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Grandstand Model 4600 Capacitor Replacement Guide

From RetroTechCollection
Grandstand 4600 colour - PCB
The component side of a working 4600's board. C37 and C38, the two lavender electrolytics whose markings can be read, stand between the RF modulator can (top centre) and the TBA520 (top right). C39 is the lavender part at the right above the second CD4069. The large black electrolytic stands between the third and fourth slide switches from the left, and a large white cylinder lies flat at the left edge above the SERVE button.

The Grandstand Model 4600 (panel name GRANDSTAND 4600 COLOUR) is a six-game colour Pong console made in Hong Kong around an AY-3-8500 game chip and a TBA520.[1][2] Its electrolytic capacitors are now more than forty years old: the chips on the photographed board carry the date codes 8138 and F8133.[1] No parts list, schematic or service manual for the 4600 has been published, and the photographed console works,[3] so there is no failure report either. What follows is every electrolytic visible in the one published photograph of the board, the two markings that can be read, what is known of the circuit around them, and how to read, record and replace the parts on your own 4600.

Opening the case is covered on Grandstand Model 4600 General Maintenance. Symptoms that may point to the capacitors are on Grandstand Model 4600 Troubleshooting Guide.

Capacitor list

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Electrolytic capacitors on the 4600 board (one photographed board, REV.2 11-00161-00)
Position (component side, modulator can at the top, SW1 to SW6 along the bottom) Capacitance Voltage Sleeve and notes Source
C38, top centre, right of the modulator can 10 µF Not legible Lavender; "10 µF" printed twice on the sleeve [1]
C37, beside C38, left of the TBA520 Not legible 16 V Lavender, Yobatron; "16V" printed twice; brown stains on the sleeve [1]
C39, right edge, above the right-hand CD4069 Not legible Not legible Lavender [1]
Above SW6, between two resistors Not legible Not legible Black, Yobatron; the C-number beside it is partly hidden [1]
Between the third and fourth slide switches from the left Not legible Not legible Black; the largest radial electrolytic on the board [1]
Between SW6 and SW5 Not legible Not legible White, with blue printing facing away from the camera [1]
Bottom edge, between SW5 and the next switch to the right Not legible Not legible Small, blue [1]
Bottom left corner, below SW6 (two parts) Not legible Not legible One black; one small with a yellow sleeve, heavily stained. Check that the second is an electrolytic before ordering parts [1]
Left edge, above the SERVE button (SW8), lying flat Not legible Not legible A large white cylinder with two leads from one end, the shape of a large electrolytic; no marking can be seen [1]

Read from File:Grandstand 4600 colour - PCB.jpg at its full size of 1789 × 1907 pixels; the owner's blog carries the same image at the same size.[1][3] Two markings are legible: C38 is 10 µF and C37 is rated 16 V. No full list of values has been published for the 4600. The board has C-numbers printed beside the parts, but only C37, C38 and C39 can be read in the photograph. Read each value from the part in front of you before removing it, and do not take the missing values from another console.

The other capacitors on the board are not electrolytics. Two green film capacitors stand beside the AY-3-8500; one is marked ".1K100" (0.1 µF, 10%, 100 V), and the other has a brown run down its body. Small ceramic discs are scattered across the board.[1] They are not part of a recap: replace one only if it is cracked, burnt or measures far from its marking.

What the capacitors do on this board

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No schematic of the 4600 has been traced, so the role of each part on this board is not known. What is known is the supply and the circuit that General Instrument published for the game chip:

  • The 4600 runs from six UM-2 (C) cells or a 9 V DC 100 mA adaptor plugged into the DC 9V socket at the rear.[2][4] GI specifies the AY-3-8500 at +6 to +7 V between pin 4 (VCC) and pin 2 (VSS), against the console's 9 V input, so measure the voltage at pin 4 and do not assume the chip sees the full supply.[5] GI's reference circuit puts a 10 µF electrolytic across the chip's supply.[5] A supply capacitor that has lost its value lets ripple and noise through to the chips; Capacitor Failure Symptoms describes the usual signs.
  • GI states that an R-C network on each bat input controls the bat's vertical position; its reference circuit uses a 1 MΩ potentiometer, a 10 kΩ resistor and a 0.1 µF capacitor for each.[5] These are small film or ceramic parts, not electrolytics.
  • For sound, GI drives the speaker from pin 3 through a transistor, with 15 kΩ and 0.2 µF at its base.[5] The 4600 board carries a transistor marked 9015.[1] Its role has not been traced.
  • The colour comes from the TBA520 and the parts around it, and the picture leaves through the screened RF modulator can at the top of the board on UHF channel 36.[1][2] C37 and C38 stand between these two blocks.[1]

Signs of trouble

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  • A domed or split top, a bulging can, a cracked sleeve, or electrolyte at the base of a capacitor.
  • Deposits. The photographed board has brown stains on C37's sleeve, a heavily stained small part in the bottom left corner, brown runs on a green film capacitor beside the AY-3-8500 and on a white part below the right-hand CD4069, and brown deposits around several slide switches and on the solder side. Their cause has not been established, and the console still works.[1][6][3]
  • Hum bars, a rolling or unstable picture, or colour that comes and goes, once the cells or adaptor, the television's tuning on channel 36 and the switches have been ruled out. See Grandstand Model 4600 Troubleshooting Guide.
  • Leaked cells in the battery compartment. Damage of this kind is covered on Battery Explosion, Capacitor or Corrosion Damage.

Reading and recording your own board

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  1. Photograph the whole component side square-on, in good light, before touching anything.
  2. For each electrolytic, write down the C-number printed beside it, the capacitance, the voltage, the maker, the sleeve colour, the diameter and height, and which side carries the negative stripe.
  3. Where the printing faces away, turn the part gently with tweezers or read it with a mirror. Do not bend it far; old leads snap at the board.
  4. Measure each part you remove with a capacitance or ESR meter, and note any that are far from their marked value.
  5. Keep the record with the photographs. The 4600 has no published parts list, so a record of a real board helps the next owner.

Replacing the capacitors on the 4600

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  1. Slide the battery cover off in the direction of its arrows and take out the six cells.[2] Unplug the adaptor and the rifle, and lift both control pods out of their bays.[7]
  2. Remove the two case screws inside the battery compartment, then the two cross-head screws beside the feet at the other end of the base.[3][2] Lift the base away.
  3. The board is now in view, solder side up, fixed to the upper case by five screws. The DC socket, the RF lead and both pod leads are wired to it, and one pod lead is knotted round a post to take the strain.[3][6] Photograph the wiring, undo the five screws and turn the board over without pulling on the leads.
  4. Work on one capacitor at a time. Read and record it as above, then desolder it from the solder side with a pump or braid. Keep the iron short on each pad: the board in the photographs has corrosion on both sides, and weakened tracks lift easily.[1][6]
  5. Clean the holes and the board around them with isopropyl alcohol. Where there are deposits, scrub them off and check the track underneath with a magnifier before fitting the new part.
  6. Fit a capacitor of the same capacitance and the same or higher voltage, rated 105 °C, with the same lead spacing, and no taller than the original. The board sits under the panel with the slide switches and game slider coming up through it, so a tall part can stop the board seating.[1] Check the polarity against your photograph.
  7. Refit the board with its five screws, lining the switches and the game slider up with their slots, and route the leads as they were. Refit the base.
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  • Temperature-controlled soldering iron, desoldering pump or braid, flux, isopropyl alcohol and a stiff brush for the deposits.
  • Multimeter, and a capacitance or ESR meter for the parts you remove.
  • Radial electrolytics from a current maker (Nichicon, Panasonic, Rubycon or similar), 105 °C, in the values read from your own board.
  • A current-limited bench supply set to 9 V for the first power-up. See also Recommended Tools.

Checks after recapping

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After recapping a 4600
Check Expected Source
Supply at the DC 9V socket or the cells 9 V DC [2]
Supply current Below the label's 100 mA; the AY-3-8500 alone draws 40 mA typical, 60 mA at most at +7 V. Start with a current limit of about 150 mA [2][5]
AY-3-8500 pin 4 to pin 2 +6 to +7 V [5]
AY-3-8500 pin 17 (clock) 2.012160 MHz ±1% [5]
Picture Colour picture on UHF channel 36, steady, with two-digit scores at the top and a dotted centre line [2][8]
Sound 32 ms tones from the AY-3-8500: 976 Hz for a hit, 488 Hz for the boundary, 1.95 kHz for a score [5]
Controls Both bats move smoothly over the full height; SERVE and GAME RESET work [9]
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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - PCB.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size (1789 × 1907 pixels): the component side of the board with "AY-3-8500 GI 8138 SFA", "TBA520 F8133 INDONESIA", two "CD4069CN MM74C04N" with the National logo, a transistor marked "9015", a screened RF can at the top, a long game-select slide switch across the middle, slide switches SW1 to SW6 along the bottom edge and a SERVE push button (SW8) at the left; electrolytic capacitors C38 (lavender, printed "10 µF"), C37 (lavender, Yobatron, printed "16V"), C39 (lavender) and seven further electrolytic-shaped parts whose markings cannot be read, as listed in the table; two green film capacitors beside the AY-3-8500, one printed ".1K100"; brown deposits on and around several parts. The uploader's description: "CPU: AY-3-8500 plus the Fairchild TBA520 (PAL TV CHROMA DEMULATOR) that produce images with colors".
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Back.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: the base, with a battery cover across one end marked with two arrows, a label reading "UHF CHANNEL 36 / POWER SOURCE: Use 6 x UM-2 Batteries or by AC Adaptor 9V DC 100mA", a "Made in Hong Kong" sticker, four feet, and two cross-head screws beside the feet at the other end.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 José Antonio Ortigueira Amor, "Consola Grandstand 4600 Colour Video Sports Centre (1977)", Retro Ordenadores Orty (collector's blog, in Spanish), December 2021 (retrieved 2026-10-19). The owner's description of his console: AY-3-8500 and TBA520; a rear jack for a 9 V DC supply, centre positive; six LR14 cells in an internal compartment reached through the lower case; four screws hold the lower case, two of them in the battery compartment; removing it shows the back of the board, held to the upper case by five screws; tested on a 9 V DC centre-positive supply and working correctly. The board photograph on the blog is the same image as the Commons file, at the same size.
  4. ↑ Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Connectors.jpg (CC BY 4.0, from Wikimedia Commons): the rear of the console, with a socket labelled "DC 9V" at one end and the fixed RF lead at the other.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 General Instrument Corporation, GIMINI TV Game Circuits, January 1978, pp. 4-7, PDF hosted by Pong-Story (retrieved 2026-10-19). AY-3-8500 data sheet: pin 2 VSS, pin 4 VCC, standard conditions VCC +6 to +7 V; supply current 40 mA typical, 60 mA maximum at +7 V; clock input pin 17, 2.012160 MHz ±1%; bat inputs pins 11 and 12, "An R-C network connected to each of these inputs controls the vertical position of the bats. Use a 10K resistor in series with each pot"; sound output pin 3, 32 ms tones of 976 Hz (hit), 488 Hz (boundary) and 1.95 kHz (score). System Diagram 1 (black and white implementation, p. 4): a 10 µF electrolytic across VCC and VSS; each bat input fed from a 1 MΩ potentiometer and 10 kΩ resistor into a 0.1 µF capacitor, through 220 Ω; the speaker (8 Ω, 2 W, with 51 Ω) driven by a 2N2222 whose base is fed from pin 3 through 15 kΩ in parallel with 0.2 µF.
  6. ↑ 6.0 6.1 6.2 Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Internals.jpg (CC BY 4.0, from Wikimedia Commons), examined at full size: the upper case from below with the base removed; the board solder side up, held by screws, with "REV.2 11-00161-00" printed at the lower left; the DC socket at the top left wired to the board; both controller leads passing into the bays, one knotted round a post; brown patches on the solder side and around the case slots.
  7. ↑ Ian Hill, "Grandstand 4600", Ian's Retro Museum (collector's site; photographs not freely licensed) (retrieved 2026-10-19): a second 4600 with a "rifle" attachment that "plugs into the side via a DIN plug"; controllers "nothing more than a potentiometer in a plastic box", permanently attached and stored in the unit; it works on a suitable supply.
  8. ↑ Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour - Screen.jpg (CC BY 4.0, from Wikimedia Commons): the picture on a colour television, with two-digit scores at the top and a dotted centre line.
  9. ↑ Photograph by José Antonio Ortigueira Amor, File:Grandstand 4600 colour (above).jpg (CC BY 4.0, from Wikimedia Commons): the panel, with the game slider, SERVE (MANU/AUTO), BAT SIZE, ANGLE, SPEED, GAME RESET and POWER switches, a SERVE button, LEFT and RIGHT score sliders, and the LEFT PLAYER and RIGHT PLAYER pods.


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