No subject

----- Original Message ----- 
From: "William Houghton" <rdrbill at pacbell.net>
To: <rbig at cox.net>; <heathkit at mailman.qth.net>
Sent: Sunday, February 17, 2013 9:51 PM
Subject: Re: [Heathkit] sure will appreciate help on getting straightenedout 
on SB-221


Softkey - the Heathkit SB-200, SB-201, SB-220, and SB-221 all used a 120VDC
relay to key the amplifier. This meant that YOUR transmitter needed to be 
able
to switch a 120VDC signal to ground. This usually was not a problem with 
vintage
tube rigs. Most modern solid state rigs cannot withstand the 120VDC on their
amplifier keying line. You need a circuit which will interface the typically 
low
voltage keying signal from a modern rig to the 120VDC keying input of the
amplifier. The SoftKey circuit installs inside the amplifier and converts it
into a low voltage keying input that should be compatible with just about 
any
solid state rig. Ameritron and others have external boxes that perform the 
same
function.

You could also drive a low voltage low current relay with a solid state rig 
and
have that relay's contacts drive the keying input of the amplifier. This 
does
add more relay switching time


SoftStart - When you first apply power to the high voltage transformer of 
your
amp, and its filter caps are discharged, the transformer sees close to a 
dead
short on the secondary. This results in a very high current in the secondary 
and
even higher current in the primary. A softstart circuit typically has a 
resistor
in series with the primary of the transformer to limit the current. 
Typically
there is also a relay who's contacts are in parallel with the resistor . 
After a
short period of time, the relay closes shorting out the resistor. So when 
you
first power on the HV in your amp, the primary current is limited by the
resistor until the caps have had time to partially charge up. Then the 
resistor
is shorted out allowing full AC line voltage to appear across the primary.

RY-220 is simply a replacement relay for the original Heathkit relay. You 
only
need this if your orignal Heathkit relay is defective.

Does that help to clear things up?

73,

Bill



________________________________
From: "rbig at cox.net" <rbig at cox.net>
To: heathkit at mailman.qth.net
Sent: Sun, February 17, 2013 7:12:08 AM
Subject: [Heathkit] sure will appreciate help on getting straightened out on
SB-221

The guy that sold it to me said I needed a buffer relay. What he says may be
protection for my tranceiver. This guy has an article on what I think I may
need:


http://www.wy6k.com/homebrew_stuff/power_amp_driver.htm

There should be some finished products available for this. Does anyone know 
of
any? I'd really rather buy a finished product that to try and build one.


Harbach has a Soft-key mod they sell (SK-220). I'm not sure if this is like 
the
buffer relay above, or not. I'll get it and put it in.

They also have a Soft-Start mod, which I'll get and put in.

I think this one is not like the buffer relay. I think this is the relay in
cabinet. It's called a Harbach Relay Replacment (RY-220.

Sure will appreciate getting straightened out on all these things.

Also, does the SB-221 have compatability between ALC from TS-430S, FT-101zd,
FT-101ee? Will those be able to have ALC on this amp?

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-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2197 / Virus Database: 2639/5613 - Release Date: 02/18/13