Hi all,
I am troubleshooting an IP20 Indigo (R4400/Elan) that was working until a couple months ago. Current symptoms on power-on are:
From what I have read, these symptoms are consistent with a missing or collapsed +12V rail. Measured at a drive power connector, the +12V rail is only about 2.2V.
During troubleshooting, I discovered a badly cracked solder joint on the +12V pin of the PSU-to-backplane connector. I reflowed that pin along with the neighboring connector pins. After doing so, I briefly tested the machine with only the PSU and IP20 board (minimum RAM installed) and got a green LED and startup chime. No drive, graphics board, keyboard, or display was connected during this test.
However, after powering the machine down and reassembling it later, the original symptoms returned, including ~2.2V on the +12V rail.
Additional troubleshooting performed:
I am troubleshooting an IP20 Indigo (R4400/Elan) that was working until a couple months ago. Current symptoms on power-on are:
- Orange LED
- No startup chime
- No drive activity
From what I have read, these symptoms are consistent with a missing or collapsed +12V rail. Measured at a drive power connector, the +12V rail is only about 2.2V.
During troubleshooting, I discovered a badly cracked solder joint on the +12V pin of the PSU-to-backplane connector. I reflowed that pin along with the neighboring connector pins. After doing so, I briefly tested the machine with only the PSU and IP20 board (minimum RAM installed) and got a green LED and startup chime. No drive, graphics board, keyboard, or display was connected during this test.
However, after powering the machine down and reassembling it later, the original symptoms returned, including ~2.2V on the +12V rail.
Additional troubleshooting performed:
- Symptoms are identical with two different recently-known-good PSUs.
- Both PSUs output stable +5V, +12V, and -12V when bench-tested with resistive loads.
- Symptoms are the same in a minimum configuration (PSU + IP20 + minimum RAM only) and with graphics board/drive installed.
- Measured approximately 2 MΩ between the +12V pin on the IP20 edge connector and the associated ground/return, suggesting no dead short on the motherboard.
- To bypass possible backplane distribution issues, I bodged +12V and GND directly from the PSU connector to the corresponding pins on a drive power connector. This made no difference.
- I also tested with only the PSU, backplane, and drive connected (no IP20 board installed) and still measured only ~2.2V on the +12V rail.
