Howdy, Stranger!
It looks like you're new here. If you want to get involved, click one of these buttons!
Penrose continuity between -12V and +12V a problem?
I built a penrose last week, and did the continuity test between power pins prior to powering it up.
After checking the board visually for shorts/incorrect parts and not finding anything obvious I pulled the IC's and plugged it into a power supply.
I got the continuity beep from the multi when probing the -12V and +12V pins, in one direction I get a continuous beep, in the other I get a short beep then nothing.
I gather the short beep suggests a capacitor is charging up then no longer conducting, and the continuous beep would indicate a short
After checking the board visually for shorts/incorrect parts and not finding anything obvious I pulled the IC's and plugged it into a power supply.
I measured +5V, +12V and -12V at the appropriate locations, suggesting that it's ok, I continued on and added the IC's and then connected both pcb's together, and powered up no worries.
I initially wasn't able to tune it. Turned out to be to a dud 10K trimmer, I swapped that out, and now have a fully functional tuned module.
Is this a concern? I didn't measure the actual resistance between power pins, just relied on the beep.
Comments
The short beep you hear is due to the capacitors charging.
In the other direction the long beep is due to the protection diodes.
They short out the power rails to GND if connected backwards.
With a real PSU connected the Polyfuses will trigger and disconnect the module, but the multimeter has not enough current to do this, so you measure a constant short.