Message	Date	From	Subject
13237	2016-10-31 17:34:56	wb8yyy_curt	HYCAS behaving strange
I am back to debugging the HYCAS, built on the through-hole version of the board, and built to the proper list of parts. But I am getting some strange behavior. The amp seems to work with the AGC turned off. With the AGC on, I get only about 0,3 volts difference between no input and a large signal input. I have some strange bias voltages: I did adjust the regulator for 9 volts out, but it required a 1446 ohm resistance on the middle pin to get there. Strange I am getting around 10 volts on each collector (yes higher than the 9 volt regulated voltage) and around 2.6 volts on each drain, The AGC voltage with no input is 3,3 volts. I did check the diode stack - it has 2 volts on it, which may be just a little high. Suggestions on how to debug this thing are appreciated. 73 Curt
13238	2016-10-31 23:25:34	Dana Myers	Re: HYCAS behaving strange

13239	2016-11-01 00:03:52	kg4rll	Re: HYCAS behaving strange
Hi Curt, Could be oscillating, maybe. Also , does the if gain control function with the AGC on and with it off? And is the amp input being driven with a 50 ohm source? Scott kg4rll
13240	2016-11-01 09:25:34	vasilyivanenko	Re: HYCAS behaving strange
A few builders suffered from the hycas IF amp working as a HF oscillator. Especially if the front end matching network sports a high Q inductor. See my thread 12329 RE: [emrfd] Re: Hycas-Cascode amp Cheers V/T

I am back to debugging the HYCAS, built on the through-hole version of the board, and built to the proper list of parts. But I am getting some strange behavior.

The amp seems to work with the AGC turned off. With the AGC on, I get only about 0,3 volts difference between no input and a large signal input.

I have some strange bias voltages:

I did adjust the regulator for 9 volts out, but it required a 1446 ohm resistance on the middle pin to get there.

Strange I am getting around 10 volts on each collector (yes higher than the 9 volt regulated voltage) and around 2.6 volts on each drain, The AGC voltage with no input is 3,3 volts.

I did check the diode stack - it has 2 volts on it, which may be just a little high.

Suggestions on how to debug this thing are appreciated.

73 Curt

12329 RE: [emrfd] Re: Hycas-Cascode amp