Editing Amstrad PC1640 Troubleshooting Guide (section)

== Power ==

The computer's rails come from the monitor through the 14-way DIN cable; check them at the plug as in the [[Amstrad PC1512 Troubleshooting Guide#Power|PC1512 guide]]. Owners who lack a working monitor power the PC1640 from a standard supply through the same pinout and use a separate display card with switch 10 on.<ref name="vcfecd">paul.brett, [https://forum.vcfed.org/index.php?threads/dead-amstrad-pc1640-ecd-monitor.31375/ "Dead Amstrad PC1640 ECD monitor"], Vintage Computer Federation Forums, May 2012. Retrieved 2026-10-02. Community report: a PC1640 run from a home-made supply cable with an ISA VGA card after its ECD failed, with switch 10 moved to disable the internal adaptor.</ref> A PC1640 can also be powered through a prototyping card in an expansion slot, since nothing sits between the supply input and the slots on the main board.<ref name="vcfleak">Wobblestone, [https://forum.vcfed.org/index.php?threads/amstrad-1640-germany-schneider-pc-1640-with-battery-damage-works-a-little-has-address-problems.1250715/ "Amstrad 1640 (germany: Schneider PC 1640) with battery damage, works 'a little', has address problems"], Vintage Computer Federation Forums, November–December 2024. Retrieved 2026-10-02. Community repair report on a Schneider PC 1640: leakage from the AA cells onto the CPU area, corroded CPU and 8087 sockets, a dead CPU, an address line stuck high after the socket was replaced, Ruud's Diagnostic ROM built as an even/odd pair, powering the board through an ISA prototyping card.</ref>

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Monitor supply faults reported by owners'''
! Monitor !! Symptom !! What was found
|-
| PC-MD || Supply dead || STK7358 hybrid regulator shorted between pins 12, 13 and 14; both optocouplers and a transistor also failed<ref name="vcfcm">Ghislain, reply in [https://forum.vcfed.org/index.php?threads/anybody-out-there-have-an-amstrad-pc-cm-monitor-sinclair-s-mm.1254162/ "Anybody out there have an Amstrad PC-CM monitor? (Sinclair S-MM)"], Vintage Computer Federation Forums, 26 August 2025. Retrieved 2026-10-02. Community report: a PC-MD supply with the STK7358 shorted on pins 12–14, both optocouplers and a transistor failed; a PC-MM with broken solder joints that still would not start.</ref>
|-
| PC-ECD || Computer runs, screen stays black || The 5&nbsp;V regulator IC503, feeding the TTL decoder board, gave 0.92&nbsp;V from a 15&nbsp;V input. A new regulator brought the picture back; the picture then rolled until the vertical hold was set<ref name="vcfecd2">VintageVic, [https://forum.vcfed.org/index.php?threads/amstrad-pc-ecd-display-black-screen-advices-welcome.1257916/ "Amstrad PC ECD display 'Black screen' – advices welcome"], Vintage Computer Federation Forums, 18–19 June 2026. Retrieved 2026-10-02. Community repair: PC-ECD black screen with the computer working; recap of the TTL decoder board (which has to be desoldered from the main board); IC503 giving 0.92 V; vertical hold adjustment.</ref>
|-
| PC-ECD || Thought dead || Worked once the brightness and contrast controls were turned up<ref name="dd2" />
|}

The PC-MD's supply regulator is IC501, an STK7358, with BA6993, LA6324 and BA707 control ICs.<ref name="sm" /> On the PC-ECD the decoder board is soldered to the main board and has to be desoldered to work on it.<ref name="vcfecd2" />