Harbach mods schematics

[Stewart D. Lyon]

Harbach has three mods for the SB-200.
1st was the power supply mod which replaces the original power supply PCB
and has modern capacitors and diodes and a better engineered voltage divider
string.
The 2nd mod (which was sold with the pwr PCB) was the "Soft Start" module.
This module has two relays on it and is mounted on the relay case by silicon
putty. It put two power resistor in series with the AC line for a couple of
seconds to inhibt the inrush current when charging the PS capacitors.

The 3rd was called a "Soft Key" and buffered the keying line so that modern
transceivers could key the amplifier. It uses an optical coupler to turn on
a power transistor which keys the antenna relay and reduces the bias to the
tubes. The transceiver is only required to handle the opto's input LED which
is about 1.5 Volts at ~2mA. This unit is a small board which mounts with a
single screw (I used a 3M mounting pad).

None of these things make a bang --you can barely hear the relays click. As
I remember, the boards came assembled and the instructions were very clear
on how to install them. Must be some other mod in there.

73, Stu, W6CUX

----- Original Message -----
From: "Mark E Schmidt" <roadwarrior at TECHIE.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Wednesday, January 24, 2001 1:16 PM
Subject: Harbach mods schematics


> Ladies, Gentlemen, and fellow GriefKit lovers,
>
> Just kidding, I've had very little grief over my 35 some odd years of
> building, fixing and using them.
>
> Now, however, I'm at loggerheads. I bought an SB-200 and when I turned it
on
> it went BANG! Trouble is there's a bunch of mods in there so it doesn't
look
> like the schematics and diagrams in the original manual. I understand
these
> mods are 'Harbach' mods. I see from the Harbach website that due to
illness
> the amp mods are 'off-line'.
>
> Now I do NOT want to bother the person! So I spent today all over the rest
> of the web, and searched this listserv database for another source of
prints
> for these mods. Any help here. I am, of course, willing to pay for the
> information.
>
> TIA es 73 de Mark KB8GC (ex WB8CKZ)
> mailto://roadwarrior@techie.com
>
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