Amstrad PenPad PDA600 Capacitor Replacement Guide
The Amstrad PenPad PDA600 runs from three AA cells, with a CR2032 lithium cell backing up its 128 KB of memory.[1][2] The Centre for Computing History credits the hardware design to Mutech Ltd.[3] No service manual, circuit diagram or parts list for it has been published, and Amstrad's user manual gives no disassembly procedure, so no capacitor values are available. The most detailed published description of the board is the chip map in the source code of MAME's PDA600 driver, which shows both sides of the main board but no passive parts.[4]
Before you start
[edit | edit source]Everything entered is held in battery-backed RAM. Amstrad's rule is never to remove the AA cells and the lithium cell at the same time, and opening the case for board work will usually mean doing exactly that.[2] Take a printout through the serial port or copy the memory to a card first; the Amstrad PenPad PDA600 Maintenance Guide explains both and their limits.
After the work the pen has to be calibrated again, and the handwriting recognition retrained if the memory was lost.[2][1]
What the board carries
[edit | edit source]MAME's chip map lists these parts on the main board:[4]
| Side | Ref | Part |
|---|---|---|
| Front | U1 | Z8S18016FSC (Z180-family processor) |
| Front | U2 | Amstrad 42069 ROM |
| Front | U3 | KM681000ALT-8 |
| Front | U4 | HD64610FP real-time clock, with crystal X1 (32.768 kHz) |
| Front | U5, U24, U31 | Amstrad 41857, 41864 and 41863 |
| Front | U12 | HD64646FS LCD controller |
| Front | U21 | MAX731CWE |
| Front | U25 | MAX641 |
| Front | U30 | MAX222CWN |
| Front | U27, U33, U35, U36 | LP324M, KM62256BLG-10, TCM5089, TL061AC |
| Back | – | 3 V cell, beeper, crystal X2 (28.6 MHz), PCMCIA connector CN1 |
| Back | U22, U26, U28 | 7673CBA, 3226NUT, MC145053D |
| Back | U11 | KM62256BLG |
The MAX731 at U21 is Maxim's fixed 5 V step-up DC-DC converter, for inputs of 2.5 to 5.25 V, a range that covers three AA cells from new to nearly flat.[5]
Recording your board
[edit | edit source]No capacitor list for the PenPad has been published, so record your own board before changing anything:
- Photograph both sides of the board, with the part numbers of U21 and U25 legible.
- For each electrolytic or tantalum capacitor, note the designator, value, voltage, size and polarity, and whether it is surface-mount or through-hole.
- Read the values from the parts. Surface-mount electrolytics carry a printed value and voltage on the top; tantalums carry a code that has to be decoded from the maker's scheme.
- Keep the record with the machine.
Where to start
[edit | edit source]Look first for leakage. Alkaline cells left in a stored PenPad can leak into the battery compartment and onto the board; clean that as described in Battery Explosion, Capacitor or Corrosion Damage before judging any capacitor. Then check the capacitors round U21 and U25, the two step-up switching regulators on the front of the board.[4][5][6] Capacitor Failure Symptoms shows what failed parts look like; on surface-mount electrolytics, look for a stain or crust round the base of the can.
Procedure
[edit | edit source]- Back up the memory, switch off and remove the AA cells and the lithium cell.
- Open the case, noting the position of every screw and clip; Amstrad publishes no procedure for this.[2]
- If the board has to come out, unplug the LCD and digitiser connectors first; MAME's map labels them CN3 and CN4.[4]
- Record and replace the capacitors one at a time; surface-mount electrolytics and tantalums are marked at one end for polarity, so note it before lifting each part.
- Reassemble, fit fresh AA cells and a new CR2032, and switch on.
- Calibrate the pen and run through the first-time set-up.[2]
After the recap
[edit | edit source]Check that the PenPad switches on and off with its button, that the battery gauges read sensibly for fresh cells, that the pen hits the icons round the screen accurately after calibration, and that the contrast control works. Test a memory card and the serial port.[2]
Related pages
[edit | edit source]- Amstrad PenPad PDA600 · Amstrad PenPad PDA600 Maintenance Guide · Amstrad PenPad PDA600 Troubleshooting Guide
- Amstrad NC100 Capacitor Replacement Guide
- Capacitor Failure Symptoms · Battery Explosion, Capacitor or Corrosion Damage · Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 Dick Pountain, "Amstrad's Modest PDA", Byte, August 1993, pp. 161–162, 164. Scan at archive.org. Retrieved 2026-10-19. Three AA cells and a lithium backup cell; 128 KB of memory; three Z80-equivalent microcontrollers for processing, character recognition and power management.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Amstrad, PenPad PDA 600 user manual (French, 1993). Hosted as File:Amstrad PenPad PDA600 User Manual (French).pdf, described at Amstrad PenPad PDA600 User Manual (French). Replacing the AA and lithium cells p. 6 (never remove the AA cells and the lithium cell together; the round screw-on lithium cover on the back); first-time set-up and pen calibration p. 9; memory cards pp. 34–35; care p. 44. No disassembly procedure.
- ↑ Centre for Computing History, "Amstrad PenPad PDA600". Retrieved 2026-10-19. Hardware designed by Mutech Ltd, operating system by the Eden Group, project managed by Cliff Lawson; 128 KB of memory, PCMCIA Type I slot and serial port.
- ↑ 4.0 4.1 4.2 4.3 Sandro Ronco, "Amstrad PenPad PDA 600" driver, MAME source file src/mame/amstrad/pda600.cpp, header comment "PCB Layout (front)" and "PCB Layout (back)", BSD-3-Clause; version of 2 August 2026 (commit 774a180df2b6). Retrieved 2026-10-19. Positions and part numbers of the ICs on both sides of the main board, the two crystals, the 3 V cell and the connectors (CN1 PCMCIA, CN2 8-pin serial, CN3 LCD, CN4 digitiser).
- ↑ 5.0 5.1 Maxim Integrated Products, MAX731/MAX752 +5V/Adjustable Step-Up Current-Mode DC-DC Converters data sheet, general description (as indexed at alldatasheet.net). Retrieved 2026-10-19. The MAX731 converts a 2.5–5.25 V input to a fixed +5 V at 200 mA.
- ↑ Maxim Integrated Products, MAX641/MAX642/MAX643 Fixed Output 10W CMOS Step-Up Switching Regulators data sheet (as indexed at alldatasheet.net). Retrieved 2026-10-19.