Build finished - no sound at OH, CH, CY and PC2

  • Some further info. This is how the handclap sounds:

    https://soundcloud.com/user-775212155/clap/s-y1pEQ

    It is very quiet and murky. However, this is how cowbell and rimshot sound at the same recording level (bear in mind that cowbell has not yet been fully tuned due to lack of scope):

    https://soundcloud.com/user-775212155/y ... ll/s-gsjeW
    https://soundcloud.com/user-775212155/yocto-rs/s-C4KfG

    Accent does not work on any of the instruments. CY, OH/CH, PC-2 have no sound. When jump a 5V pulse at trigger resistors I get a burst of normal instrument sound. Also, will order a scope tonight. Appreciate any help. :idea:
  • OK, I have a few changes to report. I've been trying to isolate the problem with multimeter only (the scope will arrive in a few days) and had no luck so far.
    What is curious, after poking around the mainboard, I had all the instruments working yesterday - but only for a few minutes. Don't really know what happened, but I got all the cymbal, hats and pc2 sounds at individual outs, however, upon plugging the right/mono, left, toms and rimshot, I was hearing a lot of background noise - which had not been present before. What I noticed was that when I pressed C190 against the IO board, the noise would stop and the instruments could be heard clearly - there was an obvious loose solder joint at C190. So I reflowed that one and turned the Yocto back on and got back to the starting point with no sound at CY, OH/CH and PC-2 and a dim handclap. :shock:

    The only thing that changed was that all 15V measuring points somehow turned into ~16.5-17V and I could no longer get a stable 13.00V at TP1 - I am getting a slow increase in voltage at this point over a short period of time. :(

    Also, the power supply hole above D7* mark has a very low voltage reading (as opposed to most of them on the board being 15V before and now 17V).

    At this point, I have no idea what to do further.
  • Hello,

    I'm not sure I can answer completely to your issues but as for the CY,OH/CH and PC2 it seems the issue comes from the accent circuit. If you look at the schematic you'll see that all the accent signals from CY OH CH and PC comes from the same circuits. So look at the TL074 in IC110 and the 4051N in IC111. Especially some 4051 work at 5V and not at 15V. I had to buy a lot of 4051 before finding one that worked. Some were heating (maybe that explained the fact that it works for a few minutes only). Anyway for that i looked at those two circuis and try to monitor the voltages.

    But i think that before the fact that you have 17V is the first issue to solve if you want not to damage your circuits but for this i have no idea sorry. For the handclap it might also be an issue with the accent circuit. Look at the voltage on IC1 corresponding to the handclap and see if you have a high level (+15V).
  • Thanks Marti for your kind reply! I will check everything around the accent circuit and post once I get back home.

    The ~17V issue occurred after reflowing the C190 on IO board, it was 15V spot-on before. Could it be that the mentioned electrolytic capacitor overburned or something and caused this?
  • OK, definitely C190 isn’t the culprit of 17V issue - I have replaced it with a new one and the same thing is happening. Tonight I will rip both C190 and C191 out and replace them with 2200uF 35V, since the ones I got in the Mouser bom were 2200uF 25V (the assembly list says 35V). Also, the scope arrived.

    Edit: Replaced C190 and C191 but to no avail. Still ~16.5-17V. I will replace REG1 and REG2 voltage regulators next and report here.
  • Reporting now. I have replaced the REG1 and REG2 (L7815 and L7915, respectively). This has not helped, now I am getting about +18V (with a tendency to grow) and almost no negative voltage (-0,35V and declining) at J8. At this point I cannot troubleshoot the mainboard since I am reluctant to even connect it to this high a voltage. All help is appreciated.
  • At this point I am suspecting that the PSU may be defective because of the 17-18V issue, so I ordered a new one. Will update on further findings.
  • As you quadruple checked each parts and an issue appeared after reflowing a component, it's likely that you have bad connections somewhere, because of missed or bad solder joints.

    Regarding measures, did you check the PSU voltages when the IO board is not connected to the main one ? Getting 17-18 V instead of 15 and 0 instead of -15 is a very serious issue and a situation where you should immediately disconnect the main board from power before having resolved the PSU issue.

    I think by "PSU" that you reordered, you mean the "external voltage transformer" ? If so, instead of suspecting it to be defective or not, just measure its output voltage with your voltmeter.
  • First of all, thank you for replying :)
    Regarding measures, did you check the PSU voltages when the IO board is not connected to the main one ? Getting 17-18 V instead of 15 and 0 instead of -15 is a very serious issue and a situation where you should immediately disconnect the main board from power before having resolved the PSU issue.
    Of course, once the voltage went this high I immediately disconnected the main board and haven’t used it since. All the voltage measurements posted are without the main board connected.
    I think by "PSU" that you reordered, you mean the "external voltage transformer" ? If so, instead of suspecting it to be defective or not, just measure its output voltage with your voltmeter.
    Yes, that, the power adapter. I’m a newbie to this, hence clumsy expressions. My multimeter has no RMS, so I suppose the measurements are way off when directly checking the AC transformer (correct me if I’m wrong).

    :|