50v Power Supply

I was in need of a decent 48v power supply to Run an HF Amplifier, And had recently acquired a Cisco Nexus N7K-AC-6.0KW 50v 120A server Power supply unit that I bought used. Plugging this unit in to AC power I notice the red FAULT light is flashing. The unit will not turn on with the main switch on the front, or do anything, so it is essentially a paperweight in its current state. I know when using these computer power supplies, 2 wires, or "pins" must be shorted to turn the unit on properly, but Cisco offers minimal support in the way of troubleshooting documentation and schematics to point me in the right direction. As I am not using this in a "server" environment, I am guessing something crucial is missing in this equation.
I know this stuff Is not considered "Ham Equipment" however, as many hams here probably know, you work with what you have available.

Any info or knowledge to pass along would be appreciated
thanks.

Some server supplies need a jumper and some do not. I have a bunch of power supplies pulled from Cisco servers but made by Sony that need a jumper and most of my other supplies will run independent of the server frame without a jumper. I suspect if you enter your power supply model number in Google you may find some info on the jumper.

Once you get your power supply going you may discover an RF noise problem as many of these supplies rely on RFI filtering inside the server chassis and the individual supplies can be very noisy by themselves.

There are several tested and known good 50V power supplies used for amateur amplifiers and my favorite is the Eltek Flatpack2 series. I've purchased several 53.5V, 2000W supplies on Ebay for $49 and a 3000W version for $75. These are RF quiet and are only 1.5" X 4.25" X 13" in size! I am currently using a 2000W version inside a single BLF188 transistor 1.2kW home made amplifier.

VA3JWO said:

I was in need of a decent 48v power supply to Run an HF Amplifier, And had recently acquired a Cisco Nexus N7K-AC-6.0KW 50v 120A server Power supply unit that I bought used. Plugging this unit in to AC power I notice the red FAULT light is flashing. The unit will not turn on with the main switch on the front, or do anything, so it is essentially a paperweight in its current state. I know when using these computer power supplies, 2 wires, or "pins" must be shorted to turn the unit on properly, but Cisco offers minimal support in the way of troubleshooting documentation and schematics to point me in the right direction. As I am not using this in a "server" environment, I am guessing something crucial is missing in this equation.
I know this stuff Is not considered "Ham Equipment" however, as many hams here probably know, you work with what you have available.

Any info or knowledge to pass along would be appreciated
thanks.

Click to expand...

Thanks very much for your insight and information, i am intrigued about the FlatPack2 series of power supplies by Eltek, and doing some research on them now, as i cannot find any info online after hours of searching and refining my search criteria and from others on the N7K Cisco unit, perhaps the Trouble light means something else internal im missing. OH WELL,
The AMplifier I will be running it with is the same variation of Amplifier you are running, however the one I have utilizes 2 BLF188XRs.
Did you have to do anything special to your Eltek FlatPack2 units prior to using them? (ie short 2 wires to turn on the psu etc)? any kind of pinout on the back? or is it a throw the switch and start using?
Thanks

VA3JWO said:

I was in need of a decent 48v power supply to Run an HF Amplifier, And had recently acquired a Cisco Nexus N7K-AC-6.0KW 50v 120A server Power supply unit that I bought used. Plugging this unit in to AC power I notice the red FAULT light is flashing. The unit will not turn on with the main switch on the front, or do anything, so it is essentially a paperweight in its current state. I know when using these computer power supplies, 2 wires, or "pins" must be shorted to turn the unit on properly, but Cisco offers minimal support in the way of troubleshooting documentation and schematics to point me in the right direction. As I am not using this in a "server" environment, I am guessing something crucial is missing in this equation.
I know this stuff Is not considered "Ham Equipment" however, as many hams here probably know, you work with what you have available.

Any info or knowledge to pass along would be appreciated
thanks.

Click to expand...

Troubleshoot Nexus 7000 6.0KW AC Power Supply Module Failures
https://www.cisco.com/c/en/us/suppo...0-series-switches/118956-technote-n7k-00.html

Cisco Nexus 7000 Series AC Power Supply Modules Data Sheet
https://www.cisco.com/c/en/us/produ...00-series-switches/Data_Sheet_C78-437761.html

Cisco tends to be pretty useless when it comes to suppling information on how to repair their gear. SOP is for them to tell you to "send it in".
Biggest issue I've run into with them is dust getting in them and building up.

However, without a chassis to plug it into, you won't be able to talk to it to find out if there is something wrong with it.

There are some good options, though.
Any big PBX system will run on 48vdc. Actually, they run at 54vdc since that is what the battery systems usually like. I've surplussed some old ones at work that were still good. They were either too small to support all the networking gear that is required now for VoIP, or they were end of lifed and I couldn't get spares.
Try taking a look for a used Alpha, Reliance, LaMarche, Delta, Emerson, Lucent, or similar 48vdc power system. They can all be run at just about anywhere from 44v to 56vdc. Very clean power, often overbuilt, and more importantly, can be pretty inexpensive.

On the Flatpack2 series you have to find or make a mating connector or what I do is solder the AC input and DC output wires directly to the circuit board using 14ga for the AC and 10ga for the DC. A pair of 2000w Flatpacks is popular for a pair of BLF188s running full tilt or a single 3kW version should give you at least 2kW of RF.

There are no jumpers needed on the Flatpack series, just turn on the AC and out comes 53.5V at a whole lot of current. Another thing I like is they are auto input sensing AC and will operate at reduced output current when running from 120V. I can get full 1200w output SSB running my amp on 120VAC but continuous keydown in CW or FM mode is reduced somewhat. At least I can run full output SSB while camping and running from a Honda 2000i generator.

With two flatpacks in parallel running your pair of BLF188s I suspect you can get over a kW out running on 120VAC and your circuit breaker will be the limiting factor. You will of course get full output running on 220VAC.

VA3JWO said:

Thanks very much for your insight and information, i am intrigued about the FlatPack2 series of power supplies by Eltek, and doing some research on them now, as i cannot find any info online after hours of searching and refining my search criteria and from others on the N7K Cisco unit, perhaps the Trouble light means something else internal im missing. OH WELL,
The AMplifier I will be running it with is the same variation of Amplifier you are running, however the one I have utilizes 2 BLF188XRs.
Did you have to do anything special to your Eltek FlatPack2 units prior to using them? (ie short 2 wires to turn on the psu etc)? any kind of pinout on the back? or is it a throw the switch and start using?
Thanks

Click to expand...