HP 2748B bulb replacement
chrise at pobox.com
Wed Oct 28 17:22:37 CDT 2009
On Wednesday (10/28/2009 at 06:11PM +0100), Philipp Hachtmann wrote:
>> ...so I bought 20 of them as a life-time
> Hm, how old are you?!?
ah... 47. It'll be a race to see if I can outlast the bulbs ;-)
>> I haven't finished my microcontroller interface to the 2748B yet but the
>> tests in the service manual indicate that the replaced bulbs are doing
>> the job nicely.
> That belongs to a minicontroller instead a microcontroller....
> You can just hook it up to your pc. I have a printer port "paper tape"
> reader that can be used by "cat tape > /dev/lp0" and connects to my
> H316. Behaves like the real thing - but incredible fast. Needed 2 or 3
> TTL ICs... So the other direction could not be much more complicated.
Nah. I want it on a serial port... which ultimately hooks to a terminal
server or various other vintage microcomputers here. The microcontroller
will understand DC2/DC4 reader on/off control from the host back to it
and optionally insert some EOF/EOT character when end of tape is detected.
This is not a hard problem you are correct... most of the time is spent
in wiring it up, machineing the enclosure, etc. But that's all stuff I
like to do. I tend to throw hardware at these problems and in my little
world, embedded processors qualify as hardware.
One thing I learned about the 2748B is that it wants to output 12V
logic levels (unless you install the 5V clamp on the I/O connector).
I was uncomfortable depending on that connection via the connector to
engage the internal zener to clamp it... so I built my circuit to accept
the 12V levels and then leave the 2748B in its default configuration.
I'll have this thing going in a few more days...
Did you mean that you have a paper tape ** PUNCH ** that can be used
by "cat tape > /dev/lp0" ?? I assume that's what you meant since that
cat operation would be outputting stuff not inputting it.
-- Chris Elmquist
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