CGS114 DUSG Debugging

[mouldi101]

Hi!

I've so far had quite a lot of success with my CGS boards: My two VCOs worked at once, my VCAs have worked, and my ring mod has too...

...sadly my CG114 Dual Slopes hasn't been quite so successful, and this is my first real dubugging of anything like here, and I'm not sure where to start.

Both sides output the original signal when there is one fed to the input.

Neither cycles when the trigger in and out are linked (according to the CGS site, it should)

The rise pot does what it should on one side, not on the other. Neither of the fall pots are working

The LEDs work on both channels!

Any ideas on where to start? I populated the board a long time ago, but I definitely checked the transistor pin-outs with a multimeter before I soldered them in. It's my first time debugging a board, and I'm not really too sure where to start!

Thanks in advance,

Andrew

[johncronan]

The asymmetry of the symptoms between the rise and fall controls suggests to me that you should check the quad-transistor core for bad transistors (I'll believe you that they're oriented correctly!). Or perhaps the collectors of those two that are supposed to be grounded ended up floating somehow? Also double check the 1.5k resistor coming off those two bases. Looking for differences in the base-emitter drop of these 4 transistors could also be helpful. They're operating in the active region, so that voltage difference should be less than about 0.6 volts, but should vary with the pot settings. -John

[tony d]

I found that when i used the 2n5089 with the 2n3906 i had similar problems so i switched the 2n5089's out for 2n3904 and they work good now.