Philips NMS 8255
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| A two-drive NMS 8255. Its front panel reads "NMS 8250", as on the one-drive model | |
| Specifications | |
|---|---|
| Manufacturer | Sanyo, for Philips |
| Type | MSX2 home computer |
| Released | 1987 |
| Intro price | ƒ2295 (Netherlands) |
| CPU | Z80A |
| Memory | 128 KB RAM, 128 KB video RAM, 48 KB ROM, 16 KB disk ROM |
| Storage | Two built-in 3.5-inch drives (720 KB formatted) |
| Display | Yamaha V9938 |
| Sound | PSG inside the Yamaha S-3527 MSX-Engine |
| Power | 220 V ±10 %, 50 Hz |
| OS / Firmware | — |
| Model no. | NMS 8255/00, /16, /19 |
The Philips NMS 8255 is an MSX2 desktop computer that Philips sold from 1987 in the Netherlands, Belgium, France and Spain. It was made by Sanyo and is a localised version of the Sanyo PHC-50FD2. It is the Philips NMS 8250 with a second built-in floppy drive; both have "NMS 8250" on the front panel, and only the label on the back says which is which.[1] Philips covered both models in one service manual and one repair method.[2]
The machine has 128 KB of user RAM; the "256K RAM" printed on the front includes the 128 KB of video RAM.[1][2]
Versions
[edit | edit source]| Version | Market | Keyboard |
|---|---|---|
| /00 | Netherlands, Belgium | QWERTY with numeric keypad |
| /16 | Spain | QWERTY with ñ key and numeric keypad |
| /19 | France, Belgium | AZERTY with numeric keypad |
Hardware
[edit | edit source]The NMS 8255 uses the NMS 8250's main board (Z80A, S-3527 MSX-Engine, V9938 with 128 KB of video RAM, WD2793A disk controller, RP5C01 clock), analogue unit, power supply and keyboard. The chip-by-chip description is on the Philips NMS 8250 page. What the NMS 8255 adds is the second drive: Philips's parts list gives the two drives as U104 and U103, both part 4822 693 91114, and the wiring diagram shows a DRIVE 1 and a DRIVE 2 cable.[3]
The two drives share the supply's +5 V and +12 V rails. An NMS 8255 owner who ran his machine from a PC supply while testing measured about 1.50 A on +5 V with the drives idle and 1.56 to 1.60 A with a drive working, and 0.22 A on +12 V rising to 0.3 A with a drive working.[4]
Power supply
[edit | edit source]The supply board (U101) is the NMS 8250's: an SI-3052V regulator for +5 V after a 22000 µF reservoir, a 7812 for +12 V and an AN79M12 for -12 V, with wire links on the board for 220 V or 240 V mains.[5] RetroTechie reported having seen an STR9005 fitted in place of the SI-3052V.[4] Faults and checks are on Philips NMS 8255 Troubleshooting Guide.
Known problems
[edit | edit source]- Overheated rectifiers in the supply. On the NMS 8255 in the forum thread above, the diodes D1050 to D1053 were coated in dust and had darkened the board; the picture and sound level rose slowly and then dropped.[4]
- A +5 V rail that is correct off load but rises to almost 6 V with the machine connected, pointing at the +5 V regulator.[4]
- Poor mixing of the internal sound with SCC and other sound cartridges.[1] An article from the Dutch Digital KC, translated by Hans Otten, blames errors in the audio circuit common to the NMS 8250, 8255 and 8280; the fixes are on Philips NMS 8255 Troubleshooting Guide.[6]
- The plastic front panel becomes very fragile with age; avoid putting any load on it in transit.[1]
Documentation
[edit | edit source]The Philips service manual and repair method for the NMS 8250 and NMS 8255 are hosted and described on Philips NMS 8250 Documentation. The MSX Resource Center links a Dutch user guide for the NMS 8255 on the Internet Archive (item philipsnms8250ug).[1]
Maintenance and repair
[edit | edit source]- Philips NMS 8255 General Maintenance
- Philips NMS 8255 Troubleshooting Guide
- Philips NMS 8255 Capacitor Replacement Guide
The Philips NMS 8250 guides cover the shared boards, the service cartridge error numbers and the alignments in full.
Related pages
[edit | edit source]- Philips NMS 8250, the one-drive version
- Philips NMS 8280, the video version in a similar case
- Philips NMS 8245
- Philips NMS 8250 Documentation
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Philips NMS 8255, MSX Resource Center wiki, 7 March 2026—link(accessed 2026-10-21) Community page: made by Sanyo for Philips, basically the PHC-50FD2 rebranded and localised; desktop with two built-in drives, dark silver and grey; almost identical to the NMS 8250, which has one drive; both carry "NMS 8250" on the front label, the rear label gives the model; 128 KB RAM, not the 256 KB printed on the case, which adds the video RAM; versions /00 (Netherlands and Belgium, QWERTY), /16 (Spain, QWERTY with ñ) and /19 (France and Belgium, AZERTY), all with numeric keypad; year 1987; launch price ƒ2295 in the Netherlands; RAM in slot 3-2; V9938; PSG in the S3527 MSX-Engine; Z80A from NEC (D780C-1); two 720 KB drives; MSX-DOS 1 and Home Office 2 on disk; known for SCC and other sound cartridge mixing problems, with several modifications to fix it; the plastic front panel becomes very fragile with age; connections listed.
- ↑ 2.0 2.1 2.2 Philips, Service Manual, Home computer NMS8250/00/16/19, NMS8255/00/16/19, cover CS 7 567, PDF page 1: specification (Z80A; 48k ROM, 16k disk ROM, 128k video RAM, 128k user RAM; V9938; S-3527 MSX controller; 3.5-inch 1 MB floppy drive; RF output on UHF channel E36, monitor output, SCART, cassette recorder, two joysticks, printer, two cartridge slots; QWERTY /00 and /16, AZERTY /19; 220 V ±10 %, 50 Hz). Hosted as File:Philips NMS 8250 and NMS 8255 Service Manual.pdf.
- ↑ Philips, Service Manual NMS8250/NMS8255, PDF page 38, mechanical parts list: item 7 floppy drive (U104) and item 23 floppy drive (U103), both 4822 693 91114; item 15 transformer 4822 148 60157; item 16 analog unit (U102); item 17 power supply (U101); item 18 main panel /00, /16, /19 (U100). PDF pages 9 and 10: wiring diagrams with DRIVE 1 and DRIVE 2. Hosted as File:Philips NMS 8250 and NMS 8255 Service Manual.pdf.
- ↑ 4.0 4.1 4.2 4.3 Philips NMS-8255 power (?) supply question and modding, July and August 2010—link(accessed 2026-10-21) Wild_Penguin's NMS 8255. 16 July 2010: picture brightness and PSG level rose slowly and then dropped, sometimes with a pop, once with a hang; a soldered wire link set the supply for 220 V or 230 V. 17 July: rectifier diodes D1050 to D1053 coated in dust with the board darkened round them; replacing them helped. 8 August: still occasional hangs; rails measured -12.01 V, +5.78 to 5.94 V and +11.86 V. RetroTechie: +5 V is usually 5.0 ±0.25 V; suspect the +5 V regulator IC1050 (S-3052V on the schematic, and he had also seen an STR9005 there) or the output capacitor C1051 (1000 µF); the NMS 8250/55 supplies have parts at mains voltage. 10 August: +5 V correct off load; C1051 replaced (1000 µF 10 V) without curing it; about 6 V with the analogue board disconnected and about 7.4 V with the drives also disconnected; RetroTechie: check the regulator's solder joints, the signs point to a faulty +5 V regulator, do not use the supply until it is repaired. 15 August: on a PC supply about 1.50 A at +5 V, 1.56 to 1.60 A with a drive working, 0.22 A at +12 V and 0.3 A with a drive working; the PSG could not be heard with an SCC cartridge fitted; C119 was already fitted the right way (opposite to the board print) and R174 was 910 Ω, and changing R428 and R429 to electrolytics made no audible difference. RetroTechie: the STR9005 is a low-drop regulator rated at 4 A; the rectifier diodes are 3 A or 5 A types and regularly fail.
- ↑ Philips, Service Manual NMS8250/NMS8255, PDF page 20 (sheet CS 7 580), power supply U101: L901, F1001 (250 V, 2 A) and SW901 on the mains side; +5 V through F1050 (6.3 A T), bridge D1050 to D1053 (DSB15C), C1050 22000 µF and IC1050 SI-3052V with C1051 1000 µF; +12 V through bridge D1054 to D1057 (DSF10C), F1051 (1 A T), C1052 4700 µF, IC1051 L7812-RA and C1053 220 µF; -12 V through R1050 (marked with a warning triangle), C1054 470 µF and IC1052 AN79M12. PDF page 32: board layout 41 674 B12 with the links J220V and J240V. Hosted as File:Philips NMS 8250 and NMS 8255 Service Manual.pdf.
- ↑ Verminkt geluid bij NMS 8250/55/80 (Distorted sound for NMS8250/55/80), from Digital KC, scanned, OCRed and converted to PDF by Hans Otten in 2001, translated into English with comments and pictures by Hans Otten in 2002, 4 pages. https://download.file-hunter.com/Technical/Hans%20Otten/nms82xxgeluid.pdf (retrieved 2026-10-21). On the main board: electrolytic C119 is polarity-sensitive, its board print is reversed and it is often fitted the wrong way round, so turn it; R174 should be 910 Ω but is sometimes 2700 Ω, giving too low a sound level, so add 1500 Ω in parallel. On the analogue board of the 8250/55, R428 and R429 (100 Ω) should be 100 µF 10 V electrolytics with the negative lead towards connector AB; on the 8280 the same applies to R426. If the sound fades at intervals of seconds with an FM-PAC, the -12 V regulator (7912, 1 A) is defective. R170 sets the PSG level in the mix with Q102.