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]
> > > > > >> >>
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >------------------------------------
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> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> _______________________________________________________________________
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> > > > > >> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
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> > > > > >
> > > > > >
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> > > > > >Yahoo! Groups Links
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> > > > > >
> > > > > >
> > > > > >
> > > > > _______________________________________________________________________
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