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Re: [Amps] Alpha 87A Power Supply Question

To: 'Amps group' <amps@contesting.com>
Subject: Re: [Amps] Alpha 87A Power Supply Question
From: Adrian <vk4tux@gmail.com>
Date: Fri, 7 May 2021 09:34:25 +1000
List-post: <mailto:amps@contesting.com>
It is dangerous, additional to my earlier post connecting neutral to chassis and wiring 120v returns to same terminal, if the neutral connection opens anywhere from within the amp back to the supply, then you have 120v on the amp chassis at turn on, waiting for you to grab.

Usually, it takes about 30 mA of current to cause respiratory paralysis. Currents greater than 75 mA cause ventricular fibrillation (very rapid, ineffective heartbeat).


vk4tux




On 6/5/21 5:03 pm, gudguyham via Amps wrote:
Some of the old Henry amps actually require a neutral to be present when using the amp on 240v.  On 120v it makes no difference because if you have two wires, hot and neutral (120v) the neutral is available.  When switching to 240vac if you lack the neutral, they instruct you to use ground to carry the fan, and low voltage transformer neutrals.  This practice is NOT good and could be dangerous.  The neutral that is required is hooked up to a separate terminal at the rear of the amp, this is the neutral being sought out by the fan and LV transformer.  The simple fix which satisfies all conditions is to NOT use ground( the green wire) to this terminal as a neutral, but rather use a jumper wire at the two terminals that series up the dual primary to that terminal.  By doing this there is no need for an external neutral and the green wire can be used as chassis ground as intended.



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