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Atari 2600 Jr Capacitor Replacement Guide

From RetroTechCollection
NTSC 2600 Jr. board: C26 is the large blue capacitor at the left, C20 the small one at the top right

The Atari 2600 Jr has five aluminium electrolytic capacitors: the 2200 µF reservoir and four 4.7 µF parts. Atari published no service manual or parts list for the Jr.; the values below come from Console5's list for the NTSC Jr. and from Jerzy Sobola's redrawn schematic of a PAL Jr. board, which agree on every designator and value.[1][2][3]

The list also covers the two 820 pF polystyrene capacitors in the sound oscillator. Console5 describes the 2600's pair as "next in line for failure, causing a loss of audio".[1]

Capacitor list

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2600 Jr. electrolytic and polystyrene capacitors
Ref Value Rating (Console5) Position on the PAL schematic Notes
C26 2200 µF 16 V Power input reservoir, after J2 and before the power switch S4 Main reservoir
C37 4.7 µF 35 V Regulator input, after the power switch Ceramic 0.22 µF on some revisions (Console5)
C27 4.7 µF 35 V Reset and timing circuit around the 4050 (A4) Ceramic 0.22 µF on some revisions (Console5); the PAL drawing uses the label C27 twice
C29 4.7 µF 35 V Output of the 4050 section A4C Ceramic 0.1 µF on some revisions (Console5)
C20 4.7 µF 35 V Supply to the controller ports, through L3
C53, C54 820 pF 50 V Sound-carrier oscillator around Q4 Polystyrene; heat sensitive

Values and ratings are from Console5;[1] the positions are read from the PAL schematic, whose values match but which gives no ratings.[2] Because some revisions have ceramic parts at C27, C29 and C37, look at what is fitted before ordering.[1]

The sound oscillator capacitors

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C53 and C54 do the same job as C206 and C207 on the CX2600 and CX2600A. Atari's 2600 service manual names that pair as the first suspects for audio failures, notes that pressing on them can bring the sound back, and says to replace both together.[3] Console5 warns that polystyrene capacitors are heat sensitive and recommends a heatsink clip while soldering.[1]

Procedure

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See Recommended Tools for equipment and Capacitor Failure Symptoms for what a failed capacitor looks like.

  1. Unplug the power adaptor.
  2. Remove the screws in the base. TBA's manual says the Jr.'s case is brittle and its internal posts can snap; take care with the screws.[4]
  3. Lift the left side of the top case first and unplug the flexible cable to the SELECT and RESET buttons, then remove the top case.[4]
  4. Release the snap levers at the left and right edges of the board and lift it out. Straighten the tabs under the board to remove the RF shield.[4]
  5. Note the polarity of each electrolytic, then replace them one at a time.
  6. Clip C53 and C54 out and fit the new ones with a heatsink clip on each lead.
  7. While the board is out, check that the regulator is fixed to its copper pad. TBA advises soldering the tab down or fitting a screw if nothing holds it.[4]
  8. Refit the shield; TBA says it is needed for a good RF picture.[4]

After the recap

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  • Confirm +5 V at the output of VR1 (7805) with the power switch on.[2]
  • Check the sound. If it is missing, check the new 820 pF capacitors for heat damage, then the tuning of the sound-carrier coil (L8 on the PAL schematic).[2][3]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 Console5 TechWiki, "Atari 2600", "Capacitor Info & Refresh Kit Installation": "NTSC Junior" electrolytics (C20, C26, C27, C29, C37) and "Junior" polystyrene capacitors (C53, C54). Secondary source (a capacitor-kit vendor's component list).
  2. ↑ 2.0 2.1 2.2 2.3 Jerzy Sobola, redrawn schematic "Motherboard C012283 rev. B, Atari 2600 Game Console", sheet 1 of 2, 8 September 2000 (PAL 2600 Jr.). Hosted here as File:Atari 2600 Jr PAL motherboard schematic (Jerzy Sobola).png.
  3. ↑ 3.0 3.1 3.2 Atari, Inc., Video Computer System Field Service Manual, Domestic Model 2600/2600A, FD100133 Rev. 02, NTSC tech tip 2 (C206 and C207) and the audio entries of the symptom checklist. The manual does not cover the 2600 Jr. Hosted here as Atari 2600 and 2600A Field Service Manual.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 The Brewing Academy, Bryan's Ultimate Atari Video Rev. D Instruction Manual, revision 1.94, 23 March 2021, "Atari 2600 Jr." (p. 12). PDF from thebrewingacademy.com.


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