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Panasonic CF-2700 Troubleshooting Guide

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Panasonic CF-2700 power supply circuit
Power supply circuit of the export CF-2700, from page 19 of the service manual

Fault-finding on the Panasonic CF-2700 starts at the supply. All four rails are made on the main board from one transformer, and two of them depend on the slot micro switches. On a machine that shows no sign of life, check the fuses, the rails and the switches before any chip.[1] The designators below are those of Matsushita's service manual for the export model. Some later boards differ, as described on the Panasonic CF-2700 page. For opening the case and the adjustments, see the Panasonic CF-2700 General Maintenance guide.

Measure the rails first

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Measure at a slot, with pin 41 as ground:[2][3]

Rails and what makes them
Rail Where to measure Expected Parts behind it
+5 V Slot pins 45, 47 4.97 to 5.03 V D7, D8, C11, Q1, Q7, Q8, Q2, VR1, T3.15A fuse, C18
+12 V Slot pin 48 +12 V D3, D5, C10, IC1 (AN7812R), C7
−12 V Slot pin 50 −12 V D4, D6, C6, IC2 (AN7912T), C12
−5 V Test point on the main board −5 V R31, R36 from −12 V, 100 µF output capacitor

The pattern of rails that are present points to the fault:

Rail patterns
Rails present Look at
None, power LED dark Mains lead, switch SW101, the T160mA fuse on the power source board, CN101 and CN102, the transformer
−12 V and −5 V only The PSW line: slot micro switches, CN5, Q9, D15, R38, C38
+12 V, −12 V and −5 V, no +5 V The T3.15A fuse, Q1, Q7, Q8, Q2, VR1, C11
+5 V and −12 V, no +12 V IC1, D3, D5, C10
+5 V and +12 V, no −12 V or −5 V IC2, D4, D6, C6
−12 V present, −5 V wrong R31, R36 and the −5 V capacitor

[1] +5 V cannot be present without +12 V, because the +5 V reference is divided down from +12 V.[1]

No sign of life

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Fuses

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There are two fuses: T160mA in the mains primary on the power source board, and T3.15A in the +5 V output on the main board.[1] A British CF-2700 that looked unused and did nothing at switch-on had a blown T160mA fuse, and worked once it was replaced.[4] Before fitting a new fuse, check the transformer primary, the rectifier diodes and the reservoir capacitors for a short; a fuse that fails again has a reason. Corroded fuse clips give the same symptom as a blown fuse, so clean them and check continuity across the holder.[4]

Slot micro switches

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On the main board schematic the normally closed contacts of the two slot switches are in series between ground and the PSW line, through CN5, and the SW1 and SW2 pins of a slot connector are wired to the same points.[5] If a switch contact is dirty, or CN5 is loose, PSW opens and +5 V and +12 V stay at about 0 V while −12 V and −5 V are normal.[1] On the MSX Resource Center forum the advice for a dead CF-2700 is to try a cartridge in each slot, since a cartridge bridges the contacts, and then to clean the switches in both slots.[4]

  1. Measure −12 V at slot pin 50. If it is present and +5 V is not, suspect PSW.
  2. Switch off, and measure from CN5 pin 3 to ground. It should read close to 0 Ω with both slot covers closed.
  3. If it does not, measure across each switch and clean or replace the one that is open. Check the CN5 plug and its three wires.
  4. If CN5 pin 3 is at ground and +12 V is still missing, check Q9, D15, R38, C38 and IC1 itself.[1]

Rails correct, no picture

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Check signs of life before the video path:

  • Press Caps Lock. If its LED toggles, the Z80, the ROM and the RAM are probably working.[4] The Caps LED (D302) is driven by bit 6 of PPI port C, lit when low.[6]
  • Check the clocks with an oscilloscope or frequency counter: 10.6781522 MHz at IC43 pin 3, 3.559384 MHz at the CPU, IC8 pin 6, and 1.779462 MHz at IC39 pin 8.[7]
  • Check RESET at the CPU. It should go from low to high about 60 ms after switch-on, timed by C13 and R26 with Q10.[7]
  • Without an oscilloscope, a Z80, VDP or RAM chip that stays cold after a few minutes of running suggests no activity. A short between the supply and ground can come from a failed ceramic capacitor.[4]
  • An external RAM cartridge is an easy test for the on-board RAM.[4]

If the machine is running but there is no picture, work along the video path:

Picture faults
Symptom Check Notes
No picture on RF, picture on video The RF channel and the trimmer The output is set for UHF channels 35 to 37.[3]
No picture on either output CN2 and the video board cable CN2 carries GND, sound, R−Y, B−Y, Y, a clock, +5 V, +12 V and −12 V to the video board.[8] Reseat it with the white lead on pin 9.[9]
Picture without colour, or colour unstable The colour clock Set CT201 for 4.43361875 MHz ±3 Hz at IC203 pin 9 on the video board.[3]
Screen garbled or sprites corrupt The VDP (IC38) and video RAM On the manual's board the video RAM is eight µPD416C-3 (IC49 to IC56), each fed from +5 V, +12 V and −5 V.[10] Check all three before condemning a chip.

Keyboard

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The keyboard is scanned through the PPI (IC45) and the 74LS145 decoder (IC46), and joins the main board by two flat cables at CN8 and CN9.[6][8]

  • A whole row or column dead: reseat CN8 and CN9, holding each cable by both sides of its stiffened end, and look for a cracked track on the flexible pattern.[9]
  • One key dead: the key switch. The keyboard uses separate switch units, listed in the parts list.[11]
  • No Caps Lock light but the keyboard types: the LED D302 or its wiring; the LED is on the keyboard assembly.[11]

Cassette

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MSX records by FSK at 1200 or 2400 baud. The input stage uses an AN6553 op amp (IC34) as a filter and a µPC311C comparator (IC41), with the cassette input terminated in 150 Ω.[12] PPI port C bit 4 switches the motor (0 = on). The parts list has one relay, RY1, which sits next to the cassette socket CN3 on a German board, and the remote contacts are pins 6 and 7 of the DIN socket.[6][2][11][13]

  • Will not load: try a known good 1200 baud recording, adjust the recorder's volume, and keep the recorder at least 30 cm from the television, as the self test instructions require.[14]
  • Motor does not start: listen for RY1 when a load command is given, and check continuity between pins 6 and 7 of the socket while it is energised.[2]

Printer, joysticks and sound

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Port faults
Symptom Check
Printer does not print The computer reads BUSY (pin 11 of the 14-pin connector) as status bit 1 at 90H and waits while it is 1. Check pin 11, the strobe on pin 1 and ground on pin 14.[2][6]
Joystick dead in one direction Pins 1 to 4 of that port, read through PSG port A by way of the 74LS157 multiplexers (IC28, IC33).[15]
Fire buttons dead on one port The 74LS09 open-collector gates (IC37, IC40); pins 6 and 7 only work as inputs while the matching PSG port B bits are high.[15][2]
Rails drop with a joystick or mouse plugged in The +5 V pin of each port is rated at 50 mA; try the device on another machine.[2]
No sound The sound socket and the SOUND line on CN2 to the video board, then the PSG (IC36).[8][15]

Self test cartridge

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Matsushita's self test, from cartridge DFWV95C0001, checks the VDP and video RAM, printer, RAM, PSG, keyboard, ROM, screen, cassette, joysticks, print-out and audio. It needs an MSX printer, a CF-2201 joystick, a television and a cassette recorder.[14] The cartridge is not part of the hosted scan.

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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Matsushita, Service Manual: Personal Computer CF-2700 (order no. IED84113035C2, 1984), printed pages 18 and 19, "Power Supply Circuit", with the diagram on page 19 (File:Panasonic CF-2700 power supply circuit.png). Power source block: SW101, line filter L101 with C101 and C102, T160mA fuse; transformer T101 to CN1 on the main board (5 V, 5 V, GND, 12 V, 12 V). +5 V: D7 and D8, C11 (16 V 6800 µF), pass transistor Q1 (2SA1061P), driver Q7 (2SC1318-Q), error amplifier Q8 and Q2 (2SA722-S), reference from +12 V through R5, VR1 and R80, T3.15A fuse, C18 (10 V 330 µF). +12 V: D3 and D5, C10 (25 V 4700 µF), IC1 AN7812R, C7 (16 V 330 µF). −12 V: D4 and D6, C6 (25 V 1000 µF), IC2 AN7912T, C12 (16 V 100 µF). −5 V: R31 (470 Ω) and R36 (680 Ω) from −12 V, 16 V 100 µF on the output. PSW at ground: +5 V and +12 V run. PSW open: Q9 (2SC1685-Q) turns on, more than about 500 µA flows from pin 4 of IC1, IC1's output falls to about 0 V and +5 V follows; −12 V and −5 V are left as they are. R38 and C38 delay the rise of +5 V and +12 V; R37 discharges C38. Test points on +12 V, −5 V and −12 V. See Panasonic CF-2700 Service Manual.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed pages 40 and 41, "Connector Pin Connection". Slots: 41 and 43 GND, 42 CLOCK (3.559 MHz), 44 SW1, 45 and 47 +5 V (300 mA or less), 46 SW2, 48 +12 V (50 mA or less), 49 SUNDIN, 50 −12 V (50 mA or less). General ports (D-sub 9): 1 FWD, 2 BACK, 3 LEFT, 4 RIGHT, 5 +5 V (50 mA or less), 6 TRG 1, 7 TRG 2, 8 output, 9 GND; pins 6 and 7 are inputs only when bits 0 and 1 (port 1) or 2 and 3 (port 2) of PSG port B are set high. Cassette (DIN 8): 1, 2, 3, 8 GND, 4 CMTOUT, 5 CMTIN, 6 REM+, 7 REM−. Printer (14-pin Amphenol): 1 strobe, 2 to 9 DATA 0 to 7, 11 BUSY, 14 GND. See Panasonic CF-2700 Service Manual.
  3. ↑ 3.0 3.1 3.2 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 39, "Adjustment": VR1 sets 4.97 to 5.03 V at pin 45 of CN7 against pin 41; CT201 on the video board sets 4.43361875 MHz ±3 Hz at pin 9 of IC203 (pin 7 ground); channel trimmer for UHF channels 35 to 37 (583.25, 591.25, 599.25 MHz). See Panasonic CF-2700 Service Manual.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Panasonic CF-2700, October and November 2025—link(accessed 2026-10-21) Crayzyian: a British CF-2700 that looked unused gave no response, power LED dark and no video. Jipe: 160 mA fuse on the power source board, 3.15 A fuse on the main board; check +5 V, +12 V, −5 V and −12 V and the two slot micro switches. Rataplan: fuses rarely go on their own, capacitors do, especially after years unused. mcolom: a toggling Caps Lock LED shows the Z80 and ROM are probably working; without an oscilloscope, check whether the Z80, VDP and RAM get warm after a few minutes; a failed ceramic capacitor can short Vcc to ground. Briqunullus: the Caps Lock test covers RAM too, and an external RAM cartridge is an easy test. AndreV: clean corroded fuse holders and reseat the plugs. sdsnatcher73: dirty or corroded slot protection switches keep the power supply off; try a cartridge in each slot. Crayzyian, 13 November 2025: a blown T160mA fuse, replaced, and the machine works.
  5. ↑ Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 44, "Schematic Diagram (Main Board)": "SWITCH SLOT 1" and "SWITCH SLOT 2", NC contacts in series from CN5 pin 1 (ground) to CN5 pin 3; pin 3 is the PSW line and goes to SW1 (pin 44) of a slot connector, pin 2 (the junction) to SW2 (pin 46). Printed page 42, "Wiring Connection Diagram": micro switches to CN5 as 1 GND, 2 SLOT 1, 3 SLOT 2. See Panasonic CF-2700 Service Manual.
  6. ↑ 6.0 6.1 6.2 6.3 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed pages 5, 6 and 11. PPI µPD8255AC-5 (IC45): port A selects the slot for each 16 KB page; port B reads the keyboard return lines; port C bits 0 to 3 drive the keyboard scan through the 74LS145 (IC46), bit 4 the cassette motor (0 = on), bit 5 cassette write, bit 6 the Caps lamp (0 = lit), bit 7 the click sound. I/O addresses: VDP 98H and 99H, PSG A0H to A2H, PPI A8H to ABH, printer 90H (strobe out, bit 0; status in, bit 1, "1" when busy) and 91H (print data). See Panasonic CF-2700 Service Manual.
  7. ↑ 7.0 7.1 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 7, "CPU Peripheral Circuit", Fig. 2 "CLOCK Waveform": VDP clock 10.67815 MHz at IC43 pin 3, CPU clock 3.55938 MHz at IC8 pin 6, PSG clock 1.77946 MHz at IC39 pin 8; the 74HC04 (IC43) oscillates at 10.6781522 MHz, divided by three by IC42 (74LS74) and IC47 (74LS107) for the CPU and halved by IC39 (74LS74) for the PSG. Reset: C13 and R26, with Q10 forcing the edge when the capacitor reaches about 1.5 V; RESET goes from low to high 60 ms after power-on. ROM: MN23257 (IC32), 32 K × 8, access time up to 325 ns. See Panasonic CF-2700 Service Manual.
  8. ↑ 8.0 8.1 8.2 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 42, "Wiring Connection Diagram": CN2 to the video board, pins 1 GND, 2 SOUND, 3 R−Y, 4 B−Y, 5 Y, 6 CLK, 7 +5 V, 8 +12 V, 9 −12 V; CN1 from transformer T101; CN5 micro switches; CN8 and CN9 keyboard; slot 1 CN7, slot 2 CN6. See Panasonic CF-2700 Service Manual.
  9. ↑ 9.0 9.1 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed pages 34 to 38, "Disassembly Instruction": CN2 is released by pressing its top and refitted with the white lead on pin 9; CN5 is refitted with the white lead on pin 1; CN1 has a latch; hold the keyboard cables for CN8 and CN9 by both sides of the reinforced portion. See Panasonic CF-2700 Service Manual.
  10. ↑ Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 9, "VDP Peripheral Circuit", Fig. 7: TMS9929 (IC38) with video RAM IC49 to IC56 (µPD416C-3), each drawn with +5 V, +12 V and −5 V supplies; 16 KB of VRAM used in MSX; PAL composite output. See Panasonic CF-2700 Service Manual.
  11. ↑ 11.0 11.1 11.2 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed pages 64 to 67, "Replacement Parts List": keyboard switch units FBM-652 series, flexible pattern assembly DFWV48A0008, power LED LN220RP (D301), Caps LED LN88RCPP (D302); cassette relay FBM-450-004 (RY1); slot micro switches FBM-438-008 (K5, two). See Panasonic CF-2700 Service Manual.
  12. ↑ Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed page 15, "Cassette Interface Circuit": FSK at 1200 baud (1200 Hz one wave for 0, 2400 Hz two waves for 1) or 2400 baud (2400 Hz and 4800 Hz); input terminated by 150 Ω, AN6553 (IC34) for gain and filtering, µPC311C (IC41) comparator with about 2.5 V reference and hysteresis from R54 and R55. See Panasonic CF-2700 Service Manual.
  13. ↑ File:Panasonic CF-2700 main board, German model.jpg, photograph of a German CF-2700 main board (DFUP0007ZBJ-1) uploaded to the MSX Resource Center wiki by Mars2000you on 7 April 2020: relay RY1 (Takamisawa MZ-5HG) beside the cassette connector CN3 at the top edge of the board.
  14. ↑ 14.0 14.1 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed pages 21 to 32, "Self Test": test cartridge part no. DFWV95C0001 (program at 8000H); equipment: printer or plotter for MSX, joystick CF-2201, TV, cassette recorder and tape; keep the recorder at least 30 cm from the TV; some audio recorders are unsuitable; wait at least 30 seconds after switching off before switching on again. See Panasonic CF-2700 Service Manual.
  15. ↑ 15.0 15.1 15.2 Matsushita, Service Manual: Personal Computer CF-2700 (IED84113035C2), printed pages 10 and 11, "PSG Peripheral Circuit": AY-3-8910A (IC36); the general ports use 74LS157 multiplexers (IC28, IC33) for input and 74LS09 open-collector gates (IC37, IC40) for output; PSG port A bits 0 to 5 read the port pins, bit 6 the keyboard layout input, bit 7 the cassette read signal; port B bit 6 selects port 1 or 2. See Panasonic CF-2700 Service Manual.



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