On YouTube, I watched JDW's video on comparing replacement PSUs for the SE and SE/30. He mentions that Apple's main wiring harness wires are 22 AWG instead of 18 AWG. Zigzagjoe had pointed this out and found 18 AWG wires precut to the right length with Molex connectors at Digikey. During this video, JDW pointed out that his 5v pin on the external SCSI connector was down to 4.55v. That is a significant loss through wires and board traces. And he shows a before and after of 4.85v and 4.91v respectively after adding the thicker wires. As I remember, he replaced a couple of ground wires and the 5v and 12v lines. This voltage loss is caused by increased current pull on the power rails and the wire resistance (Ploss =SQ of I times R), especially the 5v rail, when adding upgraded hardware in your SE or SE/30.
Anyway, I ordered a set of black and red 18 AWG wires from Digikey to upgrade all 14 wires in my main harness and replaced them last night. I don't have the heavy-duty staples JDW used but I was able to de-pin both ends using regular stapes but it took me about 90 minutes. And my fingers are sore today. After re-pinning the connectors, the harness is very stiff and harder to route from the analog board to the main board. Be sure to FULLY insert the new molex pins in the connectors. My SE/30 wouldn't power up at first but after pushing the pins in it booted normally. My 5v rail at the main CPU board connector (pins 12 and 13) are now at 4.99v and I do have an accelerator card in my PDS. I should explain why I did this. My display's raster was noisy (not video noise). After re-soldering the entire Analog board about 80% of the noise went away but there was still some. So far, I haven't seen any further raster noise but it's early yet.
Has anyone had higher than normal voltage drops on the main CPU board in the SE or SE/30? I hope this fixes mine. I also used Deoxit on both 35 year old board connectors.
Thank you,
Gerry
Anyway, I ordered a set of black and red 18 AWG wires from Digikey to upgrade all 14 wires in my main harness and replaced them last night. I don't have the heavy-duty staples JDW used but I was able to de-pin both ends using regular stapes but it took me about 90 minutes. And my fingers are sore today. After re-pinning the connectors, the harness is very stiff and harder to route from the analog board to the main board. Be sure to FULLY insert the new molex pins in the connectors. My SE/30 wouldn't power up at first but after pushing the pins in it booted normally. My 5v rail at the main CPU board connector (pins 12 and 13) are now at 4.99v and I do have an accelerator card in my PDS. I should explain why I did this. My display's raster was noisy (not video noise). After re-soldering the entire Analog board about 80% of the noise went away but there was still some. So far, I haven't seen any further raster noise but it's early yet.
Has anyone had higher than normal voltage drops on the main CPU board in the SE or SE/30? I hope this fixes mine. I also used Deoxit on both 35 year old board connectors.
Thank you,
Gerry
