[rescue] Power and Imac

Arno Kletzander Arno_1983 at gmx.de
Wed Apr 27 01:16:22 CDT 2005

Wes Will <wwill at siu.edu> wrote:
>At 08:45 AM 4/26/2005 -0400, you wrote:
>>Arno Kletzander wrote:
>>> ...an IMac DV (slot-in drive) which seems to have a bad PSU
>>> as well. It just sits there and emits a barely audible
>>> high-pitched noise, but won't turn on.
>>   That sounds like what I've been told is a bad flyback transformer,
>>though I'm no expert. COuld it also be the miserable Analog Video Board,
>>which regularly dies in these CRT iMacs?
>Yes it could very well be, but the whine is usually indicative of a
>high-voltage leak somewhere.  Open it up completely, turn it on, stand
>back a bit and don't be tempted to reach in when you can't see, and flip 
>off the lights.  Look in, see if you see any arcing or bluish glow on the
>high voltage board.  There are occassions when it's just an abraded wire
>carrying a lot of charge, and it leaks.  Sort of like spark worn-out plug
>wires on a foggy night....

Tried it with the translucent/transparent shells fitted (didn't have the
time to crack it open yet), but no light show available. Perhaps I should've
sat in the darkened room a few minutes longer before, to allow for my
"eyeball AGC" cranking up all the way...

> Not likely, but I have done televisions (and spark plugs) that way.  Turn
> the lights on and the power off before you reach in.  We did this to 
> death a few months back, the snap wouldn't likely hurt you by itself, 
> but you might fall or smack something sharp when you flexed backward if 
> the HV cap got you with anode voltage.  (We are our own worst enemy, to 
> misquote Mr. Pogo Possum.)

Anyway, I'm not sure it is even trying to drive its video circuitry yet. I
do not get any indication on the LED in the power button. Might also be the
PSU not supplying the standby voltage, or even supplying that and not waking
up when being prodded...although I think I'm hearing a faint dull *thump*
like sound when it's trying to start up the first time after it was
unplugged, as you often get them from CRT devices (perhaps degauss, perhaps
not). I'll have to find the time to make some measurements. (E.g. are the
USB ports even getting power? I don't have an USB keyboard yet...)

I'll be back when I've investigated some further. Thank you so long.


Arno Kletzander
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