Message 584 of 592
From: "vtl5c3"
Date: Fri Dec 19, 2003 7:28 am
Subject: DUSG/RES 17 Fixes

Alright folks,I got it working tonight!
I went through the trigger section on the PCB with a fine toothed comb and found that there were two issues:

1) there's a .1 uF cap between the trigger input and V+, right between the 33 K resistor and the two diodes. Dunno why that's there, but I took it out. It's not on Dean's nor Driscoll's schematic.

2) The 5.6V zener diode is connected between the end pulse output and pin 8 of the LM3900. I suspect that Ken's intention was to hook it to pin 7, i.e. ground.

Once I corrected both of those bugs, the module oscillated quite well. VC control over the slopes is excellent for waveshaping. I totally understand why Mr. Driscoll added separate CV inputs for up slope and down slope.

The only thing that isn't working yet is the LED, but that's really minor.I posted a JPG (res17_errata.jpg) to the files area showing where the components are that need to be moved.


Message 591 of 592
From: sasami@hotkey.net.au
Date: Sat Dec 20, 2003 5:47 am
Subject: Re: [resergence] DUSG/RES 17 Fixes

I reverse engineered the DUSG too, but the differences
between Dean's version and mine were so trivial I haven't
bothered distributing it, so if you worked from Dean's
I'd expect it to work.

Note that the LED driver is a
separate assembly in real Serges, not part of the main
circuit board, so I can offer no suggestion as to why
that doesn't work... The LED being a separate module wasn't
discovered to after the board was done.

As for the errors, there are two per DUSG on the board,
exactly as Romeo pointed out.
A bypass capacitor connected to a wrong trace, and the
earth end of a Zener going to the wrong pin.

Ken