Hi group,
I have had some time to take some measurements in the lab.
These measurements were taken from the unit described in this thread:
https://www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg171364/#msg171364The schematic is reproduced here:
I have added the dc voltages. These voltages were measured with a Fluke 187.
The input terminals were open circuit for all measurements and scope waveforms.
WaveformsQ3 collector voltage:
This waveform should swing from rail to rail. The average voltage should be approximately half of the supply, 2.5V. The frequency is nominally 100kHz.
TP1 Waveform
This waveform should be the voltage on Q3 collector time 3 / (150 +3) = 98mV p-p
Q4 Base Voltage
The average voltage should be 5v(10K/(10K +27K) = 1.35V
Q4 Collector Voltage
Q5 Base Voltage
Q5 Base voltage is the same as Q4 Base voltage
Q5 Collector
The voltage on Q5 Collector is the same as the voltage on Q4 collector when the input is open.
Q4 Base (AC Coupled)
Q4 Collector AC coupled
These waveforms and voltages should help you troubleshoot the circuit.
Regards,
Jay_Diddy_B