Casio PV-7 Capacitor Replacement Guide
No parts list, capacitor list or circuit diagram for the Casio PV-7 has been published, and Casio's instruction manual has none. The PV-7 has no mains supply inside: it runs from 10 V DC from the AD-4810 adaptor or the KB-7 expansion box, and a 7805 regulator on the board makes +5 V.[1][2]
What is known
[edit | edit source]- The adaptor gives unregulated 10 V DC, so the regulator's input capacitor takes about 10 V and the rest of the board runs at 5 V.[3]
- The main board is printed with the value and working voltage beside many of its electrolytic capacitors. The photograph on the MSX Resource Center wiki shows these markings, among others:[4]
| Position | Board marking |
|---|---|
| Near the RF modulator | 100 µF 6.3 WV |
| Near the TC74HCU04P | 47 µF 6.3 WV |
| Near the CSA3.58MT resonator | 33 µF 6.3 WV |
| Below the TMS9118NL video chip | 47 µF 6.3 WV |
- No marking for the capacitors at the DC input can be read in the photograph. Any capacitor there sees the adaptor's unregulated 10 V, so a 6.3 V part does not belong in that position.[4][3]
Which to replace first
[edit | edit source]Advice on the MSX Resource Center forum is to replace the main supply's capacitors whatever their condition, to judge the capacitors in the audio and video circuits by the sound and picture, and to leave the small decoupling capacitors spread over the board unless there is a reason to change them.[5] On the PV-7 that means:
- The capacitors round the DC input socket and the 7805 regulator.
- The capacitors near the RF modulator and the video and audio sockets, if the picture or sound is poor.
- The rest, only if they leak, bulge or a rail is noisy.
Recording the board
[edit | edit source]- Unplug the adaptor or the KB-7 and open the case as described in the Casio PV-7 General Maintenance guide.
- Photograph the board from above, then each electrolytic close up, with the board marking beside it.
- For each capacitor, write down the board marking, the printing on the capacitor, its diameter and height, and which side the stripe faces. Where the two disagree, follow the capacitor's own printing and note the difference.
- Order replacements of the same capacitance, at least the same voltage, and a size that fits.
| Position | Board marking | Printed on the capacitor | Diameter × height | Notes |
|---|---|---|---|---|
| DC input | ||||
| 7805 regulator | ||||
| RF modulator | 100 µF 6.3 WV | |||
| Video and audio |
Procedure
[edit | edit source]The PV-7 carries no mains voltage inside.[1]
- Unplug the adaptor or the KB-7 from the computer.
- Replace one capacitor at a time, with the stripe on the same side as the original.[5]
- Take care of the factory jumper wires on the component side while the board is out.[6]
- Clean away any electrolyte and check the tracks round the old capacitors for corrosion.
After the recap
[edit | edit source]Measure +5 V at the cartridge slot, between pin 45 or 47 and pin 41.[7] The PV-7's slot has no ±12 V, so pins 48 and 50 read nothing.[7] Any remaining fault is covered in the Casio PV-7 Troubleshooting Guide.
Related pages
[edit | edit source]- Casio PV-7
- Casio PV-7 General Maintenance
- Casio PV-7 Troubleshooting Guide
- Casio PV-16 Capacitor Replacement Guide
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 Rating label of a red PV-7 (File:Casio PV-7 rating label.jpg), uploaded to the MSX Resource Center wiki by Mars2000you on 26 June 2021: "RATING: DC 10V, 8 W; use AC ADAPTOR AD-4810 or KB-7".
- ↑ Repairing a Casio PV-7 (page 2), 11 February 2024—link(accessed 2026-10-21) lmanes: the PV-7's 7805 regulator sits on an aluminium heatsink.
- ↑ 3.0 3.1 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.
- ↑ 4.0 4.1 Photograph of the PV-7 main board, component side (File:Casio PV-7 main board.jpg), uploaded to the MSX Resource Center wiki by Mars2000you on 8 February 2016. Silkscreen markings read from it: "100µ 6.3WV" beside an electrolytic near the RF modulator; "47µ 6.3WV" near the TC74HCU04P; "33µF 6.3WV" near the CSA3.58MT resonator; "47µ 6.3WV" below the TMS9118NL. Other markings, and the printing on the capacitors near the DC input socket, cannot be read in the photograph.
- ↑ 5.0 5.1 Recap recommendations, June 2018—link(accessed 2026-10-21) Reply by RetroTechie, 23 June 2018: main power supply capacitors in an MSX are worth replacing whatever their condition; audio and video capacitors show their condition in the output; bypass capacitors round the board can often be removed without the machine stopping; replace one at a time to avoid mixing up values or polarity.
- ↑ Repairing a Casio PV-7, February 2024—link(accessed 2026-10-21) lmanes and st1mpy, 10 and 11 February 2024: the PV-7 board is single-sided with many jumper wires.
- ↑ 7.0 7.1 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; 50 −12 V. The ±12 V supplies are not connected on Casio MSX machines.
