Jump to content

Sony HB-55 Troubleshooting Guide

From RetroTechCollection
Sony HB-55P HB-75P power board circuit (service manual)
HB-55P/75P power board: bridge D6 and C1 for +5 V, D1, D2 and C2 for +12 V, D3, D4 and C3 for −12 V, the SI-3052V and SI-3122V regulator boards and the NJM79L12 (Sony service manual, page 5-24)

Fault-finding on the Sony HB-55 starts with the internal power supply, then the sixteen 4116-type dynamic RAMs that hold its video and main memory. Component references are from Sony's service manual for the HB-55P, HB-75P and HB-75B.[1] The Japanese HB-55 has a different main board, marked 1-611-737-13, so its reference numbers may not match.[2]

Warning: mains voltage is present inside the case on the fuse board, the power switch and the transformer. Unplug the mains cable before opening the machine.

Quick reference

[edit | edit source]
Symptoms, causes and actions
Symptom Probable cause Action
Dead, power indicator dark Mains fuse F401, power switch S401, transformer thermal fuse, CN2 to the LED board unplugged No power
Indicator lit, no picture or garbage on screen +5 V, +12 V or −5 V missing at the RAMs; failed 4116 RAM; video chip IC2 No picture or garbage
Colour wrong or missing on a composite or RF picture Sub-carrier or VCO out of adjustment Colour
Picture too dark or too bright on a monitor Video output level Colour
Disk drive ignored Databank skipped, or disk drive disabled by an HBI-55 cartridge Personal Databank
Slot B will not take a cartridge Receptacle not fitted Fit the receptacle supplied with the HB-55P

[3][4][5]

No power

[edit | edit source]
  1. Unplug the machine and open it (General Maintenance).
  2. Check F401 on the fuse board. Fit only a 160 mA time-lag fuse.[3]
  3. With F401 intact, check continuity through S401 and the transformer primary from the mains plug. The thermal fuse is in series with the primary.[3]
  4. Plug in and switch on. Measure across C1 (10,000 µF) and C2 (3,300 µF) on the power board. No voltage across C1 points to the 5 V winding or the bridge D6; none across C2 points to the 12 V winding or D1 and D2.
  5. With voltage across C1 but no +5 V, check IC1, the SI-3052V on the 5 V board, and the line through L1 to CN5.
  6. The power indicator is on the LED board, connected at CN2 of the power board. CN2 is one of the connectors unplugged to remove the upper cabinet, so check it is back in place if the machine works but the indicator stays dark.[6]

Before fitting a new F401, check the rectifiers D1 to D4 and D6 and the reservoirs C1 to C3 for a short.

No picture or garbage

[edit | edit source]

The HB-55P's video memory and main memory are both 4116-type dynamic RAMs, sixteen in all (IC3 to IC6, IC9 to IC12, IC58 to IC61 and IC65 to IC68). Each needs three supplies: +12 V on pin 8, +5 V on pin 9 and −5 V on pin 1, with ground on pin 16.[7]

  1. Check all three supplies at one RAM chip of each group.
  2. Check +5 V at pin 33 of IC2, the TMS9929ANL.
  3. If the supplies are correct, suspect the video RAM (IC3 to IC6 and IC9 to IC12) for a garbled screen, and the main RAM or the ROMs for a machine that never reaches BASIC or the Databank.
  4. The 4116-type RAMs can be replaced with 4116-compatible 16K × 1 parts; the HB-75P's MSM3764 is a different, single-supply part and is not a substitute.[7]

On the MSX Resource Center forum, Wierzbowsky's first suggestion for a Japanese HB-101 with a black screen was to check the supply voltages at every RAM chip.[8]

Colour

[edit | edit source]

The HB-55P has three adjustments, made in order:[9]

  • VCO phase: 7.0 V ±0.1 V at TP1 (R37 and R38), set with VC1.
  • Sub-carrier: 4.433618 MHz ±10 Hz at TP2 (C28 and C47), set with VC2.
  • Video level: 1 V ±0.1 V peak to peak at TP3 (pin 2 of CN1) into 75 Ω on a white screen, set with VR4.

The full procedure is in General Maintenance. Sony says to make the adjustments in this order, so check TP1 before touching VC2.[9]

Personal Databank

[edit | edit source]

With a disk drive connected, the HB-55's Databank is skipped at power-on. With both a disk drive and an S-RAM cartridge such as the HBI-55 fitted, the menu appears but the disk drive is disabled. The MSX Resource Center knows of no workaround; remove one or the other.[5] On the Japanese HB-55, the Databank's functions ask for the HBI-55 cartridge if it is not fitted.[10]

The BASIC ROM is IC42 (MSM38256-70RS) and the Databank ROM is IC44 (MSM38128A-77RS). Jumpers JW5 and JW7 to JW10 select mask ROM or EPROM for IC42 and IC43, and JW6 is removed for an EPROM at IC44. If either ROM has been replaced with an EPROM, check those jumpers.[11]

Test points

[edit | edit source]
Supply pins on the HB-55P main board
IC Type Supply pins
IC2 TMS9929ANL video chip +5 V 33, ground 12
IC3–IC6, IC9–IC12, IC58–IC61, IC65–IC68 4116-type RAM +12 V 8, +5 V 9, −5 V 1, ground 16
IC16 µPD8255AC-5 PPI +5 V 26, ground 7
IC41 LH0080A or µPD780C-1 CPU +5 V 11, ground 29
IC42 MSM38256-70RS MSX-BASIC ROM +5 V 28, ground 14
IC44 MSM38128A-77RS Databank ROM +5 V 28, ground 14
IC48 AY-3-8910 or YM2149 PSG +5 V 40, ground 1

[7] The CPU clock is 3.579545 MHz.[12]

[edit | edit source]

References

[edit | edit source]
  1. ↑ Sony, HB-55P/75P/75B Service Manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf). Hosted with a description at Sony HB-55P, HB-75P and HB-75B Service Manual.
  2. ↑ File:Sony HB-55 (Japanese) main board.jpg, photograph uploaded to the MSX Resource Center wiki by Mars2000you on 3 August 2016: board marked 1-611-737-13.
  3. ↑ 3.0 3.1 3.2 Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), schematic on pages 5-23 and 5-24 and parts list on page 7-14: F401 time-lag 160 mA; S401; transformer with thermal fuse; D6 RB-402 and C1 10000 µF to IC1 SI-3052V (+5 V); D1, D2 and C2 3300 µF to IC2 SI-3122V (+12 V); D3, D4 and C3 330 µF to IC3 NJM79L12 (−12 V); LED board on CN2; CN5 to the main board.
  4. ↑ Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), page 1-2: power indicator; reset clears memory; cartridge slot B needs its receptacle installed; no RGB connector on the HB-55P.
  5. ↑ 5.0 5.1 Sony HB-55, MSX Resource Center wiki—link(accessed 2026-10-21) With a disk drive connected the Personal Databank is skipped; with a disk drive and an S-RAM cartridge such as the HBI-55, the menu appears but the disk drive is disabled, with no workaround.
  6. ↑ Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), disassembly, page 2-1: disconnect CN11 and CN12 on the main board and CN2 on the power board to remove the upper cabinet.
  7. ↑ 7.0 7.1 7.2 Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), IC supply table beside the main board schematic (PDF page 52): MCM4116BP20 or µPD416C-2 at IC3 to IC6, IC9 to IC12, IC58 to IC61 and IC65 to IC68 on the HB-55P (+12 V pin 8, +5 V pin 9, ground 16, −5 V pin 1); IC2 TMS9929ANL (+5 V 33, ground 12); IC41 CPU (+5 V 11, ground 29); IC42 and IC44 ROMs (+5 V 28, ground 14); IC48 PSG (+5 V 40, ground 1); IC16 PPI (+5 V 26, ground 7); IC7 CX7925A-1 (+5 V 12, ground 14); IC14 µPD4066BC (+12 V 14, ground 7).
  8. ↑ Sony HB-101 Video Issues / Black Screen, MSX Resource Center forum, 9 May 2025 to 5 May 2026—link(accessed 2026-10-21) Wierzbowsky, 10 May 2025: in most cases a black screen means bad RAM; check all voltages on the RAM chips.
  9. ↑ 9.0 9.1 Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), alignment, page 6-1.
  10. ↑ Sony HB-55, MSX Resource Center wiki—link(accessed 2026-10-21) Japanese model: selecting a Databank option without the HBI-55 gives a message to power off and insert the cartridge.
  11. ↑ Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), section 2-2, page 2-2: BASIC ROM at IC42 (and IC43), jumpers JW5 and JW7 to JW10 to the MASK side; firmware ROM IC44, remove JW6 for an EPROM.
  12. ↑ Sony, HB-55P/75P/75B service manual (File:Sony HB-55P HB-75P HB-75B Service Manual.pdf), specifications, page 1-1.


Retrieved from "https://retrotechwiki.com/index.php?title=Sony_HB-55_Troubleshooting_Guide&oldid=28200"