I run a TR7A into an Ameritron ALS-600 amp and on more than on
occasion I have wiped out the FETs because of the leading edge spike.
I have the alc set to 120 watts on 20 meters and on 75 meters it
still only puts out 120 watts constant carrier. But on ssb with a
peak reading wattmeter
such as my Bird 43p when you key the mike and the first say syllable,
the spike can be well over 200 watts. A constant tone will be held to
120 watts.
I also have another TR7A and 2 TR7s and they all act the same. To
solve the problem of taking out the FETs I limit the amp to about 400
watts with the
alc knob on the amp and the amp can catch the spike. I also put back
to back 39 volt 5 watt zener diodes from the gates to ground on the amp because
the max source to gate voltage on the MRF150 is 40 volts. I haven't
blown the amp for over a year now.
73,
Joe KC9LAD.
On Sun, 01 Mar 2009 14:35:30 -0500, Garey Barrell wrote:
>There was a blurb about a "keying" spike when the TR-7 was
>first powered on in the early units, but I didn't think it applied to CW
>or SSB operation.
The power on spike, I think, was related to the VOX circuit. It is
fixable with a mod published by GW4ALG, but only if the parent board
trace cut for allband transmit has not been made. But then, you know
all this. :) I'm restating it for the benefit of newer members who may
have missed those discussions.
73
-Jim
--
Ham Radio NU0C
Lincoln, Nebraska, U.S.S.A.
TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A,
GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time!
"Give a man a URL, and he will learn for an hour; teach him to
Google, and he will learn for a lifetime."
HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/
http://radiojim.exofire.net
http://incolor.inetnebr.com/jshorney
http://www.nebraskaghosts.org
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