April 10, 2021 at 7:20 am #28322
Earlier today I posted here seeking for help with my built. The posts title was “Issues with HPF and continuity”. Now it has vanished from the forum. When I try to open it from my browser history, I get a “Post marked as SPAM” message.
Could an admin please get my post up again? I’m quite confident that I didn’t include anything offending and no links, just questions.
Thanks for your help.
SebastianApril 11, 2021 at 1:02 am #28355zdlAdminKeymaster
Sebastian, I am very sorry to report that your post got swept up and away by a routine, automated spam sweep. The post appears to be lost. I am very sorry for the inconvenience, but you will have to re-post. This thread seems safe, so just reply here.
GlenApril 11, 2021 at 3:38 pm #28367
Thanks for checking on this Glen!
Let’s try to tackle the issue with my build then, before the spam routine of death does its next round …
My build went good so far. As I already posted, the instructions are superb and the build itself has no bigger challenges.
Everything seems to work so far, but these things:
– the heat shrink tubbing was mangled, but I used a slightly bigger one and both optocouplers pass signal when starting in calibration mode. Maybe this has an impact on the third issue below?
– U2 pin 5 measures only 4.15V instead of 4.5, all other measurements across the board are perfectly fine. Is this a problem?
But my main issue:
– I can’t get lower than 19.5kΩ on VR8 when measuring TP1-2. The trim pots are correctly oriented, wiggle test is negative. I went through the whole troubleshooting guide and I double checked my soldering. Everything seems fine. While measuring, everything is set according to assy manual p46 ff.The overall sound is quite muffled and bassy with Harmonic Trem almost inaudible if set to full depth and mix full clockwise. More a very slight wobble but nothing like in the demo.
My next step would be to swap VR8/VR9 to see if the trim pot is damaged, but maybe you have another idea?
Thank you for your help!
SebastianApril 11, 2021 at 8:10 pm #28371brachModerator
Pin 5 of U2 is fine with that voltage.
I think you may be mistaken by the role of VR8…notice the schematic. VR8 limits the voltage of the LED on the high side optocoupler, while TP1/TP2 are connected to the high side LDR. So this makes me wonder if the solder jumpers are already soldered when you are making this measurement. If so, unsolder them and re-calibrate the trimpots. Let me know if this was or wasn’t the issue…it’s important for me to rule this out when deciding what we should do next.
-BrachApril 12, 2021 at 4:50 pm #28374
Thank you Brach for your help!
I already replied to your last message about 12 hours ago, but the message vanished again. There’s something about your SPAM filter making this a little tedious for me. One idea: I used the omega symbol for resistance values. This might be interpreted as malicious content. Maybe you can see if that’s the issue with the forum here?
The jumpers are not the issue, measurements are taken with jumpers unsoldered and checked fo no continuity. I redid the measurements: 5k on Low, 21k on High at the lowest setting of the trim pot (full clockwise until clicking through). Everything else was set as described in the manual page 46ff, LFO not pulsating.
I’ll wait on your input before attempting anything else.
SebastianApril 15, 2021 at 9:24 am #28455brachModerator
I’m sorry about this late reply. The last 2 days were very busy and hectic around here.
Thanks for answering my previous questions. I’m going to assume that your LDR pair is matched (because we matched them when we assembled your kit) so the issue has to be that the LED is not getting bright enough to cause the LDR to lower it’s resistance to a reasonable value.
-Check everything in the circuit between the microcontroller pwm output and the LED. They are: Q1, VR8, and R8.
-Check to make sure the solder joints on these components are good and there are no shorts between any of their solder pads.
-Check to make sure all these components are correct values.
-Make sure R8 is getting 5V on the correct pin (as shown in the trouble shooting guide) and compare the voltage of the other pin on R8 to the same pin on R7.
-Test to make sure the trim pot is working by measuring it’s resistance….from the middle pin to the one of the side pins. Then turn the trim pot about 10 or 12 full turns and re-measure the same pins.
-You should also compare the optocoupler LED voltage (as in the trouble shooting guide…the yellow pads in the voltage chart)…both of them should be around 1.8V.
Look into all that stuff and let me know what you find.
-BrachApril 17, 2021 at 11:36 am #28593
Thanks @brach! And no worries – my life doesn’t depend on the Quaverato. Yet. 😉 I’ll always prefer a thorough answer over a quick one.
I’ll have some free time tomorrow night and I’ll check again for all the points you mention and I’ll let you know the results.
Have a good weekend!
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