EMRFD Message Archive 13237
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.
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?
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