Coleco Telstar Troubleshooting Guide
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Fault-finding for the first Coleco Telstar (model 6040), the three-game Pong console of 1976 built on General Instrument's AY-3-8500.[1] No service manual, schematic or owner's guide for the 6040 has been found. The one detailed report on a surviving 6040 comes from Lon.TV's 2026 review, and General Instrument's data for the chip supplies the bench figures.[2][3] Coleco's own trouble-shooting chart for the wooden-cased version of the same console is on Coleco Telstar Classic Troubleshooting Guide. Cleaning is covered in Coleco Telstar General Maintenance.
What should happen at power-on
[edit | edit source]With six good C cells or a 9 V adapter, the switch box at GAME and an analogue television tuned to VHF channel 3:[2]
- ON brings up the playfield, the paddles and the scores; RESET clears the scores and starts a game.[4][3]
- The game switch selects tennis, hockey or handball.[4]
- Each knob moves one paddle up and down.[3]
- The BEGINNER/INTERMEDIATE/PRO switch changes ball speed and paddle size; at PRO the paddles should be visibly shorter.[2]
- The sounds come from the console's own speaker.[2]
- After one side reaches 15 points no further hits or scores count until RESET.[3]
Expected measurements
[edit | edit source]| Point | Expected | Source |
|---|---|---|
| Six C cells | 9 V nominal | [2] |
| Model 6041 adapter | 9 V DC; labels seen at 100 mA and 200 mA | [5][6] |
| AY-3-8500 pin 4 to pin 2 | +6 to +7 V; 12 V absolute maximum | [3] |
| AY-3-8500 supply current | 40 mA typical, 60 mA maximum at +7 V | [3] |
| AY-3-8500 pin 17 | 2.012160 MHz ±1% | [3] |
| Pin 13 (bat size) | Open for large paddles, at 0 V for small | [3] |
| Pin 7 (ball speed) | Open for low speed, at 0 V for high | [3] |
| Closed switch to ground | 1 kΩ or less | [3] |
These are GI's figures for the chip. Coleco's board voltages for the 6040 have not been published.
Symptoms
[edit | edit source]| Symptom | Likely cause | Action |
|---|---|---|
| Nothing at all | Flat cells; corroded contacts; adapter | Fit six new cells, clean the contacts, and measure 9 V at the cells and after the ON/OFF switch.[2] |
| Game switch will not move | Stuck slide switch, reported on a 6040 in 2026 | Do not force it. Work contact cleaner into it, or free it with the case open.[2][7] |
| PRO does not shrink the paddles | Difficulty switch not closing the bat-size contact, reported on the same 6040 | The AY-3-8500 draws small paddles when pin 13 is grounded. With the switch at PRO, measure pin 13: it should be at 0 V. Clean or replace the switch.[2][3] |
| Wrong game, or a soccer-style game with a third paddle | Game switch between positions or not making contact | With none of its game inputs grounded the AY-3-8500 plays its hidden game, Handicap. Clean the switch and seat it fully in each position.[7] |
| Snow, no picture | TV channel, switch box, cable | Tune an analogue set to channel 3, set the switch box to GAME, and check the cable and its plug.[2][5] |
| Steady blank screen, no game | AY-3-8500 not running | Measure pin 4 (6 to 7 V) and pin 17 (2 MHz).[3] |
| Interference on nearby sets or on the television's other channels | Excess RF from the cable | Ralph Baer's team cured the Telstar's radiation with a ferrite ring on the coaxial cable just inside the case. Check that any ring fitted is still in place.[8] |
| Paddle jumps or will not reach the screen edge | Dirty paddle control | Clean it (knob off), or measure it end to end and at the wiper.[3] |
| No sound | Speaker or its wiring | The chip's sounds come out on pin 3; follow them to the speaker under the grille.[3][2] |
Things that are not faults
[edit | edit source]- Only three games. The chip's two shooting games are not wired to the switch on the 6040.[9]
- The paddles move only up and down.[3]
- Play stops at 15 points until RESET.[3]
- Two Telstar versions exist, one drawing a solid centre line in tennis and one a dashed line.[8]
What is realistically repairable
[edit | edit source]| Part | Repairable? | Notes |
|---|---|---|
| Battery contacts | Yes | Clean or replace. |
| Slide switches and RESET | Usually | Clean first; a replacement must match the pitch and travel of the original. |
| Paddle controls | Yes | Measure the old part to choose a replacement. |
| Game cable and switch box | Yes | Keep any ferrite ring and its turns.[8] |
| Electrolytic capacitors | Yes | See Coleco Telstar Capacitor Replacement Guide. |
| AY-3-8500 | Only by transplant | Rule out supply, clock and switches first. |
Related pages
[edit | edit source]- Coleco Telstar
- Coleco Telstar General Maintenance
- Coleco Telstar Capacitor Replacement Guide
- Coleco Telstar Classic Troubleshooting Guide, with Coleco's chart for the wooden-cased version
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ David Winter, Pong-Story, "Coleco Telstar systems" (retrieved 2026-10-18): Telstar, released in 1976, played three games with three difficulty levels and was the first system to use GI's AY-3-8500; over a million units sold; variants sold as the Telstar Deluxe in Canada and by Montgomery Ward as "Telstar Video World of Sports"; Coleco's systems were sold partially assembled, with the knobs and decorative stickers fitted by the user.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 Lon.TV, "This Was the Best Selling Game Console of 1976", blog post, 4 February 2026 (retrieved 2026-10-19): a Telstar model 6040 bought for a historical-society display; launched at $50; AY-3-8500 with the game logic in the chip; sound from a built-in speaker; RF output for VHF channel 3 through a switch box; designed to run on six C cells, with a power connector for an optional supply; on his unit the game selector switch was stuck and the difficulty slider did not resize the paddles at the "pro" setting.
- ↑ 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 3.14 3.15 General Instrument, GIMINI TV Game Circuits, January 1978, pp. 4-6, File:General Instrument GIMINI TV Game Circuits (January 1978).pdf: AY-3-8500 pin functions (VSS pin 2, sound pin 3, VCC pin 4, ball speed pin 7 open for low speed and grounded for high, bat size pin 13 open for large bats and grounded for small, sync pin 16, clock pin 17 at 2.012160 MHz ±1%, game inputs pins 18 to 23 grounded to select); standard conditions VCC +6 to +7 V, +12 V maximum; supply current 40 mA typical, 60 mA maximum at +7 V; control inputs need 1 kΩ or less to VSS; vertical bat movement; scores 0 to 15.
- ↑ 4.0 4.1 Arcade-History, "Telstar [Model 6040"] (retrieved 2026-10-19): model 6040, 1976; three Pong games (tennis, hockey, handball); two knobs built into the console; RESET button; ON/OFF and Beginner/Intermediate/Pro switches; black and white; built-in beeper; on-screen score.
- ↑ 5.0 5.1 Photograph by Chris Yarzab, File:Telstar (51908701248).jpg (CC BY 2.0, from Wikimedia Commons), read at full size: a Telstar model 6040 with its box, the antenna switch box (GAME/TV, "Made in U.S.A.") and a TELSTAR AC Adaptor Model 6041 labelled "OUTPUT: 9V DC 100mA".
- ↑ Photograph by Evan-Amos, File:Coleco-Telstar-AC-Adaptor.jpg (public domain, from Wikimedia Commons): label "TELSTAR AC ADAPTOR MODEL 6041 ... INPUT: 117V 60Hz 5W OUTPUT: 9 V DC 200mA".
- ↑ 7.0 7.1 David Winter, Pong-Story, "PONG in a Chip" (retrieved 2026-10-18): two versions of the AY-3-8500 exist, the early one with a dashed central line about twice as large and solid horizontal boundaries; the undocumented seventh game, Handicap, is played when none of the six games is selected; game selection switches "(rotary or linear) which could fail after many game selections".
- ↑ 8.0 8.1 8.2 David Winter, Pong-Story, "Coleco Telstar" (retrieved 2026-10-18): first model, 1976; Ralph Baer's account that Coleco's first Telstar failed the FCC radio-frequency interference tests until he slipped a ferrite toroid over the shielded coaxial cable coming out of the unit, with two tight loops through the ring just inside the cabinet, after which the unit passed; two versions of the console, one with linear speaker holes at the upper left that shows a solid centre line in tennis and one with small round holes that shows a dashed line, believed to reflect a first run and a revision of the AY-3-8500.
- ↑ Cameron Coward, "Two Secret Games Discovered on Vintage Coleco Telestar Pong Chip", Hackster.io (retrieved 2026-10-19), on a video by Dave's Garage: the Telstar's three games (hockey, handball, tennis) come from an AY-3-8500, which needs an external clock and outputs its picture elements on separate pins; the chip also holds two shooting games not enabled on that console, reachable by modifying the game selection switch.
