Doepfer

Hi Joe,
	I looked back over my old notes on this one: I still don't fully
understand it, but can offer the following. When you get the bleed
through, do you leave the other input unconnected? If so, try
grounding it, as this seems to improve matters considerably (I've been
partially inserting an unconnected patch cord to short the input to
ground - not the most reliable of connections - but connecting a CV
input set to 0V should do it too. Make sure you get your in's and
out's round the right way - shorting the gate or trigger signals to
ground through the switch would probably not be very nice!). You may
still get some bleed through, but from my experiments it is
considerably less, i.e. instead of the full signal, its down around
100mV or so. Also swapping inputs (I/O1 <-> I/O2) makes a difference
too - its worse one way than the other. The problem is exceeding the
+/-8V limit specified in the manual: despite some diodes apparently to
protect the chip, some excess voltage does get applied to it, and so
it's normal operating range is exceeded, and it thus stops working
properly. The 'DID NOT' signals you listed will almost certainly be
within +/-5V (I don't have a 155 or 191 so can't actually check these
two, the rest certainly are); of the 'DID's the 160 and 190 signals
are 0 - 12V, and I also strongly suspect the others are too (again I
don't have these). If anyone else has knowledge of/can point me to a
suitable reference for why the FET circuitry in the 4053 chip behaves
in this manner, I'd love to know it!

Tim

[The views expressed above are entirely those of the writer and do not
represent the views, policy or understanding of any other person or
official body.]



--- In Doepfer_a100@y..., "buechlerjoe" <buechlerjoe@t...> wrote:
> I decided to try a number of signals patched to my A150's I/O2 
> (Normally Open) jack. I wanted to see which ones would trigger an ADSR 
> envelope by bleeding through the O/I jack, even though nothing was 
> patched to the A150's CV jack to close the switch.
> 
> Signals that DID NOT bleed through were:
> 
> A145 LFO Pulse
> A147 LFO Pulse
> A155 Trigger
> A156 Trigger
> A190 Clock
> A191 LFO Pulse
> 
> Signals that DID bleed through were:
> 
> A155 Gate
> A160 Clock Divider
> A162 Trigger Delay
> A165 Trigger Modifier
> A190 Gate
> 
> What's even more worrysome is that I'm fairly sure that I've 
> successfully switched an A190 Gate signal with the A150 in the past, 
> so now I'm concerned that the A150 is actually deteriorating in this 
> regard. I wish I could be more certain about this.
> 
> There was an earlier response from Dieter on this issue, in which he 
> ascribed the problem to user abuse of the A150. I'm certain that he 
> misunderstood the symptoms, though, because he was talking about 
> signals patched to the CV input, rather than the switch inputs. In any 
> case, in was in the middle of preparations for the Frankfurt show and 
> he probably didn't give the issue a lot of attention.
> 
> I've sent a copy of this post directly to Doepfer by email.
> 
> Joe