[NTLK] Newton 2x00 upgrades/repairs

[Victor Rehorst]

On 2026-02-19 21:38, Matt Materniak wrote:
> 1) To upgrade a 2000 to a 2100, is it just replacing the DRAM chips? Are
> there any specs on the necessary chips?

Hi Matt,

Yes, it's a straight swap of the DRAM chips, which are under the 
socketed ROM board on the 2x00.

You will need two DRAM chips with these specs:

  * 1M words x 16 bit (giving you 2MB of 8-bit bytes per chip)
  * 4K refresh at 128ms
  * 3.3V operation
  * EDO or FAST page
  * 50 pin TSOP II package (only 44 pins are actually populated, pins
    12-14 and 37-39 are omitted for this type of RAM chip)
  * 60ns access time? I'm not sure how important this is

One of the original parts used by Apple (perhaps the only one, IDK) was 
Hitachi HM51W16165LTT-6.  The "L" indicates that they are the low power 
chip variant, with the extended refresh cycle time and low standby power 
consumption.

Note that the 2000's original DRAM chips use the two 40 pin footprints, 
and the replacement DRAM chips use the 44-pin footprints.  Compare the 
two scans of the 2000 and 2100 motherboards and you'll notice the 
difference.

Where you would find chips with these specs in this year of 2026 is a 
whole other story.  DRAM to this spec has been obsolete and out of 
production for a while now, so you'd be looking at finding new-old stock 
somewhere, or removing the chips from a 2100 board that has other issues.

Sources:

  * Self-upgrade instructions via the Newton FAQ:
    https://web.archive.org/web/20010608125749fw_/http://user.chollian.net/~cehz/upgradeEng.htm
  * 2000 motherboard scan with ROM board removed:
    https://www.pda-soft.de/common/img/hardware/2x00/boards/5454x3289_2000PopulatedNoRomBottom.jpg courtesy
    of Frank Gründel
  * 2100 motherboard scan with ROM board removed:
    http://www.pda-soft.de/common/img/hardware/2x00/boards/5408x3548_2100PopulatedNoRomBottom.jpg
    courtesy of Frank Gründel

> 2) Im trying to repair a 2100 that slowly died - over an hour or two the
> screen would keep getting dimmer until eventually the whole unit died. I
> have it apart and checked the fuses - they all have continuity. The
> official newton psu would not turn on the unit. I tried a bench power
> supply set to 6v tied to the battery terminals - no sign of life there and
> the supply shows no current draw. Any ideas of what to check next?

Do you mean the backlight gets dimmer, or the screen itself fades out 
over time?

EL backlight film deteriorates over time, and can be replaced. But the 
LCD itself fading out like that, that's a problem I've not heard of 
before.  My wild-ass guess would be some capacitors need replacing, but 
I'm not sure which ones are involved in providing the various voltages 
to the LCD.

-V