13 Apr
2008
13 Apr
'08
6:32 a.m.
John Robertson wrote:
Curtis H. Wilbar Jr. wrote:
Called DAG I
believe.
I'll have to open this up, probably check it out in a dark room, then I
can always
discharge with my hv meter or wait patiently for at least a day (and
then double
check with the hv meter :-) ).
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
Mac.
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.
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
awaiting repair).
Currently (off topic, but possibly of interest to some) on the repair
room floor:
Star Wars (mathbox probs), Rip Off (sound problems), Tempest (flakes out
with
large vectors and crashes randomly, might be bad ram socket from a ram
someone
replaced), Major Havoc (mainboard problems, to be built into a Tempest
cab), Xevious
(the dreaded Matsushita monitor is slewing video at the edge of the
(rotated) screen),
and I'm sure I'm forgetting a couple.
My Joust leaks HV... I think the DAG coating has become damaged (flaked
off, or
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
coating. I
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 :-) ).
-- Curt
John :-#)#