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Grandstand Video Entertainment Computer Capacitor Replacement Guide

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Grandstand-video-entertainment-computer-pcb
The Grandstand Video Entertainment Computer main board. The four electrolytic capacitors sit at the top, right of centre, above the 3850 CPU (Incog88, CC BY-SA 3.0).

Electrolytic capacitors in the Grandstand Video Entertainment Computer, the UK version of the Fairchild Channel F System II. The main board has four aluminium electrolytic capacitors, all on the regulated supply rails; the larger reservoir capacitors sit in the power section, which on the Luxor and US versions is a separate board. No Grandstand parts list has been found. The values below are read from a scan of a Grandstand board and checked against two circuit diagrams of the same design, Luxor's for its Swedish version and Fairchild's own PAL drawing, and against a US owner's account of the power board.[1][2][3][4] Opening the console is covered on Grandstand Video Entertainment Computer General Maintenance, and symptoms that point to the supply on Grandstand Video Entertainment Computer Troubleshooting Guide.

Visual inspection and failure signs

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  • Bulging ends or leaked electrolyte on the four axial capacitors at the top of the main board.
  • Residue on the power-switch board around its two large reservoir capacitors. One US System II owner found electrolyte residue there and a capacitor with one leg unsoldered.[4]
  • A capacitor fitted the wrong way round by an earlier repair. On the same US console both reservoir capacitors had been fitted backwards, and the replacements overheated and burst within seconds of switching on.[4]
  • Moving bands of hum in the picture. Luxor's 1979 service bulletin for the first-generation console gives a faulty rectifier diode or reservoir electrolytic as the cause, together with the regulators.[5]
  • A green screen with no "G?" prompt points to a missing +12 V supply, and no information at all on the screen to a missing +5 V supply. Measure the regulators before blaming a capacitor.[5][6]

See Capacitor Failure Symptoms for what failing electrolytics look like in general.

Capacitor list

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Grandstand Video Entertainment Computer electrolytic capacitors
The electrolytic capacitors on the Grandstand board: two 25 V 100 µF above two 25 V 47 µF, with the arrows on every sleeve pointing the same way, towards the negative lead. Below them is the 3850 CPU (crop of Incog88's scan, CC BY-SA 3.0).

Main board

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Electrolytic capacitors on the main board
Position on the Grandstand board Value as marked Qty Rail Diagram reference Notes
Top, right of centre, upper pair 100 µF 25 V, axial 2 +12 V C52, 100 µF, on the µA7812 (Q5) output Both diagrams show one 100 µF; the board carries two[1][2][3]
Top, right of centre, lower pair 47 µF 25 V, axial 2 +5 V C50, 47 µF, on the µA7805 (Q4) output Both diagrams show one 47 µF; the board carries two[1][2][3]

The rails are taken from the diagrams. VESwiki's photograph of a System II board, with the same arrangement of two 100 µF capacitors above two 47 µF, labels the upper pair 12 V and the lower pair 5 V, and VESwiki takes +5 V for its composite video modification "directly from the capacitor".[7] Neither diagram shows the second capacitor of each pair, and no source traces where it connects, so follow the tracks before removing them.

All four on the scanned board carry an "SL" mark and arrows along the sleeve.[1] Their 25 V rating is at least twice the regulated rail each pair sits on.

The diagrams also show two 0.33 µF capacitors, C35 and C38, in the -5 V supply for the video RAM.[2][3] The scan does not show which parts these are on the Grandstand board or how they are marked. The other capacitors on the board are small disc ceramics; the ones whose markings can be read say 103Z (10 nF), matching the many 0.01 µF decoupling capacitors in the diagrams.[1][2]

Power section

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Reservoir capacitors in the power section
Version Capacitor Rail Source
Grandstand Not documented Not documented The Grandstand power section has not been photographed or described
Luxor 9583 mains unit CN02, 1000 µF +20 V (feeds the 7812 and 78L12) Luxor diagram[2]
Luxor 9583 mains unit CN03, 2200 µF +10 V (feeds the 7805) Luxor diagram[2]
Luxor 9583 mains unit CN01, 47 µF In the BC558B transistor circuit fed through a 1N4148 Luxor diagram[2]
US System II power-switch board 1000 µF 25 V (axial originally) and 2200 µF Reservoirs Owner's report[4]

Luxor's diagram gives no voltage ratings for its mains-unit capacitors.[2] US owners have measured 23.3 V at the input of the 7812, which is close to the rating of a 25 V capacitor, so fit 35 V parts on that rail when replacing them.[4]

Binary Dinosaurs' boxed Grandstand console was supplied with a plug-in mains adaptor, but no source gives the adaptor's rating or says whether it delivers AC or DC.[8] Read the label on your own adaptor and the markings on your console's power board before ordering parts for it.

Capacitor replacement procedure

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  1. Unplug the adaptor and remove any Videocart. Open the console as described on the maintenance guide.
  2. Photograph the main board and the power board from above before removing anything. Note which way the arrows point on every axial capacitor, and the polarity marks printed on the board.
  3. Work on one capacitor at a time. Desolder it, clear the holes with a desoldering pump or braid, and fit the new part in the same holes with the same polarity: the negative lead goes to the end the arrows point at.
  4. A radial replacement will fit in place of an axial one if one lead is bent back alongside the body. Keep it clear of the RF shield and the case.
  5. On the power-switch board, check each new capacitor's polarity against the board markings and against an untouched console if you can. A reversed electrolytic on a 20 V rail can burst at switch-on.[4]
  6. Before the first power-up, check for solder bridges and trimmed leads touching other parts.
  7. Switch on with no cartridge in the slot and measure the rails in the table below. Then press RESET, 1 and 4: the built-in Hockey game should start.[9] Only then try a Videocart.
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  • Temperature-controlled soldering iron, desoldering pump or braid, and a multimeter.
  • For the main board: two 100 µF and two 47 µF electrolytics, 25 V or higher, 105 °C grade. Axial parts fit the board as it was built; radial parts work with one lead bent back.
  • For the power section: read the values from the parts fitted, and choose 35 V or higher for anything on the upper unregulated rail.
  • Isopropyl alcohol and a brush to clean off old electrolyte.
  • File:Luxor TV Computer Game 1909583 Service Manual.pdf and File:Fairchild Channel F II PAL VHF Schematic 060190-A.jpg for the circuit.

Post-recap voltage checks

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Supply rails after recapping
Point Expected Source
Input of the 7812 About +20 V on Luxor's diagram; 23.3 V measured on a US System II Luxor diagram;[2] owner's report[4]
Input of the 7805 About +10 V on Luxor's diagram; 11.63 V measured on a US System II Luxor diagram;[2] owner's report[4]
Output of the 7812 (across the 100 µF pair) +12 V (12.19 V measured) Diagrams;[2][3] owner's report[4]
Output of the 7805 (across the 47 µF pair) +5 V (5.03 V measured) Diagrams;[2][3] owner's report[4]
Output of the 78L12 +14 V Luxor diagram[2]
Video RAM pin 1 -5 V (about 800 µA load) Diagrams[2][3]

If a rail is wrong after the recap, look first at the orientation of the new capacitors and at the regulator fed by that rail.

Additional tips

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  • The four main-board capacitors are the only aluminium electrolytics visible on the scanned board, so a main-board recap is a short job. The System II supply faults in the owners' reports found so far were in the power section and the regulators.[1][4][10]
  • A regulator with good input and no output has failed; replacing capacitors will not cure it. On one System II a failed 7805 left only vertical lines on the screen and no sound.[10]
  • The 7812 and 7805 on US consoles are mounted with their tabs against the metal case. Refit them the same way and tighten their screws so they keep their heatsinking.[4]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Incog88, scan of the Grandstand Video Entertainment Computer main board, from Wikimedia Commons (CC BY-SA 3.0), read at full size (2477 × 1389): "FAIRCHILD" silkscreen; four axial electrolytic capacitors, two marked "25V 100µF" above two marked "25V 47µF", each with an "SL" mark and arrows along the sleeve all pointing the same way; no other electrolytic capacitors visible; disc ceramic capacitors marked 103Z; F 3850 SL31291 CPU below the electrolytics.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 Luxor, Service Manual, TV Computer Game, type 190 9583, May 1980, document 66 79583-01. Hosted here as File:Luxor TV Computer Game 1909583 Service Manual.pdf, read at full resolution. Mains unit (NÄTDEL): 80 mA T fuse, transformer, double-pole switch, 1N4001 rectifiers, CN02 1000 µF on the +20 V output, CN03 2200 µF and a 470 ohm resistor on the +10 V output, CN04 and CN05 10 nF, CN01 47 µF with RN01 1 kohm, DN02 1N4148 and TN01 BC558B, TIL220 power LED; no capacitor voltage ratings printed. Processor board (55 30464-01): Q4 µA7805 with C46 0.1 µF in, C45 0.1 µF and C50 47 µF out, giving +5 V; Q5 µA7812 with C47 0.1 µF in, C48 0.1 µF and C52 100 µF out, giving +12 V; Q6 µA78L12 with R2 1200 ohms giving +14 V; -5 V at 800 µA from Q1 with C35 and C38 0.33 µF; many 0.01 µF decoupling capacitors; video RAM pin 1 on -5 V.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Fairchild Camera and Instrument, Video Products Division, drawing 060190-A, "IC PAL VHF Schematic". Hosted here as File:Fairchild Channel F II PAL VHF Schematic 060190-A.jpg (from VESwiki, where it is published as the SABA Videoplay 2 schematic). Q4 7805 with C50 47 µF on +5 V; Q5 7812 with C52 100 µF on +12 V; -5 V at 800 µA with C35 and C38 0.33 µF; U4 9101 video, U5 9102 audio/buffer, U6-U9 "330470" RAM.
  4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 AtariAge Forums, "Explosive Fairchild Channel F problems", August 2018 to June 2020 (read for this wiki on 2026-10-18): US System II with an external power brick; power-switch daughter board with a 25 V 1000 µF (axial originally) and a 2200 µF capacitor, both found fitted backwards by a previous repairer, the replacements overheating and bursting; electrolyte residue on the daughter board and a capacitor with one leg unsoldered; µA7812 and µA7805 mounted with their tabs against the metal case; measured 23.3 V in and 12.19 V out at the 7812, 11.63 V in and 5.03 V out at the 7805.
  5. ↑ 5.0 5.1 Luxor, Service Manual, TV Computer Game, type 1909574, August 1978, with Servicemeddelande No. 5, 15 February 1979. Hosted here as File:Luxor TV Computer Game 1909574 Service Manual.pdf: first-generation console; fault tips: green screen with no G? prompt from a faulty 12 V regulator; no information on screen from a missing 5 V supply; moving bands (hum) from a faulty rectifier diode or the electrolytics C4 and C5, and the regulators.
  6. ↑ AtariAge Forums, "Fairchild Channel F Green Screen", October 2020 (read for this wiki on 2026-10-18): advice from the author of VESwiki that a green screen means checking 12 V first, then -5 V on the RAM and 12 V on each 40-pin chip.
  7. ↑ VESwiki (channelf.se), "Modding" (retrieved 2026-10-18): composite video modification for the Channel F II, with a photograph of a System II board ("Channel F II composite video modification overview") on which the two 25 V 100 µF capacitors are labelled 12V and the two 25 V 47 µF capacitors 5V; "5V can be picked directly from the capacitor".
  8. ↑ Adrian Graham, "Grandstand VEC", Binary Dinosaurs (private collection; retrieved 2026-10-18): boxed Grandstand console "contains everything, right down to the plastic bag"; the photograph shows a plug-in mains adaptor in the box.
  9. ↑ Fairchild Video Products, Channel F System II: Playing Tennis / Playing Hockey. Hosted here as File:Fairchild Channel F System II Built-in Games Instructions.pdf: RESET gives the G? prompt; button 1 chooses Hockey; button 4 starts the game.
  10. ↑ 10.0 10.1 AtariAge Forums, "Fairchild Channel F System 2 Chip", February 2020 (read for this wiki on 2026-10-18): System II with vertical green, black and white lines and no sound, cured by replacing a 7805 whose output had failed.


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