Amiga 500 RGB Port

luvtofish · 17 September 2012, 00:19

I was testing a new RGB adapter on my A500 and using pin RGB Port pin 23 for 5 V DC. Well, it worked for awhile and now I have no 5 V DC coming through Pin 23. Pin 21,22 have 12 V power, so the problem seems to be with pin 23.

Can somebody explain what which resistor I likely blew or where to look on the MOBO?

Oh, I seem to have lost Audio as well, assuming a bad Paula chip?

Thanks

-ltf

johnim · 17 September 2012, 08:12

http://project64.c64.org/hw/amiga.htm

diagrams here

luvtofish · 17 September 2012, 23:15

I've looked through the schematic but my electrical engineering skills are meager at best. I've found the RGB connector in the schematic and its showing "EMI 4" at location RP405 on the mobo listed between pin 23 and VCC. Where is VCC at in this instance? Is there an inline fuse somewhere? What do I have to do to trace this down?

Thanks

ajk · 18 September 2012, 09:20

Vcc refers to the operating voltage, +5 volts, which comes from the PSU connector, but is spread all around the board to all chips that need it (same with ground, or 0 volts). You will need to start from the trace connected to pin 23 on the RGB port and see where it leads. If you have a multimeter you can use the continuity function to check if a pin is connected to ground or +5V.

17 September 2012, 00:19	#1
luvtofish Registered User Join Date: Aug 2012 Location: Louisburg, KS / USA Posts: 11	Amiga 500 RGB Port I was testing a new RGB adapter on my A500 and using pin RGB Port pin 23 for 5 V DC. Well, it worked for awhile and now I have no 5 V DC coming through Pin 23. Pin 21,22 have 12 V power, so the problem seems to be with pin 23. Can somebody explain what which resistor I likely blew or where to look on the MOBO? Oh, I seem to have lost Audio as well, assuming a bad Paula chip? Thanks -ltf

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17 September 2012, 08:12	#2
johnim Amibay Mod/Staff Join Date: Jun 2010 Location: birmingham uk Age: 48 Posts: 1,019	http://project64.c64.org/hw/amiga.htm diagrams here

17 September 2012, 23:15	#3
luvtofish Registered User Join Date: Aug 2012 Location: Louisburg, KS / USA Posts: 11	I've looked through the schematic but my electrical engineering skills are meager at best. I've found the RGB connector in the schematic and its showing "EMI 4" at location RP405 on the mobo listed between pin 23 and VCC. Where is VCC at in this instance? Is there an inline fuse somewhere? What do I have to do to trace this down? Thanks

18 September 2012, 09:20	#4
ajk Registered User Join Date: May 2010 Location: Helsinki, Finland Posts: 1,341	Vcc refers to the operating voltage, +5 volts, which comes from the PSU connector, but is spread all around the board to all chips that need it (same with ground, or 0 volts). You will need to start from the trace connected to pin 23 on the RGB port and see where it leads. If you have a multimeter you can use the continuity function to check if a pin is connected to ground or +5V.

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