[Drake] TR-4 question - solved

[Jerry Kincade]

Call off the dogs, and thanks for all the suggestions. As most suspected, it
turned out to be a neutralization problem after all. Found the neut cap
fully meshed - don't see that too often - cranked it out to 45 degrees for a
starting point (tip of the hat to Dave Harmon, K6XYZ), and started
neutralizing on 20m vice 10m. She came in pretty as you please at about 15%
meshed. Also checked all three PA cathode resistors (supposed to be 15 ohm
1W, 5%), they ran from 16.8 to 22 ohms. Hmmm... 5% would be +/- 0.75 ohms.
Ha. Will change them out with 2 watters (do they have to be carbon or can I
get away with "flameproof" metal film?) of correct value, then neutralize
again, then follow with a full and complete alignment from ground zero. This
should be a sweet little transceiver when I'm done, Drake sure built a nice
little rig for the money. Anyway, it's looking very promising, and thanks
for the help, guys.
73, Jerry W5KP

----- Original Message ----- 
From: "Jerry Kincade" <w5kp at direcway.com>
To: <Drake at mailman.qth.net>
Sent: Monday, June 07, 2004 5:02 PM
Subject: [Drake] TR-4 question


> I have a new (to me) nice looking TR-4 on the bench, checking it out.
> Haven't messed with Drakes for years, last one was an old beat up TR-3
years
> ago, so I am looking for some advice. This one works gangbusters on 80 and
> 40, and receives fair on 20, 15, and 10. However, the finals won't load on
> 20 and above, with all three bands (20, 15,10) giving the same indication,
> namely a nearly uncontrollable peak in plate current where there should be
a
> dip. Things seem normal as I key it and increase Transmit Gain slowly up
> from idle current to get enough Ip to be able to see a dip (with PLATE and
> LOAD controls at zero), but then Ip takes off out of control as soon as I
> tune for a dip, with the Ip peaking at about the point on the plate tuning
> where I would expect to see a dip instead. What really surprised me was
the
> Bird meter shows significant power out (80-100 watts) in consonance with
the
> unwanted Ip peak. This is no nickle-dime problem, Ip will jump to 600 mA
> plus if I let it. Needless to say, I don't leave it long in that
condition.
> :-)
>
>  Also, there is no definite noise peak on receive on the three problem
bands
> when using the RF TUNE control, although receive seems at least fair
> (sensitivity seems a bit weak to me on 20 and above). 80 and 40 have clear
> and definite noise peaks on receive using RF TUNE, with good sensitivity.
My
> first thought was improper neutralization, but per the book to neutralize
it
> you first have to tune up normally on 10, and that is not possible in this
> instance. Besides, neutralization is intended to make max power and
mininum
> plate current occur at the same point, and that doesn't seem to be the
> problem here. I'm thinking I have more wrong here than a simple
> neutralization problem, and am wondering if maybe someone in the past has
> attempted to "align" the transmit chain on 20-15-10, hosing things up.
>
> I also may have a serious parasitic problem, but I fail to see why that
> would occur in exactly the same way on three bands... ??
>
> Next I will likely try the basic book alignment to see if anything has
been
> drastically mistweaked, but first wondered if anybody has any ideas.
Finals
> are new, and work great on 80 and 40, with smooth and clean peaks/dips and
> it easily puts out 140-150 watts at 375-400 mA Ip on those bands, with
clean
> audio out on both USB and LSB.
>
> Any ideas before I wander further into the woods with this thing? This
TR-4
> is not a junker, it's extremely clean inside and out, and appears to have
> been well cared for. No mods are evident, and it does not appear to have
> ever been subjected to a soldering iron.
>
> Any sage advice from experienced Duck experts would be appreciated.
>
> 73, Jerry W5KP
>
>
>
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