Timo Rozendal SDSV+ strange behavior on powerup

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artilect99
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Timo Rozendal SDSV+ strange behavior on powerup

Post by artilect99 » Tue Sep 08, 2020 11:11 pm

Hi all,
When I power my rack on if the SDSV+ is plugged in the rack seems to receive partial power -- BIA is dead, LEDs are dim on a few modules (NLC 1050 mix/seq), and the SDSV+ itself lights on trigger but gives no audio.

This is behavior that I normally associate with a short somewhere in the power rails. The weird thing is, if I then unplug the SDSV and then plug it back in, everything fires up and everything works normally, including the SDSV. As soon as I unplug it the BIA clicks on and the 1050 LEDs go to full brightness.

Has anyone ever encountered an issue like this, or have any idea what may be the cause? I'm still thinking it must be a short to ground or something but then I have no idea why unplugging the module and then plugging it back in would fix it and allow it to work normally.

My PSU is 1 amp and I'm running about +700ma/-400ma according to modular grid (including the SDSV+ which pulls +30ma/-30ma).

Any insight would be very much appreciated!

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artilect99
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Re: Timo Rozendal SDSV+ strange behavior on powerup

Post by artilect99 » Wed Sep 09, 2020 1:56 am

After unplugging every module from my rack except the SDSV and BIA in attempt to narrow down the culprit, everything powered up fine with just those two... so I guess it is an inrush current problem.
Last edited by artilect99 on Wed Sep 09, 2020 1:46 pm, edited 1 time in total.

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artilect99
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Re: Timo Rozendal SDSV+ strange behavior on powerup

Post by artilect99 » Wed Sep 09, 2020 1:39 pm

pointless update: I built a simple test rig on stripboard and measured the SDSV+ current draw with my DMM: spec is +/- 30ma and it's sitting at ~ +/- 27ma, so no problems there --- unless this inrush current is too fast for my cheap chinese DMM to read. How long do these spikes last? A few ms?

I mean barely trust this thing with measuring resistor values but the measurement seems right in this case. So I guess I'm in the market for a second PSU... no power issues until now, but apparently adding this one 30ma module was the straw that broke the camel's back (actually, swapped it with a 17ma module). So this is a very light straw we're talking about.

Anyway I guess having a second PSU isn't a bad thing.

Props to Timo for his quick help and a great module.

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artilect99
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Re: Timo Rozendal SDSV+ strange behavior on powerup

Post by artilect99 » Wed Sep 09, 2020 6:39 pm

Side note: I've been having so much fun with the SDSV+ that my rack has remained with only it plugged in... Only problem is now I think I need 4 more of them! Seriously considering building a few more and putting them in their own rack and PSU.

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artilect99
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Re: Timo Rozendal SDSV+ strange behavior on powerup

Post by artilect99 » Wed Sep 09, 2020 6:54 pm

Came across this:
https://wmdevices.com/products/soft-start-module

for $30 it seems like a decent solution. Also looking into DIYing a simple 555 timer based delayed relay to accomplish the same goal. If anybody has any schematics for an equivalent of the above (basically switch power on via relay after a few seconds) I'd be interested to see it.

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Re: Timo Rozendal SDSV+ strange behavior on powerup

Post by forestcaver » Thu Sep 10, 2020 2:31 am

Seems a bit odd - could it be a capacitive load issue on one of the psu rails? What is the psu? The sdsv+ doesnt even have regulators that could fail to start so it sounds like your psu is falling over...

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