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://cdn.badcaps-static.com/pdfs/...fae5488f5e.pdf
Version 3 (Australia Amendments): http://lukazi.blogspot.com/2013/02/i...placement.html
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://cdn.badcaps-static.com/pdfs/...fae5488f5e.pdf
Version 3 (Australia Amendments): http://lukazi.blogspot.com/2013/02/i...placement.html
Attached Files
But today, I’m making an exception here. Why? No idea. Perhaps only because the repair details are still “fresh” in my head… which is ironic, given this is a 16 year old monitor that hardly anyone will care about today. It is new to me, though. 
I picked it up last November from someone on my local Craigslist. It wasn’t very close to where I live, but was close to a family friend that I had to go visit anyways. So after watching the posting on Craigslist for a few weeks and seeing it getting...
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