| whit3rd <whit3rd@gmail.com>: Jun 26 02:46AM -0700 On Tuesday, June 25, 2019 at 6:54:49 AM UTC-7, Don Brown wrote: > I have a Hickok 440 curve tracer that I am having difficulty troubleshooting, even though it is a relatively simple circuit. > The base generator staircase is not stable Typically, there's a monostable making a current pulse into a capacitor for each step. If the capacitor is an electrolytic, it may be leaky now (but run the staircase overnight before you replace parts, it may be that some ON-time will reform the oxide layer). If the monostable has a capacitor, it is also a suspect (unstable times). Resetting the staircase there's a charge-dump (transistor?) that could be leaky, or its drive might be picking up noise. Hanging an o-scope probe onto the step generator to show the rise/plateau qualities will tell where the problem lies. |
| Don Brown <edfredcorp@gmail.com>: Jun 26 08:15AM -0700 On Wednesday, June 26, 2019 at 2:46:50 AM UTC-7, whit3rd wrote: > Resetting the staircase there's a charge-dump (transistor?) that could be leaky, or its > drive might be picking up noise. Hanging an o-scope probe onto the step generator > to show the rise/plateau qualities will tell where the problem lies Yes, this is the way it works. I should attach the schematic and circuit description. It charges a ceramic non electrolytic capacitor, with a diode in line that keeps it from discharging each pulse. But since ceramics rarely fail I did not change it, but maybe I should. And from previous scope probing I saw various qualities of pulses but did not really understand what was normal and what was not. Thank you. |
| fahmisant29@gmail.com: Jun 26 12:41AM -0700 Hello sir, Can i get Electronic principles by Malvino 8th ed manual solution? Thank you |
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