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Need help with be 10 kw am transmitter

L

Larry the radio guy

I've got a Broadcast Electronics 10 kw be 10a

Got hit by lightening a few months back. Replaced the controller card and power supply cards.

If I place two power supply cards in the unit I can get 1kw out tops. When I place anymore than
two power supply cards in it the output of all the power supply cards drop to something like 8 volts
and the thing doesn't transmit. With two PS cards in I get normal voltage on the connectors where the
PA amps plug in. It's not a PA amp issue as they are removed when taking the PS readings. I see the
drop even before placing the PA amps back in!
The PWM and RF lights show modulation and RF is being delivered to all PA amps.

It appears to be a problem with the grounding bus that turns on the PS cards

Anyone run into a similar problem?
 
Larry the radio guy said:
I've got a Broadcast Electronics 10 kw be 10a

Got hit by lightening a few months back. Replaced the controller card and power supply cards.

If I place two power supply cards in the unit I can get 1kw out tops.
Anyone run into a similar problem?
Click to expand...

You've been running this rig at 1KW for several months? Why did you replace the controller card and power supplies? Were they killed with the lighting strike? If you run one power supply only, can you get more than 1KW? I'm not BE Tech support, nor is anyone here, but it sounds like there is a shorted bypass capacitor or zener diode tied across your +PS buss. These may be on the PS back plane. By your description, it sounds like when you plug in both power supplies they crowbar with no isolation from each other. The hint is your B+ drops to 8V. I recommend pulling out the schematic and checking the diodes and bypass caps tied across the power supply back plane with both supplies out. If you still don't find anything wrong, time to call BE support to walk you through how to troubleshoot.
 
Thanks for the reply, did all that, had former BE engineer down for 6-8 hours couldn't find problem either. yes. both controller and PS cards were fried. Schematic shows all PS cards are turned on by a buss that has no isolation between cards. Also, swapped cards back and forth what ever landed in slots one and two worked fine. Tech says number of PS modules does not equate into linear increase in power. My other 1kw be runs with only one PS board. Go figure.
 
Larry the radio guy said:
Tech says number of PS modules does not equate into linear increase in power. My other 1kw be runs with only one PS board. Go figure.
Click to expand...

That's true. I have a 5E that only makes about 1300 watts with 2 of 4 modules. Found that out when I lost one of those $900 power supply cards.

It would make sense to me that half of the modules' power would go to a reject load, though BE says the nature of the star combiner in their transmitters eliminates the need for one.

I have a couple of Ampfet transmitters that do the same. Something about how the combiner works, though I've never looked into what that formula is. I'd bet someone here probably knows though.
 
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