Grandstand Colour Programmable SD070 General Maintenance

The SD070 opened: the main board, solder side up, stays in the upper case (left); the lower case holds the speaker and the battery tube (right).

Care, opening and routine maintenance for the Grandstand Colour Programmable SD070, a PC-50x cartridge console made in Hong Kong on Soundic's SD-070 design and sold in the UK by Adam Imports around 1978 to 1980. No service manual or schematic for it has been found. The sources are the console's own labels, photographs of an opened Grandstand set and the notes of the collector who owns it, a photographed teardown of a Hanimex TVG 070C that uses the same main board, Pong-Story's descriptions of PC-50x hardware, and General Instrument's data for the AY-3-8610 chip in the Supersportic cartridge. Fault-finding is on Grandstand Colour Programmable SD070 Troubleshooting Guide.

Inside the console

The Grandstand set's main board is marked SD-070, REV F and 11-00110-13. The Hanimex TVG 070C has the same black case with orange buttons and a main board with the same number, 11-00110-13 REV F, and its owner photographed both sides of it. The solder sides of the two boards look the same in the photographs. No photograph of the Grandstand board's component side has been published, so the layout below is read from the Hanimex photographs:

• Five slide switches along one long edge of the board, under the SERVE, TEAM L, TEAM R, SPEED and POWER slots in the panel, with the VOLUME slider at the other end.
• The cartridge connector, a blue edge-card socket, across the middle of the board.
• An RF modulator on its own small board (marked 11-00081-00) at the front, with three adjustable coils (yellow, orange and red cores) and a screened can labelled CE-208E1 with an adjustment hole in its lid.
• Several radial electrolytic capacitors, the largest a dark-blue one near one end of the board.
• A seven-pin DIN socket for a joystick at each end of the board and a DIN socket for the light gun at the rear.
• Two small integrated circuits near the cartridge connector, a 14-pin and a 16-pin, their markings not legible. There is no game chip in the console: the game chip is in the cartridge.
• The game buttons on a separate board mounted in the upper case, joined to the main board by a flat flexible cable.

The Hanimex version works on VHF channel 1 to the 625-B PAL standard, where the Grandstand works on UHF channel 36 to the UK's 625-I standard, so the RF section is not the same on the two. Treat the Hanimex photographs as a guide to the layout, not to the RF parts.

Opening the console

1. Take out the cartridge and the batteries, and unplug the adaptor and both joysticks.
2. Turn the console over. Four screws hold the lower case; one of them is inside the battery compartment.
3. Lift the lower case away slowly. It stays attached to the board by the wires to the speaker and the battery contacts; the speaker is screwed to the lower case. Lay the two halves side by side, as in the photograph above, so the wires are not strained.
4. The main board now faces you solder side up in the upper case. It is held by three screws and two clips.
5. To reach the component side, remove the three screws, release the two clips and lift the board out of the upper case. Watch the flat flexible cable to the button board, the RF lead and the joystick sockets at the ends of the board.

Photograph the board, the wire colours and the cable before you take anything apart. To reassemble, reverse the steps and check that no wire is trapped between the case halves.

Power

The base of the Grandstand set: battery compartment for six UM-2 cells, the SOUND CARRIER ADJ label, and the power label with its plug drawing marked minus on the sleeve and plus on the tip.

Power requirements (Grandstand base label)

Supply	Rating	Polarity
Batteries	Six 1.5 V UM-2 (C, LR14) cells	As moulded in the compartment
Adaptor	9 V DC, 200 mA	Tip positive, sleeve negative

From the base label; the owner gives the socket as centre positive and the cells as LR14.

Adaptor polarity

Warning: the polarity marking on these consoles cannot be taken for granted.

• The Grandstand label's plug drawing marks the tip positive.
• The Hanimex TVG 070C, with the same 11-00110-13 REV F main board, has a label with the same wording ("Use 6x1.5V UM-2 batteries or AC adaptor 9V DC 200mA") but a plug drawing marked plus on the sleeve and minus on the tip.
• Grandstand's own Grandstand Universal Mains Adaptor has a polarity switch, and the leaflets for Grandstand's tabletop games tell owners to set it to negative. An adaptor left on that setting would feed a tip-positive console the wrong way round.

Go by the label on your own console, and confirm it before connecting anything: with the batteries out and the console switched off, use a continuity meter to find which contact of the DC-9V socket is joined to the battery compartment's positive terminal (a flat contact, where the positive end of a cell sits; the springs meet the negative ends). Then measure the adaptor's plug: about 9 V, the right polarity, and not far above 9 V with no load.

Mains adaptor and batteries

• A 40-year-old mains adaptor is the one part of this set that carries mains voltage. Check its case for cracks and its lead for split or perished insulation before plugging it in, or use a modern regulated 9 V DC adaptor rated at 200 mA or more with the plug polarity your console needs.
• Take the cells out before storing the console. Leaking C cells corrode the springs and the wires to them; clean any damage as described on Battery Explosion, Capacitor or Corrosion Damage.
• The cells sit in two rows of three, in bays moulded "UM-2 1.5V", with a spring at the end of each row. Fit them the way the moulding shows.

Cartridges and the cartridge slot

Inside the Supersportic PC-501 cartridge: the GI AY-3-8610 (date code 8034) is the only chip. The two trimmers sit behind the bat-adjust holes in the label; the edge contacts are numbered 19 to 36 on this side.

Each cartridge holds one General Instrument game chip on a small board with an edge connector. The Supersportic cartridge's board has 18 contacts on each side, numbered 1 to 18 on the solder side and 19 to 36 on the component side.

• Clean the edge contacts with isopropyl alcohol on a cotton bud and let them dry before inserting the cartridge. Keep dust out of the slot and do not push metal tools into it.
• Insert and remove cartridges with the console switched off.
• Pong-Story describes PC-50x cartridges as having "a bakelite circuit board with poor quality solders". If a cartridge works only when pressed or moved, open it and look at the joints under a magnifier; reflow any that are dull or cracked.
• The Supersportic cartridge opens with one screw. Its board is marked PC-501 and REV B, and the shell holds two springs; keep them in place when you close it.
• The holes in the label marked "Left bat adjust" and "Right bat adjust" reach two trimmers on the board, one marked 500K. The owner describes them as setting the vertical position of the bats. Turn them only if a bat cannot reach the top or bottom of the playfield, and only a little at a time.

The cartridges, and the chip each one uses, are listed on Grandstand Programmable Cartridges.

Joysticks

The two joysticks move in all directions and plug into DIN sockets in the sides of the case. Each has an orange button marked SERVE/FIRE. With the AY-3-8610, each bat's horizontal and vertical position is set by a variable resistor and a capacitor, so each joystick carries one potentiometer per axis.

• If a bat jitters or jumps, open the joystick, note how the wires are connected, and clean each potentiometer with a contact cleaner made for the purpose (DeoxIT D5 or similar), working the stick to its limits many times.
• If the SERVE/FIRE button works only when pressed hard, clean its contact while the joystick is open.
• Check the lead where it enters the joystick and at the DIN plug, and clean the plug's pins and the console's socket.
• The SD070's potentiometer values are not published. Measure the original before buying a replacement.

Switches, buttons and the button board

The panel has four slide switches (SERVE, TEAM L, TEAM R and SPEED), the POWER switch, a VOLUME slider, RESET and ten game buttons.

• Work each slide switch end to end a dozen times with a little contact cleaner sprayed into it.
• A game button that does not always select its game needs its contacts cleaned. On the Hanimex board the buttons sit on their own board, behind the panel.
• The flat flexible cable to the button board is the most fragile part inside. Do not fold it flat or pull on it; if several buttons stop working together after the console has been opened, check that cable first.

RF output and the sound carrier

• The console connects to the television through a fixed RF lead on UHF channel 36, 625-line PAL System I. Use a television or monitor with an analogue UHF tuner and tune it by hand.
• The owner found that continental PAL G televisions give the picture but not the sound. Use a UK-standard (System I) set, or rely on the console's own speaker.
• A label marked "SOUND CARRIER ADJ" on the base covers an adjustment hole. On earlier versions, the owner says, the hole was inside the battery compartment. Leave it alone unless the television's sound is missing or distorted with the picture correctly tuned, and mark its position before turning it.
• The coils on the RF modulator board are factory adjustments, not maintenance points. Leave them alone unless you have the equipment to realign an RF modulator.

Capacitors

No capacitor values have been published for the SD070, and none can be read from the available photographs: the Grandstand board's component side has not been photographed, and the electrolytic capacitors in the Hanimex photographs are too small to read. Their positions, what General Instrument's circuit for the cartridge chip needs from the supply, and how to record and replace them are on Grandstand Colour Programmable SD070 Capacitor Replacement Guide. If you open one, photograph the board and record each electrolytic's value, voltage and position before replacing anything.

The Supersportic cartridge board has no electrolytic capacitors; its capacitors are green film types and one ceramic disc.

Light gun socket

A DIN socket at the rear takes a light gun. No gun is included in the photographed set. Light guns of this period need a cathode-ray tube television.

Cleaning

• Wash the empty case halves in warm water with a little washing-up liquid, keeping water away from the printed panel and the labels, and dry them fully.
• Clean flux and dirt off the board with isopropyl alcohol and a soft brush.
• Do not soak the cartridge labels; the Supersportic label carries the game list and the bat-adjust markings.

Preventive maintenance checklist

1. Take the cells out; check the springs and wires for corrosion.
2. Check the adaptor's voltage and polarity against your console's own label every time, and the Universal Mains Adaptor's polarity switch if you use one.
3. Clean the cartridge contacts and inspect the cartridge's solder joints.
4. Clean the joystick potentiometers and the DIN plugs and sockets.
5. Work all the switches and buttons with contact cleaner.
6. Tune a System I analogue television to UHF channel 36 and check picture, colour and sound.

Related pages

• Grandstand Colour Programmable SD070
• Grandstand Colour Programmable SD070 Troubleshooting Guide
• Grandstand Colour Programmable SD070 Capacitor Replacement Guide
• Grandstand Programmable Cartridges
• Grandstand Universal Mains Adaptor
• Battery Explosion, Capacitor or Corrosion Damage
• Recommended Tools