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Re: [Amps] ALPHAs and momentary power outages

To: "'Tom W8JI'" <>,"'Jim Brown'" <>, <>
Subject: Re: [Amps] ALPHAs and momentary power outages
From: "Dick Green WC1M" <>
Date: Wed, 18 Jul 2007 13:35:09 -0400
List-post: <>
W8JI wrote:

> My bet is the timer has a reset line or line that monitors
> power down. It may even just be when the power to the
> microprocessor is removed, the CPU restarts.

It's the latter.
> The simplest approach would be to fool the system into not
> knowing the power ever went down. You could do that with a
> battery and R/C timer, a large electrolytic and a few
> diodes, or any other number of ways.

The microprocessor runs off it's own 110VAC transformer and power supply,
independent of the main transformer and HV/LV supplies for the amp. It would
be relatively easy to reroute the microprocessor transformer input to an
inexpensive low power UPS, or use one of the short-duration methods you
describe. However...

> Maintaining the entire power line and HV supply is probably
> not even necessary. 

Unfortunately, I don't so. The microprocessor continuously monitors all
supply voltages. If they differ significantly from nominal values, the
microprocessor will hard fault the amp. That means it will cut off AC to the
main transformer. and go into power-off standby mode. When the power switch
is cycled, the microprocessor will restart and go through the 3-minute
warmup cycle.

The only way to fool the microprocessor is to maintain all normal running
conditions, which means the HV and LV supplies have to maintained at nominal
output values. That means using a massive 220VAC UPS, or modifying one to
switch out very fast on transmit. Again, I'd call Alpha about the timer
value address before undertaking a project like that!

73, Dick WC1M

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