[Heathkit] re off topic i think

Sun, 29 Feb 2004 10:36:56 -0600

The good ol' Eico 720 xmtr used the 5AR4 as well but for a different reason.
The 5AR4 is high enough power, but still short enough to fit in the low
profile cabinet.  5U4 wouldn't fit!

73,
Tom----- Original Message ----- 
From: "Murray Grandy" <[email protected]>
To: "heathkit list" <[email protected]>
Sent: Sunday, February 29, 2004 10:31 AM
Subject: [Heathkit] re off topic i think

> It's amazing what you miss when you're trying to go the cheep route. Of
> course I am aware of these differences and they make sense. Just didn't
> think. Guess that is why 5AR4's sell for several times the cost of 5U4's
and
> other similar rectifiers. I was going to use the 5AS4 in a Dynaco ST-70.
> Guess I will look for the real thing. Thanks to all for the great info.
> Murray
>
****************************************************************************
> ***********
> The 5ar4 cathode is indirectly heated - meaning it takes 15-30 seconds to
> start working - the 5as4 filament is the cathode - heating up in a few
> seconds.  5ar4 is a good idea as the other tubes in the piece of equipment
> have warmed up and will be ready to draw current when the rectifier warms
> up.  The prevents the high voltage from attempting to rise to a much
higher
> value as it would with a directly heated rectifier or solid state diode -
> therefore stressing the filter condencers until the other tubes have
warmed
> up sufficently to draw current.
>
> Regards,
>
> Bill Riches, WA2DVU
> Cape May, NJ
>
>
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