Heathkit ID-1790
 

Hi all ....

I just assembled a Heathkit ID-1790 Digital Rain Gauge. I found it on
eBay - unassembled! - for $182.00 and believe I got a good deal. It's also
a good match for my ID-4001 weather station. (See
http://www.qsl.net/n4cro/weather.html Shack photo is at
http://www.qsl.net/n4cro/radioroom.html ) Someone had obviously been into
the kit - in particular a necessarily plastic screw used to hold a
transistor had the head ripped off - strain relief installed on AC cable -
many parts in odd boxes, one a round plastic one for electrical tape, but I
completed the kit with minimal scrounging and everything is working except
the numeric display is dim on both long term and short term displays, even
though the decimal points from the very same LED show fine. Only the 7
numeric segments are dim. The decoder/driver chips are six 14511 IC's
(Heath part 443-699), one for each of the 7 segment, dual decimal point
LED's.

Is this typical of this unit and does anyone have a suggestion how to
brighten up the numbers ?

THANKS and 73!
Bill Stewart, N4CRO

Bill Stewart wrote:

I just assembled a Heathkit ID-1790 Digital Rain Gauge. I found it on
eBay - unassembled! - for $182.00 and believe I got a good deal. It's also
a good match for my ID-4001 weather station. (See
http://www.qsl.net/n4cro/weather.html Shack photo is at
http://www.qsl.net/n4cro/radioroom.html ) Someone had obviously been into
the kit - in particular a necessarily plastic screw used to hold a
transistor had the head ripped off - strain relief installed on AC cable -
many parts in odd boxes, one a round plastic one for electrical tape, but I
completed the kit with minimal scrounging and everything is working except
the numeric display is dim on both long term and short term displays, even
though the decimal points from the very same LED show fine. Only the 7
numeric segments are dim. The decoder/driver chips are six 14511 IC's
(Heath part 443-699), one for each of the 7 segment, dual decimal point
LED's.

Is this typical of this unit and does anyone have a suggestion how to
brighten up the numbers ?

What is the current going through a given LED segment?

What is the Vcc on the LED display driver chip?

LEDs will go dim as they age, but more likely are bad capacitors pulling
the rails down. Check with the meter.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."