Amstrad CTM-644
| Amstrad CTM644 | |
|---|---|
 |
|
| CTM644 colour monitor with a CPC 664 | |
| Manufacturer | Amstrad Consumer Electronics plc |
| Type | Colour monitor and system power supply |
| Interface | 6-pin DIN (RGB and sync), 5 V DC lead, 12 V DC socket |
| Compatible | Amstrad CPC 664, Amstrad CPC 6128, Amstrad CPC 464 |
| Dimensions | 375 × 340 × 365 mm |
| Weight | 10.6 kg |
| Predecessor | Amstrad CTM-640 |
| Model | CTM644 |
| Power | 240 V AC 50 Hz |
The Amstrad CTM644 is the colour monitor Amstrad sold with the Amstrad CPC 664 and CPC 6128. Like the Amstrad CTM-640 it holds the whole system's mains power supply: the computer has no mains input and takes 5 V from the monitor on a lead. The CTM644 adds a 12 V output for the disc-drive models, on a socket that takes the computer's 12 V lead.[1][2] A 1992 article in CPC Amstrad International describes the CTM644 and CTM640 as differing only in that 12 V supply.[3]
The CTM644 contains a CRT and a mains switch-mode supply. Read CRT Discharge Procedure before opening it.
Specifications
[edit | edit source]| Item | Value |
|---|---|
| Mains supply | 240 V AC 50 Hz, double-pole switch SW501 |
| Mains fuse | F501, 2 A time-lag (part 1400253) |
| Outputs | 5 V to the computer (adjusted with VR501); 12 V for the disc drive from IC503 |
| Video input | 6-pin DIN lead: red, green, blue, sync and ground |
| CRT | V001, 3701B22-TC20 (part 170307) |
| Line output transformer | FB401, 3714004 (part 170467) |
| Line frequency | 15,625 Hz (H. hold alignment) |
| Dimensions, weight | 375 × 340 × 365 mm, 10.6 kg |
The figures are from the parts lists, the circuit diagram, the alignment instructions and the back-page specification of the CPC6128 manual.[1] The CPC 664 manual covers the same monitor.[4]
Power supply
[edit | edit source]The supply is on the main board. The circuit diagram shows the mains entering through SW501, the time-lag fuse F501 and the line filter L501, a bridge of four 20E10 rectifiers (D501–D504) charging C505 (100 µF 400 V), and a switch-mode converter built around the STK7308 hybrid (IC501) and the switching transformer T501 (8142006). The degaussing coil L502 is fed through the thermistor TH501.[1]
The 5 V output is regulated around IC502 (L78MG) and set with VR501, measured across C518, to exactly 5 V. The 12 V output comes from IC503, a µPC78M12 regulator; the circuit diagram shows 16.5 V at its input and 11.8 V at its output, with C522 (470 µF 35 V) and C523 (100 µF 16 V) either side.[1] The CTM640 has neither IC503 nor the 12 V socket.[5]
Controls and connections
[edit | edit source]- User controls: the power button (SW501) and the brightness control (VR401, 500 Ω).[1]
- Leads: the 5 V DC cord (CD005) and the 6-pin DIN cord (CD007) to the computer; the 12 V jack J501 for the computer's disc lead.[1]
- Inside: the vertical hold VR405 (20k), the service/normal switch SW401 used during alignment, the focus and screen controls on the line output transformer, and the presets listed in the Amstrad CTM-644 Maintenance Guide.[1]
Board revisions
[edit | edit source]Amstrad's amendment manual reissues the CTM644 parts list for a later chassis. It lists a different CRT (A34JLL70X10, part 170307-A), a different line output transformer (3714009, part 170468), IC protectors ICP501 and ICP502, and changes several capacitor values (C518 from 470 µF to 1000 µF at 10 V, C405 from 47 µF to 470 µF at 16 V, C512 from 47 µF to 100 µF at 50 V), and raises the sub-brightness setting from 120 V to 123–124 V.[6] Its alignment remarks refer to the monitor connected to a CPC464, and the manual's title groups the CPC464 with the GT65 and CTM644.[6] Check which parts list matches your board before ordering parts.
Faults
[edit | edit source]Amstrad's basic hardware analysis for the CPC 6128 starts with the monitor: no power LED on the computer means checking the monitor's mains fuse and the 5 V on the cable from the monitor; a computer that starts but shows no picture is tried on another monitor, and if it works there the suspects are the monitor's cable termination, internal connectors and brightness control.[1] Diagnosis, the voltage chart and the alignment procedure are in the Amstrad CTM-644 Maintenance Guide.
Documentation
[edit | edit source]- Amstrad CPC 6128 Service Manual – CTM644 parts lists, alignment, voltages, circuit diagram and PCB (pp. 26–32)
- Amstrad CPC 664 Service Manual – the same monitor with the CPC 664
- Amstrad CPC 464 / CPC 6128 / GT65 / CTM644 / MP3 / CT1 Service Manual Amendment – the later chassis
Related pages
[edit | edit source]- Amstrad CTM-644 Maintenance Guide · Amstrad CTM-640
- Amstrad CPC 6128 · Amstrad CPC 664
- CRT Discharge Procedure · Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Amstrad Consumer Electronics plc, CPC6128 Micro Computer / CTM644 Colour Monitor / GT65 Green Monitor Service Manual. Described at Amstrad CPC 6128 Service Manual. Safety test p. 2; CTM644 cabinet drawing and parts list p. 26; electrical parts list and alignment instructions p. 27; parts list and voltages p. 28; circuit diagram pp. 29–30; main PCB pp. 31–32; technical specification on the back page.
- ↑ Wikipedia, "Amstrad CPC", section "CPC 664". Retrieved 2026-10-01. The 664's disc drive needs 12 V, supplied by the updated GT-65 and CTM-644 monitors.
- ↑ Jörg Gurowski, "Hinter Glas – Ein Blick in den Farbmonitor des CPC", CPC Amstrad International (1992). Transcribed at CPCrulez. Retrieved 2026-10-01. In German. Construction of the CTM644, the difference from the CTM640, and a home alignment procedure.
- ↑ Amstrad Consumer Electronics plc, CPC664 Micro Computer / CTM644 Colour Monitor / GT65 Green Monitor Service Manual. Described at Amstrad CPC 664 Service Manual.
- ↑ Amstrad Consumer Electronics plc, CPC464 Micro Computer / CTM640 Colour Monitor / GT64 Green Monitor Service Manual, pp. 22–24. Described at Amstrad CPC 464 Service Manual.
- ↑ 6.0 6.1 Amstrad plc, CPC464 / CPC6128 / GT65 / CTM644 / MP3 / CT1 Amendment Service Manual, CTM644 section pp. 27–30. Described at Amstrad CPC 464 / CPC 6128 / GT65 / CTM644 / MP3 / CT1 Service Manual Amendment.