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Re: [Amps] Heath SB-220 Soft Start

To: amps@contesting.com
Subject: Re: [Amps] Heath SB-220 Soft Start
From: Alek Petkovic via Amps <amps@contesting.com>
Reply-to: Alek Petkovic <vk6apk@bigpond.com>
Date: Sat, 5 Oct 2024 06:42:30 +0800
List-post: <mailto:amps@contesting.com>
Another thing.

The resistor/s burnt because of a heavy load downstream, like shorted diodes, capacitors, tubes or even transformers. This increased load prevented the voltage building up to the point where the relay operates properly, resulting in the aforementioned damage.

Check every part of your amplifier after you have replaced your soft start and before switching your amplifier on.

73, Alek VK6APK.

On 5/10/2024 1:58 am, Geert Jan de Groot via Amps wrote:

In addition to what has been said already (all true and correct), Jim W7RY also used to sell softstart boards, the difference being that on his boards, the "resistor leg" of the boards have fuses in them.

If a relay fails to activate, then, while the current flows through the resistor, the fuse will open if that takes too long.

If you are worried about this failure scenario (I think it is rare and just replacing relays / resistors is enough) then you may want to ask Jim if he stilll has some left. He used to sell on ebay but he moved and I don't see him advertize.

One more comment: note that the resistance value is different for 110 and 220 volts. Order the right resistor value!

73, Geert Jan PE1HZG


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