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Coleco Telstar Galaxy Troubleshooting Guide

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Coleco Telstar Galaxy control panel (Pong-Story)
The Galaxy's control panel: PADDLE ACTION, RESET, GAME SELECTOR, MODE and NO. OF PLAYERS (photograph by Adrian Scheel, Pong-Story).

Fault-finding for the Coleco Telstar Galaxy (model 6150), Coleco's four-player colour Telstar built on General Instrument's AY-3-8600 and AY-3-8615.[1] No Coleco guide, schematic or repair report for the Galaxy has been found, and no data sheet for the AY-3-8600. The checks below rest on Pong-Story's description of the Galaxy's circuits and on GI's 1978 data for the closely related AY-3-8610 and for the AY-3-8615. Cleaning is on Coleco Telstar Galaxy General Maintenance.

How the Galaxy works

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Pong-Story and GI describe the circuits as follows.[1][2]

  • The AY-3-8600 makes the games. Its separate video outputs for the players, the ball, the field and the background go to the AY-3-8615.
  • The AY-3-8615 makes the colour picture from a 3.579545 MHz crystal and also feeds a 3.579 MHz clock to the AY-3-8600. If the 8615's oscillator stops, the game chip has no clock either.
  • A flip-flop switches the game chip's two player inputs between the console knobs and the hand controllers on alternate frames, for four-player games.
  • The Robot circuit derives a voltage from the position of the ball and feeds it to one player's input.

Reference values

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Telstar Galaxy reference values (GI data)
Point Expected Source
Game chip supply (AY-3-8610 data) +6 to +7 V; 12 V absolute maximum [3]
Game chip supply current (AY-3-8610) 40 mA typical, 60 mA maximum [3]
AY-3-8615 crystal 3.579545 MHz [2]
Game chip clock 3.579 MHz, supplied by the AY-3-8615 [2][3]

These are GI's figures for its "8600" series parts, not measurements from a Galaxy.

Symptoms

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Telstar Galaxy symptoms
Symptom Likely cause Action
Nothing at all Power, or the MODE switch at OFF Check the supply and clean the MODE switch.[4]
Steady blank raster, no game No clock: AY-3-8615 crystal oscillator stopped Check for 3.579 MHz at the crystal and at the game chip's clock input; GI's design takes the game clock from the AY-3-8615.[2]
Game present but in black and white, or wrong colours Television colour or tint; AY-3-8615 crystal trimmer or hue setting Adjust the television first; GI's design tunes the crystal with a 3 to 15 pF trimmer and has a hue adjustment.[2] Mark any trimmer before touching it.
Third and fourth players do not move, two-player games normal Hand controller lead or joystick; NO. OF PLAYERS switch; the multiplexing flip-flop Swap the hand controllers; clean the switch; then check the flip-flop's outputs toggle with the frame rate.[1][4][5]
All four paddles flicker Multiplexing fault The flip-flop should switch at frame rate, which Pong-Story says is fast enough to hide the switching.[1]
Robot paddle does not follow the ball Robot circuit (sync extraction, ramp generator or ball detection); MODE switch Clean the MODE switch; then trace the ramp, which should start at each vertical sync and stop at the ball.[1][4]
Paddles move sideways with PADDLE ACTION at VERTICAL Dirty PADDLE ACTION switch Clean the switch.[4]
Wrong game or no game at one selector position Dirty GAME SELECTOR contact Clean and exercise the selector.[4]

Things that are not faults

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  • The colours change from game to game; the AY-3-8615 sets them from the game selected.[2]
  • With PADDLE ACTION at VERTICAL the paddles move only up and down.[1][4]

What is realistically repairable

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Repairability of Telstar Galaxy parts
Part Repairable? Notes
Switches, selector, RESET, knobs Usually Clean first.
Hand controllers and leads Yes Ordinary parts.
Flip-flop and Robot circuit Yes Standard logic and discrete parts, by Pong-Story's description.[1]
Electrolytic capacitors Yes See Coleco Telstar Galaxy Capacitor Replacement Guide.
AY-3-8600 and AY-3-8615 Only from a donor The Galaxy was the only Telstar with the AY-3-8600.[1]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 David Winter, Pong-Story, "Coleco Telstar Galaxy" (retrieved 2026-10-18): model 6150, released in 1977; the only Telstar to use General Instrument's AY-3-8600; ten games in colour, the colour provided by GI's AY-3-8615 colour encoder; all games playable by up to four players, using a flip-flop that switches the chip's two paddle inputs between two pairs of hand controls on alternate frames; a Robot mode against the machine, made with extra circuitry that extracts the vertical sync, starts a ramp generator, stops it at the first line of the ball's video and feeds the ramp voltage to one player's input, which is possible only because the chip has separate video outputs for field, paddles and ball; the horizontal motion of the paddles can be switched off; released in very limited numbers, very few survive, two from former Coleco employees; photographs courtesy of Adrian Scheel.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 General Instrument, GIMINI TV Game Circuits, January 1978, p. 37, File:General Instrument GIMINI TV Game Circuits (January 1978).pdf: the AY-3-8615 colour converter takes the video signals of any of GI's "8600" game series circuits and produces one colour composite signal, with colour burst; the colours change with the game selected; it runs from a 3.579545 MHz crystal tuned with a 3 to 15 pF variable capacitor, has a hue adjustment, and supplies a buffered 3.579 MHz clock to drive the "8600" series game chip directly.
  3. ↑ 3.0 3.1 3.2 General Instrument, GIMINI TV Game Circuits, January 1978, pp. 26-36, File:General Instrument GIMINI TV Game Circuits (January 1978).pdf: AY-3-8610 "Superstar", a 28-lead circuit with ten games, two-axis player motion, scores 0 to 15 coloured by player, full colour with the AY-3-8615; separate outputs for left video, right video, boundaries and background; 3.579 MHz clock input; VCC +6 to +7 V; 12 V maximum on any pin; supply current 40 mA typical, 60 mA maximum.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Photograph by Adrian Scheel on Pong-Story, File:Coleco Telstar Galaxy control panel (Pong-Story).jpg: PADDLE ACTION switch (VERTICAL, FULL), RESET button, GAME SELECTOR knob numbered 1 to 8, MODE switch (ROBOT, MANUAL, OFF), NO. OF PLAYERS switch (A, B, C).
  5. ↑ Photograph by Adrian Scheel on Pong-Story, File:Coleco Telstar Galaxy controller compartment (Pong-Story).jpg: two hand controllers, each with a short joystick and a push button, stored in a compartment in the base under a removable cover.


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