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The top half of my A-156 has stopped working
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author The top half of my A-156 has stopped working
Leisure Cove
Has this happened to anyone else? Out of nowhere, it just stopped outputting anything. Bottom half of the quantizer still works just fine...

To test it, I've tried:

-sending the CV out from the top half to a few different VCOs (no change in pitch in any of them)
-using different cables (no change)
-trying a different socket on the distro board (no change)
-looking over the PCB (nothing seems fried/damaged)

seriously, i just don't get it

I've had this module for about a year.

I vaguely remember reading about this happening to someone else a while back, but can't find the thread. If this jogs your memory and/or you can recommend troubleshooting tips, send 'em on over. Thanks!
Johnisfaster
I don't remember which one but I think one of the sections only outputs voltage if you hit it with a gate/trigger, like one section will freely quantize voltages without gate/trigger and the other section requires it.

could that possibly be the issue?
Leisure Cove
That did it-- thanks! thumbs up It's strange, though-- I don't remember it needing a trigger in order to work before...

Anyway: problem solved. The top half of the 156 needs a trigger/gate signal to tell it when to quantize, like a quantized track and hold I guess.
Johnisfaster
awesome! it's always nice to find out you don't actually have a problem. This same thing happened to me with the 156 which is why I mentioned it.
goiks
does the top half need the trigger with the jumper in both positions, or just when the top section is independent of the bottom?
giorgio
i also found that due to not using the top half, i forgot how it worked
jonkull
Leisure Cove wrote:
Anyway: problem solved. The top half of the 156 needs a trigger/gate signal to tell it when to quantize, like a quantized track and hold I guess.


This doesn't sound right. My A156 quantizes on it's own without triggers or gates. Top and bottom. Both jumper positions.
Johnisfaster
maybe a different revision?
jonkull
Either that or mine isn't working correctly.
Leisure Cove
It is strange-- as I said, I don't remember this being the case with the module beforehand, but at least I have a temporary fix. I'll post an update if I find a workaround (one that does not involve using the Trigger In on the upper half).
Somatic
sure its all explained here

http://www.doepfer.de/a100_man/A156_man.pdf
Tim Stinchcombe
This sounds like a dodgy jack connection. The PIC outputs a 500Hz signal, which is fed onto the switching contact of the 'trig ins' of both sections, and which thus is used as a trigger unless you plug an external trigger in, when the contact for the internal trigger is disconnected and the external one used instead. Thus if the connection isn't good with nothing plugged in, you will not get a trigger!

With the module out of the rack, if you carefully observe the contact as you insert a patch cord, you should just be able to see the top contact lift off the switching contact underneath it. There are pictures of the sockets on the Doepfer DIY page, about a quarter the way down:
http://www.doepfer.de/DIY/a100_diy.htm

The movement isn't much, but if it is clearly not making contact with no plug inserted, you might be able to push on the angle of the contact to re-make it (I think there is also a picture of this at the Doepfer site, but I couldn't find it quickly - Edit, found it: http://www.doepfer.de/faq/a100_faq.htm, under 'solving contact problems' [BBCode doesn't like the space in the tag...]). Sliding a small piece of paper in there with some contact cleaner might also do the trick...

Tim
Johnisfaster
very helpful Tim!

actually in my case I kinda don't mind it since I always intend on using a trigger or gate anyway so it's never presented itself to be problem for me
dk
This actually seems like a common failure mode for the A-156. Mine has exactly the same problen: after I had it a while, the top half of the quantizer stopped working unless it was triggered. I'm virtually certain the problem is heat-related. Rearranging things so the 156 had decent airflow seemed to mitigate the problem. It's not what I'd call a proper fix, but given the problem isn't too serious I've lived with it rather than trying to ship the module to Germany for repairs.
Mans
Bookmarking this for future reference.
worker8
Did you send a note to D. Doeper ? He's friendly and helpful. If there's anything simple fix tip, he will let you know.
Tim Stinchcombe
dk wrote:
This actually seems like a common failure mode for the A-156. Mine has exactly the same problen: after I had it a while, the top half of the quantizer stopped working unless it was triggered. I'm virtually certain the problem is heat-related.
Well that comment prompted me to pull mine from the rack, and visual examination of it leads to several points.

The pin on the PIC outputting the internal trigger pulse has a pull-up resistor on it, and what do we see right next to the resistor net containing the pull-up? A stonking great L7805 voltage regulator, generating on-board 5V for the module, and probably a resonable amount of heat too! However, if that was causing bad joints/whatever nearby on the board, it would affect both sections of the module, as it is before the point where the trigger is split to both jack switching contacts.

Also the left column of jacks aren't mounted directly on the PCB, but are angled so that only the main contacts can be soldered to the board, leaving the two trigger jack switching-contacts needing a wire jumper to the board, which looks somewhat precarious. But then again, I see no reason why the top one should be prone to failure more often than the bottom one, as the same method is used for both. If the jack nut became loose, then the mechnical stress of repeated plug insertion/withdrawal could be an issue for the joint to the board, but would probably affect both jacks roughly the same, and wouldn't explain why apparently keeping the module cooler helps.

Without seeing a sample fault first-hand, its obviously hard to say what the real cause is, but it does seem that it might be simple enough to fix (like reflowing a joint or two, knowing which one to target...).

Tim
mark_snipz
It is a heat related problem with the jacks. Thats direct form Dieter himself when I had the same problem, it's on here somewhere.
Keep the A156 away from power supplies or away from hotspots in your system, mine still has the same problem on a hot day.
Will try a fix someday.....
Tim Stinchcombe
Hi Mark,
mark_snipz wrote:
It is a heat related problem with the jacks. Thats direct form Dieter himself when I had the same problem, it's on here somewhere.
Found it:
https://www.muffwiggler.com/forum/viewtopic.php?p=96945#96945
That's ultra weird though - why would it seem to affect just the top jack, and we now apparently have several instances of this?! (And yeah, OK 'heat rises', but even so.) The trigger signal goes to the bottom jack first, and then runs via a very narrow trace up to the top jack - perhaps the trace is prone to damage at manufacture in some way, which later manifests itself as an open circuit/bad joint with intermittment contact - very weird.

Tim
visible cow
Digging up this old post to say that the same thing happened to me today. Top half of my a156 only works when triggered.

Lame, but I think I might survive.
Johnisfaster
the weird thing is mine works just fine now. I love it too it's an excellent module to have around.
visible cow
yeah, I won't be surprised at all if it winds up working today. I think I may have noticed the issue several months ago but fooled myself into thinking I was doing something wrong.
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