So, I've been making a number of different adapter types for ATX to JVS, Modular PSU to JVS, etc...
And while the cables check out fine during testing, I've run into problems with majorly out of spec voltages on 3.3v on some power supplies.
Interestingly, it does NOT appear to have anything to do with actual current capacity, but instead something referred to as "Group Regulation"
It appears that group regulation has been responsible for similar system instabilities on modern PC's that do not follow the normal power usage profile between 12/5/3.3v
One such problematic power supply series is the Corsair CX (Green Label) series, and after encountering tons of problems with out of spec 3.3v on this exact series of power supplies I was led down the rabbit hole of people rating the CX green series as complete trash (disappointing as I have stacks of them from older retired PC builds, and Corsair USED to be rated as really good. It appears the newer CX (Silver Label) series should not have this issue, but I haven't tested it.
I mention all this because there's been recent interest in using ATX power supplies for powering JVS boards (i.e. Naomi), and some disagreement over the specs needed to actually power the PCB. In the end, it appears that the issues are directly related to this Group Regulation, and not actual under-spec power supplies. Especially as there's examples of Naomi running off 90W and 150W PicoPSUs also powering a netdimm AND JVS IO board.
So let's make a list- If you've got an ATX PSU and have adapted it to JVS and can test with a Naomi (or similar), measure the 3.3v lines AT the JVS power plug while attempting to power the Naomi up.
GOOD:
Antec BP350 (350W) - 3.2v
Diablotek PSEL400 (400W) - 3.2v
BAD:
Corsair CX450M Green Label (450W) - 2.6v
Corsair CX500M Green Label (500W) - 2.1v
Corsair CX600M Green Label (600W) - 2.2v
Athena AP-MFATX50P8 (500W) - 2.3v
Feel free to contribute!
And while the cables check out fine during testing, I've run into problems with majorly out of spec voltages on 3.3v on some power supplies.
Interestingly, it does NOT appear to have anything to do with actual current capacity, but instead something referred to as "Group Regulation"
It appears that group regulation has been responsible for similar system instabilities on modern PC's that do not follow the normal power usage profile between 12/5/3.3v
One such problematic power supply series is the Corsair CX (Green Label) series, and after encountering tons of problems with out of spec 3.3v on this exact series of power supplies I was led down the rabbit hole of people rating the CX green series as complete trash (disappointing as I have stacks of them from older retired PC builds, and Corsair USED to be rated as really good. It appears the newer CX (Silver Label) series should not have this issue, but I haven't tested it.
I mention all this because there's been recent interest in using ATX power supplies for powering JVS boards (i.e. Naomi), and some disagreement over the specs needed to actually power the PCB. In the end, it appears that the issues are directly related to this Group Regulation, and not actual under-spec power supplies. Especially as there's examples of Naomi running off 90W and 150W PicoPSUs also powering a netdimm AND JVS IO board.
So let's make a list- If you've got an ATX PSU and have adapted it to JVS and can test with a Naomi (or similar), measure the 3.3v lines AT the JVS power plug while attempting to power the Naomi up.
GOOD:
Antec BP350 (350W) - 3.2v
Diablotek PSEL400 (400W) - 3.2v
BAD:
Corsair CX450M Green Label (450W) - 2.6v
Corsair CX500M Green Label (500W) - 2.1v
Corsair CX600M Green Label (600W) - 2.2v
Athena AP-MFATX50P8 (500W) - 2.3v
Feel free to contribute!