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Sony HB-201 General Maintenance

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Sony HB-201 (Japanese) inside
Inside a Japanese HB-201: transformer, separate power board and main board (MSX Resource Center wiki photo)

The European Sony HB-201 (HB-201P) is built on the same PU-34 main board as the HB-101P and is covered by the same Sony service manual, so the case, keyboard and power supply procedures are those in Sony HB-101 General Maintenance.[1][2]

Safety

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Warning: the HB-201 has its mains transformer, fuse and power switch inside the case. Unplug the mains cable before removing any screws.

Sony lists the HB-201P only in its AE version for 220 V mains. Its mains fuse on the FU-29 board is therefore the AE value, T400mA, and it has no 120/240 V selector.[3] The Japanese HB-201 runs on 100 V; the transformer in the photograph above is labelled for 100 V.[4] A Japanese machine needs a step-down transformer on 220 V or 240 V mains.

Opening the case and removing the keyboard

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Follow Opening the case and Removing the keyboard. Sony's removal procedure is written for both the HB-101P and the HB-201P: five screws, the claws at the slits on each side, the power switch, then the cartridge holder, shield, grounding lug, CN13, CN14 and three board screws for the PU-34, and six plus 21 screws for the keyboard.[5]

The Japanese HB-201 has a separate power board beside the transformer, connected to the main board by a cable at CN901. Note where its connectors go before lifting the main board out.[4]

Power supply checks

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The HB-201P's rails are made in the same way as the HB-101P's:[6]

HB-201P supply rails
Rail Regulator Measure across
+5 V IC101 (SI-3052V) on the RE-23 board C903
+12 V IC48 (µPC78L12) C36
−12 V IC49 (NJM79L12A) C37

[6] The unregulated supply for +5 V is across C30 and C31. Sony gives no tolerance for the rails.

On a Japanese HB-201 the rectifiers and reservoirs are on the separate power board, among them C905, C906 and D901.[4] No schematic of that board has been published; trace it before replacing parts.

Clock adjustment

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Sony's clock adjustment covers the HB-201P: a frequency counter on pin 6 of IC6, the CPU, and VC1 set for 3.562500 MHz ±10 Hz. The steps are in HB-101 General Maintenance.[7]

Firmware ROM

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The HB-201P's Personal Databank ROM at IC8 is a TMM23128P-8712. Sony's manual says to fit it with jumper JW1 on its MASK side.[8]

Things that are not faults

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  • The Personal Databank starts at power-on. Hold CTRL, SHIFT, CODE and GRAPH while switching on to skip it.[9]
  • The PAUSE button halts the CPU until it is pressed again.[9]
  • Sony warns that switching on again immediately after switching off can stop the computer starting correctly.[10]

Maintenance checklist

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  1. Check that the mains voltage suits the model: 220 V for the HB-201P, 100 V for the Japanese HB-201.
  2. Unplug the mains cable before opening the case.
  3. Look for leaked electrolyte in the power supply section.
  4. Check +5 V across C903, +12 V across C36 and −12 V across C37 on an HB-201P.
  5. Clean the cartridge slot and controller connector contacts.
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References

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  1. ↑ Sony, HB-101P/201P Service Manual (File:Sony HB-101P HB-201P Service Manual.pdf). Hosted with a description at Sony HB-101P and HB-201P Service Manual.
  2. ↑ Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), electrical parts list, page 7-7: mounted PU-34 board A-8080-090-A for the HB-201P AE.
  3. ↑ Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), page 1-1 (HB-201P: 64 KB, 220 V ±10 %, channel adjustment knob supplied) and power supply schematic on page 5-23 (F901 T400mA on the AE version, T160mA and voltage change switch S902 on the E version).
  4. ↑ 4.0 4.1 4.2 File:Sony HB-201 (Japanese) inside.jpg, photograph uploaded to the MSX Resource Center wiki by Gdx on 24 May 2016: transformer label 1-447-996-23, 100 V, made in Japan; a separate power board with C905, C906, D901 and CN901 marked 8, GND, 8, 16, GND.
  5. ↑ Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), removal procedures, pages 2-1 and 2-2, labelled for the HB-101P (AE/E) and HB-201P (AE).
  6. ↑ 6.0 6.1 Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), power supply schematic, page 5-23: C30 and C31 (4700 µF) reservoirs feeding the RE-23 board's SI-3052V for +5 V (C903 on its output); IC48 (µPC78L12) and IC49 (NJM79L12A) for ±12 V with C36 and C37 on their outputs.
  7. ↑ Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), alignment, page 6-1.
  8. ↑ Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), section 2-2, page 2-2: firmware ROM IC8 is an MSM38128A-F6RS on the HB-101P and a TMM23128P-8712 on the HB-201P; jumper JW1 (MASK/EP) to the MASK side.
  9. ↑ 9.0 9.1 Sony HB-201, MSX Resource Center wiki—link(accessed 2026-10-21) Personal Databank and how to skip it; the PAUSE button halts the CPU; slot map.
  10. ↑ Sony, HB-101P/201P service manual (File:Sony HB-101P HB-201P Service Manual.pdf), page 1-3: caution to wait a moment after switching off before switching on again.


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