Ambika voicecard stops or acts weird after a few minutes
  • Got my Ambika all put together with 3 SMR voicecards. Works great except for one issue. After about 10 minutes of playing one of 2 scenarios happen. 1) notes from one of the cards stops playing or 2) weird noises start to happen. Sometimes this is either like white noise or other times it sounds like a squelch or similar. I think I narrowed it down to a particular card but what could it be? Capacitor, IC, pins to the motherboard? Or could it even be the motherboard?

    Any suggestions of what to look for would be great. I’m going to start by reflowing the solder on the connection pins and caps.

  • OK the plot thickens. It’s happening on a different card. Which now leads me to believe it’s the motherboard. This time I was changing the resonance and it screeched and the notes triggering on the card stopped. I should also note that the leds are all firing as they should even when the notes stop.

  • This could also simply be a problem with your (external) power adapter not being beefy enough, even for ‘just’ three voicecards.

    Or: is any of the voltage regulators getting REALLY hot (you can’t touch ‘m anymore)?

  • Nothing seems to be getting hot. The adapter is 9v AC 830mA. It’s the adapter from my Alesis Micron. I’ll try to run with just one card and see if it does the same thing.

  • Well looks like it might be the adapter. I can get it to work with 2 cards but the 3rd flumoxes it. I guess I’m buying a new adapter. What is recommended? Is there a maximum to amperage? Minimum is 1A right? If I want to use 6 cards does the number change?

  • Always use an adapter that exceed required power by about 10% or so. The ratings are often theoretical or false.

    Many issues that happen after a while will be due to warm up, things expand when they get warm and this can make flawed joint that is okay when cold become intermittent when warm.

  • Best to go for 1.5A, in my experience (three Ambikas so far :-) ).

    Indeed, ratings quoted are not always honest, so go for a little extra.

  • No such thing as too many amps. Unit will ever draw just as much current as needed so even 20A won’t damage anything.

  • Well given the AC adapter is just a step down transformer in a box if you buy a higher rated one you’re getting chunkier wire and less chance of it getting too warm.

    Buy a decent branded one too. There’s a lot of really badly insulated ones around.

  • OK I give. Where does one find an AC/AC adapter of at least 1A? I’ve looked on eBay, Amazon, mouser, etc but everything is AC/DC. Any ideas for a dude in the US??

  • This one from Texas should work (even rainproof :-) ):

  • Found a new 1.5A adapter and guess what. The problem still exists. I’m not sure what to check now.

  • Can you measure voltages (DC after the power circuits) on the motherboard when this starts to happen? Would be useful to know whether one of the voltages (positive or negative) drops when this happens.

    Cleaning the motherboard, inspecting for solder bridges and other crap, etc. might also help.

  • Reflow all the solder joints on the voice card connectors and where they connect to the mainboard.

  • Yes I can check voltages. Just checked the motherboard as shown for 1st startup no cards and all voltages look good. Checked the other pin 3s and 5s on female card jumpers and get 7.7 and -7.7v respectively. Should be 8v, could that be a problem or is that within tolerances. What other voltages should I check?

    (edit) – I’ve wired 20 to 30 guitar pedals and a MFOS noisy toaster so I’m decent at soldering and basic troubleshooting. I see there are check(measurement) points on the motherboard is there a reference to what they should be?

  • Also it looks like with just 1 card the problem exists. Regardless what card I use. Whether in mono or poly. At this point it looks like I must conclude it’s MB.

  • I find when there are ghost in the machine type issues for me I go for the crystals first. For the filter cards usually when I get card drop outs or out of tune cards, I swap out a crystal and its fixed. When there are funky things going on randomly with any card configuration or lcd screen garble, I swap out the the crystal on the Mobo.

    I’ve come across this several times on Ambika and have only ever had crystal problems on the ambika build.

  • Interesting! Are you using something special for the crystals? I never came across any bad crystal in my 10+ year DIY carreer.

  • (Edit) – more testing. Replaced Crystal on MB. No change. Noticed however if I touched the solder points of the crystal before and after replacement. Problem came on. Could atmega chip be problem? Or maybe the 6n137? Trying to figure out if problem only happens with midi feed.

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