There’s definitely something wonky going on with R165. It didn’t occur to me measuring in-circuit plugged. Board plugged I get now 1.5K as you do. Voltage across it is 15.2V. And I think my 4k comes from measuring with the board outside, makes sense. The line is still a stable 15V. I’ll try to get some time off today from the Halloween festivities to match your measurements.Mooger5 wrote:I see your point. Well TR5 is in the Chorus On/Off command path and the chorus is working, so TR5 is behaving correctly. It wouldn´t draw much current anyway, because of the resistors you mentioned. That +15V line should be the same everywhere, give or take a few mV, and there should be continuity between every +15V point. So if TR5 or any other component caused a drop in the voltage, that drop would be noticed at the other +15 points just as well.polysixer wrote:TR5 - emitter is indeed to -15 but collector goes into +15 through R46 and R50, so just wondering if a failure in this transistor explains the resistance drop of R165 in circuit. That could explain the scaling fault I guess. Furthermore, why does R17 connected to the same +15 line measure correctly and not drop resistance? My Juno seems like an early unit judging by serial number. I did make many more measurements and will post later when I get home. As always, many thanks for your input.
Anyway resistors measured in circuit aren´t very good for reference, as they are always in parallel with some other components with their own internal resistance which will cause misreadings.
Whatever the misread on r165 though, mine and yours should match but 4k and 1.5k are nowhere near so it must mean something´s not right. If anything, 4k being a higher resistance means a lesser positive bias, favouring the ratio of the negative supply...
Hold on, your logarithmic vs. linear behavior got me thinking... I changed my front panel sliders with a full set of new 50k. What if these pots are linear and the circuit expects logarithmic? My friend's Juno 106 is more modern so maybe there was a revision when this changed. If this was so, his chorus board is adapted to linear pot signals which I have in my front panel. Fortunately I've kept my old sliders around to test this if needed.