Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.sys.apple2 > #3029

AppleColor RGB all-red display

Show all headers | View raw

I was fiddling with my AppleColor RGB (for the IIgs) yesterday, and I
managed to break it.

I was trying to figure out why the voltage to the screen was increasing,
thus making the intensity slowly ramp up as the electronics got warmer over
about 10 minutes.

I measured voltage across a 4.7k Ohm resistor on the CRT board (the one that
connects to the neck of the CRT) and it was about 50 volts. I then measured
across the identical (?) 4.7k Ohm resistor on the left side of the same
board. This is where things went wrong. I have an analog multimeter, and
when I connected the leads, the needle went back, like negative voltage. I
assumed this meant that I had the leads the wrong way around, so I reversed
them. I got a spark, a zap, and a nasty smell. A second later, the display
went all red. I turned off the monitor.

I searched the Apple II FAQs, and found in the Monitors, question 008-
"Suddenly my monitor has an all-blue (all-red, etc.) screen! How do I fix
this?"

Well, I measured the resistance across all three inductors, and they were
all about 10k Ohms. I powered on the monitor and measured the voltage drop,
which was negligible (the needle barely moved).

So, now I must assume that some other component blew up and made the nasty
smell. Any ideas? I'm not really good at doing electronics, so I'm going to
have a graybeard help me with the repairs.

-- 
]DF$
Mac GUI Vault - A source for retro Apple II and
Macintosh computing.
http://macgui.com/vault/

Back to comp.sys.apple2 | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-15 17:38 +0000
  Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-15 17:41 +0000
    Re: AppleColor RGB all-red display Grent <grent3@gmail.com> - 2011-10-15 17:33 -0700
      Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-17 20:47 +0000
        Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-18 14:19 +0000
          Re: AppleColor RGB all-red display Michael J. Mahon <mjmahon@aol.com> - 2011-10-18 12:05 -0500
            Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-18 17:41 +0000
              Re: AppleColor RGB all-red display Grent <grent3@gmail.com> - 2011-10-18 23:27 -0700
              Re: AppleColor RGB all-red display Alex Freed <alex_news@alexfreed.com> - 2011-10-19 02:10 -0700
                Re: AppleColor RGB all-red display Michael J. Mahon <mjmahon@aol.com> - 2011-10-19 16:08 -0500
                Re: AppleColor RGB all-red display Kevin Dady <kevin@hackaday.com> - 2011-10-19 18:16 -0700
                Re: AppleColor RGB all-red display Alex Freed <alex_news@alexfreed.com> - 2011-10-20 01:25 -0700

csiph-web