HP-2116 front panel lamps

dwight dkelvey at hotmail.com
Wed Jul 25 11:42:01 CDT 2018

It might be worth saving the bases and buying "grain of wheat" lamps to rebuild the lights. I see ~70ma 6v lamps available. That sounds similar to the original specification.


From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Brent Hilpert via cctalk <cctalk at classiccmp.org>
Sent: Wednesday, July 25, 2018 8:21:58 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: HP-2116 front panel lamps

On 2018-Jul-25, at 6:47 AM, Christian Corti via cctalk wrote:
> On Wed, 25 Jul 2018, it was written
>> Christian, when I was restoring the HP Computer Museum's 2116A I ordered a
>> bunch of these 345 bulbs from 1000bulbs.com - but it seems they no longer
>> stock them.
>> I did find this listing though which looks current...
>> https://www.lighting-pros.com/eiko-345-t-1-3-4-midget-flanged-sx6s-case-of-1
>> 0
>> They are around 0.04A current draw - not 0.75A!
> Yes, the Installation and Maintenance Manual on bitsavers (02116-9153_2116B_Vol2_Oct70.pdf) contains several errors.
> Interesting enough, my printed copy of this manual from 1968 (that is completely different from the 1970 one; it only has parts lists and schematics, the chapters for installation and maintenance are simply not there) is right: 2140-0035  6.3V 0.04A
> In the meantime I've ordered a bunch of JKL 345 from Mouser (60 Ecent/piece)

To mention, they are actually run below-spec in the processor, which of course improves longevity and reduces the heat next to the plastic front panel.

>From actual measurements in my 2116C the lamps (CM345) draw:
                register-bit positions:           ~  31ma @ 4.1V
                inside the push-buttons:          ~  36mA @ 5.4V

                compared to the spec:     40mA @ 6V

( I obtained CM345s from Mouser in 2013.  "95 in stock", that would have left 83 after my purchase).

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