced them anyway.
This left the Darlington arrays, which probably handled signals to and
from the module. There's an oven temperature input, and probably
something that tells us if the gas is lit in the broiler, and in the
oven. And there'd be a switch input to tell if the door is open.
That's four inputs. The outputs are to the broiler gas valve, the
oven gas valve, the two ignitors for those units, and the motorized
door latch that secures the door during the cleaning cycle. That's
five outputs. Possibly something is multiplexed, or else I've added
non-existent inputs or outputs, because there are only eight
Darlington arrays, but okay.
Anyway, it seemed possible that these were ill, because a bad input
would cause illogical test results. A bad output could screw things
up too if the test procedure energized something and then measured its
effects on the system, which is what they do in cars.
And so I've replaced the two Darlington devices. One cross-references
to an NTE48, and the other to the NTE2013. They are the only devices
that look like those on the board; replacement was a straightforward
soldering job.
The stove seems to work fine now.
M Kinsler
.
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