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Author Topic: Ameritron ALS-600 PS voltage ?  (Read 1481 times)
W4PM
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Posts: 11




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« on: July 11, 2006, 02:35:27 PM »

I recently bought a used ALS-600 amp with the old linear supply.  The power supply transformer tap had been changed to the medium voltage (no buck or boost) and I measured 64.0 volts from the PS with no load.  Changing the tap to the normal buck position (I have a 125 volt line) the voltage decreased to 60.3.  Ameritron had a mod (a parallel capacitor for the filter choke) which had been removed.  After installing that, the PS voltage dropped to 58.4 volts.  Doesn't that still seems a bit high for the MRF-150's which should be run at 48 to 50 volts?

Could other ALS-600 owners advise me what voltage they get from their power supplies with no load.  Does the voltage drop down to 50 volts or less under load. Even if it does I'd still be putting over 58 volts on the finals when in standby. Is that OK?

I don't want to smoke the FET's and have not yet fired up the amp until I can be assured this high, no load, voltage will not be a problem. Perhaps the best bet would be to build an outboard regulator with a zener and some 3055 pass transistors?    
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AD5X
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Posts: 1437




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« Reply #1 on: July 11, 2006, 02:58:50 PM »

The ALS-600 manual states that the output voltage of the linear power supply should be kept below 65VDC at no load for maximum component life, and to adjust the input voltage selector if necessary to keep it below this.

Phil - AD5X
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WD8PTB
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Posts: 670




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« Reply #2 on: July 12, 2006, 12:22:55 PM »

As soon as you draw a load on an unregulated power supply the output voltage will drop considerably. I would go by the manual; If it's not to high go ahead and use it. A regulator would have to be capable of the maximum current (20 amps?) and would not make any significant difference in the transmitted signal. Don WD8PTB
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