Nan Tan 3500 Series

The Nan Tan 3500 Series (also known as the FMA3500/FMA3500SX/FMA3500C) were 486-based laptops, first released around December 1991. There are two main revisions of the series - the 3500/3500SX, and the 3500C. The 3500/3500SX have grayscale LCDs and look identical to the 386-based 3300. The 3500C uses a color display and has a different hinge design, but otherwise looks very similar to the earlier revisions. Some of the FMA3500C models have a trackball above the keyboard, others don't.

Most 3500 Series laptops have a white/beige case, but some did come in a dark gray.

One odd design quirk of these is that the battery screws on to the back of the laptop with thumbscrews, rather than slotting into any internal bay. That's definitely a dated design for the time these were released. In fact, the overall design of these (especially the earlier revisions) look a couple years older than they actually are.

The 3500 dock screwed onto the back in place of the battery and added two ISA expansion slots.

The 3500 Series laptops are fairly common. Distributors known to have sold them include Aspen, Ergo, and BSI/Broadax.

Most of the info here came from creepingnet.

Specifications

Spec	Details
CPU	Socket 1/2 80486 CPUs - Intel 486SX @25 or 33MHz - Intel 486DX @25 or 33MHz - Intel 486DX2 @50 or 66MHz
RAM	4x 30-pin SIPP memory slots (standard desktop RAM) - 32MB Maximum
Hard Disk	3.5" IDE Hard Drives - The shipping drives used a proprietary 3-pin mini power connector. Building an adapter is necessary to use a standard drive.
Display Options	FMA3500/FMA3500SX - 9.4" Passive Matrix Grayscale @640x480 (Casio MD820TT00C1) FMA3500C - 9.4" Passive Matrix Color @640x480 (Sanyo LCM-5331-22NTK) - 9.4" Active Matrix Color
Graphics Chipset	- Cirrus Logic CL-GD6420 or CL-GD5424 - 1MB VRAM
Audio	PC Speaker Only
Main Battery	8-cell external NiCad - Very reliable, and easy to rebuild. Uses standard C cells
CMOS Battery	VARTA NiCad Barrel Battery, soldered
Power Supply	FMA3500/FMA3500SX 3 or maybe 4-pin DIN connector (i've seen references to both), 20V FMA3500C Barrel Jack, 20V
Disk Drives	1.44MB 3.5" Floppy Drive
PC Cards	None
Other I/O	- 1x External FDD - 1x Parallel - 1x Expansion Dock Connector - 2x Serial - 1x PS/2 - 1x External numpad connector
BIOS	I've seen Award and Phoenix
Pointing Device	Optional Trackball, only on the FMA3500C

Resources

NOTE35C.zip - Notebook FMA3500/3500C/3500SX Utilities - gets function keys working, other stuff.

3XVGAW95.exe - FMA3500 Video Driver

Common Faults & Maintenance

CMOS Battery leaks

The 3500 uses a VARTA NiCad barrel battery to back up the CMOS. These batteries nearly always leak in their age and MUST be removed to prevent the laptop from getting nuked.