Grandstand Cosmic Invader Capacitor Replacement Guide
The electrolytic capacitors on the board of the Grandstand Cosmic Invader, VTech's 1981 Invaders game sold in the UK by Grandstand; VTech sold it as Invaders and Sonic Invader, and Prinztronic as Galactic Invaders.[1][2] No manual, parts list or schematic has been published for any of the four releases, and no capacitor value has been published for any of them. The only view of the capacitors is in Just4Parts's 2026 repair of a VTech Sonic Invader, whose board carries the same 700255 number as the Grandstand unit's; it shows five electrolytics, and their values could not be read in any frame of it.[3][4] Below are where those five capacitors are, how to record your own board's values, and how to reach and replace them. Faults that are not capacitors are on Grandstand Cosmic Invader Troubleshooting Guide; general signs of a failing capacitor are on Capacitor Failure Symptoms.
The board and its capacitors
[edit | edit source]The game runs from four AA cells, 6 V; VTech's label also allows a 6 V, 200 mA adaptor.[2][3] The single board carries the display tube on one side and the components on the other. The side that faces you when the top of the case is lifted off is the tube side, with the solder joints; the Hitachi HD38750A45 microcontroller, the capacitors, a small round ferrite-cored coil and a small transistor are on the underside, facing the black base.[4][3] The microcontroller drives the Futaba DM-26Z 1G tube directly.[1]
Nobody has traced the circuit, so what each capacitor does has not been shown. The two largest electrolytics stand beside the coil.[3]
Capacitor list
[edit | edit source]Positions are given with the component side facing you, the microcontroller across the middle, the joystick module at the right-hand end and the board-mounted DC socket at the bottom left corner, as in the Just4Parts frames. No component designators can be seen on that side in the frames, so the table numbers the capacitors from left to right for reference only.[3]
| No. | Where it is | What is visible | Value | Voltage | Source |
|---|---|---|---|---|---|
| 1 | Left-hand end of the microcontroller, lying flat beside it | Pale blue, with the maker's logo printed twice | Not legible | Not legible | [3] |
| 2 | Above no. 1, near the top edge | Pale blue, standing | Not legible | Not legible | [3] |
| 3 | Top edge, left of the coil, among resistors, glass diodes and a ceramic disc | Small blue, standing; the maker's name is not legible | Not legible | Not legible | [3] |
| 4 | Top edge, right of the coil, beside two glass diodes | Larger blue, standing | Not legible | Not legible | [3] |
| 5 | Beside no. 4, towards the joystick module | Larger blue, standing; the same size as no. 4 | Not legible | Not legible | [3] |
These are the five electrolytics on VTech's board 700255 G. The Grandstand board in the Retro Restos video is printed 700255F, and its component side is not shown, so whether it carries the same five parts has not been seen.[3][4] No value or voltage has been published for any of them.
Failure signs on the Cosmic Invader
[edit | edit source]No published repair of a Cosmic Invader or Sonic Invader has found a capacitor at fault:
- The Grandstand unit in the Retro Restos video was sold as not working. It ran at once from 6 V on its battery terminals, and the fault was a battery contact green with corrosion.[4]
- The Sonic Invader in the Just4Parts video was dead because the black negative lead from the battery compartment had come off the board.[3]
The display "takes a little while to power up" on a working Sonic Invader, so a short delay before the display appears is normal on this game.[3] If the game is dead or the display dim with good cells and intact battery leads, first apply 6 V to the battery terminals, as Retro Restos did, to tell a battery-compartment fault from a board fault; then look at the capacitors for bulging tops or leakage and measure them out of circuit.[4]
Reading and recording your own board
[edit | edit source]- Note the board's numbers: 700255F and 35-0155-00 on the Grandstand unit, 700255 G and 35-0155-01 on the Sonic Invader.[4][3]
- Photograph the component side square on before removing anything. As there are no visible designators, mark each capacitor's position on the photograph.
- For each of the five electrolytics, write down the value and voltage printed on the sleeve, the maker, the diameter and height, whether it stands or lies flat, and which way its stripe faces.
- Measure each part once it is out; a meter that reads capacitance and ESR shows a dried-out part.
Replacement procedure
[edit | edit source]- Take out the four AA cells.
- Remove the screws from the base. On the Sonic Invader there are two cross-head screws inside the battery compartment and two at the other end, and no clips.[3] On the Grandstand unit in the Retro Restos video two screw posts had broken off inside the case; check that each post is still attached before tightening the screws again.[4]
- Lift the yellow top off, holding the case level: the slide switches' knobs can fall out.[3]
- The board is held to the base by six small cross-head screws.[3] Before turning it over, note how the red and black battery leads and the piezo speaker's leads are attached. The Sonic Invader's black lead was found off the board after this step, and its repairer thought he might have pulled it off when he turned the board over.[3] The full opening sequence is on Grandstand Cosmic Invader General Maintenance.
- Turn the board over to reach the capacitors. The display tube is mounted on the solder side, so when you desolder a capacitor's leads keep the iron off the glass, and never rest the board on the tube or its sealed tip at one end.[4][3]
- Note each capacitor's polarity, remove it, and read and record it. Fit a new radial electrolytic of the same capacitance and the same or a higher voltage, the right way round, and no larger than the original, so that the board still sits flat on its posts in the base.
- Refit the board with its six screws, check the battery and speaker leads, and refit the top.
After the work
[edit | edit source]| Check | Expected | Source |
|---|---|---|
| Cells at the board, four fresh AA | About 6 V (6.1 V on the repaired Grandstand unit) | [4] |
| Switch-on | The display appears after a short pause | [3] |
| Before play | A number at the top of the display steps through the number of lives (one to five on Prinztronic's version) | [4][3][5] |
| Rocker | The missile station moves while the rocker is held over | [3] |
No supply or display voltages have been published for this game.
Related pages
[edit | edit source]- Grandstand Cosmic Invader
- Grandstand Cosmic Invader General Maintenance
- Grandstand Cosmic Invader Troubleshooting Guide
- Capacitor Failure Symptoms
- Battery Explosion, Capacitor or Corrosion Damage
References
[edit | edit source]- ↑ 1.0 1.1 MAME source, hh_hmcs40.cpp at commit d404316 (retrieved 2026-10-18). Driver notes for VTech Invaders: "manufactured in Taiwan"; Hitachi HD38750A45 microcontroller, 1-bit sound; cyan and red VFD Futaba DM-26Z 1G; colour overlay on the alien rows; known releases Invaders and Sonic Invader (VTech, USA), Cosmic Invader (Grandstand, UK) and Galactic Invaders (Prinztronic, UK); inputs left, right and fire, and a two-position difficulty switch. The chip list dates the HD38750A45 to 1981.
- ↑ 2.0 2.1 Handheld Museum, "Grandstand Cosmic Invader" (retrieved 2026-10-18): 1981, VFD, four AA batteries; "Licensed from Vtech, it's identical to Vtech's Sonic Invader"; also released by Prinztronic as Galactic Invaders.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 Just4Parts, "Can I Fix This Broken Vintage Space Invaders Handheld? Sonic Invaders Repair!", YouTube, 7 August 2026 (transcript read 2026-10-18; frames from 9:30 to 10:20 and 11:40 to 13:20 looked at at full size, 1080p, 2026-10-19). A dead VTech Sonic Invader. Transcript: the base label "Operates on 4 'AA' batteries or a 6 volts/200 MA AC adaptor"; two cross-head screws in the battery compartment and two at the bottom, no clips; the slide switches' knobs can fall off when the top is lifted; "six crossheads" hold the board (about 8:32); he turned the board over without desoldering anything, past "the bulb ... where the air has been drawn out of the screen", to "a few capacitors" and the chip marked "1F45 HD38750A45" (about 9:15-10:00); the fault was the black negative lead from the battery compartment, off the board ("Maybe I have when I've turned it over"), resoldered to the ground pad, after which the game worked (about 11:45-14:00); "It takes a little while to power up"; the number of lives is chosen at the start and shown at the top of the display; the station has to be held left or right to keep moving. Frames: the board printed "700255 G" and "35-0155-01"; its component side, with no designators visible, carries the microcontroller across the middle, the joystick module at one end, a board-mounted DC socket with a diode beside it at the opposite corner, a small round ferrite-cored coil with a small transistor beside it at the centre of the top edge, glass diodes either side of the coil, a ceramic disc, and five electrolytics: two larger blue standing parts side by side right of the coil, a small blue standing part left of it, a pale blue standing part at the left-hand end of the microcontroller and a pale blue part lying flat beside it with a maker's logo printed twice; no value or voltage is legible on any of them (about 9:54-10:18 and 12:29-12:33).
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 retro_ restos, "Grandstand Cosmic Invader 1980's Game eBay 'Untested' Repair", YouTube, 20 December 2024 (transcript read 2026-10-18; frames from 2:48 to 3:48 looked at at full size, 1080p, 2026-10-19). A Grandstand unit sold as not working: two base screws missing because their posts had broken off inside the case; the top case "comes away totally"; the game ran from 6 V on the battery terminals; a battery contact green with corrosion was ground back to clean metal, after which the cells gave 6.1 V at the board and the game worked on batteries; before play "we wait for the number of lives that we want before we press go". The frames show the board in the black base with its green solder side up and the display tube mounted on that side, printed "700255F" and "35-0155-00", with the red fire button and the joystick's rocker; the frames looked at do not show the other side, facing the base, and the narration does not mention turning the board over.
- ↑ TokyoBatman, "Prinztronic Galactic Invaders", Handheld Museum forum, 27 February 2019 (retrieved 2026-10-18): review of Prinztronic's version: two difficulty levels and a choice of one to five lives.