SV: more newbie terror

[*Star Project]

if the resistans measured to 50k in the circuit and 100k
outside my first guess would be that a connection that
shouldnt be there is present, at least maybe and its giving
a parallel connection to perhaps someother resistor giving
50K togheter. this would also mean the circuit is changed and
the currents and connection is not in order. check if anything
that shouldnt be connected isnt. at least thats a start.

/ Andreas H

-----Ursprungligt meddelande-----
Från: owner-synth-diy at node12b53.a2000.nl
[mailto:owner-synth-diy at node12b53.a2000.nl]För Egbert Teeselink
Skickat: den 5 januari 2001 20:57
Till: synth-diy at node12b53.a2000.nl
Ämne: more newbie terror


hail pros!

here are tha newbies again.

we cooked a VCO (the one at the bottom on
http://www.xavax.com/efm/cbook/vco5.html (with the LM13700)). We let away
the [pitch] part and the [1V/Oct]
part at the CV entrance, because happy harry told us it would still work
that way.

So, we plugged it in and smoke came out. At first, we didn't mind for, i
mean, we see dead people too, so why not smoke coming out of homecooked
vco's. But it got us thinking, so we decided to pull the plug again. =)

Then we switched the wires connected to the 2N3819 FET transistor so that
they were actually connected as they should, but it still didn't work. The
smoke (which was probably caused by a little bit of shortcut in the trimpot
we re-soldered) is gone now, but still nothing but some weird noises are
heard, no clear tones. So we decided to check every resistance with a
multi-meter, and found something weird when measuring the 100K resistor (the
one going
from the FET transistor to negative source): It only gave 50k Ohm. Also,
when we measured it the other way around, the multi-meter gave us _infinit_
ohm. So we removed the resistance, put another 100k in place, but the same
thing happened. Outside the circuit, they both read 100k Ohm, both ways
around.

Something is obviously wrong in our circuit, but we couldn't find anything
which might be the cause. Anyone having a clue? I mean, do problems like
this seem familiar to you gurus?

Thanks alot, Peter van Hamersveld and Egbert Teeselink

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