Apple Powerbook 150 - vinegar display problem - Repairable?
Posted by FacxaDigit@reddit | vintagecomputing | View on Reddit | 11 comments
I recently bought a non-working Apple PowerBook 150 and I suspect the display is affected by the classic “vinegar Problem”.
First of all, I will definitely need to repair the computer itself, but my main concern is the screen, especially because there doesn’t seem to be any option to connect an external monitor.
I haven’t received the device yet, but I’m already worried since replacing the display could be expensive and I’m not sure I can find a cheap solution.
I’m considering trying an “LCD polarizer replacement”, but I’m not sure whether it would actually work given the condition of the display.
I was also wondering where it might be possible to find inexpensive replacement parts.
Alternatively, I would like to convert the DSTN signal to a modern TFT panel so I could use a newer, cheaper, and higher-quality LCD. However, I imagine this would be a very complex modification.
I’m also thinking about whether it might be possible to tap directly into the signal coming from the GPU (if it is analog or digital) in order to analyze and convert it.
I know that others have attempted similar modifications on computers from that era, but I still need to do more research.
Do you have any advice for me?
Do you know anyone who has tried to convert the signal?
Is there a non-Apple PC from that period that uses the same monitor?
Thank you in advance.
#Apple
#Powerbook
#retropc
#retro
#retrocomputing
ProperEye8285@reddit
On some PowerBooks the motherboard was common between models and supported DSTN or TFT, you could unplug the dual-scan panel and plug in the upgraded TFT panel. I think there was some PRAM tomfoolery required, but it was possible. On the PowerBook 150 I don't believe that was ever the case, so i imaging upgrading the signal would be nigh impossible, the video "card" never supported TFT. Sorry to rain on the parade. In short, I think you'll have to repair the panel you have, or find a "good" new old stock panel.
FacxaDigit@reddit (OP)
At least let me believe it! I’m joking, of course.
You’re absolutely right—I picked one of those more limited models.
I know it’s probably not capable of supporting TFTs. Do you think it would still be possible, albeit difficult (more as a personal challenge), to tap into the signal from the flat cable, feed it into an FPGA that receives the signal, and then translate/reconstruct a signal suitable for a TFT?
ProperEye8285@reddit
Hey anything is possible, but here are the problems as I see them in converting DSTN to TFT (I am by no means an expert and relying on an unreliable brain, Google lookups/AI to jog memory and a little know how)
decoding/re-coding the signal: DSTN is interlaced on a slow refresh time \~300ms, which is why it is so laggy/bad for gaming. TFT refreshes the whole screen, every pixel every \~25ms. So, you have to take 2 \~150ms half frames, combine them into one \~300ms frame and create a 12x clock multiplier to kick out that frame, duplicated 12times, until the next one arrives.
timing: You're going to need at minimum an oscilloscope and maybe a logic probe to get the timing exactly right. Also, i suspect the video logic is going to need to believe it is connected to a working DSTN display in order to give you the signals you need to measure. is your display electrically good enough to serve...maybe? Can you convince the logic and the screen that your FPGA is DSTN on one side and TFT on the other? Do the voltages match?
I'm not trying to discourage you BTW. In fact, I think its a super cool idea for keeping old tech alive. I think any TV repairman/broadcast engineer with 30yrs experience could do it in a flash, unfortunately the one I knew passed several years ago.
GGigabiteM@reddit
You'll have to recap the screen before you can determine if it's usable or not. Those screens are absolutely miserable to recap, it requires invasive surgery and partially disassembling the panel.
imactheknife73@reddit
Yup! I think the 150, 140, and 165 were the hardest screens i recapped. I have done dozens of 100’s, 280c, 270c, 180c etc and not that bad.
FacxaDigit@reddit (OP)
Awesome! I took a look at your profile and you basically have every possible Apple product model hahaha
WOW!
This is my very first vintage Apple device ever; I usually collect IBM ThinkPads.
Can you give me some advice on what to watch out for when replacing the polarizer, and whether, just by looking at it, it might seem like it’s not only a polarizer issue on mine?
imactheknife73@reddit
Yeah i have about 130 vintage macs, a few windows boxes, and commodore 64 in my collection. Never replaced any polarizer films. Heard it wasn’t easy. I have a 180c and a 2300c display with that nasty vinegar syndrome. Luckily i have both of those with no issues as well.
FacxaDigit@reddit (OP)
Wow, I currently have 4 vintage PCs and 4 arcade consoles, haha.
Your collection is really nice!
FacxaDigit@reddit (OP)
Thanks for your comment.
Replacing the polarizer on these displays is a real pain, and it’s also quite expensive, to the point where it often doesn’t even make sense to do it.
The PowerBook 150 is one of those few 90s models without external video output, because Apple was trying to reduce costs as much as possible back then.
And I still keep wondering why I ended up choosing this model, haha.
At the moment I’m trying to figure out whether there’s any hardware modification that could make it possible to connect it to a modern monitor, possibly by tapping directly into the display’s flat cable signal and using an intermediate device like an FPGA for conversion, although I think it would be quite difficult to achieve.
My research continues.
Zuofu@reddit
The LCD is repairable assuming the polarizer glue is the only thing wrong with it, but I would get the computer booting and showing at least the ? folder screen. You could be in for a nasty surprise if you spend a bunch of time replacing the polarizer only to find that half the screen is black or a third of the lines are missing. You also need the screen to have power and biased to know the polarization angle of the screen anyway so you know which angle to cut the polarizer sheet. Also keep in mind that there's a rear polarizer film as well - it is usually not as damaged since it is not as exposed to environmental conditions, but given the state of the front one, the rear one might have a similar vinegar syndrome too.
FacxaDigit@reddit (OP)
You’re right.
Regarding the computer, it actually shouldn’t even power on, so the fact that it does makes me think that at least the basic parts are working.
I’ve done a few tests: I can hear the drive, it reads and ejects floppy disks correctly, and I can still see something faintly in the corners of the screen. Brightness seems to adjust, but contrast doesn’t really change much.
In its current state though, it’s basically unusable visually. The polarizer is really in bad condition.
Replacing the display would probably be the easiest solution, but just the panel alone costs at least around €100.
If I had the time I would also try the repair, but I’m afraid of ending up discovering another issue with the display.
Do you have any advice on how to proceed? With the display like this I’m really struggling to understand what’s going on 😅
Thanks a lot for the comment!