On Wednesday, October 05, 2005, at 08:43AM, Jeff Walther <[EMAIL PROTECTED]> wrote:
>However, it's sounding like you probably have leaky capacitors on >your IIsi board. The IIci is subject to this problem and the IIsi is >nearly identical only with half the SIMM sockets and no NuBus slots. > >The surface mount electrolytic caps leak corrosive onto the board >with age. Several of them are involved with the power-on circuitry, >so the machine fails to power on, either because it needs the caps >functional, or because the corrosive has eaten through a trace, >contact or solder joint on the logic board. > >This isn't that hard to repair with a bit of care, but it does >require the motivation to fix it. I've had this happen ion a IIci before, but instead of not turning on it wouldn't turn off. The problem is caused by, as Jeff stated, the electrolytic can-type Capacitors in the boards leaking. In the case of the IIci I found one under the actual power supply had leaked. I wiped the board down with a bit of dilute alcohol and a soft cloth to get the stuff off the board and it recovered and hasn't given me any trouble since. The problem is not so much that the electrolyte fluid is corrosive, although is does cause oxidation long-term, the immediate problem when a cap first lets go is the electrolyte is highly conductive, as you would expect from something called 'electrolyte' ;o). This causes random shorts around the capacitor. In the case of my IIci it was shorting something in the 'soft power' control that was stopping the signal to turn off reaching the power supply. In your case it may be shorting something to ground causing the power supply to overload and not power on, the vast majority of switch-mode power supplies just cut out or refuse to power on in the case of a short. My advice is take a look at the logic board, especially around the sound and power sections. Look out for any suspicious stains or small patches of what looks like spilled soda on the board. if you find any clean them off with a bit of dilute alcohol as best you can, let the board dry in open air, then try it again. 1989-91 was a bad patch for this. The IIci, IIsi, LCII and SE/30 all suffer from the same capacitor leakage problem, the SE/30 is the worst. I just sent 2 of my boards off to a friend who is better with an iron than me to have the caps refitted with better ones. As Jeff says it's not too hard but it's tricky and takes a lot of time. -- Mark Benson http://homepage.mac.com/markbenson -- Vintage Macs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> Vintage Macs list info: <http://lowendmac.com/lists/vintagemacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:vintage.macs@mail.maclaunch.com> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/vintage.macs%40mail.maclaunch.com/> iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com
