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Grandstand Model 4600 Troubleshooting Guide

From RetroTechCollection
Grandstand 4600 colour - PCB
The component side of a working 4600's board: the AY-3-8500 in the centre, the TBA520 at top right, the RF modulator can at the top, the game slider across the middle and SW1 to SW6 along the bottom edge. Brown deposits cover several switches and the board around them.

Fault-finding for the Grandstand Model 4600, the six-game colour Pong console built on General Instrument's AY-3-8500 with a TBA520 for the colour.[1] No repair report for a 4600 has been found. The board photographed for Wikimedia Commons works despite heavy deposits around its switches,[1][2] and a second collector's 4600 worked on a suitable supply, though its switches and controls needed cleaning.[3] The tables below use those two owners' notes, the board photograph, and General Instrument's 1978 data for the AY-3-8500. Opening the case and routine care are on Grandstand Model 4600 General Maintenance.

What should happen at power-on

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With six good C cells or a 9 V adaptor, POWER switched ON and an analogue television tuned to channel 36:

  • A colour picture appears with two-digit scores at the top and a dotted centre line.[4][3]
  • The game slider chooses PRACTICE, SQUASH, SOCCER, TENNIS, S.L. TARGET or M. TARGET.[5]
  • Each control pod moves its bat up and down the screen.[2]
  • With SERVE on MANU the game waits after each point until the SERVE button on the game plate is pressed; on AUTO it serves by itself.[5][6]
  • GAME RESET starts the game again from zero.[5][6]
  • The score sliders above the game plate do nothing by themselves; they are manual score counters.[3]

Expected measurements

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Grandstand 4600 reference values
Point Expected Source
Supply at the cells or DC 9V socket 9 V DC; adaptor rated 100 mA [7]
DC 9V socket polarity Centre positive (owner's notes, tested) [2]
AY-3-8500 pin 4 to pin 2 +6 to +7 V [6]
AY-3-8500 supply current 40 mA typical, 60 mA maximum at +7 V [6]
AY-3-8500 pin 17 clock 2.012160 MHz ±1% [6]
Closed switch contact to ground 1 kΩ or less [6]
RF output UHF channel 36 [7]

Bring a 4600 that has been stored back up on a current-limited bench supply: 9 V, limit about 150 mA. The label allows 100 mA, so a much higher draw points to a short, perhaps under the deposits on the board.

Symptoms

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Grandstand 4600 symptoms
Symptom Likely cause Action Source
Nothing on cells Flat cells; corroded contacts in the battery compartment Clean the contacts to bright metal and fit six fresh C cells. [7][8]
Works on cells, not on the adaptor Wrong polarity or voltage; dirty DC 9V socket; broken wire from the socket The owner gives the socket as centre positive. Measure the adaptor off load, clean the socket, and check its wires to the board with the base off. [2][9]
Nothing on cells or adaptor POWER switch; a track eaten by the deposits Measure 9 V before and after the POWER switch, then at pin 4 of the AY-3-8500. Inspect the board under the deposits with a magnifier. [1][6]
Snow, no picture Television not on channel 36, or has no analogue tuner; RF lead or plug Tune an analogue television, or a box with an analogue tuner, to UHF channel 36. Check the RF lead's plug and where the lead enters the case. [7][10]
Black and white picture, or wrong or unstable colours Television's colour or fine tuning; the TBA520 colour circuit; the yellow trimmer moved Fine-tune the set first. Then check the TBA520's supply and the parts around it. Do not turn the trimmer without marking it. [1]
Steady screen but no game The AY-3-8500 not running Measure pin 4 (+6 to +7 V) and pin 17 (about 2 MHz). [6]
A setting does nothing, or works only when the switch is wiggled Corroded slide switch Clean the switch and measure the closed contact: the AY-3-8500 needs 1 kΩ or less. The photographed board has deposits on several of these switches. [6][1]
Game slider gives the wrong game, or soccer with an extra bat on the right Corroded game slider; slider between positions With none of its game inputs grounded the AY-3-8500 plays Handicap, a soccer game in which the right-hand player has a third bat. Clean the slider and move it firmly into each position. [11][1]
One bat jumps, drifts or will not reach the edge Dirty potentiometer in the pod; break in the pod's lead Clean the potentiometer. Flex the lead at both ends while watching the bat. The pods are wired in, so compare the two potentiometers' readings at the board. [3][12]
SERVE or GAME RESET has no effect Dirty contact Clean it. The chip's serve and reset inputs work by being pulled briefly to ground. [6]
Rifle never scores Flat-panel television; DIN plug or socket; lead; missing parts in the rifle Test on a CRT set. Clean the DIN plug and socket and check the lead. [3]
No sound Speaker or its wiring; sound driver Check the speaker's wiring with the base off. The chip's sound comes out on pin 3. [6]

Known faults reported for this device

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  • The board photographed for Wikimedia Commons has brown deposits on and around several slide switches, the game slider and other parts, with patches on the solder side and around the slots in the case. Its owner does not give the cause, and the console still works.[1][9][2] Treat any 4600 with deposits like these as the first thing to clean, and check the tracks underneath before replacing parts.
  • A second 4600, bought untested, worked on a suitable supply but needed its switches and controls cleaning.[3]
  • The same collector's rifle was missing some parts.[3]

No other fault report for a 4600 has been found.

Things that are not faults

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  • The score sliders do not move on their own. They are manual counters; the console keeps score on screen as well.[3][4]
  • The bats only move up and down. The AY-3-8500 gives vertical bat movement only.[6]
  • Play stops when one side reaches 15. The ball keeps bouncing, but no more hits or scores count until GAME RESET.[6]
  • On MANU serve the game waits after every point.[6]
  • The rifle does nothing on a flat-panel television.
  • Wikidata lists an AY-3-8600 for the 4600.[13] The board shows an AY-3-8500, and the six games on the slider are the AY-3-8500's.[1][6]

What is realistically repairable

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Repairability of 4600 parts
Part Repairable? Notes
Corroded tracks and joints Yes Clean, then bridge any eaten track with wire.[1]
Slide switches SW1 to SW6 and the game slider Usually Clean first. A switch with corroded legs or contacts needs a replacement of the same pitch and travel, so it lines up with the panel.[1]
Control pods Yes A potentiometer in a plastic box on a lead; both parts are ordinary.[3]
DC 9V socket and RF lead Yes Ordinary parts, wired to the board.[9][10]
Electrolytic capacitors Yes Only C38 (10 µF) and C37 (16 V) can be read in the photograph; read the rest from your own board.[1]
TBA520 Yes, if a part can be found A PAL television chroma decoder IC, also used in television sets of the period.[1]
AY-3-8500 Only by transplant Out of production but fitted to hundreds of consoles, so donors exist.[11] Rule out supply, clock and switches first.
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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 1.11 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - PCB.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: "AY-3-8500 GI 8138 SFA" in the centre, "TBA520 F8133 INDONESIA" at top right, two National "CD4069CN MM74C04N", a "9015" transistor, a screened RF can at the top, a long game-select slide switch across the middle, SW1 to SW6 along the front edge, a yellow trimmer near SW2, electrolytics including C38 (10 µF) and C37 (Yobatron, 16 V), and brown deposits on and around several switches and parts. Uploader's description: "CPU: AY-3-8500 plus the Fairchild TBA520 (PAL TV CHROMA DEMULATOR) that produce images with colors".
  2. ↑ 2.0 2.1 2.2 2.3 2.4 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): AY-3-8500 and TBA520; two vertical-movement controllers attached by cable; rear jack for 9 V DC, centre positive; PAL, channel 36; six LR14 cells; tested on a 9 V DC centre-positive supply, "La consola funciona correctamente".
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Ian Hill, "Grandstand 4600", Ian's Retro Museum (collector's site; photographs not freely licensed) (retrieved 2026-10-18): controllers "nothing more than a potentiometer in a plastic box", permanently attached; "rifle" attachment plugging into the side via a DIN plug, "missing some parts"; "manual score counters at the top of the unit"; on a suitable PSU "it does work, the switches and controls will need a clean". Photographs of games on a green field with on-screen scores.
  4. ↑ 4.0 4.1 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 in colour at the top and a dotted centre line.
  5. ↑ 5.0 5.1 5.2 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour (above).jpg (CC BY 4.0, from Wikimedia Commons): the panel, with the game slider (PRACTICE, SQUASH, SOCCER, TENNIS, S.L. TARGET, M. TARGET), the SERVE button on the game plate, switches SERVE (MANU/AUTO), BAT SIZE, ANGLE, SPEED, GAME RESET and POWER, and the LEFT and RIGHT score sliders.
  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 6.14 General Instrument Corporation, GIMINI TV Game Circuits, January 1978, pp. 4-10, PDF hosted by Pong-Story (retrieved 2026-10-18). AY-3-8500 data sheet: vertical bat movement; VSS pin 2, VCC pin 4, +6 to +7 V; supply current 40 mA typical, 60 mA maximum at +7 V; clock input pin 17, 2.012160 MHz ±1%; sound output pin 3; manual serve input, which when open stops play after each score until it is momentarily grounded; reset input momentarily grounded; control inputs need 1 kΩ or less to VSS; a game ends when one side reaches 15, after which the ball still bounces but no further hits or scores are made.
  7. ↑ 7.0 7.1 7.2 7.3 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Back.jpg (CC BY 4.0, from Wikimedia Commons): base label "UHF CHANNEL 36 / POWER SOURCE: Use 6 x UM-2 Batteries or by AC Adaptor 9V DC 100mA", "Made in Hong Kong", and the battery cover.
  8. ↑ 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 its battery contacts and corroded power and RF connectors.
  9. ↑ 9.0 9.1 9.2 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Internals.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: the board solder side up in the upper case, "REV.2 11-00161-00", the DC socket wired to the board, the controller leads, and brown patches on the solder side and around the slots in the case.
  10. ↑ 10.0 10.1 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Connectors.jpg (CC BY 4.0, from Wikimedia Commons): the rear, with the "DC 9V" socket at one end and the RF lead with its coaxial plug at the other.
  11. ↑ 11.0 11.1 David Winter, Pong-Story, "PONG in a Chip" (retrieved 2026-10-18): the AY-3-8500's undocumented seventh game, Handicap, in which the right-hand player has a third paddle, is played when none of the six games is selected; the chip was used in "hundreds of different game systems".
  12. ↑ Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - With detached controllers.jpg (CC BY 4.0, from Wikimedia Commons): both pods out of their bays on leads that run into the console.
  13. ↑ Wikidata, "Colour Video Sports Centre 4600" (Q71129085) (retrieved 2026-10-18): CPU property (P880) AY-3-8600 (Q65953663).


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