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Philips NMS 8280 Capacitor Replacement Guide

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Philips NMS 8280 power supply circuit (service manual)
Power supply circuit with C1050 to C1054, from page 21 of the service manual

The Philips NMS 8280 is not known for failing capacitors. On the MSX Resource Center, members told an owner planning a full recap that the machine is "not on the suspect list", that it "doesn't usually suffer of leaking or dying caps", and that recapping a machine with no fault can do more harm than good through broken traces and placement errors.[1] In the best-documented supply fault, replacing every supply capacitor and regulator did not help; the rectifier diodes were the cause.[2] Check the diodes first; see Philips NMS 8280 Troubleshooting Guide.

Philips's parts lists for the NMS 8280 name film capacitors and one tantalum capacitor, but no aluminium electrolytics. Their values are printed only on the circuit diagrams, with a voltage code letter.[3][4]

Power supply

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Power supply and supply input capacitors (service manual, page 21)
Ref Value Code Voltage Position
C1050 22000 µF e 16 V +5 V reservoir after D1050 to D1053, input of IC1053 (STR9005)
C1051 1000 µF d 10 V +5 V, at IC1053
C1052 4700 µF f 25 V +12 V reservoir, input of IC1051 (L7812-RA)
C1053 470 µF e 16 V +12 V output of IC1051
C1054 470 µF f 25 V −12 V, input of IC1052 (AN79M12)
C102 47 µF d 10 V Main board, +5 V input
C103 47 µF e 16 V Main board, +12 V input
C101 22 µF e 16 V Main board, −12 V input

[5][4]

The NMS 8280's supply differs from the NMS 8250's: C1053 is 470 µF where the NMS 8250 has 220 µF, and the +5 V regulator is an STR9005 where the NMS 8250 has an SI-3052V.[5][6] Do not order parts from the Philips NMS 8250 Capacitor Replacement Guide table without checking. C1051 and C102 are 10 V parts on the 5 V rail; a 16 V part of the same capacitance is a reasonable choice if it fits. C1054 and C101 are on the −12 V side, so check their polarity on the board before removing them.[5]

Sound circuit

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Main board sound capacitors (service manual, page 23)
Ref Value Code Voltage Note
C119 100 µF d 10 V PPI sound coupling. The board print is reversed; check the orientation against the diagram
C121 100 µF d 10 V PSG output coupling, after R170
C122 470 µF d 10 V Decoupling for the Q102 stage

[7][8]

Hans Otten's notes add one capacitor that Philips did not fit: replace R426 on the analogue unit, a 100 Ω resistor, with a 100 µF 10 V electrolytic, negative lead towards connector AB. This is part of the fix for distorted and badly mixed sound; see Philips NMS 8280 Troubleshooting Guide.[8]

Analogue unit

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The analogue unit carries the video digitiser and superimpose circuits. The capacitors below were read from the right-hand half of its circuit diagram, which includes the video and audio inputs and outputs. Read the others from the board.[9][4]

Analogue unit capacitors read from the diagram (partial)
Ref Value Voltage Position
C350, C351, C352 470 µF 6.3 V R, G and B outputs to SCART
C353 470 µF 6.3 V Composite video output
C354 470 µF 6.3 V See the diagram
C359 220 µF 16 V +5 V supply to IC304 (V7040)
C357 10 µF 16 V See the diagram
C364 100 µF 10 V See the diagram
C376 470 µF 16 V Video input
C378, C380 10 µF 16 V Audio inputs, right and left
C381, C382 22 µF 16 V Audio input buffers Q311 and Q316
C383, C387 22 µF Not legible Audio stages; read the part on the board
C385 10 µF 16 V Left audio output
C389 22 µF 10 V Right audio output
C397 22 µF 10 V See the diagram

[9]

Procedure

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Philips NMS 8250 Capacitor Replacement Guide covers the similar NMS 8250 supply board, and Capacitor Failure Symptoms describes what a failed part looks like. For each part:

  1. Unplug the machine and take out the supply board, or the board you are working on.
  2. Write down the designator, capacitance, voltage, diameter and height, and the stripe side.
  3. Remove the old part, clean the holes and fit the new one with the stripe on the same side.
  4. On C119, follow the circuit diagram, not the board print.[8]
  5. While the supply board is out, look at the rectifier diodes and the board under them; replace the diodes if the board is darkened or the diodes are suspect.[2]
  6. Measure +5 V, +12 V and −12 V with everything connected before refitting the case.
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References

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  1. ↑ NMS8280 recapping, October and November 2020—link(accessed 2026-10-21) gianlucarenzi traced all the electrolytics on the video board, main board and power supply, "they are a LOT", and asked about a kit. meits: no known kit; the NMS 8280 is "not on the suspect list", he would just switch it on; set the PSU jumper from 220 V to 240 V, "The 4 diodes will love you for it". jltursan: "the NMS8280 (unlike the A1200) doesn't usually suffer of leaking or dying caps". Grauw: if the machine has no issues and no known problem with caps, recapping can do more harm than good (broken traces, placement errors). gianlucarenzi, 1 November 2020: his concern is the power supply's big capacitors.
  2. ↑ 2.0 2.1 PHILIPS 8280 bad picture quality...., September 2014—link(accessed 2026-10-21) japanretroCT: vertical shaking of the image that faded after about twenty minutes; "I changed all capatitors and voltage regulators on PSU but problem is still here"; there are "at least 50" capacitors in the machine. Jipe: change the four big diodes on the power supply, a common failure of the 8280's supply. New diodes cured it, with a fan to keep them cool.
  3. ↑ Philips, Service Manual, Home computer NMS8280/00/16, 4822 727 15939, PDF pages 45 to 47: electrical parts lists for the main board, analogue and sub analogue units, power supply, floppy drive and control unit; the only electrolytic-type capacitor listed is C333, 0.47 µF 35 V tantalum, on the analogue unit. Hosted as File:Philips NMS 8280 Service Manual 4822 727 15939.pdf.
  4. ↑ 4.0 4.1 4.2 Philips, Service Manual NMS8280, PDF page 49, "Symbols used in circuit diagrams" (39 301 A13): electrolytic capacitors, voltage by code letter: a 2.5 V, b 4 V, c 6.3 V, d 10 V, e 16 V, f 25 V, g 40 V, h 63 V. Hosted as File:Philips NMS 8280 Service Manual 4822 727 15939.pdf.
  5. ↑ 5.0 5.1 5.2 Philips, Service Manual NMS8280, PDF page 21 (sheet CS 9 271): power supply with C1050 22000 µF e, C1051 1000 µF d, C1052 4700 µF f, C1053 470 µF e, C1054 470 µF f, rectifiers D1050 to D1053 (C01-02F) and D1054 to D1057 (DSF10C), regulators IC1053 STR9005, IC1051 L7812-RA and IC1052 AN79M12; main board end C102 47 µF d (+5 V), C103 47 µF e (+12 V) and C101 22 µF e (−12 V). PDF page 42: supply board layout 42 082 B12. Hosted as File:Philips NMS 8280 Service Manual 4822 727 15939.pdf; reproduced as File:Philips NMS 8280 power supply circuit (service manual).png and File:Philips NMS 8280 power supply board layout (service manual).png.
  6. ↑ Philips, Service Manual NMS8250/NMS8255, PDF page 20 (sheet CS 7 580): C1053 220 µF and IC1050 SI-3052V. Hosted as File:Philips NMS 8250 and NMS 8255 Service Manual.pdf.
  7. ↑ Philips, Service Manual NMS8280, PDF page 23: PPISND through R169 12 kΩ and C119 100 µF (code d); SSGSND to Q102 (2SC536NP), its collector supply decoupled by C122 470 µF (code d); output through R170 1 kΩ and C121 100 µF (code d). Hosted as File:Philips NMS 8280 Service Manual 4822 727 15939.pdf.
  8. ↑ 8.0 8.1 8.2 Verminkt geluid bij NMS 8250/55/80 (Distorted sound for NMS8250/55/80), from Digital KC, scanned and translated into English with comments by Hans Otten (2001 and 2002). https://download.file-hunter.com/Technical/Hans%20Otten/nms82xxgeluid.pdf (retrieved 2026-10-21). C119 on the main board: "The printing on the board is reversed and the elco is often inserted the other way around"; turn it. "On the analoque board of the 8280 a resistor R426 of 100 ohm is placed. Replace with elco 100 uF/10V with the minus sign at conector AB."
  9. ↑ 9.0 9.1 Philips, Service Manual NMS8280, PDF page 32, right-hand half of the analog unit diagram (sheet CS 9 274): C350, C351 and C352 470 µF (code c) on the R, G and B outputs to the SCART connector through R344 to R346 (39 Ω); C353 470 µF (code c) on the composite video output through R347 (75 Ω); C354 470 µF (code c); C359 220 µF (code e) on the +5 V supply to IC304 (V7040); C357 10 µF (code e); C364 100 µF (code d); C376 470 µF (code e) on the video input, terminated by R407 (75 Ω); C378 and C380 10 µF (code e) on the right and left audio inputs; C381 and C382 22 µF (code e) at the audio buffers Q311 and Q316; C385 10 µF (code e) on the left audio output; C389 22 µF (code d) on the right audio output; C397 22 µF (code d). The code letters of C383 and C387 (22 µF) are not legible on the scan. Hosted as File:Philips NMS 8280 Service Manual 4822 727 15939.pdf.



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