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Trigger delay debugging [Solved]
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sonicwarrior



Joined: Dec 22, 2005
Posts: 266
Location: Cologne, Germany

PostPosted: Tue Apr 30, 2013 2:29 am    Post subject: Trigger delay debugging [Solved]
Subject description: Part of the Anyware Instruments inSEQt
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Background:
I recently changed the blue LEDs in my Anyware Instruments inSEQt (mainly a sequencer) to yellow ones. Afterwards during the check I recognized that the trigger delay part is not working correctly. The (now yellow) LED only glows a short time after powering on but not when a trigger signal is put in.

Initially I thought I put the LED in with the wrong orientation but after changing that it didn't even glow when powering on. So my guess is that the LED is not the problem but something in the circuit and so I started drawing a schematic and here is the result:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Are there any obvious errors that I made? The LED is obviously oriented backwards because in this image the anode is connected to -15 V instead of the more usual +15 V which I somehow missed when drawing the schematic.
I'm not sure about the 47K resistors as it was hard to determine if the ring color of the fourth ring was orange or red.

There are three relevant PCBs here: One with the jacks (in & out), one with pots & LEDs (and the 560 Ohm resistor) and one with the main circuit on it connected to the other PCBs via ribbon cables.
Pot and main PCB are piggy packed which makes measuring a bit difficult.

Last edited by sonicwarrior on Wed May 01, 2013 4:53 am; edited 1 time in total
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sonicwarrior



Joined: Dec 22, 2005
Posts: 266
Location: Cologne, Germany

PostPosted: Wed May 01, 2013 4:52 am    Post subject: Re: Trigger delay debugging (Anyware Instruments inSEQt)
Subject description: Help needed
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Solved:
The Delay Time pot is broken.

In the mean time I found a similar schematic:
http://www.musiksynthesizer.de/module/dokumente/dual_trigger_delay/LINDHOF-MODULAR_DUAL-TRIGGER-DELAY.pdf
(Page 2)

Apparently this is a clone of the Doepfer A-162 Dual Trigger Delay.

Corrected my schematic on base of this and additional measurements:
- Pin 1 & 2 are connected
- Pin 12 & 13 are connected
- LED connected to +15V (not -15V)
- Added 1K @ the output jack

Finally I got the idea to measure the pots themselves and found out the Delay Time pot has infinitive resistance whatsoever. Embarassed
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