Jump to content

Coleco Telstar Alpha Capacitor Replacement Guide

From RetroTechCollection
Coleco Telstar Alpha (7)
The back of a Telstar Alpha, with the game cable and the adapter socket. No photograph of the Alpha's board has been published.

The Coleco Telstar Alpha (model 6030) dates from 1977, so any electrolytic capacitors on its board are now close to 50 years old.[1] Coleco published no schematic or parts list for the Alpha, no photograph of its board has been found, and no capacitor values for it have been published anywhere. What General Instrument's data for the AY-3-8500 says about the circuit is set out below, with a method for recording and replacing your own board's capacitors. Opening the case and cleaning are on Coleco Telstar Alpha General Maintenance; other faults on Coleco Telstar Alpha Troubleshooting Guide.

What is known

[edit | edit source]
  • The Alpha runs from six C cells (9 V nominal) or Coleco's 9 V DC adapter Model 6041.[1][2]
  • Its game chip is the AY-3-8500.[3] GI specifies the chip for +6 to +7 V, below the 9 V of the cells, and GI's black-and-white reference circuit places a single 10 µF electrolytic across the supply.[4]
  • The other capacitors in GI's reference circuit are small non-polarised parts: 0.1 µF on each bat input, 0.2 µF in the sound driver, 0.01 µF on reset, 75 pF in the 2 MHz oscillator and a few tens of picofarads in the lab modulator.[4] Coleco's board need not follow GI's design, and its own modulator and supply parts are not documented.

GI's values are a guide to what kind of parts to expect, not a list for the Alpha. Every value you fit must come from the part you take out.

Signs of a failing capacitor

[edit | edit source]
  • A swollen or split top, or a capacitor leaning on its legs.
  • Brown or crusty residue at the base, or corrosion on nearby tracks.
  • A picture that rolls or buzzes on more than one television, or a game that resets itself, after the cells and switches have been ruled out.

See Capacitor Failure Symptoms for the general signs.

Leaking C cells can also corrode the board near the battery compartment; treat that damage first, using Battery Explosion, Capacitor or Corrosion Damage.

Recording your board

[edit | edit source]
Telstar Alpha electrolytic capacitors: record your own board
Position (designator, or where it sits) Capacitance Voltage Temperature Lead spacing Notes
1
2
3
  1. Photograph both sides of the board before removing anything.
  2. Note any printed designators (C1, C2 and so on) and the polarity marking beside each electrolytic.
  3. Read capacitance and voltage from each sleeve. If the printing faces away, turn the part gently on its legs to read it.
  4. Fill in the table above for your board, and keep the photographs with it.

Replacement procedure

[edit | edit source]
  1. Take out the cells and unplug the adapter.
  2. Open the case. No published source shows how its halves are fastened; see Coleco Telstar Alpha General Maintenance#Case and panel.
  3. Work on one capacitor at a time. Desolder it from the solder side with a pump or braid, keeping heat short on the old pads.
  4. Fit a new electrolytic of the same capacitance, the same or a higher voltage rating, 105 °C, with the same lead spacing, and observe polarity.
  5. When all are done, check the board for solder bridges before applying power.
[edit | edit source]
  • Temperature-controlled soldering iron, desoldering pump or braid, flux, isopropyl alcohol.
  • Multimeter; a capacitance or ESR meter for checking the parts removed.
  • Radial electrolytic capacitors from a known maker (Nichicon, Panasonic, Rubycon or similar), rated 105 °C.
  • A current-limited bench supply set to 9 V for the first power-up.

See Recommended Tools.

Checks after recapping

[edit | edit source]
After recapping a Telstar Alpha
Check Expected Source
Supply 9 V from cells or the Model 6041 adapter [1][2]
AY-3-8500 pin 4 to pin 2 +6 to +7 V [4]
AY-3-8500 pin 17 2.012160 MHz ±1% [4]
Picture Steady field, paddles and scores on channel 3; RESET starts a game [5][6]
Sound Hit, score and rebound sounds from the console [1]
[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 1.3 Coleco Industries, Telstar Installation Instructions and Game Rules, Model No. 6030, Guide No. 57659 B, 1977, p. 1, File:Coleco Telstar Alpha Installation Instructions (Guide 57659B).pdf: six C batteries; TELSTAR 9 volt AC adapter Model #6041; hit, score and rebound sounds.
  2. ↑ 2.0 2.1 Photograph by Evan-Amos, File:Coleco-Telstar-AC-Adaptor.jpg (public domain, from Wikimedia Commons): Model 6041, output 9 V DC 200 mA.
  3. ↑ David Winter, Pong-Story, "Coleco Telstar Alpha" (retrieved 2026-10-18): model 6030, 1977, uses the AY-3-8500.
  4. ↑ 4.0 4.1 4.2 4.3 General Instrument, GIMINI TV Game Circuits, January 1978, pp. 4-6 and 12, File:General Instrument GIMINI TV Game Circuits (January 1978).pdf: AY-3-8500 standard conditions VCC +6 to +7 V; clock 2.012160 MHz ±1%; System Diagram 1 (black and white implementation) with a 10 µF electrolytic across VCC, 0.1 µF on each bat input, 0.2 µF and a 2N2222 in the sound driver, 0.01 µF on the reset input and 75 pF in the 2 MHz oscillator; Fig. 10, a VHF modulator "used in the lab for test purposes", with capacitors from 10 pF to 0.02 µF.
  5. ↑ Coleco, Guide No. 57659 B, p. 2: pre-set for channel 3.
  6. ↑ Coleco, Guide No. 57659 B, p. 3: pushing the reset button starts a new game.


Retrieved from "https://retrotechwiki.com/index.php?title=Coleco_Telstar_Alpha_Capacitor_Replacement_Guide&oldid=26498"