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A working HP-2116B Minicomputer

M

mpatoray

Experienced Member
Joined
Oct 19, 2005
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76
Location
New Middletown Ohio
Hi all,

I just wanted to share a little bit of news on a project i have been working on with my friend Dave. It is his HP-2116B minicomputer. This was HP's second computer with the first being the 2116, a general purpouse computer although it was really aimed and sold as a device to interface with HP test equipment of the era, used to control and gather data from the equipment.

This particular machine has 16K of core memory, a paper tape reader interface card, and several terminal interface cards.

I was able to find a NOS TwistLock connector for the long outr of production one that is on the back of the computer, and then I made a very stout TwistLock to 15A Edison power cable.

After rack mounting the 18U high box into a similar vintage HP rack last week, we pulled all the cards out and did a "smoke test" using the Power Supply output test points on the front to make sure things where not too bad.

This past Saturday Dave and I toggled in the acceptance program as outlined in the HP manual and everything came out as expected.

We then toggled in a simple blinking lights program and where able to run that. There are a few issues that need to be sorted out.

The next plan is to mount and cable up the paper tape reader and a terminal of some sort and then run more advanced diagnostic programs on it.

Matt
 

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Impressive system. Looks like an attractive set of bulbs. Do you know what year it's from?
 
The system is from 1968. I agree it is a good looking front panel, a few of the light bulbs had burnt out and had to be replaced.
 
Indeed, very nice looking machine. The front panel resembles the one of a straight PDP-8.

BTW. Is this machine TTL chip based or does it have some other chip family like DTL? There were some different competing SSI chip families competing in those days. The later HP21MX we have seems to be all TTL, but there is a -2V used for something. I think I read somewhere that there were some chips in the I/O interface that were not TTL and thus needed the -2 V. But I am not at all sure about this.
 
From a website about the 2100 series.

"The early models are based primarily on Fairchild CTµL small-scale integrated circuits. CTµL (Complementary Transistor MicroLogic) was one of the first IC logic families, dating from the mid-1960s. Supply voltages for the logic are +4.5V and -2V.

TTL ICs, and perhaps some DTL, also show up on many of the I/O interface boards and some other boards for these early models, running (marginally) off the 4.5V supply. Such boards may have a combination of CTµL and TTL ICs on them.

The 2100 models use a mixture of TTL and CTµL.
 
mpatoray said:
From a website about the 2100 series.

"The early models are based primarily on Fairchild CTµL small-scale integrated circuits. CTµL (Complementary Transistor MicroLogic) was one of the first IC logic families, dating from the mid-1960s. Supply voltages for the logic are +4.5V and -2V.
Click to expand...

Is it possible to find replacement CTµL chips anywhere nowadays? Sometimes it is even tricky to find certain TTL parts. Or have you been lucky that it was working rightaway?
 
It did the proper "HP Thing" when power was applied and fired right up. We first powered up with the cards backed out of the edge connectors just in case something was horribly wrong with the PS, but all the voltages checked low on the test points, and low will not damage things so we reseated the cards and powered back up.

There is an issue with 2 bits in the core not setting properly, more investigation will be done as it could just be some out of spec core driver transistors( they push a lot of current) or an out of spec bias compensation thermistor.

Yes those Fairchild logic chips are made of pure unobtanium now.
 
So, not sure if this really relates but doing a completely unrelated search on my phone I ended up on this site about the hp 21xx series computer and emulating a paper tape reader. The interesting part is they have some software linked if they're not dead. Just thought it might be of interest.
 
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