Mattel Baseball Troubleshooting Guide
Fault-finding for Mattel Baseball (model 2942). Begin with the battery: Mattel's leaflet gives misbehaving lights or scoreboard as the first sign of battery wear, and says malfunctioning lights usually mean it is time for a new battery.[1] The circuit is a Rockwell B6101 microcontroller on the main board, driving the field LEDs, the scoreboard and a piezo sounder.[2][3] Read Mattel Baseball General Maintenance before opening the case.
Things that are not faults
[edit | edit source]- After each half-inning the keys stop working until SCORE is pressed to reset the game.[1]
- There is a delay of 1.5 to 2.5 seconds between pressing PITCH and the pitch.[1]
- On a fly out the fielder's light flashes and the batter cannot run.[1]
- On a home run all the lights flash and the runner does not move until RUN is pressed.[1]
- A game can end in a tie.[1]
- PRO 1 and PRO 2 set the speed of the whole game, including the pitching.[1]
- With a runner on second, a walk advances that runner. Mark Lesser, who programmed the game, lists this among the bugs that went out in the finished program.[4]
Symptoms
[edit | edit source]| Symptom | Probable cause | Action |
|---|---|---|
| Nothing lights when switched on | Flat battery; corroded or broken snap or lead; dirty OFF/PRO switch | Fit a fresh battery. Measure the voltage where the red and black leads join the main board with the switch on. Replace a corroded snap; clean the switch.[1][3] |
| Field lights or scoreboard erratic, dim or flickering | Battery wearing out | Fit a fresh 9 V battery; Mattel recommends alkaline.[1] |
| Keys do nothing in the middle of a game | Half-inning over and SCORE not pressed | Press SCORE.[1] |
| One key never works | Dirty contact under that key on the key board | Clean the key's contact pad and the underside of the key.[3] |
| Game will not run at PRO 1 or at PRO 2 | Dirty slide switch | Clean the switch with switch cleaner and work it end to end. |
| No sound, display normal | Piezo disc or its wires | Check the two wires from the brass disc to the main board; the chip has a single sound output.[3][2] |
| One field light or one segment dark | That LED, or its joint on the display board | Inspect and reflow the joint. |
| Several lights or a whole digit dark together | A shared drive line, or the row of pins between the display board and the main board | Reflow the pins along the display board edge and inspect the tracks.[3][2] |
| Display garbled after the battery, snap, switch, keys and capacitor have been checked | B6101 fault | The B6101 is a custom Rockwell part holding the game in its ROM; a donor board is the only replacement.[5] |
Checks with a meter
[edit | edit source]- Measure the battery off load and with the game running. Replace a battery that falls away sharply under load.
- With the battery fitted and the switch on, measure between the red and black leads at the main board. No voltage with a good battery means a broken snap or lead.
- With the battery out, check the slide switch for continuity in each position, and each key contact on the key board for continuity when pressed.
- Look at the electrolytic capacitor for bulging or leakage; see Mattel Baseball Capacitor Replacement Guide.
No data sheet for the B6101 has been published, so there is no published supply-voltage range for it.[5]
How the display is driven
[edit | edit source]MAME's driver models the display as a matrix of nine select lines by ten segment lines, carrying the four scoreboard digits (two with decimal points) and the 28 field LEDs.[2] A fault on one line puts out a group of lights or a whole digit; a fault on a single LED affects only that light.
What is realistically repairable
[edit | edit source]| Part | Option |
|---|---|
| 9 V snap and leads | Standard part; replace |
| OFF/PRO 1/PRO 2 switch | Clean; replace with a matching three-position slide switch if worn |
| Key contacts | Clean the pads on the key board[3] |
| Electrolytic capacitor | One 10 µF 16 V part; see Mattel Baseball Capacitor Replacement Guide[3] |
| B6101 microcontroller | Custom; donor board only[5] |
Related pages
[edit | edit source]- Mattel Baseball
- Mattel Baseball General Maintenance
- Mattel Baseball Capacitor Replacement Guide
- Capacitor Failure Symptoms
- Battery Explosion, Capacitor or Corrosion Damage
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 Mattel, Inc., Mattel Electronics Baseball Instructions, code 2942-0920, 1978; hosted here as File:Mattel Electronics Baseball Instructions 2942-0920.pdf. PDF p. 3: misbehaving player lights or scoreboard are "the first sign of battery wear"; a 9-volt alkaline battery for longer life. PDF p. 4: PRO 1 and PRO 2 "affect the speed of the entire game". PDF p. 5: a delay "of 1.5 to 2.5 seconds" before the pitch. PDF p. 6: after each half-inning "you will be unable to operate any of the other keys until you press the SCORE key to reset". PDF p. 7: on a fly out the lights flash and "it will not be possible for you to run". PDF pp. 14-15: the game can end in a tie; on a home run all lights flash and the player must press RUN; "Malfunctioning lights usually means it's time for a battery change."
- ↑ 2.0 2.1 2.2 2.3 MAME source, src/mame/handheld/hh_rw5000.cpp at commit d912c4f (retrieved 2026-10-19): Mattel Baseball (model 2942); B6100-series microcontroller marked B6101-12; 4-digit 7-segment display (two digits with decimal points) and 28 other LEDs on a 9 × 10 display matrix; 1-bit sound.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Sean Riddle, Baseball circuit board scans (retrieved 2026-10-19), hosted here as File:Mattel Baseball circuit boards, component side.jpg and File:Mattel Baseball circuit boards, solder side.jpg: red and black battery leads to the main board; a brass piezo disc on two wires; the slide switch; one Nichicon 10 µF 16 V electrolytic; the display board joined by a row of pins; the key board with its contact pads.
- ↑ Scott Stilphen, "DP Interviews: Mark Lesser", Digital Press (retrieved 2026-10-19): among bugs that were let go, "in Mattel Baseball, with a man on second, if the batter walks, the man on second advances."
- ↑ 5.0 5.1 5.2 Sean Riddle, "The First Mattel LED games" (retrieved 2026-10-19): the B6101 in Baseball is one of a family of custom Rockwell chips (B6100, B6101, B6102) with different ROM contents, which Riddle decapped to dump.
