Sorry Pat, as I couldn't find much of interest in the UK I was searching on ePay.com for digital counters & voltmeters and that is how I found the Dana, I'm looking forward to the teardown too.
I did end up buying this reversible counter though.
(Attachment Link)
David
Whoops!! I'm afraid I wound up costing you about $25, then - I took a crack at that one, too, as I'd never seen that model listed before. That's the danger of a bunch of us having similar interests. Sorry! I'd been watching it for months (he previously had it listed at $199 for a loooooong time). I'd like to see the inside of it when it gets to you, and it's nice to know it will be going to a good home.
-Pat
It's OK an extra $25 is very little compared with the international shipping & import fees, it looked unusual enough & as I didn't have a HP reversible counter in my collection I decided to bid for it, it also seems to be the third HP item I have that I can't find in any of the catalogues.
Anyway I collected the HP K20-5280A counter from the local ParcelFarce depot & paid my fees last Friday, the seller did an excellent job of packing it in a large box with plenty of foam chips & bubble wrap all round
, if only others would do the same.
After a quick check to see nothing had come loose inside, I decided to test it with the HP 3310A and found that it seems to work fine using either input A for counting up or input B for counting down, not tried both at once yet for the A-B, A+B or other functions.
Inside there are quite a few unpopulated connectors on the motherboard for other option cards.
The power supply section seems to be the same as used in the 5325A and a few others.
Input board with reed relays for the attenuators and two separate counter? cards.
Function boards and main up/down counter & display board.
There is space on the main counter & display board for an extra Nixie, but I suspect that finding an extra 20pin 1820-0732 up/down counter IC would be impossible, given that I can't find anything about it, or any other TE that uses it.
Does anyone know why the 1820-0732 IC's have bare sockets instead of the plastic ones?
David
P.S. I found a picture of another K20-5280A on the web with what looks like a preset function, there is one the same in nixiefreqq's "wall of nixie" picture on here too.