The JFET I use is 2sk170, but it needs to be powered up for 5 minutes before it can start working. I can't find the reason, I have tried many times. If an oscilloscope and a signal generator are used to measure the intact waveform, the bias voltage is 9V, and after a period of use, it will no longer work.
The following is the chart I used the software to measure in the relatively quiet room. Please help me, thank you


gyraf

..could be contamination on the PCB, maybe? Have you tried cleaning well, specially in the high-impedance area around the input?

..Hum in a microphone, if that is the problem, can ONLY come from two sources, both are really external: Poor shielding or Poor phantom power.

Jakob E.
..note to self: don't let Harman run your company..

..could be contamination on the PCB, maybe? Have you tried cleaning well, specially in the high-impedance area around the input?

..Hum in a microphone, if that is the problem, can ONLY come from two sources, both are really external: Poor shielding or Poor phantom power.

Jakob E.
Thank you for your answer.

I will try to clean it again, but the microphone will not work within five-fifths of every time I use it. I measure the bias voltage of JFET only about 2V. After five minutes, it will rise to the working voltage, about 11V, and the microphone will work.

mhelin

Faulty cap, or incorrect component values like too large resistor => too long RC time constant.
Mikko


 

Related Topics

  Subject / Started by Replies Last post
33 Replies
13790 Views
Last post May 26, 2010, 03:30:08 AM
by Kingston
3 Replies
1190 Views
Last post November 20, 2008, 04:33:39 PM
by Ptownkid
10 Replies
2691 Views
Last post June 17, 2018, 02:39:48 PM
by chefducuisine
4 Replies
472 Views
Last post June 22, 2018, 12:53:30 PM
by RuudNL