[TenTec] Argonaut 505 9 volt regulated spply

[Gary Follett]

Greetings:

I am working on an Argonaut 505.

The 9 MHz BFO is low in frequency,  cannot be pulled in. This resulted in severely reduced output power in CW or Tune since the carrier is now out of the filter passband.

My question is, has anyone actually measured the 9 volt line in one of these?

The line is nominally tagged as “9 volts”, but all of the test points in the manual call out 9.5 volts.

This particular radio measures 8.0 volts on this line, too low, in my estimation, and this could account for the frequency error in the BFO.

The regulator is pretty ingeniously simple and cheap - it actually has error measurement via Q8, whose base is established by the difference between the supply output voltage and the base of Q8. Q8 then controls the pass element, Q7, to hold the “9 volt” line constant.

However, it seems to me that a change in the gain of Q8 would affect the output voltage…

Gary

W0DVN