Mac Plus ozone?
Curtis H. Wilbar Jr.
rescue at hawkmountain.net
Sun Apr 13 08:32:36 CDT 2008
John Robertson wrote:
> Curtis H. Wilbar Jr. wrote:
>> I was given a Mac Plus a while back... and never tested it....
>> Decided to give it a quick test...
>> Other than needing a boot floppy which I'll have to dig up.... it
>> powers on, video
>> looks good, monitor is stable and all...
>> But there is a faint sound (think of it as a cross between crickets
>> chirping and clicks)
>> and after a while, it smells to me a bit like ozone at the top of the
>> I'm thinking maybe high voltage leakage ?
>> Anyone have any experiences with these old Macs that can point me at
>> what to look
>> for ?
>> It might well be OK as it is... but I don't want to risk damage
>> occuring as other
>> than a few dings and scrapes and a bit of yellowing, it is in
>> remarkable condition.
>> -- Curt
> Ozone smell is just the high voltage at work. A slight leakage that
> may indicate moisture or excessive dust on the monitor where the HV
> lead clips to the side of the picture tube. You might be able to
> reduce the smell by opening the case and (after waiting 24 hours to
> discharge) clean the glass around the HV Anode clip (may have a rubber
> disc protecting the clip) with a red (usually red) fat insulated wire
> coming out of the picture tube cone. There is a special coating on the
> tube that starts about 2 inches away from the anode clip and coats the
> glass cone - do not remove or damage this if possible. It is 1/2 of
> the capacitor element of the picture tube Lyden jar type capacitor.
Called DAG I believe.
I'll have to open this up, probably check it out in a dark room, then I
discharge with my hv meter or wait patiently for at least a day (and
check with the hv meter :-) ).
> Alternatively the flyback could be damp or filthy with dust. This is
> found at the other end of the fat wire (normally red) leading from the
> cone of the picture tube. You can wipe it with a damp cloth, taking
> particular care not to rotate or move it relative to the frame - as
> this will break wires and cause it to fail. Most flybacks are solid
> enough that this is not a concern but in my early B&W video game
> monitors the flyback coil was not well secured and subject to failure
> from being turned or twisted whilst cleanig or just day to day
> bouncing around...
which B&W video games ? Vectors or Rasters ? I have an Asteroids I haven't
repaired yet. (I have around 12 vids, aprox half rasters, half
vectors) I am the
'repair shop' for them (but sadly get very little time, so several or
Currently (off topic, but possibly of interest to some) on the repair
Star Wars (mathbox probs), Rip Off (sound problems), Tempest (flakes out
large vectors and crashes randomly, might be bad ram socket from a ram
replaced), Major Havoc (mainboard problems, to be built into a Tempest
(the dreaded Matsushita monitor is slewing video at the edge of the
and I'm sure I'm forgetting a couple.
My Joust leaks HV... I think the DAG coating has become damaged (flaked
partially 'cleaned' off by someone). Especially if there is moisture in
the air, it
crackles, and IIRC I observed a faint lighting show around the DAG
believe you can get a coating to redo the DAG, but I haven't researched
that far yet.
OK.. enough off topic (hrm... maybe not too of topic.. they are
essentially computers :-) ).
> John :-#)#
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