You have received some good advice, at least what I see that made it to the
Yes, there was a period where voodo science raised its head for awhile on
I would suggest two modifications however to include in your rebuild. That
is to remove RFC2 and replace it with a 10-15 Ohm 20-25 W vitreous enamel
wire wound resistor. That is to limit HV surges thru the tube due to a gas
arc; the type of resistor is important.
The other change is to place a pair of diodes across the multimeter (the
right hand one) terminals; they are to be connected in parallel and opposite
polarity. These will help save the rather unobtanium meter if it happens to
be on the grid position when an arc event happens. The diodes can be in the
1N4004 to 1N4007 range.
----- Original Message -----
From: "Jeff Carter" <firstname.lastname@example.org>
Sent: Thursday, March 27, 2008 11:05 PM
Subject: Re: [Amps] Retraction with regard to the SB220
> Well, I probably would, except the decision was already made for me by
> the previous owner(s). They're already in pieces. I have purposely
> acquired guaranteed non-working units, precisely because I wanted to
> go through and touch every single thing and understand fully what it
> did and why. If something inside it doesn't work, I'll buy another
> one NOS or fabricate one myself if I can. There's not *that* much to
> these, there can't be.
> When I get them working again, I will most likely lose interest in
> them if my usual pattern holds. I got into Amateur Radio back in 1992
> because I wanted to learn things and have access to the spectrum for
> experimentation. I almost never actually talk to anybody except on
> vacations or other special occasions, but I listen to 75m a good bit
> when mobile at night. I've got QSL cards enough for WAS but I've
> never submitted them. I was fascinated with the concept of working
> all the US States barefoot on a doublet antenna, but once I got there,
> I was done.
> Back to amps: Do you think there's something to be said for not
> worrying about improvements, but just going through the build manual
> and putting them back "stock", so to speak? It might be interesting
> to put at least one of them back in strict accordance with the old
> instructions, just to see what I end up with...and potentially a lot
> of fun to consider that I'm constructing a Heathkit, something most
> people around now never got to do.
> It's all in fun. When I get them working and they're no longer of any
> interest, I'm told they make great boat anchors.
> Thanks for the reply!
> ---- Original message ----
>>Date: Thu, 27 Mar 2008 22:37:03 -0400
>>From: Robert Morris <email@example.com>
>>Subject: Re: [Amps] Retraction with regard to the SB220
>>To: Jeff Carter <firstname.lastname@example.org>
>>Try one rule...if it works, don't fix it. Try them before you rip them
>>apart. When you get them back together and they don't work, was it
>>before or after? There are hundreds of SB220's on the air that don't
>>know they need to be "improved". Run them for a while, learn how they
>>work, stock, read stuff, then decide if they need anything. Do one at a
>>time, leaving one to look at.
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