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

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

Reply to
Angelo Campanella
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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

Reply to
N_Cook

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.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Reply to
Jeff Liebermann

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.

Reply to
William Sommerwerck

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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.

Reply to
nesesu

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.
Reply to
Michael A. Terrell

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.

Red. LED seems pausible.

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

Reply to
Angelo Campanella

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"+).

It could... for a price.

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

Reply to
Angelo Campanella

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

1600 Watts

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

Mfg Date May, 1976.

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

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

ange

Reply to
Angelo Campanella

True... soemthing common to all 4 digits.

Ange

Reply to
Angelo Campanella

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.
Reply to
Michael A. Terrell

Impressive.

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

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

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.

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

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
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Reply to
Jeff Liebermann

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.
Reply to
Michael A. Terrell

OK, it's gotta be LED.

Set recently but again, but here again:

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

1600 Watts (I recently measured it as 1,480 watts when running empty.) Mfg Date May, 1976.

1- War stories of new microwaves, mostly of Pacific Rim manufacture, failing after a few years of service.

My son bought me a new one a Christmas go, but it turned out to be smaller and of Pacific Rim manufacture, so I gave it back to him to give to somebody else. This Amana is still the war horse.

2- I like this size (over a cubic foot). I think I'd like another Amana... I think Raytheon bought them out some years ago. The name is still around. I looked up their web age, and several models are available . A cubic foot+ unit cost about $150 last year... It's in he back of my mind.

I'm looking for a human replacement, but so far no luck.

To keep my weight down, I eat a lot of salads; they require no cooking. I cook soups from scratch and spaghetti & pastas with the u-wave. I eat very little meat, mainly chicken, since red meats are heavy and affect my blood pressure. I eat most anything on special occasions only.

Cooking, especially frying, sends all kinds of odors into the house (3-bedroom ranch, closed tight in the winter) that odiferate for hours later... I eat meats mainly when eating out with friends.

The other son gave me a Forman burger grille. I only used it once. It really smelled up the house . The range hood was not really of much help. The Forman grille is best used outdoors.

Back to my Amana RR6W, my only hope to get display functioning back is to identify the failed component (driver chip?), or replace the entire panel module... both of which seem highly unlikely. This news group is about the place I can find to even have an intelligent discussion on the matter. What is needed is an old-timer that remembers the 7 digit LED display technology of the '70's and also know the Amana microwave oven use of them.

Getting that circuit board out in the clear to work on it seems to be nigh impossible. It is in place behind and parallel to the numbers panel. But its back side is shielded over 2/3 its area with the power supply and its heat sink. Numbers are on the top end. The bottom end is not in a connector slot, but rather it's stationary with power supply bus wires and switching relay control wires soldered in place.

Ange

Reply to
Angelo Campanella

water.

likey

just

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

Reply to
N_Cook

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).

Reply to
William Sommerwerck

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:

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
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Reply to
Jeff Liebermann

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

It's a 19mm x 10mm 14 pin (3 pins not present) HP5082-7730 609 C.

The face is a transparent matte plastic surface that seem to have red solid state material for each of the 7 segments over the interior material.

The back side, between pin rows, is pink transparent potting that covers a PC board holding the 14 (really net 11) pins.

Ange

Reply to
Angelo Campanella

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

Reply to
Angelo Campanella

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

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.
Reply to
Michael A. Terrell

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