Request for information about the PowerBook 170 inverter board and LED upgrade

Discussion in 'Apple Collectors' started by PB170, Dec 28, 2014.

  1. PB170, Dec 28, 2014
    Last edited: Dec 28, 2014

    PB170 macrumors newbie

    Dec 28, 2014
    Hi everyone!

    I have an old and classic PowerBook 170 that I'm still using (along some more recent equipment, perhaps I should add :) ). Unfortunately the screen backlight is on its last legs. Since I recently upgraded the storage to a Compact Flash-card (through the amazing PowerMonster II), an upgrade to an LED backlight is very tempting (especially since I, after some basic measurements, discovered that the backlight consumes nearly a third of the total power – much more than the physically moving hard drive). I am of course aware of the fundamental differences between the two technologies and that it's not simply a matter of switching the backlights. I would also like to preserve the machine's current functionality, i.e. allow the backlight to be controlled through software. I realize that this likely is a challenging to near impossible venture, but if it is possible (which it should be) I would very much like to give it a try. To even get close to achieving this, however, I am in need of much more background information than I currently have. So, my question is: does anyone here have any insight or knowledge about what would be required or some bits of information to help me out? Any kind of help or input would be truly appreciated.

    Below is an excerpt from the Apple's document "Macintosh PowerBook 140 and Macintosh PowerBook 170 Developer" on the display and backlighting (page. 32):

    In other words, the slider on front of the computer does not directly control the backlight, but instead sends its output to the Power Manager chip, which then adjusts the power to the CCFL. Consequently, the backlight can also be controlled through software (dimming at low battery power etc.). The CCFL connects to an inverter board (onto which the potentiometer that connects to the slider on the case is mounted), which in turn is connected to the machine's interconnect board.

    Attached are two pictures (top and bottom) of the PowerBook 170 inverter board. The brown two-pin connector connects to the CCFL, and the white 10-pin connector to the interconnect board and the rest of the computer. From what I can tell, most of the inverter board, as expected, seems to be dedicated to power inversion/transformation for the CCFL. It is a little difficult for me to tell what connects to what, but there seem to be ten solder points within the area of the potentiometer (presumably not all for the potentiometer), of which at least two connect directly to the 10-pin connector (at pins 3 and 8).

    This basically is where I am at the moment.

    To sum up, this is what I would like to do:
    • Install an LED backlight that uses the same power source as the current inverter board
    • Keep the full functionality of the brightness adjustment slider (i.e. control through software)

    Some basic questions I have at this point are:
    • Does anyone know what goes in and out of the 10-pin connector?
    • Could an LED driver board be directly driven by the power supplied through the 10-pin connector?
    • Is there an LED strip available on the market that would be suitable in size for these old PowerBooks? (I haven't yet taken it out to measure it, but would guess its roughly 140 mm / 5.5 in long)
    • Can anyone figure out how the potentiometer could be isolated?

    Again, if anyone here have any insight or knowledge about what would be required or some bits of information to help me out, any kind of help or input would be truly appreciated.

    Thank you all in advance!

    Ps. I have also posted this question in 68kmla's forums, here:

    Attached Files:

  2. MacTech68 macrumors 68020


    Mar 16, 2008
    Australia, Perth
    I'm no expert in conversions but there is at least ONE company selling kits for just this purpose.


    So long as you can find the "enable" and "adjust" return signals, it seems that it might be possible:

    and a little more "technical" here:

    The vendor does say that his kits do not support PWM dimming. However, I'm wondering if this indicates that the signal sent to the ORIGINAL inverter is analog DC rather than PWM -

    As all things "experimental" you'll be on your own with a lot of decisions. I think replacing the CCFL might just be simpler.
  3. PB170 thread starter macrumors newbie

    Dec 28, 2014
    Thank you for the information! Very interesting. I think I might have come across one of their videos earlier, but missed the more general information. Maybe I'll drop them a mail and see if they can help.

    Still, I feel I will need to know the specifics about the 10-pin connector and how the potentiometer is connected before I can move on.

    I took the machine apart again yesterday to take a closer look at the inverter board as well as the interconnect board, and it seems like pins 1-2, 6-7, and 9-10 are soldered together, effectively making it a 7-pin connector, but I'm not certain. Also, it looks like the potentiometer has six terminals, of which three seem to be connected together (to ground perhaps?), two goes directly to the 10-pin connector, and one to the rest of the circuity as well as terminal 1-2. But these are just assumptions.

    You're right in that Apple's information on the brightness signal seems a bit ambiguous. I'm certainly no expert in this field, but if a PWM signal is generated, would there be a reason not to use it? Maybe they just mean that it's amplified to the voltage level that the inverter board needs?

    The section about the Power Manager in the same document states one of the Power Manager's functions as: "It generates the brightness level (via the PWM function) for the inverter to control the backlight brightness of the display."

    Is there anyone here with more insight or experience of circuit boards who can help?
  4. PB170 thread starter macrumors newbie

    Dec 28, 2014
    While waiting for some more insightful information from you guys, I made some basic measurements of the inverter board and input connector pinout myself. In case this information might be useful to someone else, I'm posting it here. Likely, the pin assignment is as follows:

    01 Ground
    02 Ground
    03 Brightness potentiometer out (0–5.15 V)
    04 Brightness control from the Power Manager (0.22–5.00 V – probably PWM, but not sure)
    05 Unused
    06 Power in (7.5 V)
    07 Power in (7.5 V)
    08 Brightness potentiometer in (5.15 V)
    09 Contrast potentiometer in (FSTN displays)
    10 Contrast potentiometer out (FSTN displays)

    The question is if the input voltage is enough to drive a modern LED board, as modern inverter board input voltages seem to be higher. I'll send a mail to lcdparts to see if they have anything to suggest.

    If any of you have any other suggestions, or could confirm or elaborate on the connector measurements (in particular the brightness control signal), it would be very helpful.
  5. PB170 thread starter macrumors newbie

    Dec 28, 2014
  6. MacTech68, Jan 10, 2015
    Last edited: Jan 10, 2015

    MacTech68 macrumors 68020


    Mar 16, 2008
    Australia, Perth
    I tried looking thru my PB100 series parts but couldn't find the PB170 inverter, but working from your pics, that's pretty much the pinouts I came up with (except for pin 5 being NC - which is difficult to see from pictures).

    Since the fuse on the 7.5V input for the actual inverter is 1 Amp, you would NOT be able to exceed that and should probably be under 1 Amp.

    You could lift one end of the 1Amp fuse and place a multimeter in series with it set to mA reading to see what current draw there is under varying backlight intensities.

    EDIT: looking at the specs for the XB series, their quoted input voltage range is 8V to 21v. The 7.5V would appear to be derived directly from the PB170 AC Adapter (Rated 7.5v to 7.9v). It's so close to their minimum - I'd say it's 50/50, though the specs suggest potential problems.
  7. PB170 thread starter macrumors newbie

    Dec 28, 2014
    Thank you for your kind efforts! When looking at Lcdparts' not-so-easy-to-overview website earlier, I only found input voltages in the range of 12–24 volts, but 8 V looks more promising. I'll see how they respond.

    Regarding the current draw and the fuse, I was thinking to remove the input to the inverter board altogether, except for power to the brightness potentiometer. And an LED backlight would hopefully consume much less power, it being one of the general advantages of LED over CCFL.

    That aside, I would imagine even 1 A probably is too much considering that the total draw of the computer is 2 A and the CPU and drives consume more than half of that. I suspect the motherboard fuse probably would blow first.
  8. MacTech68 macrumors 68020


    Mar 16, 2008
    Australia, Perth
    There probably is a 12v source somewhere in the PB170. However, how much you could draw from it is questionable.

    Sadly, I don't have a "Schem" for a PB140/170, which would be extremely handy.

    Good luck with your experiments! :)
  9. PB170 thread starter macrumors newbie

    Dec 28, 2014
    You think? Wouldn't they have used a higher voltage power adaptor in that case? Everything I've found documentation on uses 5 V DC. It would make things easier if there was though!

    Thanks for the encouragement! :)
  10. MacTech68 macrumors 68020


    Mar 16, 2008
    Australia, Perth
    The LT1054CS near the power input connector CAN be used as a voltage doubler. Of course, you can't have more power out than power in. I don't know how they're used in the PB100 Series (circuit diagram or schematic would be wonderful).

    Two of them (which there seems to be) can be used to convert 5V to 12V.

    So, it's possible.
  11. PB170 thread starter macrumors newbie

    Dec 28, 2014
    Interesting! Thank you. I'll look into that, should it turn out that the 7.5 Volts are not enough to drive the LED boards.

Share This Page