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Atari Lynx II Capacitor Replacement Guide

From RetroTechCollection
Lynx II board C104471-001 Rev. A with the RF shield removed. C41 and C39 are at the top left; C21, C19, C64, C53 and C60 are grouped at the top right

The Atari Lynx II main board has about twenty aluminium electrolytic capacitors. K-Retro's capacitor map, published by the Atari Lynx Vault, lists twenty for the Lynx II;[1] its layout matches Evan-Amos's photograph of a C104471-001 Rev. A board.[2] Atari's own Lynx II schematic, drawing C104247 Rev. 1, is an engineering issue drawn for the Hayato version of the board, and its audio section does not agree with the production board in every position.[3] Both are given below. For the original Lynx, see the Atari Lynx Capacitor Replacement Guide.

The Atari Lynx Vault calls a recap a must-do job on any Lynx, especially one with display faults or low speaker volume.[4] Igor Kromin recapped a Lynx II whose screen showed black lines across it and whose speaker crackled; after the recap the lines were gone and the crackle with them, though the volume stayed low until he replaced the speaker.[5][6] Replace the MOSFET Q12 and the zener D13 at the same sitting if they are original (see Atari Lynx II Troubleshooting Guide).[7]

Board revisions

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The Atari Lynx Vault lists five Lynx II boards: C104129-001 Rev. 2, C104342-001 Rev. 1 and Rev. 2, C104424-001 Rev. 1 and C104471-001 Rev. A. It describes the C104129-001 as essentially a Lynx I in the Lynx II form factor, an early version of the design.[8] Positions on the C104129-001 may therefore not match the list below. The board number is printed under the "LYNX II" legend on the component side.[2]

Capacitor list

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Lynx II electrolytic capacitors
Ref K-Retro map Atari schematic C104247 Rev. 1 Where it sits on the schematic
C3 10 µF 6.3 V 10 µF 6.3 V Reset line, with D1 and R1
C11 10 µF 6.3 V 10 µF 6.3 V Cartridge supply, connector pin 33
C14 47 µF 6.3 V 47 µF 6.3 V Supply decoupling for the 74HC04 audio stage (U7), fed through R39
C16 1 µF 50 V 1 µF 50 V Audio coupling to the volume control VR2
C58 1 µF 50 V 1 µF 50 V Audio coupling to the volume control VR2
C19 47 µF 6.3 V 47 µF 6.3 V LM386 speaker amplifier (U5), pin 7
C21 220 µF 6.3 V 220 µF 6.3 V Headphone output coupling, from the NJM2073 (U12)
C64 220 µF 6.3 V 220 µF 6.3 V Headphone output coupling, from the NJM2073 (U12)
C53 47 µF 6.3 V 560 pF (not electrolytic) NJM2073 input network
C60 47 µF 6.3 V 10 µF 6.3 V NJM2073 input network
C61 not listed 10 µF 6.3 V NJM2073 input network
C36 not listed 220 µF 6.3 V LM386 output coupling to the 16 Ω speaker
C23 10 µF 35 V 10 µF 35 V +20 V supply at TP12, from the backlight transformer
C25 10 µF 35 V 10 µF 35 V LCD contrast circuit, with Q2 and Q3
C27 10 µF 6.3 V 10 µF 6.3 V LCD bias, VD2/VM lines (TP25, TP24)
C28 10 µF 6.3 V 10 µF 6.3 V LCD bias, VD2/VM lines (TP25, TP24)
C32 2.2 µF 50 V 2.2 µF 50 V LCD drive circuit, beside Q4 and Q5
C33 2.2 µF 50 V 2.2 µF 50 V LCD drive circuit, beside Q4 and Q5
C37 1 µF 50 V 1 µF 50 V ON button circuit (TP17), with R68
C39 100 µF 35 V 100 µF 25 V Unregulated input to the switching regulator
C41 470 µF 10 V 470 µF 10 V Regulated +5 V output, after L15 and D12
C47 1 µF 50 V 1 µF, no rating printed Backlight-off circuit, between Q9 and Q10

The K-Retro column is the published map,[1] and Igor Kromin's 2017 picking list for the Lynx II gives the same quantities.[9] The schematic column and the circuit positions are read from Atari's drawing.[3] Where the two disagree (C53, C60, C61, C36 and the rating of C39), read the value printed on the capacitor in your own board before ordering. Atari's drawing also uses the designator C36 twice, for the 220 µF speaker coupling capacitor and for a 0.01 µF capacitor beside Q7 in the power switching. Nothing rated below 25 V belongs in C39, which carries the battery or adaptor voltage.[3]

Procedure

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

  1. Remove the batteries. Lift the rubber hand grips with a plastic spudger; they are glued down but come away once the first few millimetres are free.[10]
  2. Take out the battery cover and remove the four Phillips screws under the grips. Unclip the two halves, starting around the battery compartment.[10]
  3. Remove the single screw holding the battery compartment and lift it out.[10]
  4. Unplug the speaker (two-pin) and backlight (three-pin) connectors. Release the locks on the button-membrane and LCD ribbon sockets by pulling the top of each socket away from the board, then pull the ribbons out and lift the board.[10][11]
  5. Most capacitors are reachable from the component side. C3 sits under the RF shield. Igor Kromin reached it by desoldering the thin copper sheet on the underside of the board and peeling it back, which he found easier than taking off the steel shield on the top; there was insulating tape over the C3 pads, which he put back afterwards.[5][1]
  6. Note the polarity mark beside each position and work one capacitor at a time. The board marks the positive side of every position.[5]
  7. Leave about 3 mm of lead above the board so each part can be bent to clear the case.[1]

Igor Kromin took just over an hour to remove the original capacitors from his board.[5]

Underside of a C104471-001 board, showing the copper RF shield sheet soldered around the cartridge connector

After the recap

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With the Lynx switched on, C41 should show about 5 V; the input voltage from the adaptor, less one diode drop, appears across C39.[12] The Atari Lynx Vault's dead or alive test feeds 5 V straight into C41 to run the board without the switching regulator, and warns that more than 5 V at that point destroys the processor.[13]

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References

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  1. ↑ 1.0 1.1 1.2 1.3 Atari Lynx Vault, "Atari Lynx Capacitor Maps" (changed 4 October 2023): K-Retro's Lynx 2 component map and picking list, with the note that C3 is under the RF shield and the advice on lead length. Vendor-published community source, CC BY-NC-SA 4.0.
  2. ↑ 2.0 2.1 Evan-Amos, photograph of a Lynx II main board C104471-001 Rev. A, 10 April 2014. Hosted here as File:Atari Lynx II motherboard (C104471-001 Rev A).jpg.
  3. ↑ 3.0 3.1 3.2 Atari Corporation, Schematic Diagram, Lynx II (Hayato), drawing C104247 Rev. 1 (engineering issue), 29 June 1990, sheet 1. Values and positions read from the drawing. Hosted here as File:Atari Lynx II schematic C104247 Rev 1.png.
  4. ↑ Atari Lynx Vault, "Atari Lynx Hardware Mods" (changed 9 October 2023), "Capacitor Replacements / Recapping". Community source.
  5. ↑ 5.0 5.1 5.2 5.3 Igor Kromin, "Atari Lynx repair - Part 2 - re-capping the motherboard", 12 September 2017. Personal repair log.
  6. ↑ Igor Kromin, "Atari Lynx repair - Part 3 - broken speaker replacement", 13 September 2017. Personal repair log.
  7. ↑ Atari Lynx Vault, "Replacing the MOSFET and zener diodes in an Atari Lynx" (changed 4 October 2023). Community source.
  8. ↑ Atari Lynx Vault, "Atari Lynx Motherboard Revisions" (changed 24 September 2023). Community source.
  9. ↑ Igor Kromin, "Picking lists for Atari Lynx capacitor replacement kits", 14 July 2017. Personal blog.
  10. ↑ 10.0 10.1 10.2 10.3 Atari Lynx Vault, "Lynx 2 disassembly steps and Screw size chart" (changed 15 April 2024). Community source.
  11. ↑ Igor Kromin, "Atari Lynx repair - Part 1 - introduction and case disassembly", 11 September 2017. Personal repair log.
  12. ↑ Retro Isle, "Lynx Repair Info", "DC power jack". Community source.
  13. ↑ Atari Lynx Vault, "Atari Lynx Dead/Alive Test - Bypassing The Atari Lynx 9V" (changed 6 November 2023). Community source.


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