Does anyone have the service manual on this model that can post the procedure of calibrating the front dB/watts meters? I’ve done a restoration of one that was given to me. Sounds great. I have zeroed the meters with the set screws on the front, but there is a variable resistor to set the calibration. It is facilitated by a variable resistor. I have attached a schematic. In the schematic the VR is 100K, but mine measure at 25K. Not sure if they changed meters and didn’t update the schematics. Anyways, any insight on how to calibrate the meters is appreciated.
HeathKit AA-1640 meter calibration
- Thread starter Chrisdski
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- heathkit aa-1640
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My AA-1640 Manual has no instructions for calibrating the meters. I suspect that procedure is addressed in the AA-1640 Meter Accessory kit.
What I did was input a 1 KHz signal and set the output for 20 watts. Then adjusted the pot on each board to match.
What I did was input a 1 KHz signal and set the output for 20 watts. Then adjusted the pot on each board to match.
Last edited:
abnormalcat
New Member
I've attached pictures of the relevant calibration pages from my reprinted copy of the assembly book. It requires a diode that I couldn't find, so when I "calibrated" I did it without the test circuit. It didn't blow up my amp, but I won't recommend doing it because if yours does release the magic white smoke I don't want to be that guy that suggested you do something... If someone here knows how the test circuit interacts with the normal meter circuit that'd be cool to know!
