Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Bill -
I think the only source for a replacement today would be a junker. The
AC switches are still available from John Kriner, but I doubt if the
pots are. It is just a dual 500k pot, and that's one style that is at
least still available. I honestly don't know if both sections are audio
(log) taper or not. I kinda think they are.
The idea for the alignment is to just detune the "other" side of the
transformer while you tune "this" side. So hanging a clip lead would
work just as well. They DO have +250 VDC on them! Be sure and keep the
plate current low, as if it's too high it makes the peak hard to see.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Bill Carpenter wrote:
"Bill Carpenter" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
Thanks Gary, I'll take a look at R79. If it's bad is there a
replacement available? Also while I have the cover off I want to run
through an alignment. Is there a better way then the procedure in the
manual which has you use a screwdriver to detune the rig? If not
would attaching a clip-on test lead work as well as a screwdriver? I
can just see myself accidentally grounding something and causing all
kinds of smoke and flame.
----- Original Message ----- From: "Garey Barrell" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Saturday, January 19, 2008 10:04 AM
Subject: Re: [drakelist] T4-XB problem
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the
drakelist gang
----------------------------------------------------------------------
Bill -
The CW Gain is a separate section on the GAIN control, R79, along
with R76, 77 and 80 form an adjustable DC voltage divider from the
+150V regulated supply. The resultant voltage is applied to the
balanced modulator to unbalance it and allow the Carrier Oscillator
signal to pass through. The frequency of the Carrier Oscillator is
also shifted by ~ 900 Hz to allow it to pass through the LSB filter.
What you are describing sounds like an open R79 resistance element.
It's possible that it's just a bit of crud on the element so a shot
of Caig MCL CaiLube or other control cleaner might clear it.
You can measure the control voltage at the center conductor of the
shielded wire going to T14, just in front of the VOX Delay pot. It
should start at 0 and come up as you increase the GAIN control (in CW
MODE only) to about 1 VDC. There are two forward biased Ge point
contact diodes in series to ground from that point, which will limit
the voltage, although the current will continue to increase as you
turn up the GAIN control. I'd guess you are going to see 0 V at
minimum GAIN, jumping to ~1V when you get to ~9 o'clock on the
control. But I've been wrong before! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Bill Carpenter wrote:
"Bill Carpenter" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
----------------------------------------------------------------------
I installed the AC4R upgrade in my AC4 this week which is a very
nice kit. The T4-XB seems to love it and was working extremely
well. I spent a couple of hours on 160 SSB last night and made a
few CW contacts with no problems on other bands. This morning when
I was tuning the transmitter on 80 I noticed that in CW mode that
the gain control suddenly had no effect on power out. It goes from
no power to full power as the control is advanced at about 9 o'clock
very suddenly. There is no gradual increase as there should be. In
tune and SSB mode it still works fine with the normal gradual
increase. Any ideas on how to begin trouble shooting this? I don't
see any obvious burned components - at least not yet. I'm hoping
it's a tube and not some hard to find component!
73,
Bill NZ0T
----------------------------------------------------------------------
Submissions: [EMAIL PROTECTED]
Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body
Hopelessly Lost: [EMAIL PROTECTED] - help in body of message
Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net
----------------------------------------------------------------------
