Roff
Well-Known Member
What is your supply voltage? How are you measuring the voltages on pins 6 and 7? A voltmeter will not give results that are very meaningful. Have you probed the circuit with an oscilloscope? If so, what results are you getting on pins 1, 3, 12, and 13 of U2?birdleg said:Hello Ron
We have just spent some time building the circuit you posted up and have so far got no satisfactory results.
the 555 timer part of the circuit is virtually identical to three PCBs we have already made up which give us our frequencies in the right range. The only difference between yours and the ones we have is that pin # 7 is not connected at all on the 555.
When we built the two stage Johnson circuit however there appeared to be some confusing results I was hoping you could maybe clarify.
Pins 6 & 7 on the 555 had a voltage present of around 6V varying up to 6.2V through the 1M pot. We have point to point tested all the circuit and it appears to be fine. We initially thought that the 555 was inserted incorrectly so we tried putting it in the opposite way this then gave us a voltage at pins 6 & 7 of between 0.75V to 1.2V but the Cd4013 U2A got hot real quick so we shut it down and replaced the ICs back to how they were previously.
Any thoughts would be much appreciated ?????
Thanks
You may have damaged the ICs if you plugged them in backwards. Try new ones. Do you have datasheets for CD4013 and **broken link removed**?