acoostix
commented
1 year ago Closing this with the fix I found:
By grounding the casing of the tapehead back to the case PSU groundrail, problem was fixed. I also swapped out the TL072 - I'm not sure switching ICs would have made a difference, though, as the TL072 that came with the kit works perfectly in another circuit.
Hopefully this helps someone!
I've received and built a Magnetophon kit from Thonk. PCB v1.1
I fully traced out all components against the schematic found on this git - while some components are not present on the board, the components that are are connected are connected correctly. Good solders. TL072 is mounted correctly, electronlytic caps are mounted correctly.
I can confirm that the TL072 is reading 24 volts at its VCC pin.
When the module is plugged in to my Intelligel performer 104 withcable coming out of case (to have module as far away as possible from other modules) I get no sound off of the tape head. Only a loud intermittent buzz based on handling. It sounds distorted and a bit lower than a mains hum.
I see that the schematic says - install C7 if the circuit doesn't work: This doesn't make a difference in my case.
Plugging in my wand gives the same results.
Is it possible that the tape head needs chassis grounding? Most tape heads are mounted to a chassis, but as far as I can tell - this one is "floating" in the IC socket- no screws holding it to the case of a reel-reel tape deck etc.
I did try googling, but perhaps I've missed something ;P