24 Oct
2009
24 Oct
'09
6 p.m.
I also found this:
http://www.pdp8.net/tu56/tu56.shtml
in which Dave G. describes a successful use of the CM2182 (14V,
80ma) bulb in this application.
I just replaced one of them again last week so I had taken a picture of
the indicator disassembled.
It is now up at
http://www.pdp8online.com/tu56/pics/p1000839.shtml?small
If your TU56 -15V input is high you may run this bulb above its rated
voltage shortening its life.
24 Oct
24 Oct
7:03 p.m.
djg at pdp8.net wrote:
Some sizes of those bare-lead grain-of-wheat bulbs are or were used for
front-panel backlighting in digital car stereos, generally 12V of course.
Places that repair car-stereos may be an adeqaute source, Radio Shack sold some
sizes as of a few years ago.
I also found this:
http://www.pdp8.net/tu56/tu56.shtml
in which Dave G. describes a successful use of the CM2182 (14V,
80ma) bulb in this application.
I just replaced one of them again last week so I had taken a picture of
the indicator disassembled.
It is now up at
http://www.pdp8online.com/tu56/pics/p1000839.shtml?small
If your TU56 -15V input is high you may run this bulb above its rated
voltage shortening its life. 
8:20 p.m.
On 24 Oct 2009 at 19:03, Brent Hilpert wrote:
Some sizes of those bare-lead grain-of-wheat bulbs are
or were used
for front-panel backlighting in digital car stereos, generally 12V of
course. Places that repair car-stereos may be an adeqaute source,
Radio Shack sold some sizes as of a few years ago.
Would not a #7220 T-1 wire-lead lamp work in this application?
(18volt .026 amp)?
--Chuck
25 Oct
25 Oct
11:51 a.m.
I recently had to find some "grain-of-rice" lamps to replace those burned
out in the illumination side of an HP 2748B optical paper tape reader.
These guys,
http://www.jkllamps.com/
had an exact replacement. My requirement was to find an exact physical
match because the bulbs have to fit down inside a machined well that
lines up with the holes in the tape. They have plenty of datasheets
with both mechanical and electrical specs for all their bulbs. I am a
happy customer.
Chris
--
Chris Elmquist
26 Oct
26 Oct
3:49 a.m.
Hi Chris,
Thank you for the link!
I recently had to find some "grain-of-rice"
lamps to replace those burned
out in the illumination side of an HP 2748B optical paper tape reader.
And? Which
lamp did you use? That device is not too uncommon. So it
would probably good to know. My lamp is still ok. But I don't really use
the machine.
Regards,
Philipp
8:47 a.m.
New subject: HP 2748B bulb replacement
On Monday (10/26/2009 at 11:49AM +0100), Philipp Hachtmann wrote:
Hi Chris,
Thank you for the link!
Hi Philipp,
My apologies for not telling the whole story.
I used the JKL model #7153 to replace the lamps in the HP2748B.
There are 10 lamps in series in that unit and a pot that adjusts the
brightness of all of them together. There's approx 50V across all ten,
so each bulb should see about 5V across it. One of the lamps is used as
a reference and does not shine across the tape. Nine of them do though,
eight are data holes and one is the feed hole.
The #7153 bulbs were US $0.75 each so I bought 20 of them as a life-time
supply.
There is a small PCB inside the head of the 2748B which these 10 bulbs
are soldered to. It's a bit tricky to align the bulbs with the holes
in the head once you have removed this PCB but I had luck poking and
pushing them with a small screwdriver until each one dropped into place.
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.
Chris
--
Chris Elmquist
I recently had to find some
"grain-of-rice" lamps to replace those burned
out in the illumination side of an HP 2748B optical paper tape reader.
And? Which
lamp did you use? That device is not too uncommon. So it
would probably good to know. My lamp is still ok. But I don't really use
the machine.
28 Oct
28 Oct
10:11 a.m.
New subject: HP 2748B bulb replacement
My apologies for not telling the whole story.
:-)
...so I bought 20 of them as a life-time
supply.
Hm, how old are you?!?
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.
Regards,
Philipp :)
12:52 p.m.
New subject: HP 2748B bulb replacement
My apologies for not telling the whole story.
:-)
...so I bought 20 of them as a life-time
supply.
Hm, how old are you?!? 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"
One minor problem is that the 2748A doesn't use TTL levels. It's a minor
problem because on the -B you have a 'TTL clamp' jumper on the interface
connector, if you fit that then you gry 5V outputs. The -A model doens't
have this., but interesting the output circuity will give TTL levels if
connected ot a TTL input terminated to +5V and ground by the appropirate
pair of reuistors (which just happen to be the ones used in the 11202)
-tony
3:22 p.m.
New subject: HP 2748B bulb replacement
On Wednesday (10/28/2009 at 06:11PM +0100), Philipp Hachtmann wrote:
ah... 47. It'll be a race to see if I can outlast the bulbs ;-)
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
-- Chris Elmquist
...so I bought
20 of them as a life-time
supply.
Hm, how old are you?!? 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.
26 Oct
26 Oct
12:12 p.m.
I recently had to find some "grain-of-rice" lamps to replace those burned
out in the illumination side of an HP 2748B optical paper tape reader.
These guys,
http://www.jkllamps.com/
had an exact replacement. My requirement was to find an exact physical
Although my 2748 (a -A model) is currently working fine, and I even have
a complete spare read head for it (picked up on E-bay), I would be
interested to know what the replacement lamps are.
-tony
25 Oct
25 Oct
11:57 a.m.
From: "Chuck Guzis":
Would not a #7220 T-1 wire-lead lamp work in this
application?
(18volt .026 amp)?
I think that should work fine. The only reservation I'd have about
it would be whether it was bright enough. It looks from the spec's
to be about half as bright as some of the other bulbs talked about.
Vince
24 Oct
24 Oct
7:59 p.m.
New subject: PDP 8/e Problem
Hello, everyone,
This weekend I decided to spend some time and fire up my PDP 8/e system.
It's been a while, and figured it was overdue for a few hours of
runtime.
The machine has EAE, 2 8K DEC Core memory units, an 8K solid state
memory board (12x8 1K static RAMs) the extended memory/timeshare option,
a PC8E paper tape interface with a PC04 reader/punch, an RX8E controller
and dual RX01 drives, and (not installed) an RK8E controller (currently
busted) with two RK05 drives, and two M8650 serial I/O interfaces.
It powered up just fine, and I toggled in a few little test programs. I
couldn't get it to talk to the terminal (a Heathkit H19). Then, I tried
a test program that runs the punch...it too would not work. Then, I
toggled in a little program that uses the OSR (OR Switch Register)
instruction, and it too wouldn't work...the accumulator remained
untouched by this instruction no matter what the state of the switch
register was.
I did some other testing, AND and TAD work, as does ISZ, and as many of
the group 7 operate instructions that I bothered to test. DCA also
works fine, as do JMP and JSR.
I could load extended address from the front panel, and address memory
beyond 4K with no problems, so at least the extended memory part of the
ext. mem./timeshare option was working.
I also noted that the HLT instruction doesn't work. So, IOP
instructions, OSR, and HLT are on the list of instructions that don't
work. It appears that these instructions just act as a No-Op.
I tried stripping the system down to just the CPU, EAE, 8K of Core, and
the console async. interface, and it still behaves the same.
It seems like the instructions that aren't working are those that would
be trapped by the timeshare option, but with that board removed from the
system, the fact that the behavior didn't change is of concern.
Anyone have any ideas what might be going on?
Thanks in advance for any help.
Rick Bensene
25 Oct
25 Oct
5:57 p.m.
New subject: PDP 8/e Problem
At 10:59 PM 10/24/2009, Rick Bensene wrote:
Hello, everyone,
I also noted that the HLT instruction doesn't work. So, IOP
instructions, OSR, and HLT are on the list of instructions that don't
work. It appears that these instructions just act as a No-Op.
That sounds like the timesharing restrictions being turned on all of
the time. I'd try pulling the KM8E and see if the IOTs start working
right. If so, the "timeshare enabled" logic is on all of the time.
-Rick
7:07 p.m.
New subject: PDP 8/e Problem
Rick Murphy wrote:
That sounds like the timesharing restrictions being
turned on all of the
time. I'd try pulling the KM8E and see if the IOTs start working right.
If so, the "timeshare enabled" logic is on all of the time.
-Rick
Hm, he wrote the following:
I tried stripping the system down to just the CPU,
EAE, 8K of Core, and
the console async. interface, and it still behaves the same.
That implies he tried
without timeshare... The memory will work without.
Of course only the lower 4K...
If the instructions don't start working without memory
expansion/timeshare control plugged in, I'd begin to track the "user
mode" signal on the Omnibus - if it has the correct level - and the
logic listening to it...
Regards,
Philipp
28 Oct
28 Oct
10:15 a.m.
I just replaced one of them again last week so I had
taken a picture of
the indicator disassembled.
It is now up at
http://www.pdp8online.com/tu56/pics/p1000839.shtml?small
Wow! That looks like out
of the factory - or did you put it into a
dishwasher?
Btw I don't recommend putting TU56s into the dishwasher - at least the
motors. I got one unit that had have a time underwater. It looks very
good, but the water stayed in the motors and they were rusted. Stuck.
Had to disassemble and clean them a bit - the unit works fine again
(after some usual repairs). But it's also the drive with all lamps blown..
Regards,
Philipp
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-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
chrise＠pobox.com -
djg＠pdp8.net -
hachti＠hachti.de -
hilpert＠cs.ubc.ca -
rick＠rickmurphy.net -
rickb＠bensene.com -
vrs＠msn.com