Further testing. Having reseated all the LEDs I have been able to conduct a proper test of the front panel switches. Input selector is now working perfectly. However the gain selector switch is playing up. The medium setting has a short circuit somewhere and I spent time tracking this down. I quickly ruled out the amp pcb side and the cable as culprits and then set to tracking it down on the front panel board.
After a deal of continuity testing I finally have my culprit. The two pole, three throw switch is outputting in a way that causes the short circuit. I suspect the culprit is that I used a substitute for my original specified switch and that substitute differs in it’s internal wiring. Having looked there is no way to rescue the circuit on the board so after all that I will be needing to redesign the front panel board after all! I am likely going to keep the under slung LEDs however. I think they will look better.
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as Bob Ross used to say, happy little accident.
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Indeed! I am not too worried. I’ve ordered the replacement parts, now back to the drawing board on the pcb.
Further investigation:
Checking my circuit design I came to the realization that the switch layout was not to blame. In fact, the circuit as is ought to have worked however…
It goes back to the initial issue with the LED units having the polarity reversed to my expectation. Yes I could physically reverse them however this fundamentally altered the way the circuit works in a way that caused one switch led circuit to short with another in one specific setting due to the way that SP3T switch works.
So regardless of any other issues, the main problem remains the LED connections and so I have redesigned the pcb and ordered new versions.
[edit] I’ve totally lost track of them being over or under slung leds at this point so they will be whatever I have made them. I suspect I’ve corrected the circuit and pcb in such a way that they are back on top in order to avoid breaking my brain completely in solving the issue on the board.
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Welcome to software engineering, it is like solving a crime except you are the investigator in your own murder.
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Part of what makes it so interesting!
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