Date: Sat, 13 Jan 2024 19:55:16 +0000 (UTC)
From: "gudguyham@aol.com" <gudguyham@aol.com>
To: "Ed Swiderski, KU4BP" <ku4bp@triad.rr.com>, <Amps@contesting.com>
Subject: Re: [Amps] QSK5-PC in a AL1200
<FWIW. I've removed more of those boards in Ameritron amps than I
installed. It's not if, but <when you have trouble with it. The diodes are
no longer available and they are so expensive!!
lou
## Alpha went back to a vac relay on all their amps yrs ago. That SS amp
made in the UK also uses a vac relay ( Kilovac HC-1). The HC-1 is cost
prohibitive.
## Having said that, the greenstone / Taylor versions of the jennings RJ1A
/ Kilovac HC1 / Gigavac GH1 have a 30% failure rate, right outa the box...
before being installed into ACOM SS / tube amps. Jay at Array solutions
tells me they have replaced a ton of the oem vac relays ( these are the 70%
that actually tested good) with the gigavac GH1
## Back when Alpha was originally using vac relays (Jennings RJ1A)....
before they switched to pin diodes, Alpha discovered that the Kilovac HC-1
was more robust...and switched to the HC-1
## Jennings is no longer in business. The Gigavac GH1 is the best version
of all of em. The GH-1 will hi-pot test to an easy 7.5 kv..... although
it's stated hi-pot test is 5 kv.
## I modified all 4 of my drake L4B amps with vac relays, 3 in each
amp..... for input / output / bias cutoff. Done that way since they have to
be able to handle max power on bypass mode...since I string the 4 x amps
nose to tail in series, tuned up on either different bands, or ssb / cw on
one band.
## On the L4B, the TR relay setup has to be able to handle max PO on bypass
anyway...to calibrate the oem internal wattmeter. In that case, one amp is
set to exactly 1 kw out cxr..and fed to the L4B under test, with test amp
completely shut off, and of course in standby / bypass mode.
## with rated coil voltage ( u can get the GH1 in either 12 vdc or 26.5
vdc, ditto with the jennings RJ1A...and the 12 / 26.5 vdc coils are
interchangeable and field replaceable / swappable), they typ operate in 2-3
msecs. Sped up, they operate in typ .9 to 1 msec.
## The issue with oem 3PDT open frame TR relays is.... on the L4B, they
have a 17 msec operate time. And 15 msec operate time on the Ameritron
amps. On the newer ameritron amps, they went to a pair of cube relays,
that operate at 5 msecs.
## On open frame relays, unless a TX delay is used, you will hotswitch the
open frame TR relay every time..when you use VOX SSB / semi breakin CW.
## I looked at the pin diode scheme, but they won't handle full power on
bypass mode....so I dumped the idea. Paul, W9AC years ago, worked out a
design, using pin diodes, that would indeed handle max PO on bypass.
## I like dead simple, and 100% reliable..so went the vac relay route.
Even then, I added an external delay, using the TX inhibit on my yaesu
FT-1000MP-MKV and also my yaesu FT-1000D's, to add enough delay on the TX
inhibit lead, to give the vac relays a head start.
## On the MK-V, it has a 0-30 msec delay feature, but that only works on
CW, not ssb.
Jim VE7RF
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