Super Drive 70’s Build Questions

[Steve]

Putting the finishing touches to a Super Drive 70’s and I have 2 questions.
First, I can’t bias the Q3 to the recommended 5.2 volts. I am using a 3k trim pot and voltage goes from a low of 1.5v to a high of 3.5v. Voltage on the Collector and Emitter are the same and the Base voltage is 4.0v. Switching the transistors around did not fix the problem either. Q5 biased perfectly at 4.5v. Suggestions??

Second question pertains to the +9v pads on the PCB. There appears to be 2 pads to connect +9v (see photo). The lower pad is not connected to the +9v circuit. I know this because I connected the +9v at that pad and I couldn’t find 9v anywhere on the board except for that pad. Is that an error or am I missing something?

Thanks, in advance.
Steve

[Barry]

It appears there is a break in the trace between the (2) 9 volt pads. Not normal but problem there is solved by using the one that is connected.

As for the voltage at 3.5v that should work but I were you I would re-flow and double check all resistor values against the build doc image. I just checked against my board and I am able to do 4.5v which is standard.

Does the Gain section of the SD70’s sound good? If so it likely isn’t an issue. Other than that do my suggestions above.

[Steve]

I haven’t plugged it in yet (wife is asleep lol!) just probed it to make sure everything was working correctly. I’ll take it for a test drive in the morning and  if there are any issues I can’t live with I’ll re-flow after checking the resistor values. Thanks!

[Author]

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