| Electronics > Repair |
| 18V/3A HY1503 PSU - weird CC/CV behavior while charging battery cells |
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| xavier60:
Maybe I'm seeing it differently. The compensation RC should be wired the same as in the original schematic. R21 from the 2N3055's Emitter to the Inverting input. C7 from the CC opamp's output to the Inverting input. |
| iMo:
Ok, with 10k in series with the 1k5 sense resistor and 6n8 ceramics or 10n ceramics (3mm long leads directly wired to in- and out of the opamp) is the amplitude at the CC opamp's output 600mVpp and period 600ns (10n ceramic). Touching the opamp's output with my finger decreases the amplitude to 400mVpp. I boosted the ground pcb from the probe point to the point near the 741's ground with a thick short wire with none change. |
| xavier60:
With 10K and 10n, it's unlikely that the 1.7MHz is coming through the opamp in any normal way. What signal level is there on both the opamp's inputs? Try touching parts of the circuit to see if anywhere changes the frequency. |
| iMo:
The signal at the in- is the ~same as the output (10n fb cap), in+ is clean. Touching the CC's in- or output decreases ampl to 400mVpp and period increases to 800ns. Other 324 pins incl 741's pins do not show any relevant impact. Transistors - the touching of the base of the first transistor - the same change as with in-/out of the CC opamp, other points around the transistors - no relevant impact. |
| xavier60:
--- Quote from: iMo on September 20, 2024, 08:20:37 am ---The signal at the in- is the ~same as the output (10n fb cap), in+ is clean. --- End quote --- That should mean that the signal is being imposed directly onto the output somehow or directly onto the Inverting input rather than via R21. I can't imagine how. Edit: try removing D12 and carefully testing CC mode. |
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