29 May
2015
29 May
'15
3:54 p.m.
JOOI, does anyone know when Panaplex 7-segment displays started going the
way of the dodo, to be replaced with LED displays (and, on the back of
that, what were the advantages of a Panaplex-type display over an LED one?)
I just saved a few boards from a dumpster with such displays on (they're
actually Beckman ones, not Burroughs), but I was a little surprised to see
IC dates into 1981; I thought by then things had moved over to LED.
I'm almost certain that they're from old gas pumps - maybe the displays are
just more readable in bright sunlight than LED? (there's a sticker on one
of the PSU boards with a 'shipping date' in 1999)
cheers
Jules
29 May
29 May
6:53 p.m.
On 2015-May-29, at 3:54 PM, Jules Richardson wrote:
JOOI, does anyone know when Panaplex 7-segment
displays started going the way of the dodo, to be replaced with LED displays (and, on the
back of that, what were the advantages of a Panaplex-type display over an LED one?)
Panaplex and other 7-seg gas discharge displays were used in calculators up to the
mid-70s. Actually one of the last uses in a calculator might be the HP-9815 (1975/6):
http://www.cs.ubc.ca/~hilpert/eec/calcs/HP9815A.html
They were mostly used in desktops for the sake of the larger digit size but there were
some pocket/handheld calcs that used the smaller versoions. In calcs, they were largely
superseded by vacuum-flourescent displays which were easier to drive, had a longer life,
and could also be made with bright, large digits.
Heathkit used them in some items into perhaps the late 70s.
They were also extensively in arcade/pinball games, as I'm sure many will recall.
I'm not sure how late they were being incorporated into new designs in that arena.
In their heyday (early/mid-70s) I'd say they could produce a larger, more uniform,
better contrast, display than the then-early LEDs. Would have to look at specs and some
calculations but they were probably more energy efficient than LEDs.
I just saved a few boards from a dumpster with such
displays on (they're actually Beckman ones, not Burroughs), but I was a little
surprised to see IC dates into 1981; I thought by then things had moved over to LED.
Yes, to be accurate, Panaplex was a Burroughs trademark. There was the Panaplex I series
which had a metal grid anode in front of the segments for the anode, and the
more-prevalent Panaplex II which has a conductive coating on the glass for the anode.
The Burroughs and Beckman displays are different in design. Generically, I refer to them
as 7-segment gas-discharge displays. There were some lesser-produced designs from Japanese
manufacturers.
Generally, their failing seems to be the cathode poisoning common to all neon bulbs, and
'burning' of the thin conductive anode coating where applicable.
I'm almost certain that they're from old gas
pumps - maybe the displays are just more readable in bright sunlight than LED?
(there's a sticker on one of the PSU boards with a 'shipping date' in 1999)
Funny, I was about to mention that use. I remember them in use on gas pumps up to
somewhere around the late-80s or early-90s. One of my bike routes takes me on a dike
behind an industrial area. Sometime around the mid-90s I remember there being a yard
filled with scrapped pumps, a lot of them missing the display/keyboard cover, so all the
displays mounted on the big controller boards could be seen. I wanted to rescue some of
them but never got around to pursuing it. I was kind of dissuaded by the thought they had
mostly seen a long and continuous service life and may now(then) be of questionable
reliability.
7:07 p.m.
I'll assume that you've seen the "roll your own" panaplex displays.
Does that count as manufacture?
http://www.imajeenyus.com/vacuum/20101115_second_panaplex/index.shtml
--Chuck
30 May
30 May
8:14 a.m.
Panaplex and other 7-seg gas discharge displays were
used in calculators up to the mid-70s. Actually one of the
last uses in a calculator might be the HP-9815 (1975/6):
http://www.cs.ubc.ca/~hilpert/eec/calcs/HP9815A.html
They were mostly used in desktops for the sake of the larger digit size but there were
some pocket/handheld
The Compucorp 320 series (and I assume 340 series, etc) used the same size Panaplex
display as the HP9815
(may even be the same part) although they were handheld-ish machines ( for those with big
hands ;-)) A little
earlier than the HP9815, so this does not invalidate your suggestion that the HP9815 was
the last calculator
to use one. To be pedantic, wasn't there are later version of the 9815 with 4K RAM on
the CPU board
(and no RAM expansion board) -- the 9815S or some such. That would probably be later than
the -A model.
When did the HP59304 HPIB display come out and when was it discontinued? It uses a 12
digit Panaplex display
calcs that used the smaller versoions. In calcs, they
were largely superseded by vacuum-flourescent displays
which were easier to drive, had a longer life, and could also be made with bright, large
digits.
I am surprised about the lifetime claim here. The VF display is a hot cathode device,
which tends to imply a
shorter life than a cold cathode part. VF displays were commonly used in consumer
electronics (VCRs, etc)
in the 1980s and 1990s over here, and uneven segment illumination due to low emission from
the filament
was a common fault. Conversely, my HP9815 and HP59304 are, AFAIK, still using the original
panaplex
display unit with no problems.
-tony
12:41 p.m.
On 2015-May-30, at 8:14 AM, tony duell wrote:
Well, I have some number of functioning calculators using both Panaplex and VF displays.
So yes, they both have the potential for longevity, but then one has to know the actual
runtime of the considered devices for an accurate comparison. In my experience, failure
over the typical use lifetime of the application device or for long runtimes is more
likely for Panaplex/7-seg GD than VF displays. I've seen more faulty Panaplex displays
than VF displays, even though the Panaplex are less prevalent.
Both Panaplex II and the Beckman displays seem to fail with a sort of 'burning'
around the segments and/or the anode coating on the glass. I'm not sure if it's
ion deposition or deterioration of the element. The segment/s then fail to ignite
uniformly. I'd say they are less reliable even than the similar-principle NIXIE
tubes.
The filaments of VF displays are run at a low enough intensity that they have a very long
life. I haven't seen problems with emission, I didn't think they were prone to
such as it's simple thermionic emission, not the 'chemically assisted'
emission of coated, indirectly-heated cathodes. I think some of the large complex VCR VF
displays had uneven illumination just from border-line design of the physical relation of
filament to segments.
I have a 6-digit clock I built in 1978, from individual VF tubes scavenged from a 1972
calculator. The calculator was used in an accounting office so it likely saw a fair degree
of daily use in that first phase of life. As a clock, they've been running
continuously 24/7 since 1978 (with the exception of the occasional power outage, repair,
and one ~ 5 month period. It does have variable pulse-width dimming on the 60 Hz filament
supply which would improve the VF tube longevity. I kept the two additional tubes from the
8-digit calculator as replacements but have yet to need them - all the clock digits are
fine and bright, while the LSI clock IC failed once. Compare that to the lifetime of neon
bulbs running continuously as power indicators on things like power-bars and freezers,
which commonly fail or start blinking after some number of years.
calcs that
used the smaller versoions. In calcs, they were largely superseded by vacuum-flourescent
displays
which were easier to drive, had a longer life, and could also be made with bright, large
digits.
I am surprised about the lifetime claim here. The VF display is a hot cathode device,
which tends to imply a
shorter life than a cold cathode part. VF displays were commonly used in consumer
electronics (VCRs, etc)
in the 1980s and 1990s over here, and uneven segment illumination due to low emission
from the filament
was a common fault. Conversely, my HP9815 and HP59304 are, AFAIK, still using the
original panaplex
display unit with no problems.
9:19 a.m.
On 05/29/2015 08:53 PM, Brent Hilpert wrote:
Yes, I've no idea how many of these ones are still working - although given
that they're intact on PCBs, my guess is that they're the result of
board-swaps and so one or two digits/modules may be out (or there are other
board faults) but the rest are still operational.
In total, not counting ones which physical damage or obviously-failed
segments, I think I have around 20 each of dual and triple-digit ones, plus
a handful of quads, which is enough to do something with while having a
spares stock. Hopefully the pair of PSUs that I rescued are OK, as they've
got handy 6V->180V DC convertor modules on them.
cheers
Jules
I'm almost
certain that they're from old gas pumps - maybe the
displays are just more readable in bright sunlight than LED? (there's
a sticker on one of the PSU boards with a 'shipping date' in 1999)
Funny, I was about to mention that use. I remember them in use on gas
pumps up to somewhere around the late-80s or early-90s. One of my bike
routes takes me on a dike behind an industrial area. Sometime around the
mid-90s I remember there being a yard filled with scrapped pumps, a lot
of them missing the display/keyboard cover, so all the displays mounted
on the big controller boards could be seen. I wanted to rescue some of
them but never got around to pursuing it. I was kind of dissuaded by the
thought they had mostly seen a long and continuous service life and may
now(then) be of questionable reliability.
3 p.m.
On 2015-May-30, at 9:19 AM, Jules Richardson wrote:
On 05/29/2015 08:53 PM, Brent Hilpert wrote:
Yes, I've no idea how many of these ones are still working - although given that
they're intact on PCBs, my guess is that they're the result of board-swaps and so
one or two digits/modules may be out (or there are other board faults) but the rest are
still operational.
In total, not counting ones which physical damage or obviously-failed segments, I think I
have around 20 each of dual and triple-digit ones, plus a handful of quads, which is
enough to do something with while having a spares stock. Hopefully the pair of PSUs that I
rescued are OK, as they've got handy 6V->180V DC convertor modules on them.
If you look closely at the displays, esp. at an angle to the glass, you can see the anode
coating on the inside surface of the glass. If you see a red/brownish non-uniform
discoloration in that coating, or discoloration around the ends of the segment bars, or
some black spots on the segment bars, that can be an indication of 'burning' or
'wear'. Not sure how bad it has to get before it's a failure/problem, or how
long it might last once that begins to appear.
There should be nice high-voltage drivers on those boards too.
. . .
I'm
almost certain that they're from old gas pumps - maybe the
displays are just more readable in bright sunlight than LED? (there's
a sticker on one of the PSU boards with a 'shipping date' in 1999)
Funny, I was about to mention that use. I remember them in use on gas
pumps up to somewhere around the late-80s or early-90s. One of my bike
routes takes me on a dike behind an industrial area. Sometime around the
mid-90s I remember there being a yard filled with scrapped pumps, a lot
of them missing the display/keyboard cover, so all the displays mounted
on the big controller boards could be seen. I wanted to rescue some of
them but never got around to pursuing it. I was kind of dissuaded by the
thought they had mostly seen a long and continuous service life and may
now(then) be of questionable reliability. At the start of the decide, certainly - but by 1980 I
would have thought that the cost had come down significantly, and LEDs surely had better
longevity than panaplex-type devices, so I don't know what the reasoning for using
them would have been.
Thinking about it though, I'm not sure that I've ever seen a gas (petrol) pump
with LED displays, although I don't know why they wouldn't exist. Mechanical
displays seemed to be the norm back in the day, to be replaced by LCD displays in the
nineties and 2000's.
No, I never saw gas pumps with LED displays. As I recall, gas pumps around here went from
mechanical to Beckman GD displays sometime in the mid-70s, then transitioned to LCD in the
late-80s/early-90s. So pumps in Britain never saw the gas-discharge display generation?
I think the display quality in the daylight may have been an issue, as you were raising
earlier. Larger-size 7-seg LED displays in the early days weren't particularly good in
high ambient light. Contrast was poor and segment illumination could be non-uniform as
they piped the light out from the LED die(s) into the clear plastic bar forming a
segment.
Theorising here, but the ability to use polarising filters on the GD displays may have
been a comparitive benefit. Not sure you could use a polarising filter on LED displays as
the emitted light may be non-uniformly polarised from differing orientations of the LED
dies, so it wouldn't make it through a polarising filter uniformly.
Speaking of old display technology, as someone who has been collecting NIXIE and
other-display-type equipment for many years, the NIXIE clock craze of the past few years
has been a bit of a surprise. And now that crowd has discovered the other old display
types such as the 7-segment incandescent Numitron & minitron displays, which are quite
rare. If you want a display technology that was obsolete almost from the day it was
introduced that would be it.
If I ever get around to building a NIXIE clock, I was going to try putting a motion
detector in it to turn the display on/off for the sake of longevity of the displays.
3:13 p.m.
On 5/30/2015 4:00 PM, Brent Hilpert wrote:
If I ever get around to building a NIXIE clock, I was
going to try
putting a motion detector in it to turn the display on/off for the
sake of longevity of the displays.
An alarm would be nice too. Ben.
PS: On the web some where, they have all transistor Nixie clock.
4:10 p.m.
On 2015-May-30, at 3:13 PM, ben wrote:
On 5/30/2015 4:00 PM, Brent Hilpert wrote:
Oh, top of the page here:
http://www.electricstuff.co.uk/nixiegallery.html
NIXIE clock built from neon ring counters, although there are numerous transistors
involved for driving the nixies.
I don't expect it's really practical in terms of reliability though.
If I ever get around to building a NIXIE clock, I
was going to try
putting a motion detector in it to turn the display on/off for the
sake of longevity of the displays.
An alarm would be nice too. Ben.
PS: On the web some where, they have all transistor Nixie clock.
31 May
31 May
7:07 a.m.
On 05/30/2015 05:00 PM, Brent Hilpert wrote:
If you look closely at the displays, esp. at an angle
to the glass, you
can see the anode coating on the inside surface of the glass. If you see
a red/brownish non-uniform discoloration in that coating, or
discoloration around the ends of the segment bars, or some black spots
on the segment bars, that can be an indication of 'burning' or 'wear'.
Not sure how bad it has to get before it's a failure/problem, or how
long it might last once that begins to appear.
I'll give that a go. So far I've not noticed any like that, just the usual
slightly-hazy appearance which every such display I've ever seen has.
There should be nice high-voltage drivers on those
boards too.
Yes, I'm missing the wiring harnesses and the interface boards which hooked
up to the pump mechanicals, but I've got the driver ICs for the displays, a
complete PSU, a second PSU board, and one of the Z80-based logic boards.
If the wiring was obvious (it's probably not) then it's possible that I
could hook everything up and that there may be some sort of test mode to
drive all the digits at once, which would save desoldering failed
displays/drivers for reuse. We'll see.
No, I never saw gas pumps with LED displays. As I
recall, gas pumps
around here went from mechanical to Beckman GD displays sometime in the
mid-70s, then transitioned to LCD in the late-80s/early-90s. So pumps in
Britain never saw the gas-discharge display generation?
I don't remember them over in the UK, just mechanical displays being
replaced by LCD. Although Nixies were used over in the UK, these types of
7-seg GD displays seemed much rarer generally.
I just noticed yesterday (now that I knew what to look for) that one of the
little old gas stations in town has pumps of the same style as the ones
which I think these boards came from, so I'll go take a look at them when I
get a chance (and maybe ask who owns them - I don't know if a gas station
typically buys their pumps outright, or if they're leased from another
company along with a maintenance contract)
Speaking of old display technology, as someone who has
been collecting
NIXIE and other-display-type equipment for many years, the NIXIE clock
craze of the past few years has been a bit of a surprise. And now that
crowd has discovered the other old display types such as the 7-segment
incandescent Numitron & minitron displays, which are quite rare. If you
want a display technology that was obsolete almost from the day it was
introduced that would be it.
If I ever get around to building a NIXIE clock, I was going to try
putting a motion detector in it to turn the display on/off for the sake
of longevity of the displays.
I'm very tempted to completely over-engineer a clock, just for the heck of
it: using one of my Nixie-based voltmeters for the display portion, keeping
it intact and sticking it in a small rack along with some sort of old
computer to drive it (either directly via the rear-panel interface, or via
a D/A convertor). The computer would have 'net access, so if I could
find/compile/write an NTP client for it, it would be perfect.
It would be way too power-hungry to just leave running all the time, of
course, but it would be kind of goofy to see. For an alarm, well I know
someone who has a 6V police siren from an old cop car... ;-)
cheers
Jules
30 May
30 May
8:19 a.m.
JOOI, does anyone know when Panaplex 7-segment
displays started going the
way of the dodo, to be replaced with LED displays (and, on the back of
that, what were the advantages of a Panaplex-type display over an LED one?)
It would appear that in the early 1970s LEDs were very expensive. I have been looking at
the
HP5930x HPIB units and in many cases the status indicators (power on, listening, etc) are
filament bulbs + driver transistors. I can think of no advantage to using a filament bulb
in this
application other than possibly cost. The 59304, which has a Panaplex display and
therefore
the HV supply to drive it, uses neon bulbs (NE2 sort of thing) as status indicators.
-tony
9:11 a.m.
On 05/30/2015 10:19 AM, tony duell wrote:
At the start of the decide, certainly - but by 1980 I would have thought
that the cost had come down significantly, and LEDs surely had better
longevity than panaplex-type devices, so I don't know what the reasoning
for using them would have been.
Thinking about it though, I'm not sure that I've ever seen a gas (petrol)
pump with LED displays, although I don't know why they wouldn't exist.
Mechanical displays seemed to be the norm back in the day, to be replaced
by LCD displays in the nineties and 2000's.
cheers
Jules
JOOI, does anyone know when Panaplex 7-segment
displays started going the
way of the dodo, to be replaced with LED displays (and, on the back of
that, what were the advantages of a Panaplex-type display over an LED one?)
It would appear that in the early 1970s LEDs were very expensive.
10:30 a.m.
On 05/30/2015 08:19 AM, tony duell wrote:
It would appear that in the early 1970s LEDs were very
expensive. I have been looking at the
HP5930x HPIB units and in many cases the status indicators (power on, listening, etc)
are
filament bulbs + driver transistors. I can think of no advantage to using a filament bulb
in this
application other than possibly cost. The 59304, which has a Panaplex display and
therefore
the HV supply to drive it, uses neon bulbs (NE2 sort of thing) as status indicators.
LEDs themselves weren't all that much more costly than the typical pilot
lamp. I recall sending $1 cash to Montsanto and receiving 2 red (was
there any other color?) LEDs in return in 1969.
By the mid 70s, LEDs in consumer applications were getting to be
ubiquitous. That microwave oven with the TMS1000 MCU (I'll look at the
date codes to get an exact date) had inch-high LED digits, driven by
discrete transistors.
--Chuck
10:40 a.m.
LEDs themselves weren't all that much more costly than the typical pilot
lamp. I recall sending $1 cash to Montsanto and receiving 2 red (was
there any other color?) LEDs in return in 1969.
Is there a good reason why filament lamps were used on minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips P850, etc
all used filament bulbs, not LEDs.
-tony
11:29 a.m.
On 05/30/2015 10:40 AM, tony duell wrote:
Is there a good reason why filament lamps were used on
minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips P850, etc
all used filament bulbs, not LEDs.
I can think of a few reasons.
First, a filament bulb has the effect of visibly "stretching" a visible
pulse.
Second, a filament lamp in an indicator application with a "keep warm"
provision can have an extremely long lifetime. Nobody knew what to
expect as the lifetime of a GaAsP device.
Third, I'm not entirely certain what the supply situation was in, say,
1974. Incandescent lamps were plentiful and available and inexpensive.
But new equipment certainly had LEDs as indicators in 1973.
Fourth, inertia. Consider how long it's taken for the automotive
industry to adapt to LEDs for even the simplest indicator applications.
Telcos were similarly slow on the adoption of LED technology.
The reliability problem was real--I still have some 7-segment displays
from the mid-70s that have non-working LED segments.
--Chuck
11:29 a.m.
On 05/30/2015 12:40 PM, tony duell wrote:
Inertia! The 11/45 was designed before LEDs were available, and so they
never changed. To do it right, the PC board would have to be
re-designed to add the current limiting resistor. I did the mod on ours
by adding the resistor to the LED lead, as the bulbs were pretty tall
above the board.
Jon
LEDs
themselves weren't all that much more costly than the typical pilot
lamp. I recall sending $1 cash to Montsanto and receiving 2 red (was
there any other color?) LEDs in return in 1969.
Is there a good reason why
filament lamps were used on minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips P850, etc
all used filament bulbs, not LEDs.
1 Jun
1 Jun
2:03 a.m.
On Sat, 30 May 2015, Jon Elson wrote:
Hold on! Most 11/45 have LED frontpanels (such as mine from 1974). The
earlierst ones might have bulbs, but they switched to LEDs during
production.
Christian
Is there a
good reason why filament lamps were used on minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips P850,
etc
all used filament bulbs, not LEDs.
Inertia! The 11/45 was designed before LEDs were available, and so they
never changed. To do it right, the PC board would have to be re-designed to
8:31 a.m.
On 06/01/2015 04:03 AM, Christian Corti wrote:
On Sat, 30 May 2015, Jon Elson wrote:
Hold on! Most 11/45 have LED frontpanels (such as mine from 1974). The
earlierst ones might have bulbs, but they switched to LEDs during
production.
OK, I know 11/70's had LEDs, but all the /45's I worked with had bulbs.
Ours was SN 343, which I guess must have been an early unit. We got it
used in 1976 or possibly 1977, and it looked pretty "well used" when we
got it.
Jon
Is there
a good reason why filament lamps were used on minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips
P850, etc
all used filament bulbs, not LEDs.
Inertia! The 11/45 was designed before LEDs were available, and so
they never changed. To do it right, the PC board would have to be
re-designed to 
8:36 a.m.
On 2015-06-01 17:31, Jon Elson wrote:
On 06/01/2015 04:03 AM, Christian Corti wrote:
Thinking about it, I seem to remember seeing some picture of an 11/70
with bulbs as well, but all 11/70 machines I've seen or worked on had
LEDs, so I suspect they might have had bulbs initially as well.
Johnny
On Sat, 30 May 2015, Jon Elson wrote:
Hold on! Most 11/45 have LED frontpanels (such as mine from 1974). The
earlierst ones might have bulbs, but they switched to LEDs during
production.
OK, I know 11/70's had LEDs, but all the /45's I worked with had bulbs.
Ours was SN 343, which I guess must have been an early unit. We got it
used in 1976 or possibly 1977, and it looked pretty "well used" when we
got it. Is there
a good reason why filament lamps were used on minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips
P850, etc
all used filament bulbs, not LEDs.
Inertia! The 11/45 was designed before LEDs were available, and so
they never changed. To do it right, the PC board would have to be
re-designed to
9:07 a.m.
Thinking about it, I seem to remember seeing some picture of an 11/70
with bulbs as well, but all 11/70 machines I've seen or worked on had
LEDs, so I suspect they might have had bulbs initially as well.
DEC used little modules containing an LED and series resistor that were
the same size as the bi-pin T1+3/4 bulbs used earlier. In a CPU panel you
had to clip out the pre-heat resistors, for obvious reasons. My 8/e is like that,
although I think some 8/e's had bulbs. I've seen RK05s with bulbs and
RK05s with LED modules. My 11/45 (I forget the serial number, it's early, perhaps
315) certainly has bulbs.
Thinking about it, I find it surprising that on later disk drives -- RL's, RK07s,
R80s etc, they used bulbs and not LEDs. By that date LEDs were easily available and
reliable.
-tony
10:38 a.m.
On 2015-06-01 18:07, tony duell wrote:
My 8/Es certainly have bulbs, while my 8/M and 8/F have LEDs.
I think I have RK05s with both bulbs and LEDs, while my RL02s are all bulbs.
Thinking about it, I seem to remember seeing some picture of an 11/70
with bulbs as well, but all 11/70 machines I've seen or worked on had
LEDs, so I suspect they might have had bulbs initially as well.
DEC used little modules containing an LED and series resistor that were
the same size as the bi-pin T1+3/4 bulbs used earlier. In a CPU panel you
had to clip out the pre-heat resistors, for obvious reasons. My 8/e is like that,
although I think some 8/e's had bulbs. I've seen RK05s with bulbs and
RK05s with LED modules. My 11/45 (I forget the serial number, it's early, perhaps
315) certainly has bulbs. Thinking about it, I find it surprising that on later
disk drives -- RL's, RK07s,
R80s etc, they used bulbs and not LEDs. By that date LEDs were easily available and
reliable.
I think it was just harder to replace the construction where you had
push buttons with lamps. Those are not bi-pins.
The first "modern" drive that used LEDs that I can think of is the RA90.
And then you didn't have the lamps in the buttons, but next to them, and
then you had a 14(?)-segment 4 digit display to show more information.
Johnny
10:42 a.m.
Thinking about
it, I find it surprising that on later disk drives -- RL's, RK07s,
R80s etc, they used bulbs and not LEDs. By that date LEDs were easily available and
reliable.
I think it was just harder to replace the construction where you had
push buttons with lamps. Those are not bi-pins.
10:53 a.m.
On 2015-06-01 19:42, tony duell wrote:
True. But there was no reason to introduce illuminated buttons, was there?
Looks nice in a dark room. :-)
And some of the lamps would flicker when the disk were busy, while
others reflected state.
The RL02 for instance. The LOAD button could be in or out. In addition
you had the lamp inside, which indicated if the drive was locked. You
could only open the lid when the lamp was on.
And when you pressed the LOAD button, that lamp went out, but the lamp
in the unit button only came on when the drive was up to speed and had
passed the initial head load. So button positions and lamps provided a
combination of indications and operational details.
On the RA8x drives, you have a write protect button, but the drive can
also become write protected through a software command, so the lamp can
go on with the button not pushed in.
But that don't really answer your question, as they could definitely
have placed the lamps separate from the buttons instead of putting them
inside. You could say that it was a space saving solution, but as you
have plenty of empty real estate on the front of the drive anyway, there
was no real need for this space saving.
Thinking about it, I find it surprising that on later
disk drives -- RL's, RK07s,
R80s etc, they used bulbs and not LEDs. By that date LEDs were easily available and
reliable.
I think it was just harder to replace the construction where you had
push buttons with lamps. Those are not bi-pins. The older drives had separate indicators. So DEC made
a change which
essentially forced them to use less reliable, higher current, indicators.
IIRC the R80 (and probably others) has a lamp test facility so that when
you get a FAULT you can be sure that the bulbs are all working and that
the indication is therefore genuine. LEDs probably wouldn't have needed
that.
Yup.
I seem to recall that CDC at about that time had a
pushbutton with a
rectangular LED on the surface of the button. That seemed quite a neat
device. I am sure DEC could have come up with something.
Right. I'm sure DEC *could* have done something clever. For some reason
they didn't. No idea why.
Johnny
12:05 p.m.
On 01/06/2015 17:07, tony duell wrote:
DEC used little modules containing an LED and series
resistor that were
the same size as the bi-pin T1+3/4 bulbs used earlier. In a CPU panel you
had to clip out the pre-heat resistors, for obvious reasons. My 8/e is like that,
although I think some 8/e's had bulbs.
One of my 8/e's has LEDs like that, the other has bulbs. Jim Austin has
at least three 8/e's and they all have bulbs.
--
Pete
Pete Turnbull
30 May
30 May
1:52 p.m.
On 2015-05-30 19:40, tony duell wrote:
By the 11/70, as well as the PDP-8/M and PDP-8/F DEC had switched to
LEDs. So they switched before 1975.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
LEDs themselves weren't all that much more costly than the typical pilot
lamp. I recall sending $1 cash to Montsanto and receiving 2 red (was
there any other color?) LEDs in return in 1969.
Is there a good reason why filament lamps were used on minicomputer
front panels until the mid 1970s? Things like the PDP11/45, Philips P850, etc
all used filament bulbs, not LEDs.
1:59 p.m.
On 2015-May-30, at 8:19 AM, tony duell wrote:
And the annoying and inconsistent use of incandescent bulbs for the power indicator and
optical tape detector in the 9830 . . when the main display is LED.
JOOI, does anyone know when Panaplex 7-segment
displays started going the
way of the dodo, to be replaced with LED displays (and, on the back of
that, what were the advantages of a Panaplex-type display over an LED one?)
It would appear that in the early 1970s LEDs were very expensive. I have been looking at
the
HP5930x HPIB units and in many cases the status indicators (power on, listening, etc) are
filament bulbs + driver transistors. I can think of no advantage to using a filament bulb
in this
application other than possibly cost. The 59304, which has a Panaplex display and
therefore
the HV supply to drive it, uses neon bulbs (NE2 sort of thing) as status indicators.
11:01 p.m.
And the annoying and inconsistent use of incandescent
bulbs for the power indicator and optical tape detector in
the 9830 . . when the main display is LED.
Indeed. I had to replace the former (but not the latter) in my 9830. I am told the LDR in
the tape sensor can
give trouble too, and it is a lot harder to find an indentical replacement for that than
for the bulb.
Another oddity is that the 9830 has the power-on indicator (a bulb and series resistor
across the 5V line)
whereas the 9810 and 9820 don't. In all cases the display is driven by firmware so it
is blanked under
certain conditions so it's not that you can use the display as a power-on indicator on
the smaller machines.
I like the power-on indicator of the 9815. It's a few ICs to display a row of dashes
across the display when
the display is not in use for displaying a number.
-tony
3492
days inactive
3495
days old
26 comments
9 participants
participants (9)
-
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
bqt＠update.uu.se -
cc＠informatik.uni-stuttgart.de -
cclist＠sydex.com -
hilpert＠cs.ubc.ca -
jonathanelson＠email.wustl.edu -
jules.richardson99＠gmail.com -
pete＠dunnington.plus.com