Article-I.D.: husc6.685
Posted: Fri Nov 21 18:57:43 1986
Date-Received: Fri, 21-Nov-86 22:15:12 EST
Sender: news@husc6.UUCP
Reply-To: may@husc4.UUCP (jason may)
Distribution: net
Organization: Harvard Science Center
Lines: 18


	Since I got my Amiga over the summer, I have had a problem with
my monitor frequently making popping or snapping noises, very quietly,
accompanied by a flash from the screen.  This is not a normal Amiga
error-screen-flash flash, but a very fast jump of the whole image.
   I bought the machine in Michigan and when I asked about the problem
was told that the difficulty was probably due to power surges.  However
upon moving to Cambridge the popping continued.  I then went to the local
dealer, who turned out to be worse than useless and kept putting me off.
By then the warranty had ran out.  I still have the problem.
   It's nothing wrong with the machine, just the monitor, and it's never
caused any performance problems.  It's just annoying.
   Has anyone else had similar problems, and what can be done about it?
I don't really want to ship my monitor away for weeks to be repaired.
  Thanks in advance,
						Jason May

may@husc4.harvard.edu			...seismo!harvard!husc4!may

Article-I.D.: videovax.4049
Posted: Sat Nov 22 14:55:18 1986
Date-Received: Mon, 24-Nov-86 00:44:11 EST
References: <685@husc6.UUCP>
Reply-To: stever@videovax.Tek.COM (Steven E. Rice, P.E.)
Distribution: net
Organization: Tektronix Television Systems, Beaverton, Oregon
Lines: 16
Summary: The problem is high-voltage arcing. . .

In article <685@husc6.UUCP>, Jason May (may@husc4.UUCP) writes:

 >  	Since I got my Amiga over the summer, I have had a problem with
 >  my monitor frequently making popping or snapping noises, very quietly,
 >  accompanied by a flash from the screen.  This is not a normal Amiga
 >  error-screen-flash flash, but a very fast jump of the whole image.

 >  . . .

The problem is arcing in the high-voltage section.  You need to find a
*good* service center before the high-voltage supply dies.

					Steve Rice

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{decvax | hplabs | ihnp4 | uw-beaver}!tektronix!videovax!stever

Article-I.D.: cbmvax.1027
Posted: Sun Nov 23 04:08:08 1986
Date-Received: Mon, 24-Nov-86 01:08:59 EST
References: <685@husc6.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Distribution: net
Organization: Commodore Technology, West Chester, PA
Lines: 28

In article <685@husc6.UUCP> may@husc4.UUCP (jason may) writes:
 > 
 > 	Since I got my Amiga over the summer, I have had a problem with
 > my monitor frequently making popping or snapping noises, very quietly,
 > accompanied by a flash from the screen.  This is not a normal Amiga
 > error-screen-flash flash, but a very fast jump of the whole image.

 >    Has anyone else had similar problems, and what can be done about it?
 > I don't really want to ship my monitor away for weeks to be repaired.
 >   Thanks in advance,
 > 						Jason May

There are two possible problems:

One is that a static charge is building up on the faceplate or elsewhere, then
arcing to ground.  This is not serious and can be fixed at your leisure.

The other is if the is internal arcing between the high-voltage circuitry and
other internal parts.  This is more serious, as it will deteriorate as time
goes on.

In either case, the best solution is probably to take the unit to a good TV/
Video repair shop, who will have sprays and lotions suited to these problems.

-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)

Article-I.D.: mcdsun.134
Posted: Sun Nov 23 14:31:41 1986
Date-Received: Mon, 24-Nov-86 21:08:16 EST
References: <685@husc6.UUCP>
Reply-To: fnf@mcdsun.UUCP (Fred Fish)
Distribution: net
Organization: Motorola Microcomputer Division
Lines: 20

In article <685@husc6.UUCP> may@husc4.UUCP (jason may) writes:
 > 
 > 	Since I got my Amiga over the summer, I have had a problem with
 > my monitor frequently making popping or snapping noises, very quietly,
 > accompanied by a flash from the screen.  This is not a normal Amiga
 > error-screen-flash flash, but a very fast jump of the whole image.

Yes!  My monitor developed this problem shortly before moving here to
Arizona, and the problem still exists.  I've been meaning to take it
in for service for several weeks now, but haven't got around to it yet.
So far no damage or other problems.  Just annoying.

-Fred


-- 
===========================================================================
Fred Fish  Motorola Computer Division, 3013 S 52nd St, Tempe, Az 85282  USA
{seismo!noao!mcdsun,hplabs!well}!fnf    (602) 438-5976
===========================================================================

Article-I.D.: amdahl.4344
Posted: Tue Nov 25 16:46:09 1986
Date-Received: Wed, 26-Nov-86 03:43:06 EST
References: <685@husc6.UUCP>
Distribution: net
Organization: Amdahl Corporation,  Sunnyvale, CA 94086
Lines: 68

In article <685@husc6.UUCP>, may@husc4.harvard.edu (jason may) writes:
 >  
 >  	Since I got my Amiga over the summer, I have had a problem with
 >  my monitor frequently making popping or snapping noises, very quietly,
 >  accompanied by a flash from the screen.  This is not a normal Amiga
 >  error-screen-flash flash, but a very fast jump of the whole image.

Yeah, my monitor started doing the same thing about a month or so after
I got it.  This was one of the early units, from over a year ago, and at
that time, someone on the net from CBM said that there had been a problem
with "overspray" of the material that's used to conduct the the high-
voltage from the connector in the side of the CRT to the front of the tube.
The suggested fix was to return it to the dealer who could remove the over-
spray.

Since it was still in the Warranty period, I took the monitor in, and of
course it didn't arc at all for the dealer :-).  Back home, it arced every
90-120 seconds.  Back to the dealer with the whole system ... no arcing.

OK, we're dealing with a high-voltage leak, which are very sensitive to
humidity, temperature, etc., so the only thing to do is shoot the bug
"in place".

I took the cover off, and inspected all around the CRT, high-voltage
connector (where the fat red wire attaches to the side of the tube), CRT
socket, and high-voltage power supply (where the fat red wire comes from)
for any sign of "overspray" or "carbon tracking" (fine lines of black soot)
on/around these areas.  Nothing.

Finally, with the cover still off, I powered the monitor up in a DARK room,
and waited until it started arcing.  After a few pops, I spotted the tiny
flash from the spark coming from underneath the high-voltage power supply,
somewhere near the left-most edge of the circuit board.

I powered down the monitor, and removed the H-V supply (after first making
SURE that the CRT was unplugged, *and* that the H-V connection at the CRT
had been discharged to ground using a wire attached to ground on one end,
and clipped to a screwdriver on the other;  you touch the tip of the screw-
driver to the H-V connection under the little plastic insulator cup where
the fat red wire attaches to the tube).

Anyway, inspection of the bottom of the H-V circuit board showed no sign
of an H-V leak (carbon tracks, etc), but some of the solder spots where
the various components are connected were "sharp".  Carefully, with a pair
of finger-nail clippers, I clipped all the little tips as close to the
PC board as possible, and then smoothed them down using a small nail file.

Reassembled the H-V supply and cover, and ... no arcing!  And none since.


Hope this little narrative helps!

/kim


P.S.  If you try this make VERY SURE that the H-V terminal at the CRT gets
      fully discharged!  That circuit can hold onea helleva big charge
      (20-30 kV) for a LONG time (hours).


-- 
UUCP:  {sun,decwrl,hplabs,pyramid,ihnp4,seismo,oliveb}!amdahl!kim
DDD:   408-746-8462
USPS:  Amdahl Corp.  M/S 249,  1250 E. Arques Av,  Sunnyvale, CA 94086
CIS:   76535,25

[  Any thoughts or opinions which may or may not have been expressed  ]
[  herein are my own.  They are not necessarily those of my employer. ]

Article-I.D.: videovax.4067
Posted: Wed Nov 26 16:32:22 1986
Date-Received: Fri, 28-Nov-86 01:45:01 EST
References: <685@husc6.UUCP> <4344@amdahl.UUCP>
Reply-To: stever@videovax.Tek.COM (Steven E. Rice, P.E.)
Distribution: net
Organization: Tektronix Television Systems, Beaverton, Oregon
Lines: 61
Summary: BE CAREFUL!!!

In article <4344@amdahl.UUCP>, Kim DeVaughn (kim@amdahl.UUCP) writes:

[ Description of how to find and fix a high-voltage arc. ] 

 >  P.S.  If you try this make VERY SURE that the H-V terminal at the CRT gets
 >        fully discharged!  That circuit can hold onea helleva big charge
 >        (20-30 kV) for a LONG time (hours).

Kim's description of how to find and fix the arcing is a very good one.
Let me add a word of caution, however!

If you discharge the HV terminal of the CRT,

  !!! *DO*  *NOT*  *EXPECT*  *IT*  *TO*  *REMAIN*  *DISCHARGED* !!!

There are two phenomena that combine to cause a voltage to reappear on
the HV terminal minutes, hours, or even days after it is discharged.
The first is dielectric absorption -- the molecules that make up the
dielectric (in this case, the glass of the tube) of what is basically
a big capacitor are stressed by the continual application of high
voltage.  When the voltage is removed by discharging the tube, the 
molecules slowly relax.  As they relax, they rearrange their internal
charges, causing a voltage to reappear at the HV terminal.

The second phenomenon stems from characteristics of the material used
on the inside of the CRT to connect the faceplate to the high-voltage
terminal.  A slurry called "Aquadag" is sprayed on the inside of the
funnel as the tube is being built.  The Aquadag is basically finely
divided carbon in a binder.  It has a very high resistance (and there
can be some sections of it that are almost -- but not quite -- isolated
from the rest).  Thus, when you short the HV terminal to ground, you
are discharging the capacitance of the tube through the resistance of
the Aquadag.  This may leave quite a bit of charge on parts of the
tube.  When the ground wire is removed, the remaining charge will
gradually redistribute itself around the tube, causing a voltage to
appear at the HV terminal over a period of hours or days.

The moral:

   1. Always treat the HV terminal with respect.  Don't get your
      fingers near the terminal or anything connected to it (for
      example, the high-voltage rectifier) if the terminal is not
      grounded  *AT*  *THAT*  *MOMENT*.

   2. Discharge the HV terminal  *EVERY*  time you start to work around
      the CRT, even if the set has been off for days.  Even better,
      ground the terminal when you start to work on it, and keep it
      grounded until you are done.  Don't trust a ground wire, though!
      Before you get close to any part of the high voltage system,
      make sure the grounding wire is making good contact at both ends.

   3. !!! *DON'T*  *WORK*  *ALONE* !!!  Have someone in the same room
      who can call for help if you should have an accident.

If you follow these precautions, your chances of being zapped will be very
small, and you can safely work on your monitor.

					Steve Rice

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{decvax | hplabs | ihnp4 | uw-beaver}!tektronix!videovax!stever

Article-I.D.: marlin.853
Posted: Tue Dec  2 15:15:01 1986
Date-Received: Tue, 2-Dec-86 22:39:51 EST
References: <685@husc6.UUCP> <4344@amdahl.UUCP> <4067@videovax.Tek.COM>
Reply-To: aburto@marlin.UUCP (Alfred A. Aburto)
Distribution: net
Organization: Naval Ocean Systems Center, San Diego
Lines: 8

Thanks for the very good advice concerning working on the video monitor!
I also have an arching Amiga monitor.  It is strange though as the arching
appears to occur most often on Sunday mornings!  I don't know why -- it
just does.  It can be quite vicious at times in that in hear the arc and
the CRT will flash.  It makes me jump once in awhile because it is 
unexpected.

Al Aburto

Article-I.D.: utcs.1986Dec3.053631.29670
Posted: Wed Dec  3 05:36:31 1986
Date-Received: Wed, 3-Dec-86 06:29:57 EST
References: <685@husc6.UUCP> <4344@amdahl.UUCP> <4067@videovax.Tek.COM> <853@marlin.UUCP>
Reply-To: wagner@utcs.UUCP (Michael Wagner)
Distribution: net
Organization: University of Toronto Computing Services, general purpose UNIX
Lines: 8
Checksum: 40125

In article <853@marlin.UUCP> aburto@marlin.UUCP (Alfred A. Aburto) writes:
 > It is strange though as the arching
 > appears to occur most often on Sunday mornings!
Perhaps it is upset at your working on the sabbath!
But seriously, is it possible that the humidity is different then?
Is sunday the only morning you work on your Amiga?

Michael

Article-I.D.: videovax.4080
Posted: Wed Dec  3 16:21:29 1986
Date-Received: Fri, 5-Dec-86 21:21:29 EST
References: <685@husc6.UUCP> <4344@amdahl.UUCP> <4067@videovax.Tek.COM> <853@marlin.UUCP>
Reply-To: stever@videovax.Tek.COM (Steven E. Rice, P.E.)
Distribution: net
Organization: Tektronix Television Systems, Beaverton, Oregon
Lines: 20

In article <853@marlin.UUCP>, Alfred A. Aburto (aburto@marlin.UUCP) writes:

 >  Thanks for the very good advice concerning working on the video monitor!
 >  I also have an arching Amiga monitor.  It is strange though as the arching
 >  appears to occur most often on Sunday mornings!  I don't know why -- it
 >  just does.  It can be quite vicious at times in that in hear the arc and
 >  the CRT will flash.  It makes me jump once in awhile because it is 
 >  unexpected.

That's God reminding you that you should be in church! [ 8^) ]

Check the power line voltage and compare it with the voltage at other
times.  On Sunday morning there are relatively few heavy users of
electricity, and the voltage will tend to rise.  Up goes the high
voltage on your monitor (it is regulated, but loosely), and zzzzap!

					Steve Rice

----------------------------------------------------------------------------
{decvax | hplabs | ihnp4 | uw-beaver}!tektronix!videovax!stever

Article-I.D.: marlin.916
Posted: Tue Dec  9 20:03:17 1986
Date-Received: Wed, 10-Dec-86 10:44:02 EST
References: <685@husc6.UUCP> <4344@amdahl.UUCP> <4067@videovax.Tek.COM> <853@marlin.UUCP> <4080@videovax.Tek.COM>
Reply-To: aburto@marlin.UUCP (Alfred A. Aburto)
Distribution: net
Organization: Naval Ocean Systems Center, San Diego
Lines: 15

In article <4080@videovax.Tek.COM> stever@videovax.Tek.COM (Steven E. Rice, P.E.) writes:
 > That's God reminding you that you should be in church! [ 8^) ]
 > 
 > Check the power line voltage and compare it with the voltage at other
 > times.  On Sunday morning there are relatively few heavy users of
 > electricity, and the voltage will tend to rise.  Up goes the high
 > voltage on your monitor (it is regulated, but loosely), and zzzzap!
 > 
 > 					Steve Rice
 > 
Steve, Kim DeVaughn, and Michael Wagner thanks for the advise. I am going
to look at the monitor this weekend.  And I do look over my shoulder on 
Sunday mornings when the arcing seems to be strongest.

Al Aburto