[Techtoolslist] Fixing the 9100...

[John Robertson]

Two of my 9100s had no screen display, yet seemed to boot- so took the 
top case off and starting probing with the voltmeter. Found +5 and +12, 
but when I checked the +70 there was nothing on one, or very low on the 
other - and one machine had a bit of a burnt smell to it. That machine 
blew a tantalum surface mount cap, shorting the output of the switching 
supply that generates the +70 as well as the isolated +5, +12, and -12 
(there are relative to the "E" test point lug). This also took out the 
driver transistors - which Digi-Key still stocks (bought ten to be safe).

To reduce the risk of future damage I lifted the end of the choke coil 
that was closest to the power connector and installed a 20mm fuse holder 
in series with it and installed a 1A fuse there in the hopes that the 
fuse will blow before the system smokes up when the next capacitor 
shorts out - note I checked all the tantalum with the ESR meter and the 
rest on all my 9100s check fine.

I'll make up a page on this with pictures in a few days and jam it up on 
flippers on the fluke.html page.

John :-#)#

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"