Hi everyone,
Just a note to the list.
As I have posted previously, I ran into a problem in the alignment of a newly
acquired TR-7. Alignment began just fine until I got to the VCO. At that
point I could not get the required 15v and 16v on the 14mhz and 28.5mhz bands
I was about 1-1.5v short on each one. Since the service manual says +/- 0.5v,
I took the question to the Sunday Drake net to get input on just how close
these settings need to be. With advice from Jeff Covelli, I checked all power
supply voltages aside from the 10v line. I found my negative 5 volt line about
a volt short (-3.97), and the 24-25v line, was only 23v.
Apparently 23v is not enough to allow the VCO to function properly. In order
to troubleshoot the cause/effect, I simply popped in another available power
supply board, and began alignment anew. This time, after setting the 10v line,
I also checked out put on the -5v, 25v traces on the main board. I found 24V
exactly and -5v exactly on these traces. Going back through alignment to the
VCO, I was now able to set both slugs to exactly 15V and 16V respectively...and
this time with relative ease.
The remainder of alignment went well.
I was surprized to see how critical the power supply output is to alignment. I
would have assumed 23v and a -4v was adequate, however it is not. We
live....we learn !!
Suggest anyone doing or attempting alignment of a TR-7, check all voltage
traces from the power supply after setting the +10v pot to exactly 10v, BEFORE
going any further in the alignment process.
The exact problem with the first board was not determined. I'll save that for
a later day.
Thanks,
David
Wd9cmd
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