I love that R7............that's while I still have mine. I did repair the
power supply on my friend's unit. The 24 volt supply has two iterations. The
early version uses a pair of TIP31s in a multivibrator configuration, is
rectified by a quad of 1N4148s, and regulated by a 78L24 regulator.
Later versions used what appears to be some kind of sine wave oscillator
that uses a TDA2002 audio amp chip. Everything else is the same, except an
LM317Z regulator is used for the 24 volt regulator.
The problem with the power supply on this unit was two bad electrolytic
coupling caps in the TDA2002 circuit. One of them is a 22uF unit whild the
other one is a 10uF unit. Replacing both of the caps solved the problem.
This is still one more problem with the unit.............the high band VCO
doesn't lock unless you are in the 28MHz range. This tells me that the
connection from the phase detector to the VCO is ok, as evidenced by the
tuning voltage being stuck high.
This also tells me that there is a break in the feedback loop between the
VCO output and the 1/N chain that feeds the input of the phase detector. I
will dig into that later...........................

Pete

"Me" wrote in message
...
On Sat, 1 Mar 2008 07:47:42 -0600, "Pete KE9OA"
wrote:

I think you are right. The only receiver that I ever had that runs hotter
than the R7 is my old HF-2050. Now, that was hot!
I do have an R7 myself that I upgraded with better performance mixer,
replaced the displays, etc.
I keep it as a museum piece, along with my other Drake equipment.

Pete


IMO, a properly working R7A still beats everything this side of a
Ten-Tec RX340.


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