Cgs synth

I have no idea why you are seeing what you are seeing. It defies logic.
All I can do is give you some trouble shooting tips.
Use your eyes (not a meter) to inspect the board. Every track, every part.
Do it with the board rotated so you are looking at it afresh. If ANYTHING
looks slightly dodgy, fix it. So often it is the slightly dodgy solder
joint/component that is the problem.
Hold the board to the light, and see if there are any unfilled holes. You
may find a link or part is missing.
Ken

>Ok, well my different manufacturer theory just went out the window.I popped

in 2 more lm3900's from the same manufacturer of the ones i had in that
didn't lock up my system and now the new ones are locking the system up.

>
>I am measuring 330 ohm resistance between pin 3 (gnd ?) and pin 14(-v)
>but only when the power is connected to the bus (unpowered) when i

disconnect it from the bus it goes open.

>
>This would leave me to believe that there's a short on my bus but all other

modules work fine until i connect this one ? And i'm not finding any shorts
when inspecting the bus.

>
>This ones really throwing me for a loop,can't wait to figure out what i did.
>
>--- In cgs_synth@yahoogroups.com, "adematteo" <adematteo@...> wrote:
>>
>> Thanks Ken, All the correct voltages are going to the correct pins (-15v

to pin 7 +15v to pin 14) I may have put the 3900 that burned up in backwards ?

>>
>> I checked all the component values and diode orientations this morning.I

still have to go through and check continuity throughout the circuit.

>>
>> I've noticed both sections outputs exhibit the same behavior which is a

negative offset around -6v with nothing feeding the inputs.I checked pin 9
in the stepped section and if i feed a slow ramp and clock the sample input
i get a varying voltage between -6 and -13v but always stays in that range.

>>
>>
>> --- In cgs_synth@yahoogroups.com, sasami@ wrote:
>> >
>> > Also check you don't have your power rails swapped about.
>> > If you have used CA3401 instead of a lm3900, and it's seeing 30V it will go
>> > pop too, as they are only good for 15V rails, unlike the lm3900.
>> >
>> >
>> > >Hey guys, I just put together the SSG and it's not working so i tried to
>> > switch out the lm3900's after giving the board some continuity testing and
>> > looking over the board briefly, i still need to do a lot more
>> > troubleshooting but what i wanted to ask about was this,
>> > >when i switched the lm3900's out it froze my system up as if there was a
>> > short in the power supply.I did some tests to see but couldn't find a short
>> > anywhere so i put the old ones back in and system powered back on fine so i
>> > switched them out with brand new ones i had and it cooked them within
>> > seconds of powering up.
>> > >
>> > >Like i said i still have a bunch of leg work to do to figure out why it's
>> > not working but am confused that some of the lm3900's would create what
>> > appears to be a short and the others seem to have no effect ?
>> > >
>> > >Thanks, Tony
>> > >
>> > >
>> > >
>> > >------------------------------------
>> > >
>> > >The CGS Modular Synth home page: http://www.cgs.synth.net/
>> > >Yahoo! Groups Links
>> > >
>> > >
>> > >
>> > >
>> > _______________________________________________________________________
>> > Ken Stone sasami@ otherunicorn@
>> > Modular Synth PCBs for sale <http://www.cgs.synth.net/>
>> > Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>> >
>>
>
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>

_______________________________________________________________________
Ken Stone sasami@... otherunicorn@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>