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Casio PV-7 Troubleshooting Guide

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Casio PV-7 manual troubleshooting
Casio's troubleshooting chart, printed page 24 of the instruction manual

No service manual or circuit diagram for the Casio PV-7 has been published. The checks below start with the troubleshooting chart in Casio's instruction manual (Casio PV-7 Instruction Manual) and go on to faults that owners have found and fixed on the MSX Resource Center forum.

Casio's chart

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Troubleshooting chart (instruction manual, printed page 24)
Symptom Casio's checks
Power lamp does not light The adaptor is plugged into the outlet; the adaptor is connected to the PV-7
Nothing on the screen The television is on; the leads are connected correctly; any ROM cartridge is fully inserted; the television channel matches the PV-7's channel switch; the television's fine tuning, brightness and contrast are set
Picture flickers The channels match; the fine tuning is right; the switch box is connected correctly and set to COMPUTER
A game cartridge does not run The cartridge is fully inserted; its contacts are clean
A cassette program will not load The recorder lead is connected; the recorder's volume is not too low; a radio-cassette recorder is switched to tape
The machine stopped suddenly A momentary power cut, the power switch or the adaptor coming out; a vacuum cleaner or microwave oven on the same outlet; loose connections; a mistake in the program

[1]

Power

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The PV-7 runs from 10 V DC: the AD-4810 adaptor gives unregulated 10 V DC, centre negative, from 100 V AC, or the KB-7 expansion box powers it.[2][3] +5 V on the board comes from a 7805 regulator.[4] Measure +5 V at the cartridge slot, between pin 45 or 47 and pin 41.[5] Pins 48 and 50 carry nothing on the PV-7, because its slot has no ±12 V.[2]

Faults found by owners

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Symptom Found Notes
Black screen, no clock signal at the CPU or the video chip A dead TMS9118NL video chip Replacing the TMS9118NL brought the machine back.[6][4]
Black screen; the CPU, ROM and RAM are active The TMS9118 video chip On a PV-7 with a KB-7, the video chip gave only a black NTSC signal; it was replaced with a Pico9918.[4]
Border and background colour only, no text or graphics, sound works The wrong video chip fitted A TMS9918A does not suit the PV-7's TMS4416 video RAMs; fit a TMS9118.[6]
Black screen after a supply failure The MB64H131 gate array and the video chip On one PV-7, probably after a blown power supply, both the MB64H131 and the video chip had failed, and each gave a black screen.[7]
An FM-PAC or other cartridge needing ±12 V does not work The slot has no ±12 V and no Sound IN Casio left these pins unconnected. See the Casio PV-7 General Maintenance guide for an owner's modification.[2][8]
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References

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  1. ↑ Casio, PV-7 取扱説明書, printed page 24 (PDF page 26), 困ったときは!?. See File:Casio PV-7 manual troubleshooting.jpg and Casio PV-7 Instruction Manual.
  2. ↑ 2.0 2.1 2.2 Casio PV-7—link(accessed 2026-10-21) AC adaptor AD-4810: input AC 100 V, 50/60 Hz, 16 VA; output up to 800 mA, unregulated DC 10 V, centre negative. The KB-7 has its own power supply. Cartridge connector pins Sound IN, SW1, SW2, −12 V and +12 V are not connected. Video TMS9118NL; audio AY-3-8910; gate array Fujitsu MB64H131; RAM 8 KB in slot 0.
  3. ↑ Rating label of a red PV-7 (File:Casio PV-7 rating label.jpg): "RATING: DC 10V, 8 W; use AC ADAPTOR AD-4810 or KB-7".
  4. ↑ 4.0 4.1 4.2 Repairing a Casio PV-7 (page 2), 11 February 2024 to 15 December 2025—link(accessed 2026-10-21) lmanes, 11 February 2024: with a TMS9118NL taken from a PV-16, the PV-7 works and the fault was the VDP; the board's 7805 sits on an aluminium heatsink. hexbus, 15 December 2025: a PV-7 with a KB-7 dock had a black screen; the VRAM data lines showed static patterns on an oscilloscope while RAS and CAS were working, the Z80 lines and the SRAM and ROM were active, and the TMS9118 put out only a black NTSC signal; replacing it with a Pico9918 fixed the machine.
  5. ↑ MSX Cartridge slot, 6 July 2026—link(accessed 2026-10-21) Pin table: 41 and 43 GND; 45 and 47 +5 V; 48 +12 V; 49 SOUNDIN; 50 −12 V.
  6. ↑ 6.0 6.1 Repairing a Casio PV-7, February 2024—link(accessed 2026-10-21) lmanes, 10 February 2024: the issue was the VDP; there was no clock signal on the CPU or on the VDP. After fitting a TMS9918A from a Toshiba, only the border and background colour appeared, with no text or graphics, and sound worked; the TMS9918A uses 16K × 1 video RAM, while the PV-7's TMS9118NL uses two TMS4416-12 (16K × 4) chips, so the replacement must be a TMS9118. The VRAM chips tested good in another machine.
  7. ↑ Black Screen, March 2018—link(accessed 2026-10-21) jltursan, 13 March 2018: the MB64H131 MSX-Engine at the bottom of the board failed in a PV-7 he repaired, which was badly damaged, most probably by a blown power supply; he also replaced the VDP; both failures gave a black screen. The same chip is used in the PV-16.
  8. ↑ MSX PV-7をFMPACが使えるように改造しました, 22 April 2019—link(accessed 2026-10-21) The PV-7's cartridge slot has no +12 V or −12 V, so the FM-PAC's FM output could not be used without modification.


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