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Grandstand Model 4600 General Maintenance

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Grandstand 4600 colour - Internals
A 4600 with its base removed. The board is fixed solder side up to the upper case, with REV.2 11-00161-00 printed at its lower left. The DC socket is at the top left, and the controller leads coil into the bays either side.

The Grandstand Model 4600 (panel name GRANDSTAND 4600 COLOUR) is a six-game colour Pong console made in Hong Kong for Grandstand. Its two rotary control pods lift out of bays in the case but stay wired to it, and its picture comes out on UHF channel 36.[1][2] The board is built around General Instrument's AY-3-8500 game chip with a TBA520 for the colour.[3] No Grandstand manual or schematic for the 4600 has been found. The sources are the photographs and notes published by the owner of a working 4600,[2][3] a second collector's notes and photographs,[4] and General Instrument's 1978 data for the AY-3-8500.

Fault-finding is on Grandstand Model 4600 Troubleshooting Guide.

The 4600 at a glance

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What is inside a Grandstand 4600
Part Detail Source
Game chip General Instrument AY-3-8500, date code 8138 [3]
Colour TBA520, marked F8133 Indonesia; the owner calls it a PAL chroma demodulator that produces the colours [3][2]
Other parts Two National CD4069CN / MM74C04N hex inverters; a transistor marked 9015; a screened RF modulator can; a yellow trimmer [3]
Board REV.2 11-00161-00 on the solder side; held to the upper case by five screws [5][2]
Supply Six UM-2 (C) cells, or 9 V DC 100 mA through the DC 9V socket at the rear; centre positive according to the owner [1][6][2]
Controls Six-position game slider; SERVE (MANU/AUTO), BAT SIZE, ANGLE, SPEED, GAME RESET and POWER switches; SERVE button; LEFT and RIGHT score sliders [7]
Accessory A rifle that plugs into the side of the case with a DIN plug [4]

Wikidata gives the 4600's chip as an AY-3-8600, citing the owner's blog.[8] The photograph of the board shows an AY-3-8500, and the blog names the AY-3-8500 too.[3][2]

Before you start

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  • Take out the six cells and unplug the adaptor and the rifle.
  • Lift both control pods out of their bays, so their leads can move freely when the case is open.
  • Tools: a cross-head screwdriver, isopropyl alcohol, a stiff and a soft brush, switch cleaner, a multimeter and a magnifier for reading the board.

Opening the case

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Grandstand 4600 colour - Back
The base: the battery cover across the top with its two slide marks, the label panel, and the two case screws beside the lower feet.
  1. Slide the battery cover off in the direction of its two arrow marks and take out the cells.[1]
  2. Two of the four case screws are inside the battery compartment. Remove them.[2]
  3. Turn the console over. Remove the two cross-head screws beside the feet at the other end of the base.[1]
  4. Lift the base away. The back of the board is now visible, fixed to the upper case by five screws.[2][5]
  5. The DC socket, the RF lead and both controller leads are wired to the board. The controller leads pass through the floors of the bays, and one is knotted round a post in the case to take the strain.[5] Do not pull on them.
  6. Before unscrewing the board, photograph it and every wire. The six setting switches and the game slider come up through the panel, so line them up with their slots when you refit the board.[3]

Cleaning

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  • Clean the grey case with a cloth barely damp with soapy water. Keep solvents off the brushed-metal game plate and the printed panel legends.
  • The board in the photographed console has brown deposits on and around several slide switches, the game slider and parts near them, and patches on the solder side. Its owner does not say what caused them, and the console still works.[3][5][2] Brush them off with isopropyl alcohol, then look at the tracks, the switch legs and the component leads underneath with a magnifier.
  • A second owner found that his 4600 worked on a suitable supply, but that its switches and controls needed a clean.[4]
  • Clean the rear DC socket and the plug of the RF lead.

Power: cells, adaptor and polarity

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  • Six 1.5 V UM-2 (C, LR14) cells go behind the sliding cover in the base.[1][2]
  • The label asks for a 9 V DC adaptor rated 100 mA. The socket is at the rear of the case, at the opposite end from the RF lead, and is labelled DC 9V.[1][6]
  • Neither label gives a polarity. The owner of the photographed 4600 describes the socket as 9 V DC, centre positive, and the console worked from a 9 V centre-positive adaptor.[2] Confirm it on your own console by measuring the socket against the battery terminals with cells fitted.
  • Grandstand's own A.C. adaptor for its TV games, photographed with a Model 6000 that carries the same base label, gives 9 V at 150 mA and was made by Adman Electronics of Harrogate.[9]
  • The Grandstand Universal Mains Adaptor was sold for the tabletop and handheld games, with a polarity switch,[10] and the tabletop leaflets set it to negative.[11] Check its switch, and the plug with a meter, before using one on a 4600.
  • Inside, the AY-3-8500 runs from +6 to +7 V, with +12 V the absolute maximum on any pin.[12]

Remove the cells for storage. A console stored with leaking cells can lose its battery contacts and corrode its power and RF connectors.[13]

Control pods

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Grandstand 4600 colour - With detached controllers
Both pods lifted out of their bays. Each lead stays wired into the console.

Each pod has a rotary knob over a potentiometer in a plastic box, marked LEFT PLAYER or RIGHT PLAYER. The pods press into bays either side of the panel; their leads are permanently attached and coil into the bays.[14][4][2]

  • A bat that jumps or will not reach the top or bottom of the screen points to a dirty potentiometer track. Open the pod and clean the track with potentiometer cleaner, turning the knob end to end.
  • A bat that cuts in and out as the lead moves points to a break in the lead, most often where it enters the pod or where it passes into the console.
  • Because the pods are wired in, they cannot be swapped between sides. Compare the resistance of the two potentiometers at the board end instead. GI's reference design for the AY-3-8500 uses 1 MΩ bat potentiometers with a 10 kΩ resistor in series; the values in the 4600's pods have not been read.[12]
  • On the Deluxe version of the 4600, the owner reports, the reset button is on the controllers.[2]

Switches, buttons and score sliders

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The panel's six switches (SERVE, BAT SIZE, ANGLE, SPEED, GAME RESET and POWER) sit over six board-mounted slide switches, SW1 to SW6, along the front edge of the board. The long game slider runs across the middle of the board.[3][7] On the AY-3-8500 each game and setting is chosen by connecting a pin to ground, and GI asks for no more than 1 kΩ through a closed contact,[12] so corrosion on these switches is enough to stop a setting or a game working.

  • Work switch cleaner into each slide switch and the game slider and move them end to end a dozen times. Then measure each closed contact.
  • The SERVE button on the game plate is used when SERVE is set to MANU.[7][12]
  • The two sliders marked 0 to 10 under LEFT, SCORE, RIGHT are manual score counters. The console also keeps score on screen.[4][15]

Rifle

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A collector's 4600 came with a rifle, a black pistol on a grey lead, which plugs into the side of the case with a DIN plug. His was missing some parts.[4] The AY-3-8500's two target games are the ones it is used for (S.L. TARGET and M. TARGET on the 4600's slider).[12][7]

  • Clean the DIN plug and socket and check the lead.
  • Test the rifle on a cathode-ray tube television, not a flat panel.

RF output and colour

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  • The base label gives UHF channel 36.[1] The RF lead is fixed and ends in a coaxial plug.[6]
  • The modulator is the screened can at the top of the board. The colour comes from the TBA520 and the parts around it, and a yellow trimmer sits near SW2.[3] Its purpose has not been traced. Do not turn it unless the colour is wrong, and mark its position first.

Electrolytic capacitors

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About eight electrolytic capacitors are visible on the photographed board, some of them Yobatron parts. Only two markings can be read: C38 is 10 µF, and C37 is rated 16 V. The rest are not legible in the photograph, so there is no capacitor list for the 4600.[3] If you have a 4600 open, record the values.

Wearing parts

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What wears on a 4600
Part Why Check
Slide switches SW1 to SW6 and the game slider Corrosion seen on the photographed board; the AY-3-8500 needs under 1 kΩ when closed[3][12] Clean; measure the closed contact
Control pod potentiometers Dirty tracks make the bat jump Clean; compare left and right
Control pod leads Coiled and uncoiled in the bays at every game Check for breaks at both ends
DC 9V socket Plugged and unplugged often Clean; check its wiring to the board
Battery compartment contacts Attacked by leaking cells[13] Store the 4600 without cells
Board tracks under the deposits Deposits seen on both sides of the board[3][5] Inspect with a magnifier after cleaning

Test points

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The 4600 uses the same game chip as the Grandstand TV Game 3600 Mk II. GI's supply, clock and pin values for the AY-3-8500 are listed under test points on the 3600 Mk II; they apply to the chip on the 4600 board. The 4600's colour and RF circuits are different, so do not use the Mk II's notes for those.[3]

Storage

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  • Remove the cells.
  • Coil the pod leads loosely into the bays and seat the pods.
  • Store the rifle and its lead separately, and keep the console dry.

Preventive maintenance checklist

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  1. Take out the cells and look at the contacts in the battery compartment.
  2. Check the adaptor's output voltage and centre polarity with a meter.
  3. Open the base and clean any deposits from both sides of the board.
  4. Clean SW1 to SW6, the game slider and the SERVE button.
  5. Clean both pod potentiometers and check both leads.
  6. Tune an analogue television to channel 36 and check the colour, the scores and both bats.
  7. Test the rifle on a CRT television.
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Back.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: the base, with a battery cover across one end marked with two arrows, a raised label panel reading "UHF CHANNEL 36 / POWER SOURCE: Use 6 x UM-2 Batteries or by AC Adaptor 9V DC 100mA", a "Made in Hong Kong" sticker, four feet, and two cross-head screws beside the feet at the other end.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 José Antonio Ortigueira Amor, "Consola Grandstand 4600 Colour Video Sports Centre (1977)", Retro Ordenadores Orty (collector's blog, in Spanish), December 2021 (retrieved 2026-10-18). The owner's description of his console: a General Instrument AY-3-8500 (one sentence calls it Texas Instruments) and a TBA520 ("PAL TV CHROMA DEMULATOR") for the colour; two vertical-movement controllers permanently attached by cable that press into compartments either side; on the Deluxe version the reset button is on the controllers; a rear jack for a 9 V DC supply, centre positive; RF lead to the TV, PAL channel 36; six 1.5 V LR14 cells in an internal compartment reached through the lower case; serial number 09-81-01 inside the battery compartment; four screws hold the lower case, two of them in the battery compartment; removing it shows the back of the board, held to the upper case by five screws; tested on a 9 V DC centre-positive supply and working correctly.
  3. ↑ 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 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - PCB.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: the component side of the board, with "AY-3-8500 GI 8138 SFA", "TBA520 F8133 INDONESIA", two "CD4069CN MM74C04N" with the National logo, a transistor marked "9015", a screened RF can at the top, a long game-select slide switch across the middle, slide switches SW1 to SW6 along the front edge, a yellow trimmer near SW2, about eight electrolytic capacitors (C38 marked 10 µF; C37 a Yobatron marked 16 V; the others not legible), and brown deposits on and around several switches and parts. The uploader's description: "CPU: AY-3-8500 plus the Fairchild TBA520 (PAL TV CHROMA DEMULATOR) that produce images with colors".
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Ian Hill, "Grandstand 4600", Ian's Retro Museum (collector's site; photographs not freely licensed) (retrieved 2026-10-18): a second 4600, bought untested at a table-top sale with its box; batteries or an optional mains adaptor; fixed TV lead; controllers "nothing more than a potentiometer in a plastic box", permanently attached and stored in the unit; a "rifle" attachment that "plugs into the side via a DIN plug", missing some parts; "manual score counters at the top of the unit"; tried on a suitable PSU and "it does work, the switches and controls will need a clean". Photographs: the same base label, a "BATCH NO. 08-80-01" sticker, the pistol on a grey lead, and soccer and tennis games on a green field.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Internals.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: the upper case from below with the base removed; the board solder side up, held by screws, with "REV.2 11-00161-00" printed at the lower left; the DC socket at the top left wired to the board; both controller leads passing into the bays, one knotted round a post; brown patches on the solder side and around the case slots.
  6. ↑ 6.0 6.1 6.2 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Connectors.jpg (CC BY 4.0, from Wikimedia Commons): the rear of the console, with a socket labelled "DC 9V" at one end and the fixed RF lead, ending in a coaxial plug, at the other.
  7. ↑ 7.0 7.1 7.2 7.3 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour (above).jpg (CC BY 4.0, from Wikimedia Commons): the panel, with LEFT and RIGHT SCORE sliders marked 0 to 10, a six-position game slider (PRACTICE, SQUASH, SOCCER, TENNIS, S.L. TARGET, M. TARGET) with a SERVE button on the game plate, switches SERVE (MANU/AUTO), BAT SIZE, ANGLE and SPEED (AMATEUR/PROFESSIONAL), GAME RESET and POWER (OFF/ON), "GRANDSTAND" and "4600 COLOUR", and the LEFT PLAYER and RIGHT PLAYER pods.
  8. ↑ Wikidata, "Colour Video Sports Centre 4600" (Q71129085) (retrieved 2026-10-18): CPU property (P880) given as AY-3-8600 (Q65953663), with the owner's blog post as its reference.
  9. ↑ Ian Hill, "Grandstand 6000", Ian's Retro Museum (collector's site; photographs not freely licensed) (retrieved 2026-10-18): a Grandstand Model 6000 with the same base label as the 4600 ("Use 6 x UM-2 Batteries, or by AC Adaptor 9V DC 100mA"), photographed with a Grandstand A.C. adaptor labelled "AC INPUT: 240v - 50Hz, OUTPUT: 9v - 150mA ... MADE BY ADMAN ELECTRONICS HARROGATE".
  10. ↑ Handheld Museum, "Grandstand Universal Mains Adapter" (retrieved 2026-10-18). Collector's entry: model UGT, sold by Grandstand in the UK for its handheld and tabletop games; 240 V input; 6-9 V DC output; a switch for the polarity and for off.
  11. ↑ Grandstand, Astro Wars instruction leaflet (Adam Leisure Group, 1981), p. 2: "Set polarity switch to negative polarity." Hosted here as File:Grandstand Astro Wars Instructions.pdf.
  12. ↑ 12.0 12.1 12.2 12.3 12.4 12.5 General Instrument Corporation, GIMINI TV Game Circuits, January 1978, pp. 4-7, PDF hosted by Pong-Story (retrieved 2026-10-18). AY-3-8500 data sheet: six games, including two rifle shooting games; VCC +6 to +7 V, -0.3 to +12 V maximum on any pin; games and options selected by connecting inputs to VSS, with a contact resistance of 1 kΩ or less; manual serve made by momentarily grounding the serve input; bat inputs fed by R-C networks from 1 MΩ potentiometers, "Use a 10K resistor in series with each pot".
  13. ↑ 13.0 13.1 Raphaël Assenat, "APF TV Fun console repair", raphnet.net (retrieved 2026-10-18): an AY-3-8500 console stored with its batteries in had heavy verdigris on the battery contacts, which were removed, and corroded power and RF connectors, which were replaced.
  14. ↑ Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - With detached controllers.jpg (CC BY 4.0, from Wikimedia Commons): both pods lifted out of their bays, their leads running into the floors of the bays.
  15. ↑ Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Screen.jpg (CC BY 4.0, from Wikimedia Commons): the picture on a colour television, with two-digit scores at the top and a dotted centre line.


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