Grandstand Model 6000 Troubleshooting Guide

The inside of a Grandstand 4600, the six-game model in the same style of case. No photograph of the inside of a 6000 has been published; expect the board to be fixed to the upper case in the same way, but with different chips and wiring for the joysticks.

Fault-finding for the Grandstand Model 6000, the ten-game colour TV game with X-Y joysticks. One fault report exists, a 6000 that gives only a blank screen and has something loose inside. No board photograph has been published, so the chip is unconfirmed, but its ten games, its joysticks and its controls all match General Instrument's AY-3-8610. The values below come from GI's 1978 data for that chip and apply once you have confirmed the marking on your board. Care and cleaning are on Grandstand Model 6000 General Maintenance.

What should happen at power-on

With six good C cells or a 9 V adaptor, POWER switched ON and an analogue television tuned to UHF channel 36:

• A colour picture appears, with the score shown on screen.
• Each joystick moves its player across and up and down the screen.
• Play starts when the player whose turn it is presses SERVE/FIRE; in the basketball games both players press their buttons.
• In the target games each player moves a cursor with the joystick and presses SERVE/FIRE to shoot; no gun is needed.
• GAME RESET sets both scores to zero.

Expected measurements

Grandstand 6000 reference values

Point	Expected	Source
Supply (cells or DC 9V socket)	9 V DC, 100 mA adaptor per the label
RF output	UHF channel 36, PAL
AY-3-8610 VCC (pin 16) to VSS (pin 1), if fitted	+6 to +7 V; 60 mA maximum at +7 V
AY-3-8610 clock (pin 9), if fitted	GI gives 3.579545 MHz, the NTSC colour-burst frequency, and no separate figure for the 625-line part
Closed switch or button contact to ground	1 kΩ or less
Joystick potentiometers	100 kΩ per axis in GI's reference design; the 6000's values are not published

First power-up after storage, and any power-up of a 6000 that rattles, should be from a bench supply at 9 V with its current limit near 150 mA.

AY-3-8610 pins used in fault-finding (GI, 1978)

Pin	Function	Pin	Function
1	VSS (ground)	16	VCC
2	Sync output	9	Clock input
10, 11	Left player horizontal and vertical inputs	14, 15	Right player horizontal and vertical inputs
12	Left serve	17	Right serve
13	Sound output	18	Reset
19, 20	Left and right bat size	21	Ball speed inhibit
22 to 25	Game strobes 4 to 1	26 to 28	Game select inputs 3 to 1

Symptoms

Grandstand 6000 symptoms

Symptom	Likely cause	Action	Source
Blank screen, and something rattles inside	A loose part inside; possible short	Do not power it. Open the case, find the loose part, and inspect the board where it may have lodged. One 6000 with these two symptoms has been reported, undiagnosed.
Blank or plain screen, nothing rattles	Supply; game chip not running; RF	Measure 9 V at the socket and after POWER, then the chip's supply and clock. Check the RF lead and channel 36.
Nothing on cells	Flat or leaked cells; corroded contacts	Clean the contacts in both rows of the compartment and fit six fresh C cells.
Works on cells, not on the adaptor	Adaptor voltage or polarity; DC 9V socket	Measure the socket against the battery terminals, then the adaptor off load. The 4600, with the same label, is centre positive.
A bat drifts, jumps or will not reach one edge	Dirty or worn joystick potentiometer for that axis; stick not reaching full travel	Clean both potentiometers in the pod. GI warns that the joystick must give full adjustment for the bat to cover the screen.
A bat moves on one axis only	One potentiometer open, or its wire broken in the pod lead	Measure each potentiometer at the board end of the lead while moving the stick.
Ball will not serve, or a target game will not shoot	SERVE/FIRE button or its wire	Clean the button and check its wires. On the AY-3-8610 left and right serve are separate inputs (pins 12 and 17).
Wrong game, or no game on one slider position	Dirty game slider; worn slider plate	The AY-3-8610 selects a game by joining one of four strobe outputs to one of three select inputs, so one bad contact can lose several games. Clean the slider and check it in each position.
TEAM L, TEAM R or SPEED has no effect	Dirty slide switch	Clean and measure: 1 kΩ or less when closed.
No sound	Speaker or its wiring; sound output	GI's AY-3-8610 drives a 100 Ω speaker directly from pin 13. Check the speaker and its wiring.

Known faults reported for this device

• One of Ian Hill's two 6000s gives only a blank screen, and something can be heard rattling inside it. He had not opened it when he described it.
• His second 6000 was described to him as working; he had not yet powered it.

No other fault report for a 6000 has been found.

Things that are not faults

These follow from GI's description of the AY-3-8610 and apply if your 6000 uses it.

• The ball starts slowly and speeds up after seven hits in a row without a score, unless high speed is inhibited.
• Two-player games stop when one player reaches 15. The bats then have no effect until GAME RESET.
• In the target games there is one shot per pass of the target; further presses of SERVE/FIRE are ignored until the next pass.
• In basketball practice only the left basket is used.
• The score sliders do not move by themselves: they are manual counters, as on the 4600.

What is realistically repairable

Repairability of 6000 parts

Part	Repairable?	Notes
Joystick potentiometers and mechanism	Usually	Ordinary potentiometers; a replacement must fit the joystick mechanism and give full travel.
SERVE/FIRE buttons and pod leads	Yes	Ordinary push buttons and multi-core leads.
Slide switches and game slider	Usually	Clean first; replacements must fit the panel slots.
Battery contacts, DC 9V socket, RF lead	Yes	Clean, or replace like for like.
Game chip	Only by transplant	If it is an AY-3-8610, a donor must come from another console built on the same chip; confirm the marking before buying one.

Related pages

• Grandstand Model 6000
• Grandstand Model 6000 General Maintenance
• Grandstand Model 4600 Troubleshooting Guide, the six-game model in the same style of case
• Grandstand Universal Mains Adaptor
• Capacitor Failure Symptoms