PowerBook 100 Video Problem

[Mac128]

So I plugged in this old PowerBook 100 and everything seems to work fine. The backlight comes on, the HD spins up and seems to load a system and the same for the floppy drive and a copy of system 7.5. (FYI, the PB100 HD will almost boot my MacPlus in SCSI Disk Mode, then the Plus says there are errors*)

However, I have no idea what is actually happening since the brightly lit screen is completely blank. Not a problem or stuck screen, but nothing at all. In particular, I hear the floppy drive working completely through an entire startup sequence, so I'm sure it's booting properly, it's just nothing shows up on the screen. The brightness controls work just fine on the backlight after the hard drive or floppy disk boot.

I am using the power adapter running with and without a battery and the results are the same.

I found on the PB 100 FAQ a reference to the possibility that if a 100 isn't used a lot the screen will go black and it takes a while for the 100 to heat up and the screen to reappear. So far nothing after 1/2 hour or so of keeping the screen active. I've since run it in SCSI disk mode which keeps the screen and disk constantly active for several hours and no change.

Any other ideas? Thanks.

*As a related question, how does one get the PB100 to show up on the Plus in SCSI Disk Mode? HDSC Setup sees the PB100 HD on the SCSI bus, but I can't seem to get it to mount. ANSWER: Termination Power. Neither the Plus nor 100 have it. It works fine on a Classic.

 

[benjgvps]

It could be the video cable. I had the horror of seeing a blank screen when the left hinge on my PowerBook 145B snapped, bringing the display cable with it... I could be dead, but its a good idea to check the cable first.

 

[tomlee59]

In the case of the 100 (as opposed to the generic 1xx series), the display cable seems not to be a common source of trouble. However, the -21V supply that biases the LCD does seem to be a weak spot. More specifically, the electrolytic cap across that supply output (those darned electrolytics, again!) seems to develop enough leakage that the converter has trouble starting up. Sometimes, just leaving it on for a long period of time will fix it (at least temporarily).

By all means first check for loose cables, zap the pram, etc. But if those standard operations don't fix it, you may want to look into the dead LCD bias theory. Somewhere around here I have notes identifying which pin to check, but if you just measure all of them and don't find anything that measures around minus 21V, then that's your problem.

 

[Mac128]

the -21V supply that biases the LCD does seem to be a weak spot. More specifically, the electrolytic cap across that supply output (those darned electrolytics, again!) seems to develop enough leakage that the converter has trouble starting up. Sometimes, just leaving it on for a long period of time will fix it (at least temporarily).

Tom, is there anything you don't know? I'll look into it. Will have to dismantle it first ...

 

[equill]

Quod tomlee59 profitetur, tomlee59 scit, unless he is pleading temporary memory lapse, or lack of a round tuit ...

de

 

[tomlee59]

Alas, equill, there are too many daily reminders of the breadth and depth of my ignorance for me to accept your kind compliment.

Sed gratias ago tibi.

 

[Mac128]

FYI, opened it up and the video started working. Clearly it was a pinched wire or loose connector. Never used a portable, but it's a damn fine little machine. The passive display is not as bad as I have heard.

Turns out it only has 2MB RAM. Running System 7.0.1 is just too little. With the 20 MB HD, it's everything they wanted the Mac to be when they started the project, only 10 years late!

Now I need to find a 6MB RAM module for the 100 to bring it up to the full 10MB. Not sure I need an internal modem. Rated at only 2400k it doesn't seem very practical in this day and age. Though with 10MB RAM, a low power 68000, 16MHz bus and the ability to turn off the display, it might make a handy little web server and live up to the same boast as running off a Plus even though it was 5 years later. The technology is basically the same.

 

[tomlee59]

Glad to hear it's working now -- I hope it continues to!

Memory for the 100 is a bit of a problem. Electrically, the modules are compatible with those for the 140, 145, 170...etc. Unfortunately, there's no room in the 100 for those modules beyond 2MB. Special (read: extra expensive) '100-specific modules are needed. They are hard to find, and costly when found.

In desperation, I've made my own. You can desolder the chips from a 140's expansion card, e.g., and stack them atop the chips in a 2MB module. Solder all the pins together except for the enable lines, then separately wire the latter to the appropriate card pins.

(And btw, the 100 maxes out at 8MB, IIRC, not 10MB.)

 

[Mac128]

(And btw, the 100 maxes out at 8MB, IIRC, not 10MB.)

Fantastic advice. I'm glad you brought up the latter.

What do you know about the Portable's Max. RAM capability?

This came up with Paul Pratt's Mini vMac as he informs me the 100's ROM is located at 0x900000, suggesting 9MB is the top limit for the 100 anyway, which is supposed to be identical to the Portable according to Apple.

I've also seen reference to the Portable being able to use 10MB RAM. If it is truly identical to the 100 ROM, theoretically the 100 could use 10MB as well, though Paul's revelation on the ROM memory address would indicate 9MB as the top configuration.

Apple may clear it up with this TIL: http://docs.info.apple.com/article.html?artnum=14870

It indicates the original Portable with 1MB and an 8MB card could reach 9MB. The backlight Portable and 100 though can only accommodate up to 8MB. Which is odd because the Backlit Portable still only has 1MB base RAM meaning it would need an odd 7MB RAM card to reach 8MB. Given that the ROM can support up to 9MB RAM based on address, I would think at a minimum adding an 8MB RAM card to either (the lack of one might be the reason the 100 never exceeded the 8MB limit), would push it to 9MB & 10MB respectively, though only the first 9MB would be accessible.

This may shed some info on the Portable differences:

http://developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-68K_Portable/Portable_BackLit.pdf

This article seems to indicate the 9MB is achieved in the Portable via the PDS slot which the 100 does not have. However, that does not explain why the backlit Portable would be limited to only 8MB.

http://docs.info.apple.com/article.html?artnum=10199

I see what you mean about prices!

http://www.edgetechcorp.com/memory/upgrade.asp?cid=15553

Also, is it possible to upgrade the 100's screen to an active matrix one? Or is that specific to the LB video driver,not the LCD?

Tom, is the 180 compatible? If it has 14MB, does that mean It has a 10MB module? Is that RAM card compatible with the 100 and can the extra RAM be removed and re-soldered to fit? How about the 190, or is that closer related to the 520?

 

Also, I read somewhere that the 100 uses Duo-type RAM and as such is that compatible or does it require a custom card for the 100?

 

[shred]

Most of the higher capacity RAM expansion cards for the Mac Portables were 8MB PDS cards. In the backlit Portable, the top 1MB is simply never decoded and so doesn't get used. I guess that something else is occupying memory at that address.

 

[Mac128]

In the backlit Portable, the top 1MB is simply never decoded and so doesn't get used. I guess that something else is occupying memory at that address.

Yes, I think there MUST have been a ROM revision coinciding with the backlit portable, the only way to know for sure, notwithstanding expertise within the forum, is to compare an original Portable ROM with that of a backlit one. It would make sense then that the PB 100 uses the same ROM as the backlit Portable. Looking at the backlight upgrade procedure for the Portable, the backlight card plugs into the ROM slot and more than likely it is the new video data (backlight state) that uses that last 9MB address.

 

[tomlee59]

Looking at the backlight upgrade procedure for the Portable, the backlight card plugs into the ROM slot and more than likely it is the new video data (backlight state) that uses that last 9MB address.

I believe that you're right. A friend of mine who worked at Apple when the Portable debuted told me the same thing, and it makes sense.

As to your other questions, I don't have solid answers, unfortunately. I don't know for certain how the LCD hardware is partitioned between the display itself and the logic board in the 100. My guess (and it is only that), based on typical practice (as well as the 100's Portable heritage), is that you could replace the passive display with an active one without having to touch the logic board. One might further speculate that using an active matrix display from a Portable could be a straightforward operation.

And your question about possibly being able to use a 180's ram module in the 100 is an interesting one. Even if the module were electrically compatible (a fact yet to be determined), though, I worry that it wouldn't fit in the tiny space allotted in the 100. I have a broken 180 that I've been meaning to crack open "one of these days," and your question might just be what motivates me to pop it open sooner than later.

 

[Mac128]

Spoke too soon. No sooner than I got it working than I let it sit for several days unplugged and then turned it on to find it was back to square one.

Leaving it on for several days in SCSI disk mode to see if taking it apart was just a coincidence that it began working after several days of previously charging a bad capacitor or some other malady.

No amount of jiggling seems to affect it. It might be a connection in the display side, too, but nothing changed between the last time I shut it down to present, to work it loose. I will check it nevertheless.

Otherwise I will disassemble and check out those caps.

Added 3/5/08

Tom, do you think the original Active Matrix screen is identical to the backlit one? Or would I have to get a backlit one to swap with the PB100?

 

[tomlee59]

There may be several flies in the ointment. From checking the physical dimensions of the LCDs, it seems that the Portable and the 100 differ a lot (1", diagonal measure). That alone may make swapping a bit of a challenge, even if the electrical connections turn out to be identical (something which is yet to be determined). I don't know if the 100 would physically accept a Portable display without major (or impractical) modifications, but if you happen to have all the pieces before you, perhaps you can make that determination.

You are navigating uncharted waters, my friend. I hope your pioneering experience ends more happily than it has for some other pioneers... !

 

[Mac128]

There may be several flies in the ointment. From checking the physical dimensions of the LCDs, it seems that the Portable and the 100 differ a lot (1", diagonal measure).

Ah. Indeed. No Portable yet, so the process is moot for the moment.

The GOOD NEWS, is that the display is working again. After disassembling the display housing, I tightened all the connections and the display pops on again perfectly. It could have been a loose connection that pulled apart when flexing the screen. I believe this unit had a modem originally (as the control panel is still on the hard drive) and someone likely loosened the connections when salvaging it. Probably had more RAM too, given the System and other software on it. HOWEVER, I'm going to let the thing sit for several days just to ensure the caps just hadn't finally reached sufficient charge, in which case they will discharge and it won't work again.

Having now SEEN the inside of the display housing, you may well be correct that the Portable's display will NOT fit, even with substantial modifications. I'll just have to wait and see one. I'll post some pictures and measurements for other Portable owners to review and post their own internals. Perhaps we can nip this whole thing in the bud without ever lifting a knife! Also, the Portable appears to use a ribbon cable to connect its LCD works, something that would have to be adapted to the 100's more traditional headers and wires.

Added 5/5/08 (Happy Cino De Mayo)

 

Tom, I was thinking the best way to go about upgrading the 100 to an Active Matrix display. I've decided one way to go about it is to use the 170 which already uses the 9.8" diagonal 1-bit active matrix display. I should be able to swap the 100 logicboard into it and use all the same connectors. The rear ports are likely not going to line up, but thankfully any changes required will be hidden behind the rear port door/cover. The battery may not fit, but the lead acid battery is virtually useless anyway. I think that is likely the better way to proceed with this experiment.

 

AND before anyone jumps down my throat, the reason I want to do this is to run a 68000 laptop under System 6, but with the crisp display I am used too with LCDs and CRTs. Also, the 170 case design is technically the very first PowerBook design after the Portable anyway. The 100 was delayed due to Sony's miniaturization and its case was actually improved upon based on what they learned with the 140/70. Also, the PowerBook uses an inverted SnowWhite scheme, raised 2mm x 10mm ridges rather than indentations. Sony simply shrunk the 140 design to fit the smaller 100 case thereby altering the proportion, so while the later PBs echo some of the changes the 100 brought about, it is the only one with that unique altered style. In that sense the 140/70 are the most authentic original examples of the first PowerBook. Though one could argue the 100 with it's 9" diagonal screen is closest to the original compact CRT.

LASTLY, A NEW consideration: I am going to try the HDI-20 Floppy drive cable with the HD20 to see if my theory that the HD20 which Apple says will work on the Portable will also work on a PowerBook 100. At the moment the header is a mini version of the standard floppy drive connector which means I will have to adapt it to mate with the HD20 header. But first I am going to make sure the pinouts are 1-to-1 as the adapter may be more involved than just mating connectors.

Here's the relevant signal info:

PIN 5-10 DB-19/HDI-20

5 -12/NC

6 +5/+5

7 +12/+5

8 +12/+5

9 NC/+5

10 PWM/NC

 

Given that the HD20 is self-powered, I suspect that none of these voltages are critical. Pin 10 is likely ignored by the HD20 as well since it neither used the PWM signal nor the later Superdrive voltage. The only question is pin-9 ... if the PowerBook 100 generates +5v on a pin the HD20 doesn't expect, will it affect the HD20 or will it ignore it completely? Also, if the PowerBook 100 is generating no signal on pin 5, will the absence of any voltage affect the HD20?

 

A helpful link: http://www.fantasticthings.co.uk/Hacks/duo_floppy/superdrive_to_duo.htm

 

[Mac128]

And your question about possibly being able to use a 180's ram module in the 100 is an interesting one. Even if the module were electrically compatible (a fact yet to be determined), though, I worry that it wouldn't fit in the tiny space allotted in the 100. I have a broken 180 that I've been meaning to crack open "one of these days," and your question might just be what motivates me to pop it open sooner than later.

Tom, the Apple developer notes seem to indicate that a good RAM card design should work in all of the 1xx series PBs (except possibly the 190 which was based on the 5xx series). It says the 100/140/170 is electrically compatible with the 160/180 which use 85ns RAM. The older RAM will work but imposes a wait state. The newer RAM will work in the older but limits the available RAM. So I should be able to stick a 6MB module in the PowerBook 100 assuming it would fit AND THE MANUFACTURER FOLLOWED ALL OF APPLE'S GUIDELINES.

 

[tomlee59]

That's great! Saves me a session with a Torx driver. Thanks for looking up that information -- it's very helpful to know that they're all electrically compatible.

 

[Mac128]

Unfortunately, there's no room in the 100 for those modules beyond 2MB. Special (read: extra expensive) '100-specific modules are needed. They are hard to find, and costly when found.
In desperation, I've made my own. You can desolder the chips from a 140's expansion card, e.g., and stack them atop the chips in a 2MB module. Solder all the pins together except for the enable lines, then separately wire the latter to the appropriate card pins.

So, this card would not fit in the PB100? It's actually not a bad price.

http://www.welovemacs.com/po146mb.html

It appears as though it would extend over the top of the daughter card. There's certainly enough room between the top of the daughter card and keyboard (as there is a spacer there already) and if necessary, I wonder if one could fabricate an extension to raise the RAM card high enough to sit on top of the daughter card if it won't. I've done a similar thing with a spare LC PDS connector and card in order to use a PDS card with a 575 & PPC upgrade which otherwise blocks the slot.

I misread your solution which indicates I actually need the PB 100 card in order to add RAM to it. Perhaps I should pick up one of these RAM cards in anticipation of the say I find a 2MB 100 card ...

 

[JRL]

This is a bit cheaper:

Link