connecting two old PC supplies for more current
 

I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel
to increase current ? Ive thought of adding a stud mount diode in the
positive
leads to isolate them and connect the commomn or neg togather. I can
raise the voltage to makeup for the .6 volt drop without any problem.
Not having alot of switching supply experience, Im wonder if this
will work or
just go up in smoke?

It should work except that these power supplies generally won't start up
unless there is a substantial load on the +5 Volt line. I suppose you could
put a load on that line and when the output stabilizes, reduce it to a
negligible value with a relay or something.

Radio gear designed for 12 Volts often won't deliver full output unless the
supply is at around 13 Volts or more. Check your own gear and see what it
takes to work properly. I like running my rigs at around 12.5 to mazimize
lamp life but that doesn't work with one rig, the IC-751, which won't put
out the full 100 Watts unless the supply is above 13 Volts.

73, Bob

It should work except that these power supplies generally won't start up
unless there is a substantial load on the +5 Volt line. I suppose you could
put a load on that line and when the output stabilizes, reduce it to a
negligible value with a relay or something.

Radio gear designed for 12 Volts often won't deliver full output unless the
supply is at around 13 Volts or more. Check your own gear and see what it
takes to work properly. I like running my rigs at around 12.5 to mazimize
lamp life but that doesn't work with one rig, the IC-751, which won't put
out the full 100 Watts unless the supply is above 13 Volts.

73, Bob

clc wrote:

I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel to increase current ? Ive thought of adding a stud
mount diode in the positive leads to isolate them and connect the
common or neg together. I can raise the voltage to makeup for the .6
volt drop without any problem.
Not having a lot of switching supply experience, I wonder if this
will work or just go up in smoke?

I wouldn't recommend it. There are computer power supplies made for
N+1 hot swapping that will work well in parallel, but they are designed
for that application. Look around for a surplus power supply big enough
to handle the radio.
--


Michael A. Terrell
Central Florida

clc wrote:

I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel to increase current ? Ive thought of adding a stud
mount diode in the positive leads to isolate them and connect the
common or neg together. I can raise the voltage to makeup for the .6
volt drop without any problem.
Not having a lot of switching supply experience, I wonder if this
will work or just go up in smoke?

I wouldn't recommend it. There are computer power supplies made for
N+1 hot swapping that will work well in parallel, but they are designed
for that application. Look around for a surplus power supply big enough
to handle the radio.
--


Michael A. Terrell
Central Florida

I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel to increase current ? Ive thought of adding a stud
mount diode in the positive leads to isolate them and connect the
common or neg together. I can raise the voltage to makeup for the .6
volt drop without any problem.
Not having a lot of switching supply experience, I wonder if this
will work or just go up in smoke?

I wouldn't recommend it. There are computer power supplies made for
N+1 hot swapping that will work well in parallel, but they are designed
for that application. Look around for a surplus power supply big enough
to handle the radio.
======================
Another consideration is to use a 12 V lead acid battery (sealed) and a say
8 Amperes charger set at 13.8 V. being 1 PC -SMPS

The peak current required for 100 Watts RF operation might be 20 Amperes
,but the average current for SSB during tx is below 8 Amperes ,even when
applying compression. With the current required during rx around 2 Amperes
,the overall average current will probably not exceed 6 Amperes.
With this setup the voltage will hardly drop below 13 volts ever.

An additional advantage of having such a supply system is emergency
operation during an AC power outage. In the latter case you should consider
a large marine type of battery of say 110Ah.
If prolonged operation during an emergency is an important aspect , the
addition of 1 or more solar panels would be beneficial if not essential.

Frank GM0CSZ / KN6WH

I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel to increase current ? Ive thought of adding a stud
mount diode in the positive leads to isolate them and connect the
common or neg together. I can raise the voltage to makeup for the .6
volt drop without any problem.
Not having a lot of switching supply experience, I wonder if this
will work or just go up in smoke?

I wouldn't recommend it. There are computer power supplies made for
N+1 hot swapping that will work well in parallel, but they are designed
for that application. Look around for a surplus power supply big enough
to handle the radio.
======================
Another consideration is to use a 12 V lead acid battery (sealed) and a say
8 Amperes charger set at 13.8 V. being 1 PC -SMPS

The peak current required for 100 Watts RF operation might be 20 Amperes
,but the average current for SSB during tx is below 8 Amperes ,even when
applying compression. With the current required during rx around 2 Amperes
,the overall average current will probably not exceed 6 Amperes.
With this setup the voltage will hardly drop below 13 volts ever.

An additional advantage of having such a supply system is emergency
operation during an AC power outage. In the latter case you should consider
a large marine type of battery of say 110Ah.
If prolonged operation during an emergency is an important aspect , the
addition of 1 or more solar panels would be beneficial if not essential.

Frank GM0CSZ / KN6WH

clc wrote:
I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel
to increase current ? Ive thought of adding a stud mount diode in the
positive
leads to isolate them and connect the commomn or neg togather. I can
raise the voltage to makeup for the .6 volt drop without any problem.
Not having alot of switching supply experience, Im wonder if this
will work or
just go up in smoke?

A couple of interesting websites..I'm sure there are more..
73 de Eskay VE3JUA..

http://www.antennex.com/preview/archive3/powers.htm

http://www.webx.dk/oz2cpu/radios/psu-pc1.htm

clc wrote:
I need around 20amps to run my mobile HF rig in the house. I have lots
of old PC switching power supplies that put out 8 - 10 amp @ 12v
without any problem.
Im wondering if anyone has ever had any luck connecting two or more
in parallel
to increase current ? Ive thought of adding a stud mount diode in the
positive
leads to isolate them and connect the commomn or neg togather. I can
raise the voltage to makeup for the .6 volt drop without any problem.
Not having alot of switching supply experience, Im wonder if this
will work or
just go up in smoke?

A couple of interesting websites..I'm sure there are more..
73 de Eskay VE3JUA..

http://www.antennex.com/preview/archive3/powers.htm

http://www.webx.dk/oz2cpu/radios/psu-pc1.htm