I recently repaired this exact problem on a TR-7 that I have here.
When I changed bands with the band switch, it would stay on the previous
band. If I switched the AUX switch to 1 and back, it would change to the
band selected by the band switch. I did not have an AUX-7 installed.
My problem was a chip U9002 on the DR-7 board. This is a quad NAND gate,
14011.
This chip is the second one back from the front of the radio, on the
left side of the DR-7 board.
There are two inputs to this NAND gate.
* Pin 1 comes from the special wire that goes from the DR-7 over to the
band switch. When you turn the band switch it sends a short pulse to pin
1 causing the frequency select to switch.
* Pin 2 comes from the NORM/AUX switch. It sends a pulse signal when it
switches AUX positions causing the frequency to switch.
In my case, I was able to look at the pins with an oscilloscope and see
that I was getting a good pulse input at both pins. But pin 1 would not
always send a pulse out pin 3.
I changed out U9002 and everything is working normally now.
There is one other easy cause for this problem. That special wire that
runs separately from the DR-7 across the top to the band switch may come
unplugged. When it does, the band change pulse will not reach the DR-7.
73 Ernie W8EH
On 11/7/2010 9:31 AM, Ron wrote:
All,
I have e-mailed Demis, and the problem is:
When the BAND switch is rotated, the rig does not move bands. Then if you move
the AUX switch from normal to 1 and back the rig then changes bands. This is
occurring on all bands.
For example:
Currently on 80 meters, and use the BAND switch to go to 40 meters.
The radio stays on 80 meters.
Next move the AUX switch from normal to 1 and back.
Now radio moves to 40 meters.
I have never studied the TR7 logic closely, so I am only guessing. It is as if
the radio has set the BCD counter, but not issued a store to the
counter/divider of the PLL/VCO chain. Then when the AUX switch comes back to
the normal position it issues the store.
Demis, do you have an AUX-7 board installed in your radio? That might make a
difference.
73,
Ron WD8SBB
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