2½ years later... the problem was with the cliff jack that did not close the connection for the tip. Removed the old one and put a new one there, the A-155 works as it should!
I had the same problem with a A-143-2 where one of the four ADSR-channes did not react to gates sent to the first jack, the other three worked as they should. Swap the jack for a new one and it works fine!
/Janne
> To: doepfer_a100@yahoogroups.com
> From: tapirkillen@hotmail.com
> Date: Fri, 24 Aug 2012 15:19:19 +0200
> Subject: RE: [Doepfer_a100] Re: Troubleshooting A-155
>
>
> I have tried with external signal in for the offending pot, but to no avail. Still nothing happens. Its value is still zero, no matter what I send as external signal.
>
> As far as I remember I tried tracing all connections with the multimeter, comparing to the working row of pots, but could not find any difference. But I will check once more and see what might turn up.
>
> /Janne
>
> To: Doepfer_a100@yahoogroups.com
> From: richyho@virginmedia.com
> Date: Fri, 24 Aug 2012 14:11:22 +0100
> Subject: [Doepfer_a100] Re: Troubleshooting A-155
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Hi
>
>
>
> It could be a problem with the jack socket below the pot instead of the pot
>
> itself. I believe that when a lead is plugged into this the knob becomes an
>
> attenuator of this signal. If the socket 'thinks' a cable is plugged in
>
> then that knob may be attenuating zero volts so not doing anything. This
>
> can happen when the metal contacts in the socket become damaged and touch
>
> even when nothing is plugged in. You need to check continuity with a
>
> multimeter, comparing the results with another working socket. Quite a
>
> simple fix with a small screwdriver if this is the case.
>
>
>
> Rich
>
>
>
> Hi everyone!
>
>
>
> I have got an A-155 sequencer where one of the pots on the bottom row does
>
> not work. At all.
>
>
>
> In order to try to pin down the error I have swapped the ICs from the top
>
> row to the bottom row (http://www.doepfer.de/A100_pictures/doepfer_a155.jpg,
>
> the two PCBs with the knobs), but the problem was still there. Is there
>
> anything else I can do? I have also tried to measure resistance what is
>
> happening when turning the pot, but I did not see anything that made the
>
> offending pot differ from working pots.
>
>
>
> Is the pot itself broken, or is there anything else I should try to pin
>
> down the problem?
>
>
>
> Modular regards,
>
>
>
> Janne
>
>
>
> [Non-text portions of this message have been removed]
>
>
>;
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
> <*> To visit your group on the web, go to:
> http://groups.yahoo.com/group/Doepfer_a100/
>
> <*> Your email settings:
> Individual Email | Traditional
>
> <*> To change settings online go to:
> http://groups.yahoo.com/group/Doepfer_a100/join
> (Yahoo! ID required)
>
> <*> To change settings via email:
> Doepfer_a100-digest@yahoogroups.com
> Doepfer_a100-fullfeatured@yahoogroups.com
>
> <*> To unsubscribe from this group, send an email to:
> Doepfer_a100-unsubscribe@yahoogroups.com
>
> <*> Your use of Yahoo! Groups is subject to:
> http://docs.yahoo.com/info/terms/
>