Hi everyone.
I have recently resurrected an old school project of 40 years ago. It's a magnetometer that we never got around to building.
A nearby changing magnetic field is supposed to trigger the relay, which latches on until reset.
I know there are much better designs now, but for nostalgic reasons I'd like to build it in its original form. I've started, but not getting very far...
The circuit uses (unconventionally drawn!) PNP germanium transistors and I have them in my workshop - all tested and working.
TR4 appears to be drawn in error with the collector/emitter reversed. The pick-up coil I'm using at present is an old Post Office 2000Ω solenoid.
I've replaced the 50Ω relay with a 50Ω resistor for test purposes and running it from a 9 volt battery.
The first stage appears to be working more or less like a conventional amp, but that's about all that's happening. At the Darlington pair TR2/3 everything seems to stop! No current flows through the 'relay resistor', even with a volt or so tapped onto C1.
Is there something more seriously wrong with the circuit as drawn?
Thank you.
Nick
I have recently resurrected an old school project of 40 years ago. It's a magnetometer that we never got around to building.
A nearby changing magnetic field is supposed to trigger the relay, which latches on until reset.
I know there are much better designs now, but for nostalgic reasons I'd like to build it in its original form. I've started, but not getting very far...
The circuit uses (unconventionally drawn!) PNP germanium transistors and I have them in my workshop - all tested and working.
TR4 appears to be drawn in error with the collector/emitter reversed. The pick-up coil I'm using at present is an old Post Office 2000Ω solenoid.
I've replaced the 50Ω relay with a 50Ω resistor for test purposes and running it from a 9 volt battery.
The first stage appears to be working more or less like a conventional amp, but that's about all that's happening. At the Darlington pair TR2/3 everything seems to stop! No current flows through the 'relay resistor', even with a volt or so tapped onto C1.
Is there something more seriously wrong with the circuit as drawn?
Thank you.
Nick