Sperry PC/HT Model 3070-02 -- PC/XT Compatible -- Help Requested on Keyboard

bansod · 29 Jul 2020, 21:56

I am looking for a keyboard (lost the original one) for a Sperry PC Model 3070-02, aka Sperry PC/HT. Every keyboard I have tried I get the - .... . set of beeps indicating missing keyboard.

Does anyone know what keyboard I would need? The keyboard socket takes a 5 pin DIN plug (fatter than the 6-pin used with IBM PS/2. It seems there are 2 IBM 5 pin DIN plug keyboards (PC Type 1 and XT Type 2) [see: https://en.wikipedia.org/wiki/IBM_PC_keyboard ]. There is also a Model F (PC/XT) which might be same as Type 2? Or did Sperry use a completely different type?

I have tried using a PS/2 keyboard with a 6-pin to 5-pin adapter, and also an Elite KB-5181 which does have the 5 pin DIN connector. Neither has worked. I think the problem is that the keyboard needs to support XT protocol, not AT protocol, in addition to having the right physical connector.

I've done some checking, seems like the Elite KB-5181 is really a Chicony KB-5181. It is supposed to have a switch to select between AT and XT protocol, but some versions don't have that switch and of course mine doesn't. So, would anyone know how to still convert it to XT protocol?

I am attaching a few photos of the circuit board inside the keyboard case (and also of the Sperry PC). There appear to be some jumper wires (J64, J65) and a provision for two switches (SW1 and SW2), is there maybe a way to do something with those to convert to XT?

Any advice is much appreciated!

juspek · 29 Jul 2020, 22:58

Not familiar with that keyboard, but according to the time stamp on the controller chip of Chicony it is made after week 29 of 1994. So not sure if it still supports XT protocol.

hasu · 01 Aug 2020, 06:51

Probably SW1? Share your result.
wiki/File:ARC_KB-5181_--_assorted_2.jpg
wiki/Chicony_KB-5181#Cherry_MX_blue_switches

As you already found AT2XT converter is another option.
http://www.vcfed.org/forum/showthread.p ... post370330

bansod · 12 Aug 2020, 23:45

@hasu -- thanks for the pictures etc (and sorry for the late reply, I was tied up last week).

I will definitely try SW1 -- I assume it is simply an on-off switch, and since there is none there right now (in other words open), that presumably is for AT and if I short it I should switch to XT? Please do let me know if that seems right.

Thanks again!

bansod · 16 Aug 2020, 00:38

Reporting back -- it worked!

SW1 was in a closed state -- there was a blob of solder acting as a jumper on the board between the SW1 contact points (there is of course no switch actually mounted there in my keyboard). Removed (desoldered) the blob and now it works with my Sperry PC! I guess this indicates closed is AT protocol and open is XT protocol and the keyboard firmware version does still support both protocols.

Thanks for all your help.