"Bill Carpenter" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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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
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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
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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
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