[Elecraft] KPA 500 voltage drop on key down

[Ron D'Eau Claire]

Matt, refer to your Owner's manual section, "Power Supply Transformer Tap"
starting in page 8 to set the transformer tap.

Your goal is for a voltage of 85V maximum "key up" as described in the text.
You can't hurt the amp. If the voltage goes too high, the power supply will
fault and shut down automatically. 

The KPA500 does heavily load a 115 VAC circuit. Most of the drop is likely
between your breaker panel and the outlet and, of course, the further from
the breaker panel you are the more drop you'll experience. One key point of
loss is a bad wall outlet. The spring contacts in the outlet can grow weak
over time and not make good contact. Be sure the wall plug fits snugly and
does not come out easily. 

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Matt
Murphy
Sent: Friday, November 20, 2015 7:46 AM
To: Elecraft Reflector
Subject: [Elecraft] KPA 500 voltage drop on key down

I just set up my KPA 500 and the HV on standby is 72.5 volts.  On key down,
however, it drops to 48 volts and the lights in the shack noticeably flicker
a bit.

Would changing a the tap on the transformer potentially help things? Or is
the real issue the voltage drop between the pole and the wall socket?

Suggestions/ideas would be much appreciated, as well as tips for debugging
any issues with the household wiring.

Per the KPA 500 manual, the amp may fault if the voltage under load gets
below 60VDC, so running in it with reduced drive may be necessary. While
doing that wouldn't be the end of the world, I'd like to address the root
cause if possible.

73,
Matt NQ6N
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