Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Computer Displays
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
 
Thread Tools Display Modes
Prev Previous Post   Next Post Next
Old 11-25-2021, 04:28 AM   #1
nauseous
New Member
 
Join Date: Nov 2021
City & State: QLD
My Country: Australia
I'm a: Knowledge Seeker
Posts: 2
Default Apple IIgs RGB Color Monitor (A2M6014x)

Hi All,

I have an Apple IIgs RGB Monitor on the bench for repair that I am struggling to get working again. This is a 240v Australian Delivered model. I found the monitor at a local boot sale, seller was unable to provide any details if it worked or used to work etc.

Initial inspection revealed a blown 5 Watt wire wound resistor directly after the rectifier. I replaced the 5 watt resistor at the same time checked ESR on capacitors and replaced only those on primary side of power supply.
I happened to have a voltage regulator (STR54041) on hand so replaced this as well. Diodes / Resistors checking OK, I did find a Suspect 2SC1213 and used a BC337 as replacement whilst waiting on correct parts to arrive.

The monitor straight away blows the 5W resistor (R901), no smoke or failure - just goes open circuit.

At this point I have B+ isolated from the board and just using lightbulb for dummy load (Jumper B4 Disconnected from chassis).

The second time while running up on a variac - everything seemed OK till around the 200v mark when the Resistor failed open again. I could see the B+
was running a bit high around 128v but this was coming down as I increased the voltage on variac. (According to schema should be arround 115v)

Looking for any and all advice.
Thanks


See R901 (5 Watt Resistor) highlighted in attachment.

Schematics:
Version 1 (Best): https://console5.com/wiki/File:A2M60...-Schematic.png

Version 2: https://www.brutaldeluxe.fr/document...%20diagram.pdf

Version 3 (Australia Amendments): http://lukazi.blogspot.com/2013/02/i...placement.html
Attached Images
File Type: jpg Capture.JPG (154.1 KB, 8 views)

Last edited by nauseous; 11-25-2021 at 04:32 AM..
nauseous is offline   Reply With Quote
 

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2022
Powered by vBulletin ®
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 06:24 AM.
Did you find this forum helpful?