Encouraged by Marks comments on computer SMP supplies and the possibility of altering the voltage I have found an old supply from an "Unreal Dave" HP PC I forgot I still had. I had disposed of the PC but kept the PSU.
One of the other requirements I wanted, apart from about 15 amps and 14 volts, was a supply isolated from the mains earth in order to feed a CB transceiver into a dipole aerial.
Previously when I tried my transceiver with an "Avair AV-2025D", I had purchased specifically for this use, the DC negative supply to the transceiver was connected to the mains supply earth. This had the unfortunate result in the RF signal leaking from the coax into the mains earth and going all around the house. This was tested by using a non earthed 13 amp plug and lead to supply the PSU, which cured the problem of RF leaking into the mains earth.
Anyway I sent the PSU back as not being suitable as a supply for a transceiver or as a bench supply.
I was advised that all their SMPS's had an earthed negative, which seemed strange to me.
Anyway this HP PC PSU was working when I removed it from the PC so it could do the job if I can get it working as need. I have taken it apart to make a few checks.
It has what appears to be a 6.3 amp internal fuse soldered to the PCB. (seems a bit high for a 240W supply)
It has good separation between the mains side and the low voltage side.
The 2 separate +12 volt feeds for the CPU and the peripherals do come from a single supply but fed via 2 very low value resistors, so can the yellow and brown wires simply be joined together?
There are 2 trimmers on a small daughter board.
The earth is connected to the output ground with a small link.
There are various other blue capacitor looking like components which also link to the bolt hole pads which would be grounded to the metal case when it is assembled.
So it looks like I will need to arrange for the green wire to be connected to a black wire. Also maybe add a load resistor to fool the supply to think it is connected to a PC.
Some advice on the load resistor and how to alter the voltage would be very appreciated..
I would probably add the following;
Accessible voltage control pot.
One of these devices to monitor the output. https://www.ebay.co.uk/itm/352445411956?
Fit an accessible fuse holder.
By the way I recently acquired some half inch 1A fuses which go in these Bulgin inline fuse carriers.
If anybody needs a couple please let me know.
Thanks
Mike
One of the other requirements I wanted, apart from about 15 amps and 14 volts, was a supply isolated from the mains earth in order to feed a CB transceiver into a dipole aerial.
Previously when I tried my transceiver with an "Avair AV-2025D", I had purchased specifically for this use, the DC negative supply to the transceiver was connected to the mains supply earth. This had the unfortunate result in the RF signal leaking from the coax into the mains earth and going all around the house. This was tested by using a non earthed 13 amp plug and lead to supply the PSU, which cured the problem of RF leaking into the mains earth.
Anyway I sent the PSU back as not being suitable as a supply for a transceiver or as a bench supply.
I was advised that all their SMPS's had an earthed negative, which seemed strange to me.
Anyway this HP PC PSU was working when I removed it from the PC so it could do the job if I can get it working as need. I have taken it apart to make a few checks.
It has what appears to be a 6.3 amp internal fuse soldered to the PCB. (seems a bit high for a 240W supply)
It has good separation between the mains side and the low voltage side.
The 2 separate +12 volt feeds for the CPU and the peripherals do come from a single supply but fed via 2 very low value resistors, so can the yellow and brown wires simply be joined together?
There are 2 trimmers on a small daughter board.
The earth is connected to the output ground with a small link.
There are various other blue capacitor looking like components which also link to the bolt hole pads which would be grounded to the metal case when it is assembled.
So it looks like I will need to arrange for the green wire to be connected to a black wire. Also maybe add a load resistor to fool the supply to think it is connected to a PC.
Some advice on the load resistor and how to alter the voltage would be very appreciated..
I would probably add the following;
Accessible voltage control pot.
One of these devices to monitor the output. https://www.ebay.co.uk/itm/352445411956?
Fit an accessible fuse holder.
By the way I recently acquired some half inch 1A fuses which go in these Bulgin inline fuse carriers.
If anybody needs a couple please let me know.
Thanks
Mike