Sharp X1 Capacitor Replacement Guide
No Sharp service manual for the first Sharp X1 (CZ-800C) was found on the Internet Archive or X1 Center, so there is no Sharp parts list to work from. The best published source of capacitor values is the full schematic of the CZ-800C, revision 4, that I/O magazine printed and X1 Center now offers for personal use.[1] The tables below are read from that schematic. Boards from other production runs may differ, so check every part against your own board before ordering. The power supply is not in the schematic.
Before any work inside the computer, read the safety notes in General Maintenance: the power supply's primary side charges to about 144 V DC.[2]
Main board
[edit | edit source]| Ref | Value as drawn | Sheet | Circuit |
|---|---|---|---|
| C103 | 100 µF 16 V | 1 | 5 V (Vcc1) supply, bulk |
| C102 | 10 µF | 1 | 5 V (Vcc1) supply, bulk |
| C50 to C125 | 10 µF electrolytics among 1 µF capacitors; the schematic gives the range, not each part | 1 | Supply decoupling across the board |
| C11 | 33 µF | 1 | Power-on reset |
| C14 | 1 µF | 1 | Reset switch |
| C3 | 100 µF 16 V | 2 | Clock chip (µPD1990AC) supply, beside the backup cell |
| C7 | 47 µF | 2 | Clock chip circuit |
| C35 | 47 µF | 2 | Clock chip circuit |
| C6 | 10 µF 16 V | 2 | Power control line to the power supply (connector W) |
| C34 | 47 µF 35 V, tantalum | 2 | RC network with R56 and D5 on an 8255 port line |
| C15 | 10 µF 16 V | 2 | Sound: AY-3-8910 output to the buffer transistor Q1 |
| C16 | 100 µF 10 V | 2 | Sound: external sound output |
| C17 | 100 µF 10 V | 2 | Sound: sound output to the television |
| C23 | 10 µF 16 V | 2 | Sound: volume control to the BA526 amplifier input |
| C21 | 47 µF 10 V | 2 | Sound: BA526 amplifier |
| C20 | 47 µF | 2 | Sound: BA526 amplifier |
| C22 | 100 µF 10 V | 2 | Sound: BA526 amplifier |
| C77 | 100 µF | 2 | Sound: BA526 amplifier supply |
| C18 | 100 µF 10 V | 2 | Sound: BA526 output to the speaker |
| C30 | 10 µF, tantalum | 3 | Sync circuit beside the CRT controller |
The schematic also uses the reference C17 for a 390 pF capacitor on sheet 2, so match parts by position and value, not by reference alone.[1] Where the schematic gives no voltage, read it from the part on your board.
Graphics board (CZ-8GR)
[edit | edit source]| Ref | Value as drawn | Circuit |
|---|---|---|
| C410 | 100 µF 10 V | 5 V supply from the main board |
| (unnumbered) | 10 µF 10 V | 5 V supply from the main board |
Cassette deck control board
[edit | edit source]The board that drives the deck's solenoids and motor takes a separate 12.8 V supply from the power unit.[1]
| Ref | Value as drawn | Circuit |
|---|---|---|
| C210 | 100 µF 16 V | 12.8 V supply input |
| C202 | 47 µF 10 V | Write circuit supply (Q200, Q201) |
| C204 | 22 µF 16 V | Read amplifier |
| C208 | 22 µF 16 V | Read amplifier |
| C209 | 47 µF 10 V | Read amplifier |
| C211 | 33 µF 10 V | Write LED and relay line |
| C212 | 22 µF 16 V | Comparator circuit (NJM2903D) |
| C213 | 22 µF 16 V | Comparator circuit (NJM2903D) |
| C214 | 10 µF 16 V | Comparator circuit (NJM2903D) |
Keyboard
[edit | edit source]The keyboard's 80C48 controller board has two electrolytics: C303 (10 µF) on the 5 V supply and C304 (10 µF) on the controller's reset input.[1]
Power supply
[edit | edit source]No schematic or parts list for the CZ-800C power supply has been published. X1 Center believes it was made by ZEBRA, whose name appears on many of its parts.[2] When repairing a failed supply, X1 Center replaced every electrolytic except one, in case they had caused the fault. Tested afterwards, the large first-stage primary capacitor had lost 12 per cent of its capacitance and the rest measured normal, although X1 Center points out that a capacitor can pass a capacitance test and still leak more current at high voltage. The failure in that supply turned out to be a timing transformer, not the capacitors.[2]
To work on the supply, record every capacitor before removing it:
- Unplug the computer and let the primary capacitor discharge; measure across it before touching the board.
- Photograph the board from above and note each capacitor's reference, value, voltage, temperature rating, size and polarity.
- Replace like for like, using parts of the same capacitance, the same or higher voltage, and 105 °C rating where the original is 105 °C.
- Test the repaired supply from a current-limited source with a wattmeter, as X1 Center did, before running it from the mains.[2]
Clock backup cell
[edit | edit source]The 2.4 V nickel-cadmium cell BA1 beside the clock chip is not a capacitor but is the part on the main board most likely to cause damage, because it leaks electrolyte that corrodes the tracks and plated holes around it. X1 Center suggests removing it, or fitting a 5.5 V supercapacitor in its place, if clock backup is not needed.[1][3] The trimmer capacitor C1 beside the clock crystal is not an electrolytic; if the clock will not start, see clock and timer faults.
Replacement
[edit | edit source]- Work on one board at a time, and replace one capacitor at a time, checking the polarity marking on the board and on your photographs.
- Use the value and voltage from your board where they differ from the tables above, and keep the same lead spacing so the parts sit flat.
- C30 and C34 are drawn as tantalum parts. Replace them with tantalum or electrolytic parts of the same value and at least the same voltage, and observe polarity.
- Clean flux from the board, check for solder bridges, then refit the board.
- Check the computer reaches the IPL screen and loads a program from tape before refitting the cover; see what a working X1 does.
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 CZ-800C(X1) Rev.4 全回路図 (I/O誌), X1 Center—link(accessed 2026-10-21) Seven-sheet schematic reprinted from I/O magazine. Sheet 1 (CPU, main RAM, IPL ROM): C103 100 µ 16 V and C102 10 µ across Vcc1; decoupling C50 to C125, 1 µ and 10 µ; C11 33 µ in the power-on reset with D4 and R50 and R51; C14 1 µ on the reset switch. Sheet 2 (8255, sub-CPU, clock, sound): µPD1990AC with crystal X1 (32.768 kHz), trimmer C1, C2 22 pF, cell BA1 2.4 V, D1 1SS119, R8 3.3 kΩ, C3 100 µ 16 V, C7 47 µ, C35 47 µ; C6 10 µ 16 V with R9 10 kΩ and a 1SS99 diode on the line to connector W of the power unit; C34 47 µ 35 V (TA) with R56 33 kΩ and D5 on an 8255 port line; AY-3-8910 output through C15 10 µF 16 V to Q1 2SC2308; C16 100 µF 10 V to EX SOUND OUT; C17 100 µF 10 V to SOUND OUT for the television; BA526 amplifier IC55 with C23 10 µF 16 V, C21 47 µF 10 V, C20 47 µ, C22 100 µF 10 V, C77 100 µ and C18 100 µF 10 V to the speaker; C17 390 pF also appears on this sheet. Sheet 3 (CRTC): C30 10 µ (TA). Sheet 5 (graphics board, 24 × 8118): C410 100 µ (10 V), C453 0.1 µ and a 10 µ (10 V) on Vcc. Sheet 6 (cassette board): Vcc3 12.8 V from the power unit with C210 100 µF (16 V); C202 47 µ (10 V) on the supply to the write transistors Q200 and Q201; C204 22 µ (16 V), C208 22 µ (16 V) and C209 47 µ (10 V) around the NJM2904D read amplifier; C211 33 µ (10 V) on the write LED (write relay on) line; C212 22 µ (16 V), C213 22 µ (16 V) and C214 10 µ (16 V) around the NJM2903D comparator. Sheet 7 (expansion slots and keyboard): keyboard controller IC300 with C303 10 µ on +5 V and C304 10 µ on RESET. X1 Center's schematic index states that the schematics are copyright and must be kept to personal use.
- ↑ 2.0 2.1 2.2 2.3 CZ800C電源修理・・・できなかった。, X1 Center—link(accessed 2026-10-21) Many parts marked ZEBRA; no supply schematic among the X1 schematics; all electrolytics but one replaced in case they caused the failure; on measuring the removed parts, the large first-stage primary capacitor had lost 12 per cent and the others were normal, but leakage at high voltage may have risen; primary-side charge +144 V; test rig with a current-limited 12 V supply, inverter and wattmeter; the failure was traced to the T2 timing transformer.
- ↑ 時計バックアップ用ニッカド電池, X1 Center—link(accessed 2026-10-21) The clock backup NiCd cell leaks with age or over-discharge and corrodes the board; if backup is not needed, remove it or replace it with a 5.5 V supercapacitor.