[Boatanchors] Drake TR-7 Xmit Question

[Garey Barrell]

Bill -

The "drifting upward" count indicates that the VCO's in the TR-7 have 
lost lock.  There are two different VCO's, hence the two different 
frequencies read depending upon band selected.  When the VCOs are 
unlocked, the transmit is inhibited.

First, ensure that the front panel pushbuttons are set correctly, 
particularly the FIXED VFO and RCT buttons, which must be "out".

IF these are set correctly and the AUX PROGRAM knob is set to NORM, then 
you may have a power supply problem.  The +13.8V from the PS-7 should 
not change when you key the transmitter.  There are three voltages to 
check on the bottom of the Parent board.  These are +10v, +10R and 
+10T.  They are identified by lettering near the traces, which run the 
length (front to back) of the board.  The +10 should be very close to 
10.000 VDC, the +10R should be about 9.7V in receive and near 0 VDC in 
transmit.  In Receive, these two voltages will reverse.

Let us know what you find!

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>



w0ng at comcast.net wrote:
> I'd appreciate some help identifying the cause of an all-of-a-sudden problem with my Drake TR-7 (serial 66xx). The rig was, up until this morning, working fine...no issues. 
>
> Now when I key the transmitter there is no measurable rf output (regardless of mode selected or setting of carrier control) and the digital display immediately counts upward to around 17+Mhz or 33Mhz depending on what band is selected. Un key the xmtr and receive is still fine. 
>
> Front panel controls are set correctly. Using a dummy load instead of an antenna made no difference. I also noticed the meter backlight flickering when I try to insert a bit of carrier upon key-up. (???)
>
> Before I take it out of the case and start looking, does anyone have a suggestion as to why it started doing this? I don't have a lot of digital experience. Still stuck in an analog/tube world, hi. Thanks a lot. Bill, w0ng 
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