Grandstand Colour Programmable SD070 Troubleshooting Guide

The SD070 main board seen from the solder side, marked SD-070 and REV F. The game chip is not on this board but in the cartridge.

Fault-finding for the Grandstand Colour Programmable SD070. No service manual, schematic or published repair of this console has been found. The console has no game chip of its own: each PC-50x cartridge holds a General Instrument chip that generates the games, and the console supplies power, controls, colour and the RF connection to the television. Most faults can therefore be narrowed down by asking first whether the problem follows the cartridge or stays with the console. The checks below use the console's labels, photographs of an opened set and its owner's notes, photographs of a Hanimex TVG 070C with the same main board, and General Instrument's published data for the AY-3-8610 in the Supersportic cartridge. Opening the console and routine care are on Grandstand Colour Programmable SD070 General Maintenance.

What should happen at power-on

With the Supersportic cartridge in the slot, a UK television tuned to UHF channel 36 and the console switched on:

• The television shows the playfield and the scores. The AY-3-8610 keeps the score on screen from 0 to 15, each score in its player's colour.
• Pressing RESET clears the scores: on the AY-3-8610, reset sets both scores to zero and returns the ball to the service position.
• Each of the ten game buttons selects the game with that number on the cartridge label.
• Bat hits, wall rebounds and scores make short tones from the console's speaker, at a level set by the VOLUME slider, and through the television.

Before you start

• Have a second PC-50x cartridge to hand if you can. The cartridges work in many SD-050, SD-070 and SD-090 consoles sold under different names, so one sold with another brand's console will do.
• Use a television with an analogue UHF tuner to the UK System I standard, tuned to channel 36.
• Check the adaptor against the console's own label. The Grandstand label asks for 9 V DC with the tip positive, but a Hanimex TVG 070C built on the same main board is labelled tip negative, and a Grandstand Universal Mains Adaptor set to negative for the tabletop games would feed a tip-positive console reversed.
• For a first test after a repair, a bench supply with its current limit set a little above the label's 200 mA is safer than an adaptor.

Power

Power

Symptom	Probable cause	Action
Dead on batteries and on the adaptor	Flat or corroded cells; corroded springs; broken battery wire; faulty POWER switch	Measure the cells in place: six fresh cells give about 9 V. Check continuity from the battery terminals through the POWER switch to the board.
Works on batteries, not on the adaptor	Adaptor of the wrong polarity or voltage; dirty or worn DC-9V socket	Measure the plug and compare it with the console's label, not with another console's. Clean the socket.
Works on the adaptor, not on batteries	Corroded springs or a broken battery wire; the wires to the lower case pulled off when the case was opened	Clean the springs (see Battery Explosion, Capacitor or Corrosion Damage). The battery wires run from the board to the lower case and are strained each time it is lifted off.
An adaptor of the wrong polarity has been connected	Possible damage to the supply section	Disconnect it. Look for burnt or bulging parts near the power socket and measure the supply to the cartridge chip before trying again with the correct supply.

Picture and game

Picture and game

Symptom	Probable cause	Action
Only noise on the television	Set not tuned to UHF channel 36, or no analogue tuner; broken RF lead or plug	Tune by hand around channel 36. Check the RF lead where it leaves the case and at the plug.
A tuned but empty picture, or no game, with a cartridge in	Dirty cartridge contacts or slot; cracked joints on the cartridge board; failed cartridge chip	Clean the cartridge edge and the slot. Try a second cartridge: if it plays, the fault is in the first cartridge. Pong-Story notes that PC-50x cartridge boards have "poor quality solders"; open the cartridge and reflow any doubtful joints.
No cartridge will play	Console fault: the supply, the slot or the circuits between the slot and the RF lead	With a cartridge open and inserted, measure the chip's supply: on the AY-3-8610 that is pin 16 (VCC) to pin 1 (VSS), and GI's operating range is +6 to +7 V. If the supply is missing, trace it back from the slot to the power switch.
Picture in black and white only	Television colour setting or fine tuning; a fault in the console's colour circuit	Fine-tune the set and check its colour control first. The AY-3-8610's own outputs give a black-and-white picture: GI's data offers full colour only with a second chip, the AY-3-8615 colour encoder. The Supersportic cartridge holds only the AY-3-8610, so the SD070's colour circuit is in the console; which circuit it uses has not been documented.
A bat cannot reach the top or bottom of the playfield	Bat-adjust trimmer on the cartridge out of position	Turn the trimmer behind the "Left bat adjust" or "Right bat adjust" hole in the cartridge label a little at a time.
A bat jitters or jumps	Dirty joystick potentiometer	Clean the joystick, as described in the maintenance guide.
A bat does not move on one axis	Open potentiometer, broken wire in the joystick lead, dirty DIN plug or socket	On the AY-3-8610 each bat has a horizontal and a vertical input: pins 10 and 11 for the left player, 14 and 15 for the right. Swap the joysticks between the sockets to see whether the fault follows the joystick.
A SERVE/FIRE button does nothing with SERVE set to MANU	Worn button contact in the joystick; broken wire in the lead; dirty DIN plug	Each joystick has an orange SERVE/FIRE button. On the AY-3-8610 the serve inputs are pin 12 (left player) and pin 17 (right player). Swap the joysticks; if the fault follows the joystick, open it and clean or repair the button contact.
RESET does nothing; the scores never return to zero	Dirty RESET button; broken line to the cartridge	The AY-3-8610 resets when its pin 18 is briefly connected to VSS (pin 1). Check the button and the line from it to the slot with a meter.
Bats always large or always small, or the ball never speeds up, whatever the TEAM and SPEED switches say	Dirty slide switch or a broken line to the cartridge	The AY-3-8610 has an input for each bat's size (pin 19 left, pin 20 right; connected to VSS for a small bat) and a fast-ball inhibit input (pin 21). The label of Radofin's "1001 Superstar", an AY-3-8610 cartridge for another console with the same PROFESSIONAL/AMATEUR switches, spells out the settings: professional gives the handicap (small) bat and the fast ball, amateur the full-size bat and the slow ball. Clean the switches, then check with a meter whether they reach those pins.
One or more game buttons do nothing	Dirty button contacts; the flat cable to the button board; a broken line between the panel and the slot	See the game-selection table below. If several buttons failed together just after the console was opened, check the flat flexible cable to the button board first.

Game selection on the Supersportic cartridge

The AY-3-8610 chooses its game by which of its four strobe outputs is connected to which of its three select inputs. Each game button therefore joins one strobe line to one select line. If several buttons fail together, look for the line they share.

AY-3-8610 game selection (General Instrument, 1978)

	Select 1 (pin 28)	Select 2 (pin 27)	Select 3 (pin 26)
Strobe 1 (pin 25)	Tennis	Hockey	Squash
Strobe 2 (pin 24)	Practice	Soccer	Basketball
Strobe 3 (pin 23)	Basketball practice	Gridball
Strobe 4 (pin 22)	One-player target	Two-player target

Source: General Instrument's 1978 catalogue. For example, if Hockey, Soccer, Gridball and the two-player target game all fail while the others work, suspect the select 2 line. The pin numbers are those of the chip in the Supersportic cartridge; other PC-50x cartridges use other chips with their own selection schemes.

Sound

Sound

Symptom	Probable cause	Action
Picture but no sound through the television	Television working to PAL G rather than System I; sound carrier adjustment out	The owner found no television sound on continental PAL G sets. Try a UK set. Only then consider the SOUND CARRIER ADJ adjustment under the label on the base, and mark its position first.
No sound from the console's speaker	VOLUME slider turned down; broken speaker wire; faulty speaker	The speaker is screwed to the lower case, so its wires are strained each time the case is opened. Check them, then measure the speaker; the Hanimex version of this console uses an 8 ohm speaker.
No sound from either the speaker or the television	Fault in the cartridge chip's sound output or in the console's sound circuit	Try a second cartridge. The AY-3-8610's sound output is pin 13; it gives tones of about 500 Hz, 1 kHz and 2 kHz for about 24 ms each.

Things that are not faults

• A two-player game stops at 15 points. On the AY-3-8610 the bats then have no effect on the ball, and the ball cannot be served again until RESET is pressed.
• The ball starts slowly and speeds up after seven hits in a row without a goal, unless the fast ball is inhibited.
• No sound through a continental PAL G television.

Reference values

Reference values

Point	Expected	Source
Adaptor	9 V DC, 200 mA rating; polarity as on your console's label (tip positive on the Grandstand)	Base label
Six fresh UM-2 cells	About 9 V	Base label
AY-3-8610 pin 16 to pin 1	+6 to +7 V; never above +12 V on any pin	GI data
AY-3-8610 supply current	60 mA maximum at +7 V	GI data
RF output	UHF channel 36, PAL System I	Base label

What can be repaired

Parts and repairability

Part	Repairable?	Notes
Battery springs and wires, switches, buttons, DIN plugs and sockets	Yes	Clean first; replace with like parts.
Flat cable to the button board	With difficulty	A cracked flexible cable can sometimes be bridged with fine wire; there is no published replacement part.
Joystick potentiometers	Yes	Measure the original before buying a replacement; no values are published.
Cartridge solder joints and edge contacts	Yes	Reflow and clean.
Capacitors and other passive parts on the main board	Yes	No values have been published; read each one from the part.
RF modulator	Adjustments only	The coils and can on the modulator board are factory-set.
Cartridge game chip	Only by transplant	The chips have long been out of production. A cartridge of the same number from any PC-50x console is the practical replacement.

Related pages

• Grandstand Colour Programmable SD070
• Grandstand Colour Programmable SD070 General Maintenance
• Grandstand Programmable Cartridges
• Grandstand Universal Mains Adaptor