JVC HC-7 Capacitor Replacement Guide
No parts list, circuit diagram or capacitor list for the JVC HC-7 has been published, and no service manual for it is among those held by the MSX Archive.[1] The values have to be read from the parts on your own board. The published photographs of an HC-7E show where the electrolytics are, but the printing on them cannot be read at the size they were published.[2][3]
Where the electrolytics are
[edit | edit source]- Power supply board, mains side: one large electrolytic after the bridge rectifier. This part holds a dangerous charge after the plug is pulled.[2]
- Power supply board, secondary side: the radial electrolytics marked C13, C14, C16, C17, C19, C20 and C21 among others, beside the output chokes and the wires to the main board.[2]
- Main board: a group near the rear connectors, two larger blue parts beside the processor and the HD27L019, C273, C274 and C275 by the RAM, and others near connector CN001.[3][4]
- The blue C7 and the yellow C3 and C5 on the mains side of the supply are not electrolytics.[2]
The HC-7GB main board in the MSX Resource Center's photograph differs from the HC-7E's round the large blue capacitor to the left of the processor, where resistors have been added.[5] Record your own board before assuming it matches either photograph.
Which to replace first
[edit | edit source]Forum advice on recapping an MSX is to replace the main supply's capacitors regardless of condition, to judge the audio and video capacitors by the picture and sound, and to replace parts one at a time.[6] On the HC-7 that means:
- The secondary electrolytics on the power supply board.
- The large mains-side electrolytic, if it shows bulging or leakage or the supply will not start. Use a part with at least the same voltage rating and of a type rated for switch-mode supplies.
- The main board electrolytics near the video and audio connectors, if the picture or sound is poor.
- The rest only if they leak or a rail is noisy.
Recording the board
[edit | edit source]- Unplug the mains lead and wait several minutes before touching the power supply board.
- Photograph both boards from above, then each electrolytic close up so its printing can be read.
- For each capacitor, note the designator, capacitance, voltage, temperature rating, diameter, height and stripe side.
| Ref | Capacitance | Voltage | Diameter × height | Notes |
|---|---|---|---|---|
| Mains-side reservoir | Mains voltage; check the rating | |||
| C13 | ||||
| C14 | ||||
| C16 | ||||
| C17 | ||||
| C19 | ||||
| C20 | ||||
| C21 |
Procedure
[edit | edit source]- Unplug the five-wire lead from CN001 on the main board, noting its orientation.[4]
- Free the power supply board and lift it out. Its fixings have not been documented; photograph them first.
- Discharge the mains-side capacitor through a suitable resistor and confirm 0 V with a meter. See Capacitor Failure Symptoms for what failed parts look like.
- Replace one capacitor at a time, stripe to the same side as the original.[6]
- Check the solder joints round the transformer, the chokes and the output wires while the board is out.[5]
- Refit the board and the lead.
After the recap
[edit | edit source]With the slot covers closed and no cartridge fitted, switch on and measure the rails at a cartridge slot: +5 V on pin 45 or 47, +12 V on pin 48 and −12 V on pin 50, against pin 41.[7] The yellow inhibit wire should be near 0 V.[8] Remaining faults are covered in the JVC HC-7 Troubleshooting Guide.
Related pages
[edit | edit source]References
[edit | edit source]- ↑ Index of /pub/msx/docs/service_manuals, MSX Archive—link(accessed 2026-10-21) Directory of MSX service manuals; it lists none for JVC or Victor machines.
- ↑ 2.0 2.1 2.2 2.3 File:JVC HC-7E power supply board.jpg, photograph of the internal power supply of an HC-7E uploaded to the MSX Resource Center wiki by Mcolom on 26 November 2022. Read from it: on the mains side a glass cartridge fuse, a line filter choke marked 502Y0R3, a relay marked SDE8S-E 4A/32A 250V, a bridge rectifier, one large electrolytic capacitor, a blue X capacitor (C7) and yellow ceramic Y capacitors (C3, C5); a ferrite transformer marked F5S-84147 and an optocoupler PC1; on the secondary side radial electrolytics with designators including C13, C14, C16, C17, C19, C20 and C21, chokes L3 to L6, regulator IC1 and a trimmer. The printing on the capacitor sleeves is not legible at the published resolution.
- ↑ 3.0 3.1 File:JVC HC-7E main board.jpg, photograph of the inside of an HC-7E uploaded to the MSX Resource Center wiki by Gdx on 1 April 2016. Read from it: a group of small electrolytics near the rear connectors at the top left; two larger blue electrolytics beside the processor and the HD27L019; C273, C274 and C275 along the lower edge beside the RAM; others near the power connector; most of the remaining capacitors are ceramic discs.
- ↑ 4.0 4.1 File:JVC HC-7E power supply connector.jpg, photograph uploaded to the MSX Resource Center wiki by Mcolom on 26 November 2022: connector CN001 with an electrolytic capacitor on either side, one marked C106.
- ↑ 5.0 5.1 For sale: JVC HC-7E MSX, January 2017—link(accessed 2026-10-21) Reply comparing the MSX Resource Center's photographs: the HC-7GB board has resistors added beside the large blue capacitor to the left of the Z80, and the HC-7E board, apparently a later revision, has the change built in. The seller also reported that the HC-7E did not always power on, but tapping around the power supply made it work.
- ↑ 6.0 6.1 Recap recommendations, June 2018—link(accessed 2026-10-21) Reply by RetroTechie, 23 June 2018: supply bypass electrolytics round an MSX board can often be removed without the machine stopping; those in the audio and video circuits show their condition in the output; those in the main power supply are worth replacing regardless of condition; compare the parts list with the board where there is one, and replace capacitors one at a time. Other replies recommend Rubycon, Chemi-Con, Nichicon or Panasonic parts from established distributors.
- ↑ Victor Company of Japan, Instructions, Personal Computer HC-7GB, page 37 (PDF page 37), cartridge bus: 41 and 43 ground, 45 and 47 +5 V, 48 +12 V, 50 −12 V. See File:JVC HC-7GB Instructions.pdf.
- ↑ Got a JVC hc-7e worked at first but now refueso to power on, March 2016—link(accessed 2026-10-21) The yellow wire at the supply connector read 0 V with the machine running and about 1 V when a slot microswitch was pressed, which switched the machine off.
