Panasonic JR-200 Troubleshooting Guide
Fault-finding on the Panasonic JR-200 can follow Panasonic's JR-200U service manual, which has a RAM test and a ROM test that name the failing chip, a function test program, and twelve troubleshooting flowcharts.[1] The reference numbers below are those of the U.S. JR-200U. Japanese and PAL machines may differ; the PAL JR-200UP, for one, generates its timing from a different crystal.[2]
Before you start
[edit | edit source]- The power supply is inside the case and runs from the mains. Unplug the computer before opening it.[1]
- Check the simple things in Panasonic's owner troubleshooting table first: power and leads, the RF channel switch (channel 3 or 4) against the television, and the colour/monochrome switch underneath, which must be on "color" for a colour picture and on "monochrome" for a monochrome monitor.[3]
- Take care with the flat lead (the "multi lead") between the keyboard and the main board when lifting the top case; several of Panasonic's flowcharts end at it.[1]
No power
[edit | edit source]Panasonic's flowchart (1), "Power indicator does not light up":
- If the computer resets when switched on but the indicator stays dark, check the LED wire and the multi lead, then the LED itself.
- Otherwise check, in order: the mains supply, the power switch, the noise filter FL1, the output of the power transformer, the fuse, the output of the rectifier DB1, and finally whether IC34 delivers 5 V. Replace the first part that fails.
[1] The fuse is F1, 1.0 A, 125 V, on the transformer secondary. After the bridge rectifier DB1, the regulator IC34 has a 470 µF, 50 V input capacitor (C38) and a 1000 µF, 10 V output capacitor (C37) after the choke L2. The machine has a single +5 V rail.[1] Capacitor values for the whole board are on the Panasonic JR-200 Capacitor Replacement Guide.
Diagnostic programs
[edit | edit source]The service manual prints three diagnostic programs as listings; Panasonic's procedure loads them from cassette.[1]
| Message | Faulty chip |
|---|---|
| D-RAM ERROR! DEVICE = IC8 (or IC9, IC10, IC11) | The named dynamic RAM (HM4864P3) |
| V-RAM ERROR! DEVICE = IC7 | Video RAM (HM6116P3) |
| C-RAM ERROR! DEVICE = IC6 | Character RAM (HM6116P3) |
| ROM ERROR! DEVICE = IC4 (or IC5) | The named ROM (MN4864CA2 or MN4864CB2) |
| RAM-TEST NORMAL END | All RAM passed |
[1] The RAM test is machine code loaded with MLOAD and started with F=USR($1100). It overwrites all of memory, so switch the computer off and on before loading anything else. The function test is part BASIC and part machine code (LOAD, MLOAD, then RUN). It checks the printer output, colour bars (black, blue, red, magenta, green, cyan, yellow, white), screen distortion, block graphics, user-defined characters, the keyboard, the joysticks, the speaker and cassette MSAVE, MLOAD and VERIFY.[1]
Display faults
[edit | edit source]| Symptom | Checks, in Panasonic's order |
|---|---|
| No picture on the RGB output (monitor good) | Composite output working? If not, does the CRT controller IC1 produce RGB? Then IC27, the RGB cable and the DIN socket CN3 |
| No picture on the composite output (TV good) | CRT controller IC1 producing composite; IC28; transistor Q1; the composite cable and DIN socket CN3 |
| Composite picture but no colour | DIP switch in the colour position; clock at 14.31818 MHz; colour burst from IC1; IC29, IC30, IC31, IC33; then adjust the colour tone with VC1 |
| No picture on RF (TV good) | Composite output working (if not, follow the composite chart); DIP switch setting; lead to the RF converter; the RF converter |
Cassette faults
[edit | edit source]| Symptom | Checks, in Panasonic's order |
|---|---|
| Cannot SAVE or MSAVE | Recorder volume; signal at pin 27 of the PIA IC17; pin 22 of IC17 low; then IC21 and IC22, a resistor, the DIN socket and the cassette cable (these boxes are partly smudged in the scan) |
| Cannot LOAD or MLOAD | Recorder volume; plug and connector CN7; fuse resistor R13; output of the amplifier IC35; PIA IC17 |
| Recorder motor control does not work | Relay RL1 (pins 7 and 12 joined when it operates); cassette cable and CN7; pin 23 of IC17 high; transistor Q2 |
[1] The transfer speed selection switch sets 600 or 2400 baud for the cassette, and the setting is read when the computer is switched on.[4]
Keyboard, joystick, printer and sound
[edit | edit source]| Symptom | Checks, in Panasonic's order |
|---|---|
| Printer does not print (printer good) | Printer socket CN8; IC24 and IC25; PIA IC17 |
| No sound | Volume not at minimum; key-click tone; BEEP command (if silent, PIA IC17); external speaker socket; multi lead, speaker wires and speaker; volume control VR1; amplifier IC32; pulse from pin 10 of the sub-CPU IC18; pin 7 of IC17 high; IC21 |
| A key does not register | Scan signals from the sub-CPU IC18 (if absent, replace IC18); multi lead disconnected; IC18 pins 29 to 36 going low when a key is pressed (if not, IC19) |
| Joystick does not work (joystick good) | Scan signals from IC18; sockets CN1 and CN2; IC18 pins 29 to 36 going low when the stick is moved (if not, IC19) |
Related pages
[edit | edit source]- Panasonic JR-200
- Panasonic JR-200 General Maintenance
- Panasonic JR-200 Capacitor Replacement Guide
- Panasonic JR-200 Documentation
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Matsushita Engineering and Service Company, Service Manual: Personal Computer JR-200U, order no. EDCD 83-001: diagnostic programs pp. 1–16, power supply schematic p. 21, disassembly p. 73, troubleshooting flowcharts pp. 75–78 (PDF pages 74–77, printed sideways), replacement parts list. Hosted here as File:Panasonic JR-200U Service Manual EDCD 83-001.pdf; see Panasonic JR-200 Documentation.
- ↑ Markku Reunanen, Discovering the Panasonic JR-200U—link(accessed 2026-10-01) Hardware notes, including the different clock crystal of PAL machines.
- ↑ Matsushita Electric Industrial Co., Operating Instructions: Personal Computer JR-200U, troubleshooting p. 49. Hosted here as File:Panasonic JR-200U Operating Instructions.pdf.
- ↑ Matsushita Electric Industrial Co., Operating Instructions: Personal Computer JR-200U, section on the transfer speed selection switch. Hosted here as File:Panasonic JR-200U Operating Instructions.pdf.