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Grandstand Firefox F-7 General Maintenance

From RetroTechCollection
Grandstand Firefox F-7 Instructions controls drawing
The Firefox F-7 controls as drawn in Grandstand's booklet: power and speaker switches below the display, joystick, start, skill level select and firing button.

Care, cleaning and opening of the Grandstand Firefox F-7, the cockpit-shaped space game with a vacuum fluorescent display (VFD) and two speakers that Epoch made in Japan and Grandstand sold in the UK from 1983. It is Epoch's Astro Thunder 7, also sold by Radio Shack as Astro Thunder, so repair accounts for those apply.[1][2] Its electronics differ from Astro Wars and Scramble: an owner's schematic shows an NEC D7528C microcontroller and a second chip, a D1771C, behind the two speakers.[3] What follows comes from Grandstand's and Radio Shack's leaflets, that schematic and repair videos from seven channels published between 2019 and 2024. Faults are on Grandstand Firefox F-7 Troubleshooting Guide.

The Firefox F-7 at a glance

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Firefox F-7: what is inside
Part Detail
Fixings Six screws in the base and a tiny screw under a sticker on the end of the joystick[4][5][6]
Cells Four C cells (Duracell MN1400) in a compartment on the bottom[1][7]
Adaptor 6 V DC, centre negative (Radio Shack); the Grandstand Universal Mains Adaptor set to negative (Grandstand)[7][1]
DC socket On the right-hand side; a switched socket that disconnects the cells when a plug is in[7][3]
Main board Microcontroller D7528C 011, sound chip D1771C 011, transformer TX-30, power transistor D882 (S04) driven by a C945 (S03); held by a screw at the back and one at the front[3][6][4]
Control board Contacts for the joystick, select, start and fire, and the power and two speaker switches; held by a small screw in the middle and joined to the main board by a ten-way cable[3][4][6]
Display NEC FIP-series VFD on a bracket above the main board, behind a window with a built-in Fresnel lens[8][9]
Sound Two piezo speakers, a small one and a large one, each with its own switch[3][1]

Before you start

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  • Take out the cells. Repairers test these games from a bench supply set to 6 V, connected to the board or the battery contacts.[9][4]
  • Photograph the wiring before unsoldering anything: the board cannot come out until the battery wires are freed.[10][6]
  • Expect a Firefox F-7 to have been opened before, with missing or wrong screws, screws in the wrong holes and broken posts.[10][11][12][5]
  • The joystick sticker is easily lost; keep it with the screw.[11][9]

Opening the case

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  1. Take out the cells.
  2. Peel the sticker off the end of the joystick and remove the tiny Phillips screw beneath it, then lift the knob off so the stick can pass through the case. Retro Tech Repair found the top can also be lifted with the knob in place by turning it round the stick.[4][11][9]
  3. Turn the game over and remove the six screws in the base. They tend to stay in their holes; tilting the base back lets them drop out.[4][5][6]
  4. Lift the top straight off.[4][9]
  5. A vinyl overlay covers the board, and the control panel unclips.[11]
  6. A small screw in the middle holds the control board; its contacts are on the back. It stays joined to the main board by the ten-way cable.[4][3]
  7. One screw at the back and one at the front hold the main board. The DC socket lifts out of its hole in the case with the board.[4]
  8. Unsolder the battery terminal wires, which are marked positive and negative, to free the board completely.[6][9]
  9. The two speakers are held in the case; Retro Tech Repair eased them out with the electronics.[11]

Reassembly. Put the board screws back in their own holes: one owner found an earlier opener had swapped them, leaving one only half in.[12] Screw the display window back properly; retro_restos found it loose.[5] Do the case screws up gently. Posts crack: on one game a crack at a screw post had split the board beneath it, and retro_restos had to weld a broken stud back.[10][5] The keypad must be in place to test the game, or the contacts have to be bridged by hand.[9]

Cleaning

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  • Grandstand's care note: move the joystick gently, do not press hard on the firing button, keep the game out of the sun and dry.[1] Radio Shack adds: keep it away from heat, dirt and dust, do not drop it, and clean it with a damp cloth, not solvents or strong detergents.[7]
  • Polish only the plain black plastic. The printed and painted areas wear through.[5]
  • Sticky residue inside one game cleaned off with 99.9% alcohol.[12]

Batteries and battery contacts

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The game takes four C cells, and both Grandstand and Radio Shack say it will not work properly on weak ones; check the cells first if it malfunctions or the display is erratic.[1][7] Radio Shack warns that even leak-proof cells can leak and ruin the game, and asks for them to be removed if it will not be used for a week or more.[7]

  • A thin film of oxidation on the contacts is enough to stop the game. Contact cleaner and very fine abrasive paper cleared it on one game; another showed corrosion around the battery box.[5][11]
  • The cover is often lost, and without it the cells fall out.[5][9] The 3D-printable Epoch cover is listed for the Firefox F-7 and Astro Thunder, and moulded reproduction doors for Astro Wars and Firefox F-7 are "not a perfect fit" but close.[13][9]

DC socket and adaptor

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The DC socket is on the right-hand side. Radio Shack specifies its 273-1650 adaptor on the 6 V range with the centre tip negative; Grandstand's booklet says only to set the Universal Mains Adaptor to negative.[7][1] A centre-negative Mega Drive power lead fits the socket.[6] See Grandstand Universal Mains Adaptor.

  • The socket is switched: with no plug in, the battery positive passes through it to the power switch; a plug disconnects the cells, and the plug's centre pin is the negative side.[3]
  • A dirty socket can leave the game dead on both cells and adaptor. Contact cleaner and working the plug in and out revived one.[5]
  • 8Bit Retro ReFix believes his game's blown power transistor was caused by a reversed adaptor, and says that is the usual cause.[4] Measure any adaptor before use.

Controls

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Joystick

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The joystick moves the ship left and right; pushed up it selects high speed (H) and down low speed (L), each for a few seconds.[1] It works by contacts on the control board.[3] A stick that would not move the ship right was cured on one game by cleaning the joystick contacts and pads with isopropyl alcohol; on another, the fault was the ten-way cable between the boards.[5][6]

Buttons

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SELECT, START and the firing button press carbon pads onto contacts on the control board.[9][10] The firing button is the one that wears: StezStix measured its pad at about 240 kΩ against 15-45 kΩ for the others. Copper tape on the pad worked, and both he and Retro Tech Repair moved the select pad to the firing button instead, since select is pressed far less.[10][9] Scrubbing a pad too hard removes its carbon; Retro Tech Repair took most of it off the fire pad that way.[9]

Power and speaker switches

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The three slide switches are on the control board: power, and one for each speaker.[3][1] They can be dirty and greasy; one repairer bridged the power switch with a wire while testing.[6][4][11]

Speakers

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The Firefox F-7 has two piezo speakers. Radio Shack's manual says the left switch turns the music on and off and the right switch the sound effects; Bryden's schematic puts the small piezo on the left switch and the large one on the right, and Retro Tech Repair believed the small one is driven by the main processor and the large one by the second chip.[7][3][9] The two speakers therefore make different sounds, and a notice packed in the box explains this, because owners thought their games faulty.[5]

  • The speaker wires and their solder joints break; Retro Tech Repair remade them and replaced a tired foam pad behind one speaker with a piece of kitchen sponge.[9][6]
  • There is no volume control, and the game is loud.[6][10]

Display

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The VFD sits on a bracket above the main board, behind a window with a Fresnel lens moulded into it.[8][9] Bryden's schematic labels the tube 7AM33T.[3]

  • The getter, the dark spot inside the tube, should be black. On a spare board Retro Tech Repair found it white and the tube's vacuum port knocked off: the tube was dead.[9][6]
  • Do not leave the game in the sun.[1]

What wears, and what to check

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Firefox F-7 wear points
Part What happens Check
Power transistor (D882, S04) Fails, leaving the game dead Grandstand Firefox F-7 Troubleshooting Guide[11][6]
Battery contacts, DC socket Oxidation stops the game Clean[5]
Firing button pad Carbon wears away Swap with the select pad[10][9]
Ten-way cable between the boards Breaks; intermittent sound and joystick Replace with wire[6]
Screw posts Crack, sometimes cracking the board Tighten gently; check tracks nearby[10]
Speaker wires and foam Joints break, foam perishes Resolder, replace foam[9]

Storage

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  • Take the cells out if the game will not be used for a week or more.[7]
  • Keep it dry, out of the sun and away from heat and dust.[1][7]

Preventive maintenance checklist

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  1. Check the cells and contacts for oxidation.
  2. Check any adaptor: 6 V DC, with the centre negative.
  3. Try both speaker switches before deciding the game is silent.
  4. Test the firing button; if it is unreliable, swap its pad with the select pad.
  5. While the case is open, check the screw posts, the ten-way cable and the speaker wires.
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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Grandstand, Firefox F-7 instruction booklet (Adam Imports Ltd, Ripon Way, Harrogate; © 1983; made in Japan), hosted here as File:Grandstand Firefox F-7 Instructions.pdf (PDF page numbers). p. 1: drawing of the controls (power switch, left and right speaker switches, joystick, start, skill level select and firing buttons) and the batteries box: four Duracell MN1400 cells; the Grandstand Universal Mains Adaptor, not included, with its polarity switch set to negative; the game will not work properly on weak batteries; if it malfunctions or the display is erratic, check or replace the batteries; switch off after play and remove the batteries when the game is not used for long periods; care note: "move the Joy Stick gently. Do not press hard on the Firing Button ... Do not leave in the sun or allow it to get wet." At switch-on an electronic tune plays and the display lights; skill level 1 shows at the top right; START plays a tune; joystick up selects high speed (H) and down low speed (L) for a few seconds. p. 2: either speaker or both can be switched on, or both off to play in silence. p. 8: a perfect game is 1,000 points.
  2. ↑ Handheld Museum, "Grandstand Firefox F-7" (retrieved 2026-10-18): 1983, VFD, four C cells, model 11279; the same game as Epoch Astro Thunder 7, Epoch Galaga X6 and Radio Shack Astro Thunder.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Philip Bryden, "Grandstand Firefox F7" schematic, three sheets ("Power rail", "Data", "Control Board"), KiCad 6, revision 1, 8 June 2022, PDF on MEGA linked from his video (retrieved 2026-10-18). Drawn by the owner from his own boards and described by him as a first attempt that may need revision. It shows the microcontroller labelled D7528C 011 and a second chip labelled D1771C 011; the display labelled 7AM33T, with its filament on display pins 1 and 2 and 30 and 31; a ten-pin transformer TX-30 driven by transistor S04 (882), whose base is driven by S03 (C945); diodes S05 to S12; electrolytic capacitors C01 to C04 and other capacitors C05 to C15, without values; a 5 MHz resonator X01 (FCR5.0M); and a ten-way cable L01 to the control board, carrying 6 V DC on pin 4. Control board: the power switch; up, down, left and right joystick contacts; select, start and fire; a "sound L" switch for the small piezo speaker and a "sound R" switch for the large one; and a switched DC socket whose centre pin is the negative (ground) side.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 8Bit Retro ReFix, "Grandstand Fire Fox F7 Repair Part 1", YouTube, 10 April 2021 (transcript read 2026-10-18). Dead, even powered at the battery contacts with the switch bypassed (1:38-6:36). Disassembly: peel the sticker on the end of the joystick and remove the tiny screw so the stick can pass through the case; six base screws, which drop out if the case is tilted back; lift the top straight off (2:26-4:06). A small screw in the middle holds the control board, whose contacts are on the back; one screw at the back and one at the front hold the main board; the DC socket lifts out of its hole in the case (5:39-7:51). The power switch felt greasy (6:36). The D882 had visibly blown, with a burn mark on the board beside it; he believed a wrong-polarity adaptor had done it (11:16-15:10). A mark at the top of the screen was, he said, made in manufacture (10:39-10:43).
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 retro_restos, "Grandstand Firefox F-7 Repair. Vintage Electronic Game Repair 1980's Retro", YouTube, 30 May 2023 (transcript read 2026-10-18). A boxed game with a printed notice explaining that the left and right speakers make different sounds, because owners thought their games faulty (0:58-1:13). Missing battery cover; DC inlet 6 V, negative pin (2:15-2:36). Dead on cells and adaptor: contact cleaner and wiggling the DC socket brought it to life, and contact cleaner and very fine abrasive paper on the battery contacts cleared "a very thin film of oxidation" (3:37-6:23). The ship would not move right; cleaning the joystick contacts and pads with isopropyl alcohol cured it (7:25-19:14). Six screws in the base and a tiny screw in the joystick; an earlier opener had not screwed the screen back properly; a broken stud was plastic-welded (8:58-11:17). Do not polish the printed and painted areas (22:53-23:20). The battery cover is shared by "three or four different models" (25:51). The flicker seen on camera is not visible in person (6:56).
  6. ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 6.10 6.11 6.12 6.13 Philip Bryden, "Grandstand Firefox F-7 | No Power | Faulty Audio | Fiasco", YouTube, 29 May 2022 (transcript read 2026-10-18). A dead Firefox F-7 drawing no current; a centre-negative Mega Drive power lead fits the socket; the case marking calls for negative polarity; six screws (0:10-3:51). The battery terminal wires, marked positive and negative, have to be unsoldered to take the board out (6:41). 6 V reached pin 4 of the ribbon cable and the transformer; the D882 power transistor had died; its base is driven by a small C945 (8:56-11:37). A salvaged substitute fitted the wrong way round drew 0.8 A and burnt his finger (12:50-17:41). Lifting every diode changed nothing (21:02-22:03). Removing the capacitors did not reduce the current, though some measured out of tolerance (23:31-24:01). A new D882 failed again and a second one was fitted; the game then drew about 300-400 mA and the display worked (24:10-28:22). The transformer has ten pins and the board carries an arrow to align it; he found no fault in it (27:29-28:01). The getter was black, "a good sign" (25:31). There is no volume control (25:22). Intermittent sound and a joystick that would not go right were caused by the ten-way ribbon cable inside, which he replaced with wires from an IDE cable (28:35-40:12). The in-game sound effects were still missing at the end; he suspected the sound chip or X01 (40:35-41:03).
  7. ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 Radio Shack, Astro Thunder owner's manual (cat. no. 60-2197; custom manufactured for Radio Shack; printed in Japan), hosted here as File:Radio Shack Astro Thunder Manual.pdf. The same game as the Firefox F-7. p. 1: four C cells in the compartment on the bottom, or Radio Shack's 273-1650 adapter on its 6 V range with the centre tip set negative (270-7001 for 240 V in the UK); check the batteries if the game malfunctions or the display is erratic; take them out if the game will not be used for a week or more, because "even leak-proof type batteries can leak damaging chemicals, which will ruin your unit permanently"; the drawing shows the adapter jack on the right-hand side. p. 2: the LEFT SOUND switch turns the musical sound on and off and the RIGHT SOUND switch the sound effects. p. 7: maintenance: keep it dry, out of heat, dirt and dust; do not drop it; no harsh chemicals, solvents or strong detergents, only a damp cloth; use fresh cells of the correct type.
  8. ↑ 8.0 8.1 Handheld Museum, "Guts" (retrieved 2026-10-18): photograph of an opened Grandstand Firefox F-7 showing the display on a bracket above the main board, with "FIP" and an illegible number in the silkscreen beside it, and a control board with round contact pads below.
  9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 9.12 9.13 9.14 9.15 9.16 9.17 Retro Tech Repair, "Fixing a Broken Astro Thunder Handheld - What's Wrong With It?", YouTube, 1 October 2021 (transcript read 2026-10-18; the game is a Grandstand Firefox F-7). The joystick knob can be removed, or lifted and turned, to free the top cover (2:08-2:33). The Fresnel lens is built into the display window (2:41). The battery tabs are soldered and must be unsoldered to free the board (5:04). The getter in the display should be black; on a spare board it had turned white and the tube's vacuum port had been knocked off (6:05-6:44). The D882 tested as "two resistors"; a salvaged one was also bad, and a second worked (7:36-9:14). The keypad must be in place for testing (8:56). The sound was then quiet: cleaning had taken the carbon off the fire pad, so he swapped it with the select pad; the speaker's solder joints and foam pad were renewed (9:31-13:51). The sound chip ran very hot and the current was high; a chip from a spare board behaved the same, and recapping the two supply capacitors changed nothing; the cause was a solder bridge between two tracks on a badly soldered connector, one of them to the sounder (14:24-22:16). The smaller speaker is driven by the main processor and the larger by the second chip, for the more complex sounds (5:28-5:50). Remanufactured moulded battery doors for Astro Wars and Firefox F-7 are "not a perfect fit" but close (22:47-23:02).
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 10.7 StezStix Fix?, "I Paid £30 For an 'UNTESTED' Grandstand FIREFOX F-7", YouTube, 23 April 2022 (transcript read 2026-10-18). A boxed Firefox F-7 with 6 V at the batteries but no power; two case screws missing and a loose broken post rattling inside (0:18-2:47). A crack at a screw post had cracked the board and broken a track; a wire jumper and reflowing some poor joints restored power (2:15-8:21). The board cannot come out without desoldering; he photographed the wiring first (3:20-3:30). The fire button's carbon pad measured about 240 kΩ against 15-45 kΩ for the other pads; copper tape on the pad worked, and he then swapped the fire and select pads (10:05-11:55). The sound is very loud (8:25).
  11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Retro Tech Repair, "This Vintage VFD Game Has a Hidden Problem", YouTube, 13 August 2019 (transcript read 2026-10-18). A dead Grandstand Firefox F-7 with some battery corrosion, two case screws missing and others replaced with wood screws (1:22-2:56). Peel the sticker off the joystick and undo the Phillips screw to lift the knob off; a vinyl overlay covers the board; the control panel unclips; two sounders, where Astro Wars has one (3:09-4:47). The power switch is in the middle of the board and was bridged with a wire for testing (5:38). The D882 read short between pins 1 and 3; a used D882 from another game cured it (6:26-8:47).
  12. ↑ 12.0 12.1 12.2 Tech Restore AD, "Grandstand Firefox F-7", YouTube, 6 October 2024 (description read 2026-10-18; captions disabled): a game that would not turn on, with a clean board; sticky residue was cleaned off with 99.9% alcohol; an earlier opener had left one outer screw loose and put the inner board screws in the wrong holes.
  13. ↑ YoxxxoY Jorge, "Battery cover Epoch electronic games", Thingiverse 3399673 (2 February 2019), archived on the Internet Archive (retrieved 2026-10-18). 3D-printable battery cover; the designer lists Astro Thunder, Astro Thunder 7, Firefox F-7, Astro Command, Astro Wars, Space Defender, Galaxy II, Star Force and Scramble. Licensed CC BY.


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