Sunday April 30, 2017

Whirlwind Pinball Repair - Battery Corrosion / Display Repair

Author: Wayne Eggert
Date: 02/20/2011


Introduction
Picked up a Williams Whirlwind in late 2010 that came with quite a few issues since it had its share of owners.  The machine booted and would start a game, however some switches did not work, the playfield was very worn (playfield touchup was performed), the Player 1 display had a missing segment, the MPU board showed battery corrosion damage to a few 40-pin PIA chips underneath the battery holder, the G.I. connector on the interconnect board was heating up & burnt.  This repair log is a description of what was done to fix the missing segment on the Player 1 display.

Symptoms
Top display (Player 1 display) is missing the top segment on all characters on the display.  Referring to the Whirlwind Operations Manual, this is the "a" segment on the Player 1 display.  It corresponds to U41 pin #10 on the MPU board.  U41 is a 6821 PIA (Peripheral Interface Adapter) IC.

Missing Segment - Whirlwind Player 1 Display
Picture: Missing top segment (segment "a") on Player 1 Display


Analysis
Of course some of the usual resources were consulted like the Clay's Williams System 11 Repair Guides at pinrepair.com.  Since all of the digits on the Player 1 display exhibited the same behavior, it seemed to narrow the issue down to either the 4049 chip for the Player 1 display located on the display board, or the signal entering this chip.

Tracing the connection from the schematics, the ribbon cable for the display goes from J3 on the display board to IJ22 on the MPU board.  Also the schematics showed that the "a" segment corresponded to U41, a 6821 PIA (Peripheral Interface Adapter) IC -- specifically pin #10 on this IC.  Both U41 and U42 (also a 6821 PIA) directly below it had very noticeable battery corrosion damage, so this had to be addressed first.

Battery Corrosion on PIA ICs
Picture: Battery corrosion on 6821 PIA ICs.  Pin #10 definitely on U41 definitely amongst the worst

The board had a number of previous repairs done on it, most of which appeared to have been performed with too high of a temperature soldering iron where solder pads had lifted and components then had to be soldered directly onto traces or components the solder pads had connected to.

The weird thing was the battery holder appeared to have been replaced.  So the original battery holder must have been so corroded it was no longer making the proper connections with the batteries and the owner/operator soldered in a new battery holder (with too high temperature of a soldering iron of course).  Anyway, since the PIA chips under the battery holder had not been replaced and showed obvious battery damage, these were the most obvious suspects causing the display issue.


First up, repairing the battery corrosion..

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Comments:
Whirlwind Display Problem
Posted 01/04/13 2:49PM by Anonymous Techdoser
Thanks for posting this! Just picked up a WW project and my U41 and 42 look very similar to yours. My problem is the top segments of the upper display are all stuck on rather than off. This is with a known good display board from another pin. I've cleaned up the corrosion as best I could with no change. Do you think my U41 chip is bad? I've got a logic probe and diagnostic rom on the way, but would appreciate your thoughts.

Thanks