Operator Panel Registers
   (Hex 0108-010F) for more information). 

HDLG-4216LED Display (pdf data sheet)
   Smart Alphanumeric Display Built-in RAM, ASCII Decoder, and LED Drive Circuitry Software Controlled Dimming Levels and Blank 128 ASCII Character Set.

   Now this is where I went to work. Imagine what if you took the codes that are output to the parallel port and hooked them into the HDLG-4216? We would need a hex to ASCII converter to feed the HDLG, but with the capabilities and features afforded by the 4216, why not take the time?

1) Remove the bezel containing the LED panel cover.
2) Pop the scratched up plastic cover off.
3) Look at the locking tabs on the sides - one is a tad wider than the other.
4) Using an X-acto, benchtop belt sander, whatever... make the long tab the same depth as the short one.
5) Reinstall modified LED cover with the scratched side facing inwards.
6) Voila - now your LED panel looks like new and doesn't have any unsightly scuffs or scratches on it.

From Peter 
   Err ... that won't work that easy - you will have to rework the thing a bit more. The Power LED has +5V as common and GND over resistor, while the HD-Led signal supplies +5V activity signal and common GND ... except you have a LED with 4 wires (2 separated LEDs in one unit). 

From Jim Shorney 
And I found this out, too. Although the idea is still kicking around in the back of my mind, behind some other distractions from down south... 
  It should certianly be possible to wire in a simple switching circuit with an NPN transistor on the HD LED to take care of the difference and allow use of a common-anode bicolor LED, providing the +5 can source a few extra milliamps.  I haven't figured out (yet) if this comes from hard power or is a signal output from the PS/planar.  The other possibility is to use a common-cathode LED and share the resistor for the power LED, but I'm not sure how well this would work.  LED's are diodes, after all, so the two sources would be isolated from each other (in theory), but I'm not sure what this would do to the brightness of the LED's.  I may play around with these ideas in the future, but I wanted to keep the initial mod as simple as possible for those who might be comfortable with a soldering iron but don't possess sufficient knowledge to handle wiring up transistors and such. 

From Peter 
    About the HD-bicolor LED: I still think it is no good idea. The difference in the color change is ... well ... hard to see while the green power part is permanently on. This could work however if you have a "common cathode" LED and replace the resistor on the printboard with a small 2-transistor 10mA constant current circuit. In this case the pin 4 (HD-LED) could be fed directly to the anode of the red LED part and the +5VDC (Power) to the green LED part and the two LEDs share the common GND and the current limiter. 
    *But* the visibility is still bad. What you need were a "NAND" function that switches off the green power LED when the red HD LED comes on ... that would make the color either green *or* red but not a diffuse orange when both come on. 
    To simplify the circuit: you only need to check the HD signal. As long as it is low the green LED part is on (if there were no power it were dark anyway) and once the HD signal pin comes "high" the red LED comes on and the green is switched off ... In this case you could even use a "common cathode" bi-color LED, which are more familar than "common anode" types IIRC and keep the existing current limiting resistor on the printboard. 
      Still too complicated I think. Faster and -to my opinion- better results are obtained with installing a bright red LED behind the LED "window" ... 

From Peter 
   >I thought of that as well.  But, as you say, it it starting to get complicated.  I'm perfectly capable of whipping somethign like that up, but not sure that I want to go to the trouble.  I'm trying to stick to something that just about anyone can whip up. 
     Currently I have broken down the "logic" to 2 additional resistors and a PNP-transistor :-) I'll try out if that works on Thursday maybe and let you know ... I only need to buy a two-color LED. My first "experimental assembly" will most likely consist out of two standard-LEDs. 
   >An LED behind the display window seems to be the best overall solution. 
   Yep. The current "implementation" looks pretty cool. I really wonder why the heck IBM did not include a standard HD-LED  in their darn expensive flagship at that time. I think it might be a reason that they "recycled" an existing panel-unit from a mainframe controller - and that simply had no HD ... 
   >One of the triangular ones used in tuning indicators and tape player directional indicators might look cool. 
   It sure does - but the rectangular types can be easily fixed with some superglue on one of the existing LED arrays. Whatever - it is possible to integrate a LED without damaging the panel bezel ... and that counts :-) 
   >I think I would go with green, myself.  And I'm still thinking about replaceing the power LED with a blue one... 
   Matter of personal taste ... and I recently found some "blue LEDs" which are pretty cheap ... and no LEDs at all. They are small lamps (bulbs) with a blue-colored glass. I think VW used them in earlier years for the "hi-beam" indicator lamp in their cars. They *look* like LEDs - even have the flattened side - but unlike to LEDs they work in either polarity. :-) 

                         +-----+-------o HD (Pin 4)
                         |     | 
Op-Panel Cable          +++    | 
                        47K    |
                        | |    |
                        | |    |
                        +++    |
                         |     |
                         | B   |
                      +--+--+  | 
                    E | 2SA |  | 
               o------+ 608 |  |
             +5VDC    |(PNP)|  |
       from existing  +--+--+  |
             LED       C |     |
                         o     o
                         |     |
                  Green \T/   \T/ Red LED
                   LED  ---   --- 
                         |     |
                         +-----+ 
                            o
                            |
                           +++
                      330R | |
existing resistor          | |
on card panel              +++
                            |
                            o---------+  GND

           ------------------------------------------------------------ 

                                         * Principle of Operation * 
   You need to unsolder the existing green LED. The +5VDC contact needs to be fed to the above circuit. Only the common cathode of the bi-color LED gets soldered back in the place where the original LED cathode was. 
      The two LED-parts use the existing 330 Ohms resistor in common. The PNP transistor gets minus-potential over the  47K resistor and the green LED lights up. Even when the HD-pin does not feed minus to the resistor (tri-states) the GND connection is given over the red LED part and the current-limiting resistor, so that the green LED will light under any circumstance. 
      Once the HD-pin gets positive (on HD operation) the positive +5V pulse will turn Base of the transistor positive and the green LED goes blank - the red LED is then on and indicates HD activity. 
    The type of the PNP-transistor is uncritical. Any type will do. I used this 2SA608 while I had it ... In case you want to return to original condition you only need to remove the circuitry and resolder the single green LED. Pretty easy, eh ? 
     ------------------------------------------------------------ 
     (C) 1999 by Peter H. Wendt (peterwendt@aol.com) 
      ------------------------------------------------------------ 

I found out that my original concept works only with *one* panel card, which sits in a very early Mod. 8595-AH9 (without shutter). All my machines have the same panel card that Jim described and to which he pulished a "revised version" of my PNP-transistor solution. The two cards only differ through the position of the current-limiting resistor for the "power LED" - but that makes 
a bit difference. Sigh. 

Tools required: 
Soldering iron
Wire strippers/cutters

Intructions: 

1. Trim the leads of the resistor and the anode lead (the long leg) of the LED short, and solder one lead of the resistor to the anode of the LED. 

2. Solder the two lengths of hookup wire to the other resistor lead and the cathode (short leg) of the LED. 

3. Cover the soldered connections with the heat-shrink tubing and, well, "heat shrink" it. 

4. Pull your 95 apart, and unplug and remove the operator panel display PCB (you do know how to do this, right?). 

5. Secure the LED in your desired mounting location (more on this in a bit) and cut and strip the two free wire ends to length; the anode lead (the one coming from the resistor) will be soldered to pin 4 of the ribbon cable connector, and the cathode lead will be soldered to the frontmost of the two speaker connector pins (ground).  Make your connections on the bottom of the PCB. 

6. That's it!  Install the PCB back in your model 95, taking care not to snag your wires as you slide the PCB back in.  Enjoy your hard disk light! 

Now, as to mounting location for the LED... Being into vintange ham radio gear, I subscribe to the "drill no holes" school of mods.  Finding a suitable location for the LED, without altering or detracting from the aesthetics of the machine, is the hardest part of this adventure. 
My first experiment was to tie the new (red) LED to the existing power LED with a cable tie, so they are side-by-side.  This results in an interesting green-to-red/green effect when disk access occurs that can be varied by adjusting the positioning of the LED's behind the bezel, but the result is not easily discernable from a distance or over a very wide viewing angle.  Another thought that occurs it to somehow fix a square or rectangular (or some other interesting shape) green LED 
behind the operator panel window, either dead center above or below the operator display, or in one of the corners.  I may experiment along those lines when I get my hands on some LED's that are other than round. 
   While I'm at it, I may just replace the power LED with one of these blue LED's that I have around here.  Seems apropriate... This info will appear on my web site.  Someday. 

Subject:  Peter's LED circuit 
Author:  Jim Shorney <jshorney@inebraska.com> 

   I finally got around to trying Peter's nifty circuit for a two-color HDD LED in a model 95.  In the process, I discovered that there are at least two varaitions of the info panel PCB.  Mine differs from Peter's in the location of the LED resistor, so I had to change the circuit as shown below: 
___________________________________________________. 
                                                   .
                                                   .
                     +-----+------o HD (Pin 4)     .
                     |     |          Op-Panel     .
                    +++    |            Cable      .
                47K | |   +++                      .
                    | |   | | added                .
                    +++   | | 330R                 .
    330R             | B  +++                      .
on panel card     +--+--+  |                       .
     +----+     E | 2SA |  |                       .
  o--+    +--o----+ 608 |  |                       .
  +5 +----+       |(PNP)|  |                       .
from existing     +--+--+  |                       .
    LED            C |     |                       .
                     o     o                       .
                     |     |                       .
              Green \T/   \T/  Red                 .
               LED  ---   ---  LED                 .
                     |     |                       .
                     +-----+                       .
                     |                             .
                     o power LED cathode pad       .
                     |                             .
                     |                             .
                     |                             .
                     |                             .
                     |                             .
                     |                             .
                     |                             .
           o---------+  GND                        .
- --------------------------------------------------- 
   Circuit function is essentially the same, the change was required because my board has the 330 ohm on the anode of the power LED instead of the cathode, as shown in Peter's diagram.  The green LED does not fully extinguish in this configuration because the HD output only seems to source about 3.6 volts under load, but it is dim enough that the red is clearly visible from an angle or a distance of a couple of feet (meters?). 
   That having been said, I also tried a rectangular red LED behind the display panel on another 95.  I must say, I like the way it looks.  I fixed it with hot glue to the bottom of the rightmost operator display LED so it appears directly below the rightmost character of the display.  Now I need to decide which way I like better.... 

Button Sizes
   The button size between "lefthand" and "righthand" panels is different - respectively the *length* of the buttons. Ed. Ran into this when I swapped a button from the 8595 onto. the 9585. 

Power Switch Shutter
   The protective shutter over the power switch is missing on early, first series 8595 models only, it came standard in early 1992. 

Test Switch Function
Rick Starich made me!
   Pull Op Panel out front of system. Leave PSU plugged in. Short 3-6 OR 5-4 and system should power up if Op Panel board and cable are good. Nothing will happen if 5-6 or 3-4 are shorted .
 

Replacement Power Switch
   If you can, unsolder the other switch on op panels with two switches. Same type of switch. I used a GC 35-491 (Push On DPDT Power Pushbutton Switch) and it fit perfectly. Pull off the round button and pop the original rectangular button on. Fits perfectly. 

   I had a 9585 that would not turn off reliably. You could push the switch up to five (or more!) times before it would turn off. I tried slowly wiggling the switch and the 85 would come up... 

LED Panel Odd Behavior
 From Alfred Arnold 
   Last week, I was able to get my hands on a 8595-AKF (Type 1 complex, 486DX33, no cache module :-( ).  The price was on a per-kilogram basis, so I was quite happy.  However, when installing Linux and my own tool to display some system statistics on the LED display, I noticed a strange behaviour  I hadn't seen before on a 9595 with a P60 complex: Even under Linux, there seems to be some type of 'demon' that regularly clears the right half of the display.  I also saw this under plain DOS, but I thought  first this were a 'feature' of the BIOS.  However, since this also happens under Linux, either something on the planar is slightly broken, or there are some implicit links between the LED display and other parts of the planar's hardware I'm not aware of.  I don't hope it's the first case ;-) 

From Peter 
   >Even under Linux, there seems to be some type of 'demon' that regularly clears the right half of the display. 
   On the -AKF this is surely a bug rather than a feature. The LED-panel is directly controlled from the sysboard I/O ports and it looks like a buggy display element (2 x 4 digits). Check if it is properly seated or has bad solder spots. Also check if the panel cable is in good order and properly seated. 

Alfred Arnold retorts 
   Hi Peter, took out my Tek yesterday evening and probed around a little bit.  It doesn't seem to be a problem in the display element itself, since swapping them doesn't help...the interesting thing is that during POST, the write signal for the bottom display half is overlayed with a 250 Hz signal, which however has not full level.  So either the driver chip on the planar has gone bad or there is a short to another signal.  Seems I have to unassemble the whole beast :-/ 

And finally, the moment of discovery- 
   By the way, I was able to fix the display yesterday evening.  There was a bad contact in the display module's socket, but one that can make you tear out your hair...there was no contact to the Vcc pin of the display, but it still somehow worked because it supplied itself with power via the 
other signal pins (probably via the usual CMOS protective diodes).  You could put a scope on the /CLR pin of the display module and see how the voltage started to ripple when one digit was turned on.  Turn on a second digit, and the voltage broke down finally and the display resets... 

Mod 95 with 8 "Lights" on panel
   I have been having some trouble with getting a Mod 95 to see the optical SCSI drive being added.  I went in and unplugged the SCSI cable, and power cable to reset everything and start over.  Now I have 8 positions across the op panel with a pattern of small dots (LEDs) and the machine goes no farther in the boot process.  What do the 8 position, all LEDs on suggest.

   It suggests you pulled one end of the cable going to the LED display loose at one end or the other or that you somehow damaged the cable to it.  Check for this small flat cable and make sure its OK.

   Jack, I had high hopes that it would be that simple. I checked and re-plugged both cables and did not change my symptom.  Any other ideas. I have an HMM dated Sept 1993.  Where did you find the symptom info.? Did you get it from the HM manual?

From Jack GULLEY 
   The HMM will not give you details on what's wrong.  The symptoms indicate one of the lines to the operator panel has a hot or shorted bit.  If it is the same bit in each of the 8 display position, it indicates a common line or driver problem.  If the bit come on as soon a power comes on and 
nothing else ever displays, then it very likely the operator panel is blown.  Problem isolation is simple - replace the cable, then the electronics at each end of the cable, after first making sure everything was plugged in and the cable not damaged. 

Bob Eager has these- 
DLITEDOS   DOS device driver for HD display on Model 95 LED Panel 
PANEL OS/2 device driver for character display on Model 95 LED Panel 

BASIC Way
Peter sez:
If you use this little Basic program you can write anything into the panel if you substitute A$ with your text:

A$ = "133 MHz "
FOR q = 1 TO 8
OUT (&H107 + q), ASC(MID$(A$, (9 - q), 1))
NEXT q

You can as well use DEBUG's "OUT {portnumber} {value}" command to pipe into the display. Write a text that includes 8 lines of out-commands to the ports 108 - 10F with the hex character values for {value} and use DEBUG<mytext.txt to bring it into the panel.

30 is "0", 39 is "9", 41 = "A" 5A = "Z" ... you will get the scheme.

Linuxinfo
   If you have a model 95 (8595, 9595), you can get the source of linuxinfo, that is linuxinfo.c. This program shows you the current CPU-load, date, time and the kernel-version on the 95s' LED display. The information is continuously scrolled from right to left. This allows system-load-control, even if you are not logged-in and no monitor is connected to the system (like in central computing rooms). As the two very right LED-letters are kept blank, it works great together with the IBM SCSI-Subsystem driver with the command line-parameter ibmmcascsi=display.