06-05-2020, 03:46 PM
Chassis is together and working! 
Thank you everyone who's helped out with advice and ideas. There is still an issue with instability/very touchy on bias (over about 30mA it starts to run away with itself) and at one point the 7N80 FET smoked, but didn't blow. (I have 315mA fuses in circuit as that's the lowest I had in stock)
I do need to address my potential divider side of things as the values are not what I wanted just the closest I had in at the moment (post is verrrry slow!) and hopefully that will rectify the instability problem, but for the moment it's working at a lower bias voltage and doesn't sound too bad at all. Video of the circuit in action here- https://www.youtube.com/watch?v=e5WfigqFGqI
Thanks again to all, Dan
Thank you everyone who's helped out with advice and ideas. There is still an issue with instability/very touchy on bias (over about 30mA it starts to run away with itself) and at one point the 7N80 FET smoked, but didn't blow. (I have 315mA fuses in circuit as that's the lowest I had in stock)I do need to address my potential divider side of things as the values are not what I wanted just the closest I had in at the moment (post is verrrry slow!) and hopefully that will rectify the instability problem, but for the moment it's working at a lower bias voltage and doesn't sound too bad at all. Video of the circuit in action here- https://www.youtube.com/watch?v=e5WfigqFGqI
Thanks again to all, Dan
