Booked in by shop as a 'Bingo calling unit'. It has a large 5 digit 7 seg
display made from discrete LEDs. Has two 5 digit BCD encoded switch units to
set start and end number. Has jack input to which is connected a hand-held
push button unit. Chip date codes indicate that this thing is from 1981. It
looks 'professionally' hand built, if you see what I mean. It has stickers
on with a company name, but that could be largely meaningless. Two problems
reported. First that it had a problem with the LEDs, and secondly that it
had "lost its memory".

LED problem was straightforward enough. One segment of one digit was not
lighting due to one LED in the series chain of five which made up the
segment, being open circuit. A replacement LED restored that.

Now, the second problem. For playing bingo, the start number would be set to
"1", and the end number to "90". All ok so far, and if this is done, it does
indeed generate random numbers in the range 1 to 90, one per button push.

The next requirement is that the unit is going to need to know for any game
in progress, which of the numbers between 1 and 90 that it has already
produced so that they are not duplicated, and this is where it all goes tits
up.

After a while, numbers *do* start to duplicate. If you set the start and end
numbers to say "1" and "10", it might take 15 button pushes to get all ten
numbers out, the other five being one or more times dups.

So I have a good look at what's in it. 2 x 4027 dual J-K, 3 x 4011 quad
NAND, 2 x 4081 quad AND,
1 x 4040 12 stage counter, 1 x 4020 14 stage counter, 1 x 555 timer and
last but not least, 1 x MK50395 decoder / driver. Now I don't know if I'm
just being dumb-arsed here, or having a senior moment, but I'm buggered if I
can see any chips in that line up that could form a memory and comparator
for potentially 99999 numbers. Or even for 90 numbers come to that ... If
this is what it was meant to do, even back in '81, I would have expected to
see a couple of CMOS memory chips, and a Z80 or 8080 processor, maybe.

What am I missing here ? Could it be that they are mistaken in thinking that
it can be used to properly call a game of bingo ? Is it in fact a raffle
ticket drawing machine, where you would set the serial numbers of the first
and last tickets sold out of a batch of perhaps 1000 and then draw maybe 10
prize ticket numbers with the chances of it duplicating any when it's only
generating ten random numbers out of a pool of 1000, being at worst, slim ?

Haven't managed to get hold of the owners again yet to check if they feel
that it has ever worked as a bingo calling machine, but at the moment, my
feeling is that it is a 'new acquisition' to some little club, and that it
has been given to them after sitting long forgotten in an attic somewhere
for 20 years.

Any thoughts anyone ?

Arfa