Adjustment of Compensation capacitors.

[JimmyG]

I've just about completed the project however in step 3 with the compensation capacitors I adjust C8 and nothing seems to change. My output still looks like image "Not enough"
Anyone else come across this ?? Ideas ?? Comments ??


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[jye1]

Did you see any change in waveform while adjusting C8? Usually C7 too large or C6 too small (open) will result in the phenomenon you saw.

[pmk2015]

Did you see any change in waveform while adjusting C8? Usually C7 too large or C6 too small (open) will result in the phenomenon you saw.

I have the same problem, I have checked the values of C6 and C7, they are correct, any advice?

[jye1]

This may be due to large tolerance in C6 and C7. You can use different values to try out.

[Flakeout]

Hi, I managed to damage trimmer C5 (25 pF), I removed it and manged to hook the bent legs of a 6.8-40 pF trimmer under each side of R3 which worked really well though it was very fiddly.

[anatol]

Hi. I when setting input 1 volt is no reaction to changes in the tuning capacitor C8. The image is always in the picture as the "Too much". How can I check the serviceability of the tuning capacitor? Entrance to 0.1 volts responsive to the setting. Entrance 0.01 volts is working correctly.

[anatol]

Problems arose when setting up the oscilloscope because of the bad solder the variable capacitor C8. The picture on the screen was always as in Figure 6 "Too much". While I found that the variable capacitor C8 loose contact with the ground, had to tinker. After soldering the capacitor became clear that the need to reduce the capacity of the C7. The condenser is replaced by another with a capacity of 105 pF. In parallel tuning capacitor C5 had to add a capacitor is 10 pF. After that I was able to fill the screen as in Figure 6, "Good". I checked at frequencies of 1, 10 and 100 kHz. I think that you need or improve the accuracy of the nominal value chain components Responsibility scheme, or increase the nominal value of the adjustment elements. During assembly, I checked the ratings of resistors and capacitors, but to measure the capacity of less than 20 pF, I can not.

[gregma]

Same exact problem here. Any way of troubleshooting without having to remove the capacitors and trying different values? I wouldn't expect to have to try and redesign the circuit to make it work. All I get is "Not Enough". Adjusting C8 does nothing to affect the waveform.

[jye1]

Same exact problem here. Any way of troubleshooting without having to remove the capacitors and trying different values? I wouldn't expect to have to try and redesign the circuit to make it work. All I get is "Not Enough". Adjusting C8 does nothing to affect the waveform.

Please check C6. Small C6 or large C7//C8 will result "not enough". On the opposite, large C6 or small C7//C8 will result "too much".

[gregma]

Same exact problem here. Any way of troubleshooting without having to remove the capacitors and trying different values? I wouldn't expect to have to try and redesign the circuit to make it work. All I get is "Not Enough". Adjusting C8 does nothing to affect the waveform.

Please check C6. Small C6 or large C7//C8 will result "not enough". On the opposite, large C6 or small C7//C8 will result "too much".

Check for what?