06-04-2016, 09:37 PM
Hello,
I've just come across an old HCD Research oscillator - a HCD81 running at 10MHz.
As you'll see from the picture, pretty much everything I need to know is on the label. But with one exception - how to use the Vf input. I presume it'll be a preset between 5V and GND, perhaps with a series resistor, but I'd like confirmation first as it would be a shame to damage it.
The unit works quite well, but the output frequency is a few hundred Hz away from 10MHz, and it doesn't quite settle down - well, not in the 30 or so minutes I've run it for. The lash-up on the bench probably didn't help - just test leads, no decoupling or anything. Leaving Vf open-circuit probably didn't help.
I do have another one of these, running at 8.86MHz (guess where that came from
). That one has a 9V heater voltage - I guess these things were pretty customisable. As I'll never use it, I could open it up and reverse-engineer it, but I'm hoping that someone like Jeffrey will have used these in the past and might still have some data.
Thanks in advance,
Mark
I've just come across an old HCD Research oscillator - a HCD81 running at 10MHz.
As you'll see from the picture, pretty much everything I need to know is on the label. But with one exception - how to use the Vf input. I presume it'll be a preset between 5V and GND, perhaps with a series resistor, but I'd like confirmation first as it would be a shame to damage it.
The unit works quite well, but the output frequency is a few hundred Hz away from 10MHz, and it doesn't quite settle down - well, not in the 30 or so minutes I've run it for. The lash-up on the bench probably didn't help - just test leads, no decoupling or anything. Leaving Vf open-circuit probably didn't help.
I do have another one of these, running at 8.86MHz (guess where that came from
). That one has a 9V heater voltage - I guess these things were pretty customisable. As I'll never use it, I could open it up and reverse-engineer it, but I'm hoping that someone like Jeffrey will have used these in the past and might still have some data.Thanks in advance,
Mark
