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PowerBook 160 Bleached / No Contrast Screen

desertrout

Well-known member
BOTH of my PB160s had the same issue - literally nothing on screen. So it's entirely possible that if there is a fault beyond the screens - it's present across both.
For clarification, do you have two 160 displays that exhibit the same symptoms on the same base, or two complete and completely different 160 machines that exhibit the same symptoms as each other? Because if the former, then it's something on the interconnect or inverter boards; if it's the latter, then it has to be something common between the two - PSU is one possibility (Is it in spec? Should read between 7.5 and 7.9V.), or the caps that were used (unlikely though based on the pics), or... I hate to say it.. something you did or didn't do.

However, the pics don't look so terrible to me. @AndyO is absolutely correct in that these displays weren't good even when new, and you find inconsistent 'quality' among them. The image in your pic just looks to me like it needs the contrast / brightness adjusted, which makes me wonder if you got the pots and the sliders lined up when reassembling...? Just spit-balling.

Echoing @3lectr1cPPC I'd recommend a good IPA cleaning of *both sides' of the display pcb, especially between the IC legs. Just to be sure - that electrolyte is pervasive and pernicious.

I agree though that the ceramics on the inverter are unlikely to be an issue. It looks like you replaced the radials though - I assume like for like?
 

Spode

Active member
(I will add here that I believe the original "bleaching" issue was because I used the wrong size capacitor to replace the 22uf, so don't let that confuse matters.)

I have two displays and two units and the combinations don't seem to make a difference.

The sliders are functioning, and as I say - I've tried 3 separate inverters.

I've also got multiple PSUs - original and aftermarket. Doesn't make a difference which I use.

If I adjust the contrast settings, it does improve, but still feels like it's a far cry from the results I'm seeing in that video of a PB160. If I run on 2 colour mode, they look fantastic!

When you consider all the combinations of things being swapped around etc. the idea that it's "something you did or didn't do." is far more likely. But if I've swapped everything out for exact equivalents - what on earth is it? The PCBs are clean, and if it was something along those lines I wouldn't expect to see the same behaviour across both units - the chances of me making the exact same mistake twice seems unlikely.

https://oldcrap.org/2020/12/20/apple-macintosh-powerbook-160/ - in this piece, he suggests he replaced the power regulator chip on his display.

Both PB160s had exactly the same problem - literally nothing on screen. Perhaps an effect of the failed caps, if left long enough is that it damages the regulator chip?


I've uploaded a video - here you can see in 2 colour mode is looks great, then as I go 4/16 it gets gradually worse. Adjusting contrast doesn't fully remove the ghosting, but does ruin the colours. Adjusting to the point where the Trash can looks correct results in terrible ghosting.
 

3lectr1cPPC

Well-known member
By “literally nothing”, do you mean that it showed the minimum contrast, making the screen look blue with no image, or was it just completely black?
 

Spode

Active member
By “literally nothing”, do you mean that it showed the minimum contrast, making the screen look blue with no image, or was it just completely black?
I had a backlight, but no image. Adjusting either slider didn't seem to make a difference other than shutting the backlight off completely. I would say that's likely the "minimum" contrast setting, but even with that I would expect to see an image if I shine a torch against it, which I didn't.

I could however, hear it booting up successfully listening to a) hard drive crunch and/or floppy disk boot.
 

3lectr1cPPC

Well-known member
Yeah, that sounds like what my 145 did before a recap. The contrast behavior in your video looked off to me, it’s still not gradual enough to be normal I’d say. I have a grayscale passive matrix PC laptop with pretty bad ghosting (after a recap) but the contrast slider change is still very gradual. It’s just baffling to me that you have the same problem on two separate laptops!
 

Spode

Active member
Yeah, that sounds like what my 145 did before a recap. The contrast behavior in your video looked off to me, it’s still not gradual enough to be normal I’d say. I have a grayscale passive matrix PC laptop with pretty bad ghosting (after a recap) but the contrast slider change is still very gradual. It’s just baffling to me that you have the same problem on two separate laptops!

Yeah I would describe my contrast change as quite sudden - I have to be very careful moving my fingers and the top 50% of it is pretty useless as it's off the chart bleached out.

I guess the most obvious thing is the choice of caps. @Mac84 used Tantalums on his video, I've used electrolytic. The 3.3uf were from Farnell, as were the 22uf, and the 100uf from a BoJack set I got on Amazon. They all test fine on my ESR meter - but it's possible some have higher resistance than the circuit is designed for - i.e they want a lower ESR.

I wonder if it's worth recapping with Tantalums and see if that makes any difference (Frustrating though with minimum orders on Farnell.) - it's the only consistent thing between both machines.
 

3lectr1cPPC

Well-known member
As much of a pain that is, that would be my next course of action as well. I can confirm that ceramics work as well. I used an odd assortment of caps on mine, ceramics for the 3.3ufs, a tantalum for one of the bigger caps, and an electrolytic for the other. My inverter board hasn’t been recapped yet (I should really do that soon). The only issue with ceramics is that the ones I got were microscopic, smaller than half a grain of rice. I still got them on, but I do have a very steady hand.
 

Spode

Active member
I'd soldered those before - I can do it again. Although last time I used ceramics I was lectured about the noise issues they can generate and the DC Bias issue (https://www.murata.com/en-eu/support/faqs/capacitor/ceramiccapacitor/char/0005), which is why I went electrolyte this time.

The frustrating aspect is not the re-capping, but the minimum order, or paying over the odds for shipping. If I could be certain it would definitely fix it, I'd give it a go. I *might* have enough ceramics to replace the 3.3ufs so I could start there I guess?

Although both the caps on my inverter boards were leaky, I didn't notice any difference after I replaced them FYI.
 

3lectr1cPPC

Well-known member
I’d replace the 3.3s and then see how it behaves. You said your 145 had the same contrast issue on my thread (where the slider isn’t gradual) and the caps you used are the only factor that’s the same between them all. If you have spare ceramics I would go for it and see if that fixes your issues.
 

Spode

Active member
Yes, that's true - although from memory I had used 4.7s, not 3.3s on the 145 and put the difference down to that. I might not have some 3.3s in ceramic, but considering the DC bias, I could potentially throw some other values in there and see how they do. I'll measure the voltage over those 3.3s first and do some maths.

This is, of course, assuming that I've exhausted all other options, which I think I probably have!
 

Spode

Active member
I just tested these 3.3s for ESR and its 3.5 ohms and 5ohms for the 4.7s. That seems very high compared to the 100uf which only has 0.5ohms.

I pulled out my selection of 603 SMDs and found some 475s - they measured in at 3.5uf (!) but sub 0.1ohms. It will be tricky soldering, but should at least answer the question of if ESR is the issue.

https://electronics.stackexchange.com/questions/109385/when-should-i-use-a-low-esr-capacitor - this suggests it might increase ripple voltage?
 

desertrout

Well-known member
Thanks for sharing that video. From what I can see, I think what you have now is actually better than in that Snazzy Labs video - he was showing his 160 in 1 bit mode, and yours looks actually better than his in 1 bit. What you're seeing in 4 and 16 greyscale is - as far as I know - totally normal. My 160 does the same thing, and I used tantalums for the 3.3uF's. Remember that these old passive matrix FSTN displays are from the early days of greyscale technology and were pretty crappy even in their day. That's why the 170 and 180 were so much more expensive - their displays were active matrix and had significantly better refresh and greyscale performance.

To wit - Macworld Magazine, December 1992 (https://archive.org/details/MacWorld_9212_December_1992/page/n209/mode/1up):

Screen Shot 2022-02-07 at 6.24.00 PM.png
Screen Shot 2022-02-07 at 6.24.19 PM.png

Having said that, I don't want to dissuade from trying improve greyscale performance. But I personally don't think there's much to be gained.
 

Spode

Active member
Thanks for sharing that video. From what I can see, I think what you have now is actually better than in that Snazzy Labs video - he was showing his 160 in 1 bit mode, and yours looks actually better than his in 1 bit. What you're seeing in 4 and 16 greyscale is - as far as I know - totally normal. My 160 does the same thing, and I used tantalums for the 3.3uF's. Remember that these old passive matrix FSTN displays are from the early days of greyscale technology and were pretty crappy even in their day. That's why the 170 and 180 were so much more expensive - their displays were active matrix and had significantly better refresh and greyscale performance.

To wit - Macworld Magazine, December 1992 (https://archive.org/details/MacWorld_9212_December_1992/page/n209/mode/1up):

View attachment 38224
View attachment 38225

Having said that, I don't want to dissuade from trying improve greyscale performance. But I personally don't think there's much to be gained.

Thank you so much for this. I genuinely did not notice that he was running that video in monochrome. Mine is at least that good in monochrome.

I did a bit more hunting for other PowerBook 160 videos and found at least 2 that looked just as bad as mine - which corroborates with those articles above too!

I'm now starting to think that I've done nothing wrong! There's a reason the PowerStrip has the ability to change the screen depth I guess - you would likely run it in monochrome unless you really needed the greyscale?

I think I'm going to just put it back together and leave it there - thank you for everyone trying to help diagnose. I think it goes beyond my electronics knowledge to try and make something better than even the manufacturer could :p
 

desertrout

Well-known member
I think it goes beyond my electronics knowledge to try and make something better than even the manufacturer could :p
Haha it's tempting though, and many in our hobby spend a lot of time doing just this sort of thing.

One thing that I actually enjoy about this hobby is that serves as a reminder of just how good we have it now compared to 20 or 30 (or 40) years ago... and that similar levels of improvements are just over the horizon.

So, yeah, I agree that you've done nothing wrong! In fact, you've done very well - thanks for saving a couple more 160's! :)
 

Spode

Active member
Haha it's tempting though, and many in our hobby spend a lot of time doing just this sort of thing.

One thing that I actually enjoy about this hobby is that serves as a reminder of just how good we have it now compared to 20 or 30 (or 40) years ago... and that similar levels of improvements are just over the horizon.

So, yeah, I agree that you've done nothing wrong! In fact, you've done very well - thanks for saving a couple more 160's! :)
Oh, if I *could* I would. Part of the reason I enjoy this hobby is to improve my electronics knowledge. But I think it would go beyond simple capacitor replacements to get these screens working better.

One of these 160s is a little beaten up, but the other one is immaculate and has a 120MB hard drive that works, which was nice :)
 

Spode

Active member
So I've been reinstalling the OS on the PowerBook, which has given me much more usable time with the screen and with a lighter background, it's actually not too bad.

However, what I have starting noticing is that the contrast can start pulsing/changing. Like it will for a split second fade to black (as if you've dropped the contrast all the way down) and then return back to where it was.

Other times, I've noticed that just, over time the contrast slowly creeps in one direction - so I find myself adjusting it.

Honestly starts to make me question some sort of power regulation - inconsistent voltages, as I know all the caps are good.

The other option is the potentiometer sliders are just a bit noisy and need cleaning up.

Has anyone else seen this kind of behaviour?
 

3lectr1cPPC

Well-known member
That would normally be indicative of bad inverter board caps I believe, but you’ve replaced those. My apologies if you’ve mentioned this before, but what power adapter are you using? Is it an original? If so it would certainly needs caps replaced itself.
 

Spode

Active member
I'm not entirely sure what combination of things fixed it - potentially it was deoxit in the screen controls, but it all seems to be working well now!
 
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