Basically, we need to configure a power supply for a machine that has +24, +8, +5, -5 volts. We have a supply here that has 2, 5, 5, 12, 24 volt modules in it. Bought it used. Everything works but the dual 12V module will start smoking after about 1min run time. Current into the whole supply is only .4A at 120V so with PF considered, probably 10 watts.
I quickly unplugged and inspected the module. There seems to be obvious heat around the resistor array shown in pic. The bands are even a little cooked. I think these are supposed to be blue and they are now gray. I am curious if this seems like an isolated resistor issue or (probably) if this is pointing to a bigger problem and possibly the output caps not doing their job? I rarely see power resistors go bad for no reason and they all seem roasty except for one.
Also, This will come as possibly in idiotic question but the OEM does not support these supplies and we REALLY need to get our 8V somehow. I was considering just installing a regulated on the 12V module to buck down to 8V or maybe add a transformer but kind of concerned about that. Can a reg fail shorted? This circuit seems pretty smart so I am not sure I can fool it. It might just shut down but comparing modules of different voltages, it is obvious there is more than a couple differences. Transformers, resistors, diodes, not to mention any chip programming there might be.
For anyone not familiar, this is a modular supply in which the front end is just a DC rectifier and supplies 330VDC to a common rail for these modules to soak up.
I quickly unplugged and inspected the module. There seems to be obvious heat around the resistor array shown in pic. The bands are even a little cooked. I think these are supposed to be blue and they are now gray. I am curious if this seems like an isolated resistor issue or (probably) if this is pointing to a bigger problem and possibly the output caps not doing their job? I rarely see power resistors go bad for no reason and they all seem roasty except for one.
Also, This will come as possibly in idiotic question but the OEM does not support these supplies and we REALLY need to get our 8V somehow. I was considering just installing a regulated on the 12V module to buck down to 8V or maybe add a transformer but kind of concerned about that. Can a reg fail shorted? This circuit seems pretty smart so I am not sure I can fool it. It might just shut down but comparing modules of different voltages, it is obvious there is more than a couple differences. Transformers, resistors, diodes, not to mention any chip programming there might be.
For anyone not familiar, this is a modular supply in which the front end is just a DC rectifier and supplies 330VDC to a common rail for these modules to soak up.
Attachments
Last edited: