Cgs synth

Take some high res photos - IN FOCUS - of both sides so we can look at it.
Ken

>Yup, only connected to 1n cap and not using pad T. No shorting when chip

is out. Burn mark on pin 9 appeared from first LM3900 going poof. I've
checked solder joints and traces many times over. I can't help but think
it's something else.. maybe a weird transistor or cap or mislabel resistor
here? btw, same behavior on both LM3900s... extreme heat. Ouch.

>
>--- In cgs_synth@yahoogroups.com, "cg_synth" <sasami@...> wrote:
>>
>> pin 9 should be connected only to a 1n capacitor. Pad T is not used.

There should be no current flow through it. Find out what pin 9 of the
socket is short circuited to.

>>
>> --- In cgs_synth@yahoogroups.com, "Sean" <solidratestudios@> wrote:
>> >
>> > Been testing my voltages (with blown LM3900s removed) btw, pin 9 is

getting burns on IC socket.

>> >
>> > 1) +7.50
>> > 2) 0
>> > 3) -7.41
>> > 4) -14.01
>> > 5) +3.59
>> > 6) -0.06
>> > 7) -14.87
>> > 8) -0.01
>> > 9) 0
>> > 10) -0.10
>> > 11) -0.06
>> > 12) +8.06
>> > 13) -3.34 (stepped), +5.82 (smooth)
>> > 14) +14.86
>> >
>> > Strange voltages I'm getting.
>> > -Sean
>> >
>> > --- In cgs_synth@yahoogroups.com, "adematteo" <adematteo@> wrote:
>> > >
>> > > Sorry, that came out as a big garbled mess.
>> > >
>> > >
>> > > 1) +13.54
>> > > 2) 0
>> > > 3) -9.23
>> > > 4) -14.35
>> > > 5) +11.13
>> > > 6) -0.113
>> > > 7) -15
>> > > 8) -.010
>> > > 9) 0
>> > > 10) -.112
>> > > 11) -.115
>> > > 12) +13
>> > > 13) -4.92 (Stepped U5) +12.64 (Smoothed U2)
>> > > 14) +15
>> > >
>> > > --- In cgs_synth@yahoogroups.com, "adematteo" <adematteo@> wrote:
>> > > >
>> > > > So all the voltages read the same on both chips except for pin 13

which i make a note of :

>> > > >
>> > > > 1) +13.54 14) +15
>> > > > 2) 0 13) -4.92 (U5 Stepped) +12.64 (U2 Smooth)
>> > > > 3) -9.23 12) +13
>> > > > 4) -14.35 11) -.115
>> > > > 5) +11.13 10) -.112
>> > > > 6) -0.113 9) 0
>> > > > 7) -15 8)-.010
>> > > >
>> > > > --- In cgs_synth@yahoogroups.com, sasami@ wrote:
>> > > > >
>> > > > > Seriously, chip frying is indication of serious power routing issues.
>> > > > >
>> > > > > With the chips OUT, read the voltages on each pin of the socket,

then list

>> > > > > them here.
>> > > > >
>> > > > > Ken
>> > > > >
>> > > > > >Thanks again Ken, and Rich for all the helpful suggestions.
>> > > > > >I've triple checked component values at this point,replaced
>> > > > > trannies,ic's,gone over continuity testing and visually inspected

the board

>> > > > > under a magnifying lens with no luck.
>> > > > > >
>> > > > > >There has to be a short or something that i am just not seeing

because i'm

>> > > > > getting inconsistent results when i plug it in every time i make

a change.I

>> > > > > fried another lm3900 in the smooth section only this time it took

a few

>> > > > > minutes.I've been able to get a slewed/smoothed signal to pass but no
>> > > > > control over the hold or rate, i've gotten a steady tone from

plugging the

>> > > > > cycle into the in of the smooth section but again no control to

change the

>> > > > > pitch and now i'm back to were i started with no effect and a strong
>> > > > > negative voltage on the outputs ?
>> > > > > >
>> > > > > >I'm gonna take a little break but at this point i'm seriously

considering a

>> > > > > do over.
>> > > > > >
>> > > > > >Thanks again guys i really appreciate you taking the time to

offer your

>> > > > > time and experience !
>> > > > > >
>> > > > > >--- In cgs_synth@yahoogroups.com, sasami@ wrote:
>> > > > > >>
>> > > > > >> Been thinkng about this - The problem may also be caused by

putting a

>> > > > > >> voltage on the input pins, which are designed for current, not

voltage.

>> > > > > >> Check nothing is shorted to them. Check your resistor values.

Maye sure you

>> > > > > >> haven't installed 15 ohms instead of 1M.
>> > > > > >>
>> > > > > >> Ken
>> > > > > >>
>> > > > > >> >Will do.Thanks guys!
>> > > > > >> >I'll report back when i get this working.
>> > > > > >> >
>> > > > > >> >--- In cgs_synth@yahoogroups.com, Richarius Molindarius
>> > > > > >> <richmolindarius@> wrote:
>> > > > > >> >>
>> > > > > >> >> Use a well lit magnified lamp. Especially for that board.

Hard to find

>> > > > > >> >> small trace breaks and bad solder joints.
>> > > > > >> >>
>> > > > > >> >>
>> > > > > >> >> [Non-text portions of this message have been removed]
>> > > > > >> >>
>> > > > > >> >
>> > > > > >> >
>> > > > > >> >
>> > > > > >> >
>> > > > > >> >------------------------------------
>> > > > > >> >
>> > > > > >> >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/>

>> > > > >
>> > > >
>> > >
>> >
>>
>
>
>
>
>------------------------------------
>
>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/>