Microwave timer/clock 4 digit 7-segmnt display is out. Timer

[Angelo Campanella]

My ancient Amana Microwave oven numerical display is out. Has been acting up
for years, but I now use it daily. (Batching it. Dear Wifey now in heaven.)

I can punch in the time I want, and the oven will run and turn off
accordingly. But I can't see the countdown any more because the display
digits are out.

Well they really are not out... just that the lower left segment on all four
are lit continuously, not other segments ever avtivate. Once and a while #1
"4" and occasionally #2 "2" light on cue during the countdown. I've opened
it up and measured power supply voltages and they are correct and normal at
the power supply.

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

Any suggestions?

Ange

 

[N_Cook]

Angelo Campanella <a.campanella@att.net> wrote in message
news:igbg0p$l9g$3@speranza.aioe.org...

My ancient Amana Microwave oven numerical display is out. Has been acting
up
for years, but I now use it daily. (Batching it. Dear Wifey now in
heaven.)

I can punch in the time I want, and the oven will run and turn off
accordingly. But I can't see the countdown any more because the display
digits are out.

Well they really are not out... just that the lower left segment on all
four
are lit continuously, not other segments ever avtivate. Once and a while
#1
"4" and occasionally #2 "2" light on cue during the countdown. I've opened
it up and measured power supply voltages and they are correct and normal
at
the power supply.

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

Any suggestions?

Ange

I assume it has a dedicated LED driver, that sort of age probably internal
metalisation drift inside the chip or die carrier. Will it go to a museum?,
I would not have said uwave ovens were around in 1976

 

[Jeff Liebermann]

On Sun, 9 Jan 2011 00:10:53 -0500, "Angelo Campanella"
<a.campanella@att.net> wrote:

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

Sounds more like a Nixie tube. Red would mean LED. 1976 vintage
would probably be red LED. How about making life easier and disclose
the Amana (Radar Range) model number?

The bad news is that if all the digits are equally bad and they're
individually unpluggable, then it's probably something in the
electronics. Stuck digits and working timer sounds like a display
multiplexer/driver circuit. It would probably cost less to replace
the oven than repair it, but such an old Amana is a collectors item
and is probably worth restoring. I'm rather surprised that the
magnetron is still functional.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[William Sommerwerck]

Nixie tubes were relatively expensive. I don't think any microwave oven used
them. Certainly not in 1976, when LEDs were common and cheap.

If all the lower-left segments are on continuously, I'd suspect a problem in
the logic driving them.

 

[nesesu]

On Jan 8, 9:10 pm, "Angelo Campanella" <a.campane...@att.net> wrote:

My ancient Amana Microwave oven numerical display is out. Has been acting up
for years, but I now use it daily. (Batching it. Dear Wifey now in heaven..)

I can punch in the time I want, and the oven will run and turn off
accordingly. But I can't see the countdown any more because the display
digits are out.

Well they really are not out... just that the lower left segment on all four
are lit continuously, not other segments ever avtivate. Once and a while #1
"4" and occasionally #2 "2" light on cue during the countdown. I've opened
it up and measured power supply voltages and they are correct and normal at
the power supply.

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

    Any suggestions?

        Ange

It sounds likely that it is the multiplexing circuit that drives the
displays. That probably consists of one chip and 4 transistors. From
your description the displays may be flat plasma displays made, IIRC,
by Burroughs. If you look under Heathkit on eBay, new ones sometimes
come up, but they are relatively expensive.
I worked on an old Amana years ago and it had an intermittant on the
front panel but I cannot remember if it was the display or the keypad
but I rather think itr was the latter. The problem was that corrosion
had developed between the contact fingers that reach from the PCB to
the back of the front panel where they touch the contacts on the
panel. It was a simple matter of sliding the board out and cleaning
the tips of the fingers then sliding it back together. It worked for
at least another 10 years until replaced due to low power output.

Neil S.

 

[Michael A. Terrell]

Jeff Liebermann wrote:

On Sun, 9 Jan 2011 00:10:53 -0500, "Angelo Campanella"
a.campanella@att.net> wrote:

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

Sounds more like a Nixie tube. Red would mean LED. 1976 vintage
would probably be red LED. How about making life easier and disclose
the Amana (Radar Range) model number?

The bad news is that if all the digits are equally bad and they're
individually unpluggable, then it's probably something in the
electronics. Stuck digits and working timer sounds like a display
multiplexer/driver circuit. It would probably cost less to replace
the oven than repair it, but such an old Amana is a collectors item
and is probably worth restoring. I'm rather surprised that the
magnetron is still functional.

What color is the display? VFD were common in early microwaves.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

 

[Angelo Campanella]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:K7adnTQAfL-lN7fQnZ2dnUVZ_vqdnZ2d@earthlink.com...

Jeff Liebermann wrote:
The bad news is that if all the digits are equally bad and they're
individually unpluggable, then it's probably something in the
electronics. Stuck digits and working timer sounds like a display
multiplexer/driver circuit. It would probably cost less to replace
the oven than repair it, but such an old Amana is a collectors item
and is probably worth restoring. I'm rather surprised that the
magnetron is still functional.

I checked to output by measureing the time to boil an 8oz cup of water.
The tag say 700 watss of cooking power, and my timing result was
approximately that... close enough to sy the magnetron was still OK.

What color is the display?

Red. LED seems pausible.

VFD were common in early microwaves.

I can see blinking when I san my gaze across it, so it's swithced likey
at 60 Hz or 120 Hz.

If it's not a power supply bus, then it's a bus driven by logic. I just
don't have a schematic for that generic sort of diplay logic.

I know you guys recommend that I replace it, but I don't see anything I
like. The chamber is nice and big... I've been eating meals prepared in it
for over two years now. Soups and pastas, coffee every day... It's my
mechanical mama.

Ange

 

[Michael A. Terrell]

Angelo Campanella wrote:

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:K7adnTQAfL-lN7fQnZ2dnUVZ_vqdnZ2d@earthlink.com...
Jeff Liebermann wrote:
The bad news is that if all the digits are equally bad and they're
individually unpluggable, then it's probably something in the
electronics. Stuck digits and working timer sounds like a display
multiplexer/driver circuit. It would probably cost less to replace
the oven than repair it, but such an old Amana is a collectors item
and is probably worth restoring. I'm rather surprised that the
magnetron is still functional.

I checked to output by measureing the time to boil an 8oz cup of water.
The tag say 700 watss of cooking power, and my timing result was
approximately that... close enough to sy the magnetron was still OK.

What color is the display?

Red. LED seems pausible.

VFD were common in early microwaves.

I can see blinking when I san my gaze across it, so it's swithced likey
at 60 Hz or 120 Hz.

If it's not a power supply bus, then it's a bus driven by logic. I just
don't have a schematic for that generic sort of diplay logic.

I know you guys recommend that I replace it, but I don't see anything I
like. The chamber is nice and big... I've been eating meals prepared in it
for over two years now. Soups and pastas, coffee every day... It's my
mechanical mama.

I didn't recommend you replace it. One of my microwaves was made in
1985.


--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

 

[Jeff Liebermann]

On Mon, 10 Jan 2011 14:17:07 -0500, "Angelo Campanella"
<a.campanella@att.net> wrote:

I checked to output by measureing the time to boil an 8oz cup of water.
The tag say 700 watss of cooking power, and my timing result was
approximately that... close enough to sy the magnetron was still OK.

Impressive.

What color is the display?
Red. LED seems pausible.

Red is LED. Orange could be vacuum fluorescent or LED. I'll be on
LED.

If it's not a power supply bus, then it's a bus driven by logic. I just
don't have a schematic for that generic sort of diplay logic.

Could I trouble you for the Amana model number so we don't have to
continue guessing.

I know you guys recommend that I replace it,

Please re-read the previous comments. Nobody suggested you replace
it. This isn't a newsgroup dedicated to appliance salesmen. If it
cooks well, it should be possible to fix it.

but I don't see anything I like.

What's the problem? Too many features? Short lifetimes? Bizarre
warranties? Lousy construction? All of these?

The chamber is nice and big... I've been eating meals prepared in it
for over two years now. Soups and pastas, coffee every day... It's my
mechanical mama.

I think you might find it useful to learn how to cook. Think of it as
chemistry and not an art form. Microwave cooking is ok for many
things, but there's plenty of dishes that are best cooked over a
flame, on a grill, or in a real oven. Then there's barbecue.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Michael A. Terrell]

Jeff Liebermann wrote:

Red is LED. Orange could be vacuum fluorescent or LED. I'll be on
LED.

It could also be an orange VFD behind a red filter.


--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

 

[N_Cook]

Angelo Campanella <a.campanella@att.net> wrote in message
news:igflvh$9qr$3@speranza.aioe.org...

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:K7adnTQAfL-lN7fQnZ2dnUVZ_vqdnZ2d@earthlink.com...
Jeff Liebermann wrote:
The bad news is that if all the digits are equally bad and they're
individually unpluggable, then it's probably something in the
electronics. Stuck digits and working timer sounds like a display
multiplexer/driver circuit. It would probably cost less to replace
the oven than repair it, but such an old Amana is a collectors item
and is probably worth restoring. I'm rather surprised that the
magnetron is still functional.

I checked to output by measureing the time to boil an 8oz cup of
water.
The tag say 700 watss of cooking power, and my timing result was
approximately that... close enough to sy the magnetron was still OK.

What color is the display?

Red. LED seems pausible.

VFD were common in early microwaves.

I can see blinking when I san my gaze across it, so it's swithced
likey
at 60 Hz or 120 Hz.

If it's not a power supply bus, then it's a bus driven by logic. I
just
don't have a schematic for that generic sort of diplay logic.

I know you guys recommend that I replace it, but I don't see anything
I
like. The chamber is nice and big... I've been eating meals prepared in it
for over two years now. Soups and pastas, coffee every day... It's my
mechanical mama.

Ange

So what are some of the numbers on the chips inside and any numbers seen on
the sides of the display/s ?

 

[William Sommerwerck]

The chamber is nice and big... I've been eating meals
prepared in it for over two years now. Soups and pastas,
coffee every day... It's my mechanical mama.

I think you might find it useful to learn how to cook. Think
of it as chemistry and not an art form. Microwave cooking
is ok for many things, but there's plenty of dishes that are
best cooked over a flame, on a grill, or in a real oven. Then
there's barbecue.

A microwave oven doesn't actually "cook" anything -- it just heats it. That
works great with soup, pasta, bacon, and a few other things.

Have you seen Betty Crocker "Warm Delights"? It's actually a repurposing of
her awful microwave brownies (which were actually more trouble to make than
regular brownies).

 

[Jeff Liebermann]

On Mon, 10 Jan 2011 23:05:57 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Jeff Liebermann wrote:

Red is LED. Orange could be vacuum fluorescent or LED. I'll be on
LED.

It could also be an orange VFD behind a red filter.

Touche. Actually, I think we both goofed. Vacuum fluorescent
displays were blue-green and aren't made in orange or red. However,
plasma discharge displays were red or orange. Maybe one of the exotic
incandescent 7 segment displays? This gives a good survey of the
available display technologies:
<http://www.vintagecalculators.com/html/calculator_display_technology.html>

As for my cooking (or warming), everything I try to cook or warm is an
experiment. Sometimes it works, but more often not. Some of it is
actually edible. Maybe if I read and follow the instructions?

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Angelo Campanella]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:igh3nm$i55$1@news.eternal-september.org...

So what are some of the numbers on the chips inside and any numbers seen
on
the sides of the display/s ?

I managed to pry out 7-segment digit #2 chip for inspection.

It's an HP 5082-7730 609-C, 19mm x 10 mm, 14-pin (3 missing) pluggable chip.

It has a matte face, transparent at the 7 segments to interior solid state
material.

The bottom side is filled with clear pink potting where a PC board holding
the pins is visible.

Ange

 

[Michael A. Terrell]

Jeff Liebermann wrote:

On Mon, 10 Jan 2011 23:05:57 -0500, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Jeff Liebermann wrote:

Red is LED. Orange could be vacuum fluorescent or LED. I'll be on
LED.

It could also be an orange VFD behind a red filter.

Touche. Actually, I think we both goofed. Vacuum fluorescent
displays were blue-green and aren't made in orange or red. However,
plasma discharge displays were red or orange. Maybe one of the exotic
incandescent 7 segment displays?

The RCA Numitron? I may still have a datasheet. I considered them
for a portable homebrew frequency counter, till I saw how much power
they wasted. I ended up using 10 VFD display tubes with wire leads.
After assembly, I used a thin line of contact cement to keep them
aligned. I built my first switching power supply to provide all the
required voltages. This was in the late '70s or early '80s

This gives a good survey of the available display technologies:
http://www.vintagecalculators.com/html/calculator_display_technology.html

As for my cooking (or warming), everything I try to cook or warm is an
experiment. Sometimes it works, but more often not. Some of it is
actually edible. Maybe if I read and follow the instructions?

I use a crock pot for a lot of cooking.


--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

 

[Spehro Pefhany]

On Tue, 11 Jan 2011 13:06:03 -0500, the renowned "Angelo Campanella"
<a.campanella@att.net> wrote:

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:igh3nm$i55$1@news.eternal-september.org...

So what are some of the numbers on the chips inside and any numbers seen
on
the sides of the display/s ?

I managed to pry out 7-segment digit #2 chip for inspection.

It's an HP 5082-7730 609-C, 19mm x 10 mm, 14-pin (3 missing) pluggable chip.

It has a matte face, transparent at the 7 segments to interior solid state
material.

The bottom side is filled with clear pink potting where a PC board holding
the pins is visible.

Ange

That's just a regular old 0.3" seven-segment common-anode LED display,
like the old Monsanto MANxxx displays.

http://www.datasheetcatalog.org/datasheets2/31/319472_1.pdf

Extremely low efficiency by modern standards, but good quality for the
day.

We've got an antique Amana Radarrange with similar red LED displays.

Here's a more modern equivalent that is pin-compatible:
http://www.kingbrightusa.com/images/catalog/SPEC/SA03-11EWA.pdf
(but more than 10x as bright at the same current)


But it's not likely the displays that are causing the problem-
probably the drivers or some connections or circuitry further back.





Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Spehro Pefhany]

On Tue, 11 Jan 2011 21:12:40 -0500 Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

On Tue, 11 Jan 2011 13:06:03 -0500, the renowned "Angelo Campanella"
a.campanella@att.net> wrote:


"N_Cook" <diverse@tcp.co.uk> wrote in message
news:igh3nm$i55$1@news.eternal-september.org...

So what are some of the numbers on the chips inside and any numbers seen
on
the sides of the display/s ?

I managed to pry out 7-segment digit #2 chip for inspection.

It's an HP 5082-7730 609-C, 19mm x 10 mm, 14-pin (3 missing) pluggable chip.

It has a matte face, transparent at the 7 segments to interior solid state
material.

The bottom side is filled with clear pink potting where a PC board holding
the pins is visible.

Ange


That's just a regular old 0.3" seven-segment common-anode LED display,
like the old Monsanto MANxxx displays.

http://www.datasheetcatalog.org/datasheets2/31/319472_1.pdf

Extremely low efficiency by modern standards, but good quality for the
day.

We've got an antique Amana Radarrange with similar red LED displays.

Here's a more modern equivalent that is pin-compatible:
http://www.kingbrightusa.com/images/catalog/SPEC/SA03-11EWA.pdf
(but more than 10x as bright at the same current)

(well, pin compatible on the segments, but it has a right-hand decimal
point rather than the rare left-hand on the microwave oven, so not
really 100% compatible...)


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Angelo Campanella]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:igbtmv$6vq$1@news.eternal-september.org...

I assume it has a dedicated LED driver, that sort of age probably internal
metalisation drift inside the chip or die carrier.

True... but which component? "Driver" comes to mind.
But I have no schematic to identfy components. The model numer is

Model: RR6W, P72110-4M
S/N: H56559799
1600 Watts

(I recently measured it as 1,480 watts when running empty.)

Mfg Date May, 1976.

The cook space chamber is over a cubic foot in volume (14"x14"+x9"+).

Will it go to a museum?,

It could... for a price.

I would not have said uwave ovens were around in 1976

They came out that year or the year before. This unit is:
Ange

 

[Angelo Campanella]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:j61ji6h03itt4sergf1aj4g1poaan05ga8@4ax.com...

On Sun, 9 Jan 2011 00:10:53 -0500, "Angelo Campanella"
a.campanella@att.net> wrote:

I suspect it to be a power supply problem somewhere in the + busses, or
possibly a common ground not making ground. But I have no clue as to where
to start probing. Each digit is red gas discharge unit, unpluggable from
their socket... really ancient... 1976 vintage.

Sounds more like a Nixie tube. Red would mean LED. 1976 vintage
would probably be red LED. How about making life easier and disclose
the Amana (Radar Range) model number?

Model: RR6W, P72110-4M
S/N: H56559799
1600 Watts

(I recently measured it as 1,480 watts when running empty.)

Mfg Date May, 1976.

The bad news is that if all the digits are equally bad and they're
individually unpluggable, then it's probably something in the
electronics. Stuck digits and working timer sounds like a display
multiplexer/driver circuit.

I need a schematic, or a generic schematic to hunt down the bad driver.

It would probably cost less to replace
the oven than repair it, but such an old Amana is a collectors item
and is probably worth restoring. I'm rather surprised that the
magnetron is still functional.

I checked it via boiling time for a cup of cold watrer... it's close to the
rated 7oo watts.

ange

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Angelo Campanella]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:igc7sr$cku$1@news.eternal-september.org...

Nixie tubes were relatively expensive. I don't think any microwave oven
used
them. Certainly not in 1976, when LEDs were common and cheap.

If all the lower-left segments are on continuously, I'd suspect a problem
in
the logic driving them.

True... soemthing common to all 4 digits.

Ange