MSF5000 PS question

Post by Pj » Wed Oct 13, 2004 4:21 pm

I don't have the part number off hand, but what is the output of a MSF5000 ac/dc power supply? Voltage/Amps?

kcbooboo · Post by **kcbooboo** » Wed Oct 13, 2004 4:56 pm

For stations up to 110 watts (C7x), it's a bit more than 15 volts in receive and a bit more than 14 volts on transmit. It is a ferro-resonant power supply, and they are different for 50 Hz or 60 Hz.

Also, a 110 watt UHF power amp draws about 22 amps when putting out 60 watts through one circulator and the factory duplexer/filter (this equates to very close to 110 watts out of the PA itself).

The entire 110 watt UHF station uses about 500 watts of AC input power when transmitting and producing 60 watts into a dummy load. Terribly inefficient but these things are just about impossible to destroy.

Hope this helps.

Bob M.

Will · Post by **Will** » Sun Oct 17, 2004 4:03 pm

Right outa the book...

13.1 V DC at 36 amps, to 16.3 VDC, at 2 amps.

11.5 VDC Minimum at 36 amps.

JAYMZ · Post by **JAYMZ** » Mon Oct 18, 2004 3:37 am

How would one regulate one of those supplies for a consitant 13-14 VDC? Or is the voltage and amperage based on the load on the supply?

bernie · Post by **bernie** » Mon Oct 18, 2004 12:02 pm

My two bits worth:
The battery charging version of the MSF power supply is adjustable.

The normal "Ferro-Resonant" power supply has a winding on the transformer that is in resonamce on the mains frequency.

This keeps the core in saturation, thereby stablizing the output voltage, and limiting the output current.

The idea is to keep the voltage from varying very much due to key/unkey, as well as variations in input voltage. The voltage is not adjustable.

Critical circuits in the station use their own regulators supplied by the rough regulated A+ from the ferro resonant supply.

kcbooboo · Post by **kcbooboo** » Mon Oct 18, 2004 6:01 pm

Regarding regulation, I would say that it depends on what kind of load you want to put on the supply. As the voltage can vary quite a bit, you would not be able to adequately regulate it to 13 - 14 Volts for running a mobile radio, especially if the MSF5000 was also transmitting. However, you can certainly use a 7812 type three-terminal regulator with appropriate bypass capacitors, for powering a repeater controller or some other device that draws under an amp, as the power supply seems to be able to provide 14 volts or so, giving the 7812 about two volts to work with. This is the minimum it needs to have.

Alternatively, if the load can stand it, don't even bother with a regulator - just use the raw, varying voltage from the MSF5000's power supply and let the load "live with it". Not all loads can handle 16 or so volts, so take care hooking things up.

I'm doing this in my C64RLB station running at 80 watts output and the 7812 powers a CAT200 repeater controller. Granted, it only draws about 50 mA, but I've had no problems with it so far.

Bob M.

Post by **batdude** » Mon Oct 18, 2004 6:33 pm

i have NEVER (EVER) known or even heard of a problem running auxilliary things (within reason) off the MSF ferro power supply.

i've seen DUAL link radios run (each drawing 6-8a on xmit) at the same time... all while the msf is cranking out power.

never a problem.

ever.

i have seen one that was broken.

ups ran over the darn thing with the plane.... but the 30lb transformer was still good...

there's a reason that this power supply has been in service for about 20 years now - it's good... and still used in quantro high power repeaters (they use TWO of these)

i would add however, that you CAN be fooled. the low(er) power MSF stations use a power supply that looks like the high current (550w?) version.. but it's missing several of the large caps... and isn't good for near as much power as the biggie.

doug