Venerable Amana RR-10 Microwave

[Larry B]

We love our RR-10 and are the original owners (since 1979). Chromed out
with stainless interior and digital touchpad. I do have a service manual but
it does not go into detail on the digital module. The digital module in this
particular model was made by Essex.

Last weekend, someone used it (not personally witnessed) and the digital
module (Touchmatic II) went dead. I don't know what mortal code they entered
on the touchpad but it is truly dead. I have a rusty old RR-10 in the garage
for parts. So, I replaced the tube thermal cutout switch (which was open)
and the digital module. The rusty digital module works great but has a poor
Wife Acceptance Factor. Unfortunately, the original module is still dead. As
a further clue, when the the connector plug for the module is plugged in,
the buzzer should chirp. The original doesn't even chirp.

I took it apart and found a cap that had caused the underside of the PC
board to turn color so I replaced it. I also cleaned to the contacts on an
unenclosed relay, too. Still dead. Since a new digital module is $170 I was
hoping to get some hints as to what would be the most likely part(s) at
fault. Since whatever happened took out the thermal cutout sw, I thought
there may be some kind of deductive logic that could be applied here.

Thanks for any and all insights,

Lar

 

[**THE-RFI-EMI-GUY**]

First, check to see if there is a rectifier diode shorted which may have
caused the capacitor to burst. Next if the capacitor caused the board to
change color then you have electrolyte all over the PC board causing
current leakage. Try cleaning with strong alcohol, dry it and then check
for corroded solder connections. If it still won't work, its likely
trashed.

We love our RR-10 and are the original owners (since 1979). Chromed out
with stainless interior and digital touchpad. I do have a service manual but
it does not go into detail on the digital module. The digital module in this
particular model was made by Essex.

Last weekend, someone used it (not personally witnessed) and the digital
module (Touchmatic II) went dead. I don't know what mortal code they entered
on the touchpad but it is truly dead. I have a rusty old RR-10 in the garage
for parts. So, I replaced the tube thermal cutout switch (which was open)
and the digital module. The rusty digital module works great but has a poor
Wife Acceptance Factor. Unfortunately, the original module is still dead. As
a further clue, when the the connector plug for the module is plugged in,
the buzzer should chirp. The original doesn't even chirp.

I took it apart and found a cap that had caused the underside of the PC
board to turn color so I replaced it. I also cleaned to the contacts on an
unenclosed relay, too. Still dead. Since a new digital module is $170 I was
hoping to get some hints as to what would be the most likely part(s) at
fault. Since whatever happened took out the thermal cutout sw, I thought
there may be some kind of deductive logic that could be applied here.

Thanks for any and all insights,

Lar

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

 

[Larry B]

There appear to be 3 identical bridge rectifiers on this board. Two are
side by side and the 3rd is off doing its own thing. One of the pair is
directly connected to the cap in question. Should I replace just the one or
both in that group? Now the question is, "with what?".

The markings are : 7839, VM 08. The mfg symbol is a sylized V (kind of like
\') in a circle or it could be an A if the printed markings like 7839 are
not necessarily an indicator of what is right-side up. I read somewhere that
they may be half-wave rectifiers. They look more like IC's than full wave
rectifiers with the terminals coming out the side and down like spider legs,
and somewhat rectangular. The PC board calls them BR201, 2 and 3.

I have searched Google for 7839 bridge rectifier and came up empty. Sorry I
am not up on my rectifier specs. Thanks,

Lar

 

[Larry B]

Oh, I neglected to mention that there is also a little beige diode marked
ITT (D202 on the PC baord) that is connected to the cap on the same (-) leg
that the BR was. Its smaller that the standard looking black diode next to
it.

If you suggest its replacement, any suggestions on a spec?

Thanks, Lar

 

[Andy Cuffe]

Last weekend, someone used it (not personally witnessed) and the digital
module (Touchmatic II) went dead. I don't know what mortal code they entered
on the touchpad but it is truly dead. I have a rusty old RR-10 in the garage
for parts. So, I replaced the tube thermal cutout switch (which was open)
and the digital module. The rusty digital module works great but has a poor
Wife Acceptance Factor. Unfortunately, the original module is still dead. As
a further clue, when the the connector plug for the module is plugged in,
the buzzer should chirp. The original doesn't even chirp.

Why don't you swap the good electronics onto the good chrome? The
glass touch panel and all the electronics come off as a single unit.
Andy Cuffe
[email protected]

 

[Larry B]

Why don't you swap the good electronics onto the good chrome? The
glass touch panel and all the electronics come off as a single unit.
Andy Cuffe
[email protected]

I was hoping to do just that except that the second unit is actually an
RR-10A. Everything interfaces the same but the module is a whole different
animal inside. Same basic individual parts but the layout, boards, etc are
all different. The touchpad is similar ("orangier" pads), mounting holes,
9-pin connector and switches are the same but it ends there. Thanks for your
thoughts.

Lar

 

[Bill Jeffrey]

There appear to be 3 identical bridge rectifiers on this board. Two are
side by side and the 3rd is off doing its own thing. One of the pair is
directly connected to the cap in question. Should I replace just the one or
both in that group? Now the question is, "with what?".

The markings are : 7839, VM 08. The mfg symbol is a sylized V (kind of like
\') in a circle or it could be an A if the printed markings like 7839 are
not necessarily an indicator of what is right-side up. I read somewhere that
they may be half-wave rectifiers. They look more like IC's than full wave
rectifiers with the terminals coming out the side and down like spider legs,
and somewhat rectangular. The PC board calls them BR201, 2 and 3.

I have searched Google for 7839 bridge rectifier and came up empty. Sorry I
am not up on my rectifier specs. Thanks,

Larry -

Since your oven was new in 1979, it may be that 7839 is a date code -
39th week of 1978. How many leads on this beastie? I would expect a
full-wave bridge to have 4 leads, and a half-wave to have 3.

Bill

 

[Larry B]

Larry -

Since your oven was new in 1979, it may be that 7839 is a date code -
39th week of 1978. How many leads on this beastie? I would expect a
full-wave bridge to have 4 leads, and a half-wave to have 3.

Bill

:Hi Bill, it has 4 so it must be full-wave. In cruising some parts websites
a popular spec is DB104.

Lar

 

[Larry B]

Larry -

Since your oven was new in 1979, it may be that 7839 is a date code -
39th week of 1978. How many leads on this beastie? I would expect a
full-wave bridge to have 4 leads, and a half-wave to have 3.

Bill

Without knowing much about such things, could the cutoff switch failure
cause a surge that could harm the module's power supply. Typically, what
part fails in a downstream power supply in such a situation?