Date: Wed, 11 Sep 2013 18:37:25 -0700
From: Richard Solomon <dickw1ksz@gmail.com>
To: "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Clipperton-L question
I actually had to check the schematic ... I couldn't believe they switch
the
HV side of the Xfmr, but they do.
That's a terrible design.
73, Dick, W1KSZ
## No its not. Alpha did the same for years..at least a long tine ago on their
smaller desk top amps. They used an OPTIONAL $80.00 spdt vac relay
to do the job. Of course nobody bought the optional vac relay...and just
wired it
permanently in the SSB-higher B+ position.
## The real trick is that when you switch from CW to SSB, your typ step start
circuit
is non-functional..and u get one helluva surge. On my HB B+ supply, with the
253 lb
Dahl xfmr, I use a multi-tech industries model 88 switch, 13 kv rated, to
change the various HV sec taps.
Even then, I have to 1st shut off the 240 vac primary, then change the sec
taps, then turn the B+ supply
back on. Then it goes through its normal step start sequence.
## Now if going from a higher B+ to a lower B+... there is no need to shut
off the supply. I have loads
of sec taps on the big dahl xfmr...and all that is required is to grab ANY two
sec taps. IE: Its tapped at
0-2300-3900-4800-5200 vac. Since I don’t have a 2900 tap... what I do is use
the 5200 + 2300 taps.
5200-2300 = 2900 vac. Problem solved. To pull that off I used a 2nd model
88 switch. On switch
is wired to half the sec taps...and the 2nd switch is wired to the other half
of the sec taps.
## On my other HB B+ supply, that uses a 10 kva, 4800 vac pole pig xfmr...
I used a
DPDT relay....with all contacts in parallel, to handle more current.... to
toggle between
one hot leg of the 240 line...and neutral. That way I can stuff either 120
OR 240 vac into the
240 vac primary. That results in either the full 6800 vdc... or 3400 vdc.
## To get around the step start issue, I used a SPDT- CENTER OFF type of
toggle switch to
switch back and forth between 6800-3400 and 3400-6800. When passing through
the CENTER OFF
middle position of the SPDT toggle, the step start timer drops out, and also
the big relay that
does the actual shunting of the step start resistors. That way, whether it
switchs from low to high,
or from\high to low, the step start circuit always does its thing. I used the
spare set of contacts
on the dpdt 0-15 sec timer module, to run the amp key line in and out of.
That way, during the 15 sec
step start sequence, the amp cant be keyed.
Later... Jim VE7RF
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