Quoted from mtmellum:Hi, thanks for all the guidance in this guide. I have some questions.
I've rebuilt the power supply and checked the outputs/inputs to the cpu. On the 5v circuits good results. On the 3J6 12v output to 1j2, I get 12.6v on the output header pin at the ps board. All good, so I re-connect and check the input voltage at 1J2 and its 10.5v. I trace back to the IDC on 3J6 and at the IDC socket output, the voltage is 10.6v.
Is this a normal drop across the pin/socket of the IDC or should I replace the connector w a new Molex header and socket? And if so, should I replace all the IDCs?
Would the cpu not boot/run or gave issues because of that low voltage input? Just curious there as I am still to update the cpu board to Vid specifications. (Scanbes to replace and combo ROM mod to install).
Thanks!
The drop actually comes from the load of the circuit when you connected the board back up. I have my recorded measurements when I rebuilt my PSU and I was getting 12.53V at 3J6 with everything disconnected. After I connected everything back up I was getting about 11V. Since the line is unregulated it can vary a bit and from all the reading I did it's completely normal.
I've also read elsewhere that rebuilding 3J6 to molex is virtually mandatory much in the same fashion as replacing Scanbe sockets on the CPU is. I think the big reason is that in particular there is only a single 12V wire that leaves that connector (pin 6) that powers the reset circuit. If it's a 35 year old single point of contact (opposed to three-point trifurcon) fatigued connector touching an equally old round header pin then having issues isn't too much of a stretch. Having since replaced this connector and header pins my boot issues have been eliminated where as before it booted when it felt like it.
Green Brook Township, NJ
