Grandstand Scramble Troubleshooting Guide
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Fault-finding for the Grandstand Scramble and its twins, Epoch's and Radio Shack's Astro Command.[1][2] No service data has been published for any of them. The faults below are the ones owners have actually found and fixed on these games, in a Handheld Museum forum thread and in repair videos from 2018 to 2025. Opening the case is described on Grandstand Scramble General Maintenance.
How the power circuit works
[edit | edit source]Like the other Epoch games of its time, Scramble runs on 6 V from four C cells, but its NEC μPD553C microcontroller (D553C 202) is a PMOS chip that needs about −10 V and drives the display directly at higher negative voltages.[1][3] A switching supply provides them: the D882 power transistor chops the incoming DC to drive a small round transformer, and diodes rectify its output into the voltages the processor and display need.[4][5] The other transistors on the Astro Command's board are C2785s.[5] On the Scramble board, two diodes in the transformer circuit, S06 and S11, are wired in series; Retro Tech Repair took that pair from a scrapped Scramble to repair an Astro Wars, whose own S06 breaks down at about 140 V.[6]
The power from the battery box and the DC socket passes through the control board and its flat cable before it reaches the main board, so a break anywhere on that path leaves the game dead.[5][7]
What should happen at power-on
[edit | edit source]- POWER on: the game starts up and SELECT chooses one of four skill levels before START.[4][8]
- The ship moves in four directions with the joystick; MISSILE fires ahead and BOMB drops downwards.[4]
- Play runs through five phases. The game ends when the ships are lost or at 3,000 points, the perfect score.[8][9][2]
Expected measurements
[edit | edit source]| Point | Reading | Source |
|---|---|---|
| Supply at the board | 5.8-6.2 V from fresh cells or a 6 V supply, falling slightly at switch-on | [10][11] |
| After the POWER switch | About 6 V | [7] |
| DC socket, no plug in | Continuity from the battery box to the board | [10][12] |
| DC socket, plug in | Battery path open | [10] |
| Good D882, diode test | About 0.6 V from base to each of the other two pins, nothing in reverse | [13] |
No owner has published the internal supply voltages of a Scramble or Astro Command. On Astro Wars, the closest Epoch game, they are about −10 V for the microcontroller and −39 V for the display; see Grandstand Astro Wars Troubleshooting Guide#Expected measurements.
Symptoms
[edit | edit source]| Symptom | Likely cause | Action | Source |
|---|---|---|---|
| Completely dead on cells and adaptor; about 6 V reaches the board | Failed D882 power transistor | Test the D882 out of circuit; replace it. | [10][7][11][13] |
| Dead, and the supply input reads short to ground | Failed D882 | Lift the D882 and measure again. | [10] |
| Dead, with a burst or leaking capacitor | Electrolytic failed, often with the D882 | Replace both; see Capacitors. | [13] |
| A new D882 overheats | Not reported on Scramble. On Astro Wars the cause is a shorted S06 | Check S06 and S11 before fitting another transistor. | [6] |
| Works on and off with the adaptor, dead on cells | Corroded DC socket | Check continuity through the socket with no plug in; replace the socket. | [12] |
| Dead on cells only | Corroded battery contacts; DC socket contact not closing | Polish the contacts; check the socket. | [10][5] |
| Plays wrongly and the display flashes rapidly, then dies | Seen on one Astro Command; cause never found | Check the supply path through the control board and its flat cable; see Known faults. | [5] |
| Joystick does not return to centre or feels rough | Dirty or dry mechanism | Clean; dry lubricant. | [8] |
| MISSILE or BOMB unresponsive | Dirty spring or contacts | Contact cleaner on the springs; clean the board contacts. | [8][4] |
| No sound | Broken piezo wire | Resolder; the wires are thin. | [4] |
| Game sounds but the display is dark | Display supply fault (power section or transformer); broken tube | The game runs without its display, so look at the power section first. | [5] |
Known faults
[edit | edit source]D882 power transistor
[edit | edit source]The failed part in most of the published Scramble and Astro Command repairs:
- Retro Tech Repair's Scramble: base shorted to collector and open to the emitter.[13]
- Buy it Fix it's Scramble: a dead short across the transistor (the captions read its type as D992, probably a mishearing of D882).[11]
- retro_restos's Scramble: the supply input read short to everything until the transistor came out.[10]
- Kip Hakes's boxed Scramble: an NEC D882Q that tested dead.[7]
- Rust Belt's Radio Shack Astro Command: tested as "two resistors in series".[4]
In every case a new power transistor brought the game back, together with a new capacitor in Retro Tech Repair's case.[13][11][10][7][4] Kip Hakes says these transistors "go open circuit" when they fail, but every repairer who measured one found a short or a low resistance instead.[7][13][4] On Retro Tech Repair's board the transistor was mounted lying flat, and the replacement went in the same way.[13]
A common cause of the failure, according to a repairer who sees many of these games, is the wrong adaptor: one Scramble arrived with a positive-centre adaptor reading nearly 13 V.[14]
DC socket
[edit | edit source]retro_restos's second Scramble cut out on the adaptor and did not work on cells. With no plug in there was no continuity from the battery box to the board through the socket, and the socket was corroded inside. A new-old-stock replacement cured it.[12]
Capacitors
[edit | edit source]Retro Tech Repair's dead Scramble had a burst electrolytic: a 330 μF 10 V part, mounted lying down, that had sprayed its contents onto the case. He fitted a 330 μF 25 V part in its place, replacing the D882 at the same time, so the video does not show which part had stopped the game.[13] Rust Belt replaced the three electrolytic capacitors on his Astro Command as a precaution, with the same capacitance and the same or a higher voltage, but did not give their values.[4] Kip Hakes found no bulging capacitors, and the owner of the dead Astro Command replaced all of them without curing it.[7][5] No full list of Scramble's capacitors has been published; read the values off the parts before ordering replacements.
The Astro Command that could not be saved
[edit | edit source]In 2016 the owner of an Epoch Astro Command cleaned and filed its rusted battery contacts. It then ran only occasionally, playing wrongly with the display flashing rapidly, before dying completely. He replaced the electrolytics, then swapped almost every part with a working Radio Shack Astro Command, repaired the control board's flat cable (which had frayed from being turned over), rewired the battery box to the DC socket and reflowed every joint, with full voltage reaching the main board. The game stayed dead; the only parts he did not swap were the microcontroller and its crystal.[5] The Handheld Museum's administrator has a game in the same state and assumes its microcontroller is damaged, adding that the dead games he gets normally have a transistor or two blown by an incorrect power supply.[5]
Display faults
[edit | edit source]- The game logic and sound do not need the display or its transformer. If the game can be heard playing with a dark display, the fault is in the display supply or the tube.[5]
- Kip Hakes judges the tube by its getter: black is good, a white powdery deposit is bad.[7]
- VFDs fade unevenly over years of use, and a broken filament wire leaves part of the display dim.[5]
- A replacement tube has to be an NEC FIP9AM20T from another Scramble or Astro Command.[1]
Things that are not faults
[edit | edit source]- Flicker on video: it comes from the camera's shutter; in person the display is steady.[13][10][7]
- Small surface-mounted parts on the back of the main board, which Kip Hakes had not seen on similar boards.[7]
- Background scenery that does not move: it is printed on the film and laminate behind the window.[15][5]
What is realistically repairable
[edit | edit source]| Part | Status | Source |
|---|---|---|
| D882 power transistor | Standard part, cheap | [11][10] |
| DC socket | Replaceable; three-pin sockets are available | [12] |
| Electrolytic capacitors | Standard parts; read the values off the board | [13][4] |
| Battery contacts | Clean, or take from a donor | [13] |
| Joystick, buttons, switch | Clean and lubricate | [8] |
| Display tube | Donor only (NEC FIP9AM20T) | [1] |
| Microcontroller (D553C 202) | Mask-programmed; donor only | [1][3] |
Related pages
[edit | edit source]- Grandstand Scramble
- Grandstand Scramble General Maintenance
- Grandstand Astro Wars Troubleshooting Guide: the related Epoch game, with measured voltages and the S06 fault.
- Grandstand Universal Mains Adaptor
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 MAME source, hh_ucom4.cpp at commit d404316 (retrieved 2026-10-18). Driver notes for Epoch Astro Command: PCB labels 96111 and 96112; NEC μPD553C microcontroller labelled D553C 202, 1-bit sound; cyan and red VFD NEC FIP9AM20T no. 42-42 (nine grids); colour overlay with the right three columns yellow and six columns of the bottom row pink; released in Japan by Epoch, in the USA by Tandy and in the UK by Grandstand as Scramble. The program in MAME was dumped from a Tandy Astro Command. The input map has a four-way joystick, SELECT, START, MISSILE and BOMB.
- ↑ 2.0 2.1 Handheld Museum, "Grandstand Scramble" (retrieved 2026-10-18): 1982, VFD, four C cells; licensed from Epoch (Astro Command); found with the word "Scramble" unpainted and painted red; maximum score 3,000. Also "Epoch Astro Command": 1982, VFD, four C cells, model 8230; also licensed to Tandy and Radio Shack under the same name.
- ↑ 3.0 3.1 NEC Electronics USA, 1982 Microcomputer Catalog, data sheet "μPD552/μPD553 4-bit single chip microcomputers with vacuum fluorescent display drive capability", p. 165, Bitsavers copy on the Internet Archive. PMOS, 42-pin DIP, single −10 V supply; outputs that can be pulled to −35 V to drive a VFD directly; the μPD553 has 2000 × 8 mask ROM and 96 × 4 RAM.
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 Rust Belt Vintage Toy Repair, "1987 Radio Shack Astro Command Electronic Game Repair", YouTube, 31 October 2024 (transcript read 2026-10-18). Radio Shack's version, in its 1987 catalogue: four difficulty levels; the missile fires horizontally and the bomb drops vertically; a four-way joystick (0:23-1:57). Dead on four C cells (2:27-2:32). Disassembly: remove the batteries; peel the sticker off the joystick knob and remove the screw beneath; six screws separate the base from the top cover; the bezel unclips; two screws hold the main board's bracket (2:45-3:07). The D882 power transistor drives a switching supply whose transformer output is rectified to the voltages the processor and display need; it had failed, testing as "two resistors in series", and a new D882 cured the game (3:24-4:13, 6:11). He also replaced the three electrolytic capacitors as a precaution, same capacitance and same or higher voltage, observing polarity; no values given (4:22-4:44). Do not strain the thin piezo speaker wires; the battery contacts are wired and were removed for polishing; three screws free the control board and three more the joystick mount; contacts cleaned with denatured alcohol (4:54-5:22). The bezel clips back and the knob screw is hidden by the sticker (5:40-5:50).
- ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 Handheld Museum forum, "EPOCH Astro Command - dead or dying", January 2016 (retrieved 2026-10-18). Rik (site administrator): an Epoch VFD game will play and make its sounds even without the display or the small transformer that powers it; he has never had a VFD die unless its glass was broken; with heavy use the displays fade, unevenly, over years; a broken filament wire leaves an area of the display very dim; a dead game is normally a transistor or two blown by an incorrect power supply. The owner of the Astro Command (the Epoch version of Grandstand Scramble) found its supply runs from the control board to the main board through a flat cable, which frayed and broke after the board had been turned over repeatedly.
- ↑ 6.0 6.1 Retro Tech Repair, "Astro Wars Repair (sound but no display or faint display)", YouTube, 29 January 2021 (transcript read 2026-10-18). Faint sound and no display on several games. Measured on a working board: about −1.5 V at the D882 base, −3 V at the base of S03 (a C945), fed from a −9 V line through the zener S09, and the −10 V microcontroller supply (24:00-33:00). A 10 μF capacitor next to the transistor and transformer, rated 16 V, was replaced with a 25 V part, and later the whole board was recapped, without effect (21:00-31:00). Earlier boards, with the Epoch logo, have one diode S06 under the display; later boards have two, S06 and S11, in series (39:00-46:00). The removed diodes broke down at about 140-143 V when tested on a stack of 9 V batteries, which he warns is not safe (48:00-54:00). On a Japanese Astro Wars ruined by the wrong charger, the D882 was burnt; a new D882 still overheated until S06 was replaced with a 1N5275B; the game then drew about 0.2 A with the D882 a little warm, and ran for several hours (57:00-67:00). S06 sits under the bottom edge of the display; bending the tube risks cracking it (61:00). The flat cables to the joystick board and power board broke after repeated handling (39:00).
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 Kip Hakes, "Grandstand Scramble - Boxed, Beautiful, Broken - Fix it Friday", YouTube, 1 March 2024 (transcript read 2026-10-18). A boxed Grandstand Scramble, dead on batteries, with worn button lettering (2:06-3:25). A screw under the top of the joystick; six screws in the base (3:01-3:35). The battery leads run to the DC socket, which cuts the batteries when a plug is in and can fail; about 6 V reached the power switch (5:58-7:31). He judged the display good because its getter was black, and said a white, powdery getter is bad (8:08-8:29). The capacitors were not bulging (8:51). Small surface-mounted parts on the back of the board, which he had not seen on similar boards (9:44-10:01). The NEC D882 tested dead on a component tester; a new one cured the game (10:32-14:38). Flicker on camera only (13:25).
- ↑ 8.0 8.1 8.2 8.3 8.4 Vintage Gaming Memories, "Joystick Repair & Full Cleaning: 1982 Epoch Astro Command", YouTube, 4 March 2025 (transcript read 2026-10-18). An Epoch Astro Command whose joystick did not return to centre (4:50-5:08). Six screws in the base; the joystick cap comes off after peeling a small sticker and removing the screw beneath (5:13-5:52); three screws release a part joined to the board by a flat cable, to be handled carefully (6:58-7:26); four screws hold the joystick cover over its contacts (7:44-7:58). The joystick was cleaned and given dry lubricant; contact cleaner was sprayed on its spring and on the springs under the MISSILE and BOMB buttons; the slide switch was polished where it rubbed (8:18-10:52). The inside of the display window and the plastic film with the base and space imagery were cleaned (11:28-11:37). Five phases and four skill levels (12:24).
- ↑ Mike's Retro Tech, "55 - Grandstand Scramble - Electronic Game - Testing after 2 years on a shelf", YouTube, 15 December 2019 (transcript read 2026-10-18). A boxed Grandstand Scramble with its leaflet: the box reads Adam Leisure Group Limited, Harrogate, England, copyright 1982, and had faded on a shelf near the sun (0:43-1:09); the game ends when the ships are lost or at 3,000 points (2:37-2:49); the screen had been scratched by an adaptor packed in the box (4:51-5:04); controls joystick, on/off, SELECT, START, MISSILE and BOMB (6:48); the base label calls for four HP11 C cells or the Grandstand Universal Mains Adaptor with negative polarity (6:59-7:11); the leaflet names HP11 zinc-carbon or MN1400 alkaline cells and the Universal Mains Adaptor but gives no voltage (8:39-9:07). It worked on a universal adaptor set to negative.
- ↑ 10.00 10.01 10.02 10.03 10.04 10.05 10.06 10.07 10.08 10.09 retro_restos, "Grandstand Scramble Repair. No Power Fix", YouTube, 19 May 2023 (transcript read 2026-10-18). Dead on mains and batteries. Without a cover the cells "make a bid for freedom" (0:33-0:39). Adaptor: 6 V DC, negative (1:14). The DC socket's battery contact checked by continuity, open with a plug in as it should be (3:08-3:45); 5.8 V reached the board (3:58-4:18). The supply input read short to everything; the D882 power transistor had failed and a new one cured it; "the power transistors do tend to go after a while" (6:20-12:00). He covered the display while working (7:00). Battery contacts polished; it then worked on batteries (11:18-11:35). Flicker on camera only (11:50).
- ↑ 11.0 11.1 11.2 11.3 11.4 Buy it Fix it, "Repairing A Vintage Grandstand Scramble", YouTube, 20 May 2022 (transcript read 2026-10-18). A dead Scramble with no battery cover: about 6.2 V at the board, dropping slightly when switched on (2:39-4:40); the large power transistor measured a dead short out of circuit; the diodes and small transistors tested good; a new transistor (the captions read the type as D992, probably a mishearing of D882) cured it, for about £1.50 in parts (7:35-14:04).
- ↑ 12.0 12.1 12.2 12.3 retro_restos, "From Delivery to Repair in 10 Minutes. Grandstand Scramble 'No Power' Fix", YouTube, 8 February 2024 (transcript read 2026-10-18). Worked on and off from a 6 V negative-tip adaptor and not at all on batteries (1:38-2:57). In the DC socket the negative lead runs straight through and the positive lead from the batteries passes through the socket's contact to the board; a plug separates the two pins; old sockets "fall apart" and can switch the game off (3:43-4:24). With no plug in there was no continuity from the battery box to the board; the old socket was corroded and was replaced with a new-old-stock one with three pins, one negative and two positive (7:12-8:57). The cap over the joystick screw is glued; soak it off with acetone or alcohol and glue it back (4:45, 11:33-11:39). Six screws in the base, then lift the top away (5:25-6:06).
- ↑ 13.00 13.01 13.02 13.03 13.04 13.05 13.06 13.07 13.08 13.09 13.10 Retro Tech Repair, "Grandstand Scramble / Astro Command Repair - Retro Games", YouTube, 7 December 2018 (transcript read 2026-10-18). A dead Grandstand Scramble with surface corrosion in the battery box (1:18-3:40). The joystick knob is held by a small screw under a sticker on its top, and the sticker cannot easily be replaced (2:12-2:42). Tip for the plastic screw posts: turn each screw backwards until it drops into its thread before tightening, so as not to strip the post (5:46-5:53). An electrolytic capacitor had burst, a 330 μF 10 V part mounted lying down, and was replaced with a 330 μF 25 V part (6:30-11:17); the D882 power transistor, also mounted lying down, read short base to collector and open to the emitter, and was replaced (9:33-13:28). With both replaced the game worked from a 6 V bench supply, so the video does not show which part was the cause (13:56-14:43). Battery contacts were taken from a second, damaged Scramble (15:08). VFD flicker on camera is not visible in person (16:56). Fire buttons: missile and bomb (17:20).
- ↑ retro_restos, "Astro Wars 'No Display' Repair ... VFD Game Transformer Replaced", YouTube, 14 November 2023 (transcript read 2026-10-18). Repairer who reports fixing 5-10 Astro Wars a week. Phone chargers and the wrong adaptors blow the power transistor; a Scramble that came with a 9 V positive-pin adaptor reading nearly 13 V; "all of these games were a negative polarity and only run at 6 volts" (1:00-3:00). His repair kit contains a power transistor, all the electrolytic capacitors, a DC input socket and a diode, and its notes say to replace S02, the input socket and S06, in that order, as the commonest faults; a broken display tube, rotten battery terminals or a broken joystick need donor parts (3:00-6:00). Seven screws, some holding the silver hood and three holding the control panel, the smallest in the middle; hold the base of the controls and lift up and forward (8:00-10:00). Inside: Fresnel screen and backdrop; fire button and its spring, power and start switches whose contact leaves can be bent for more spring; felt cover over the joystick; carbon contacts on the SELECT, START and FIRE pads (10:00-12:00). Four screws hold the cover with the colour lens; on overheated games this lens burns, distorts and its tape comes off (12:00). This game had sound and no display because its transformer coil had fallen apart, a failure he had not seen in 50-100 repairs; a transformer from a donor board, fitted by its orientation arrow, cured it (12:00-24:00). He greases the power switch slider (26:00).
- ↑ Centre for Computing History, "Grandstand Scramble", CH49305 (retrieved 2026-10-18): 1982; the player flies from left to right, dropping bombs on missiles and ground targets and firing at missiles and aircraft; the VFD can show different images in one square, "a bullet one moment and a spaceship the next"; an industrial landscape laminate under the screen; joystick, on/off switch, select, start and two fire buttons, which the record calls missile and bullet.