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ASys RS95e + Doepfer power problems
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author ASys RS95e + Doepfer power problems
flts
I'll cross-post here from Modularsynth if you don't mind, in case someone knowledgeable with this stuff is frequenting here but not there:

I bought an Analogue Systems RS95e VCO and finally received the Doepfer power adapter cable (the shop forgot to send it with the rest of the order so I had to wait). Double checked visually that the cable pins are going to right places in both the ASys module and the Doepfer bus board, plugged in... And suddenly the whole system is silent and there's only hum coming out from the mixer outputs.

Powered off, unplugged RS95e, powered on and everything seems to still work. Phew. Unplugged all the other modules, double- and triple-checked that all the leads are going to right places and everything is fastened and inserted tight, plugged in RS95e... No sound, just hum coming from the outputs.

Which leads me to the question: do I in fact have a broken VCO? Does the RS95e actually need the +5V and if so, could the absence of that volt rail mess up everything? I don't have the 5V adapter in my case, but I couldn't find any mention about the module actually needing it and I Googled beforehand that some owner seemed to run it just fine without +5. Or maybe the power adapter cable is just fscked up?

If anyone can give any tips or has had similar experiences, feel free to post. I'll have to continue troubleshooting at some point - already tried checking continuity between the cable endpoints and all rails seem to be connected to the right places. Hope I'll figure it out myself, but quite frankly I'm too damn tired to continue right now...
Muff Wiggler
without being an expert, it sounds to me like the connection of the RS95e is shunting your power to ground

-try using a different power cable to hookup the RS95e, in case there's a short in the power cable you are using.

- (duh) make sure the pins are lined up properly on the power cable, if you misalign them you hookup a power rail to ground, and then all power just goes straight to ground

- if neither of these work, carefully inspect (and trace with a DMM if you have one) the traces and solder work around the power inlet on the RS95e. Try to make sure each power rail's inlet trace (and solder pad) is 'clean', look for accidental solder bridges between the power rail trace & pads and the ground trace & pads.

hope this helps. definately sounds like you are grounding out your power. I really don't think this can hurt anything, it just makes for a system that doesn't work. When you correct it everything will be happy again.
flts
Muff Wiggler wrote:
without being an expert, it sounds to me like the connection of the RS95e is shunting your power to ground
...
hope this helps. definately sounds like you are grounding out your power. I really don't think this can hurt anything, it just makes for a system that doesn't work. When you correct it everything will be happy again.


Yeah, I was thinking about that myself, thanks for confirming that. I'm just kind of scared that power to the ground rail would destroy things easily - I remember my friend recalibrating a System 100 modular and doing that accidentally, that VCO was as good as gone.

And what I'm hoping that hasn't happened is that something's been busted / short-circuited for good on the RS95e, and it's basically dead. I filed the mounting holes a bit larger on it so I could line it up to my Doepfer rack better, so I'm pretty sure I can't return it in any case. Lucky the rest of my system seems OK in any case and I couldn't find anything evident yet.

Quote:
-try using a different power cable to hookup the RS95e, in case there's a short in the power cable you are using.


I should try that one, only I don't have any extra ASys -> Doepfer cables and I had to wait a week extra for that one... Maybe I'll try to make one myself eventually.

Quote:
(duh) make sure the pins are lined up properly on the power cable, if you misalign them you hookup a power rail to ground, and then all power just goes straight to ground


Yeah, that was the first thing I checked - should be OK.

Quote:
- if neither of these work, carefully inspect (and trace with a DMM if you have one) the traces and solder work around the power inlet on the RS95e. Try to make sure each power rail's inlet trace (and solder pad) is 'clean', look for accidental solder bridges between the power rail trace & pads and the ground trace & pads.


I already tried checking for continuity between the power rails on the PCB with a multimeter, oddly enough I didn't find anything. TBH I got kind of tired and pissed off (long day and then this thing happened) so I just checked everything as quickly as I could and decided to look at it more carefully some other day.

Thanks a lot for the ideas, much appreciated!
Muff Wiggler
power to ground shouldn't hurt anything. As long as the system is actually grounded and there is an actual path to ground. Otherwise, yeah, put power into the ground bus with no-where for it to go, and there's no telling where it will end up.

But, standard electrics rule of thumb - electricity very badly wants to go to ground, as directly as possible, and WILL, whenever given the chance.

I have mis-aligned power connectors before, and had exactly this effect - power shunted through the ground bus, to system ground, to ground in my power inlet, right down to earth. No damage to any modules (yep, I tested them all afterwards because I was TOTALLY nervous and freaking out a bit over doing something so stupid).

Again, I'm NOT an expert at electronics so please take anything I say on the issue with a grain of salt - luckily there are some smart cats hanging around here (like The Alison Project and Liquidcolor) who KNOW their EE stuff, and I'm sure will correct me when I'm wrong. I welcome and appreciate these corrections whenever possible! Can never learn enough....

But that's my understanding. Your friend may not have had his system grounded when the power killed his VCO. I don't know anything about System 100 wiring schemes, but if there's no path to earth and you apply power to a ground plane, my guess is that it could wind up all over your system.....
flts
Muff Wiggler wrote:
power to ground shouldn't hurt anything. As long as the system is actually grounded and there is an actual path to ground. Otherwise, yeah, put power into the ground bus with no-where for it to go, and there's no telling where it will end up.


Ah yeah, figures - sometimes I think for a while that I actually know the basics of electronics (having done some DIY stuff, reading and a little course on the subject) and then I realize I don't actually _understand_ it worth damn very frustrating

Quote:
Again, I'm NOT an expert at electronics so please take anything I say on the issue with a grain of salt - luckily there are some smart cats hanging around here (like The Alison Project and Liquidcolor) who KNOW their EE stuff, and I'm sure will correct me when I'm wrong.


I should really talk about this with my roomie a bit more too, he's about as close to an EE that you can get without actually studying the subject full-time, and would probably explain that to me carefully. He was giving some helpful suggestions for the problem earlier too, but we stopped throwing around ideas since I realized I'm just getting cranky trying to solve the problem right now

Thanks again! I think I'm gonna catch some sleep now.
thetwlo
not sure if you have an older Doepfer rack/PSU but if that put you over your power limit which I think is around 600-650mA on the early PSU, that could do it. Also, I noticed Big City Music sells a separate ASys>Doep cable just for the RS95 and RS35, but when I asked about the difference, they never replied.
I have an RS95 in my doep case and it works fine--and I don't think it needs the +5v.
flts
thetwlo wrote:
not sure if you have an older Doepfer rack/PSU but if that put you over your power limit which I think is around 600-650mA on the early PSU, that could do it.


Nopes, I'm using the Doepfer linear DIY PSU (not sure about the number, the one with proper non-switching power), it should give about 1-1,25A and I barely have a half of a 6U case filled. Thanks for the suggestion though!

Quote:
Also, I noticed Big City Music sells a separate ASys>Doep cable just for the RS95 and RS35, but when I asked about the difference, they never replied.


I think the difference is that those two modules have two PCBs which to connect power to (-> two power connectors on one end of the cable) and the rest might have just one. Schneider guys made me one with two connectors, I don't think it's an "official" one but the wiring looks right.

Quote:
I have an RS95 in my doep case and it works fine--and I don't think it needs the +5v.


I just got a confirmation mail from ASys that RS95e shouldn't need it either. Hmm, that leaves me with either bad cable or a bad unit...
flts
Okay, I measured again more carefully and noticed that one of the ground leads in the cable was connected to +12 point in the VCO. Eek! Fixed it myself, now the VCO works and I have a connector that stays together with duct tape...
Muff Wiggler
w00t


glad to hear that it worked out - and that your VCO wasn't fried!
flts
Oh yeah, and thanks for the help guys - especially Muff! Seems like you were correct in the diagnosis. For that: Guinness ftw!

(The ASys guy was really helpful via mail too and he asked me to clarify that the adapter cable wasn't their official one and there was indeed nothing wrong with the VCO, so it wasn't their fault that I messed up...)
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