Varkon (Williams, 1982): common faults and System 7 replacement boards

June 26, 2026

Does your Williams Varkon have its flippers no longer responding to the controls, fail to boot, reset or have no sound? These symptoms are typical of Williams System 7 pinball machines, whose original boards (MPU, Driver, power supply) are now over 40 years old. The good news: the WillFA7 replacement board, Plug & Play and battery-free, brings your machine back to life.

Varkon (Williams, 1982): overview

Released in September 1982, Varkon is an unusual Williams System 7 pinball machine: housed in a video-game cabinet (similar to a Robotron), it presents its playfield vertically thanks to a mirror, with a lower playfield that has its own ball. The flippers are operated by vertical paddles (joysticks) rather than buttons. Very rare, it had a production run of only about 90 units.

Manufacturer: Williams
Year: 1982
Electronic system: Williams System 7
Type: solid-state pinball in a video cabinet, dual playfield, joystick controls
Theme: novelty / arcade

WillFA7 MPU/Driver board for Williams System 3 to 7 — The WillFA7 board replaces the original MPU and Driver of Williams System 3 to 7.

Common faults (System 7)

On Williams System 3 to 7, the recurring faults come from ageing: leaking NiCad battery on the MPU (corrosion, the No. 1 cause of dead boards), worn 40-pin MPU↔Driver connector (the best-known weak point), resets/reboots on a 5 V drop (power headers and connectors to be resoldered), tired power-supply capacitors, displays with missing segments, and a solenoid fuse that blows (slingshot or stuck bumper).

Issues specific to Varkon (forum feedback)

Flippers no longer responding to the vertical joysticks: check the paddle micro-switches and control mechanism before suspecting the electronics.
Ball stuck on the lower playfield: accessible through the window in the upper playfield; switches and guides to clean.
No boot or resets: corroded battery and worn 40-pin connector, typical of System 7.
No sound: Type 2 sound board to be diagnosed.
Displays and 'lightning' lamps faint behind the mirror: as the mirror is a semi-reflective plastic, clean it and check the display power.
Rare specific parts: only ~90 units and a video-type cabinet; keep and repair the original parts.

Checking voltages with a multimeter on a Williams System 7 — A multimeter is used to check the 5 V and diagnose the boards of Williams System 7 machines.

Replacement boards compatible with Varkon

WillFA7 — 2-in-1 board (MPU + Driver) compatible with System 3 to 7, System 7 included.

WillFA7 replacement board for Williams pinball — The WillFA7: Plug & Play installation, battery-free, with tutorials and free support.

📚 Further reading: Guide: which board for a Williams System 3 to 7?

The WillFA7 replaces the original MPU and Driver board (boot-up, logic resets, coil driving, battery-free memory) and removes the fragile 40-pin ribbon. The sound board and the specific mechanics (paddles, lower playfield) must still be maintained separately; our support team will guide you.

Plug & Play installation, battery-free, free tutorials and support. Contact us.

FAQ — Varkon Williams

My Varkon's flippers no longer respond to the controls.
First check the micro-switches and mechanism of the vertical joysticks, then the flipper-coil driving. The WillFA7 (MPU + Driver) makes the logic and coils reliable.

My Varkon won't boot or resets.
A corroded original battery and worn 40-pin connector are the No. 1 causes. The WillFA7 replaces the MPU and Driver and boots without a battery.

Is the WillFA7 compatible with System 7?
Yes. It covers System 3 to 7, System 7 included, and drives the logic and coils.

Should I keep the original battery?
No. The WillFA7 works without a battery and removes the No. 1 cause of corrosion on System 7.

How long does it take to install a replacement board?
Installation is Plug & Play: a few minutes, no soldering, with tutorials and free support.

Does a battery-free board keep the settings and high scores?
Yes. Modern replacement boards use non-volatile memory: no more battery, no more corrosion, and the settings are kept when powered off.

Step-by-step diagnosis

Powered off, visual inspection: look for any battery or corrosion trace on your Varkon's MPU; remove the NiCad battery if it is still present.
Power supply: measure the 5 V and check it actually reaches the MPU and Driver (redo the power solder joints and connectors if the voltage drops); check the fuses.
Grounds and power connectors: resolder the tired headers between the boards to eliminate resets and reboots.
40-pin MPU↔Driver connector: re-pin the oxidised link with trifurcon pins, the No. 1 weak point of Williams System 7.
Displays: never plug or unplug a display while powered on; test with a known-good display.
Final test: check boot-up, credits, coils and displays; reminder: the WillFA7 replaces the MPU and Driver and boots without a battery. If needed, contact our free support.