Dotcomformat

I just built a MOTM Ultra 300 VCO. It is only the second module I've assembled. Now that it's all put together, and all connections doublechecked with no shorts, I find it doesn't work. I only have a cheap oscillator and two multimeters (one analog, one digital), along with a toolbox full of newly purchased tools for module assembly.

Where should I start in debugging? It is powered from a synth.com cabinet, using a synth.com QMPSA MOTM/Blacet Power Adapter.

Thanks, those are exactly the kind of suggestions I need! I am very green at this. The chips and capacitors are all oriented correctly. How exactly do I measure the power rail voltages? Pretend you are explaining it to a kindergartener :-)

What would constitute overly warm in a chip?


--- In dotcomformat@yahoogroups.com, Mark Rivera <marr@...> wrote:

>
> What does "doesn't work" mean?
> What do the power rails measure as for voltages?
> Polarized capacitors (electrolytics or tantalum) in the correct orientation?
> Chips also correct orientation?
> No chips getting overly warm when plugged in?
> 
> 
> On Wed, Nov 9, 2011 at 8:36 AM, Welton Barker <weltonb@...> wrote:
> > I just built a MOTM Ultra 300 VCO. It is only the second module I've assembled. Now that it's all put together, and all connections doublechecked with no shorts, I find it doesn't work. I only have a cheap oscillator and two multimeters (one analog, one digital), along with a toolbox full of newly purchased tools for module assembly.
> >
> > Where should I start in debugging? It is powered from a synth.com cabinet, using a synth.com QMPSA MOTM/Blacet Power Adapter.
> >
> >
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>

What does "doesn't work" mean?
What do the power rails measure as for voltages?
Polarized capacitors (electrolytics or tantalum) in the correct orientation?
Chips also correct orientation?
No chips getting overly warm when plugged in?

On Wed, Nov 9, 2011 at 8:36 AM, Welton Barker <weltonb@pobox.com> wrote:
> I just built a MOTM Ultra 300 VCO. It is only the second module I've assembled. Now that it's all put together, and all connections doublechecked with no shorts, I find it doesn't work. I only have a cheap oscillator and two multimeters (one analog, one digital), along with a toolbox full of newly purchased tools for module assembly.
>
> Where should I start in debugging? It is powered from a synth.com cabinet, using a synth.com QMPSA MOTM/Blacet Power Adapter.
>
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>

> What would constitute overly warm in a chip?

Overly warm:  either uncomfortable for a finger placed on top, or
noticeably hotter than the other chips on the board. If so, disconnect
power immediately. It indicates a short circuit.


Power rail checking: Fourth bullet point here:
http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&VPW=1920&VPH=768

If the power rails are okay (i.e., 15V and -15V) then it is something
else. If they are not +/- 15V, then immediately turn off power. Check
for shorts with a magnifying glass under at least two different light
sources and angles. Shiny solder can be deceiving under certain
lights/angles of view.


Go through that whole document at
http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&VPW=1920&VPH=768

hth,
Mark

On Wed, 9 Nov 2011, Mark Rivera wrote:

>> What would constitute overly warm in a chip?
>
> Overly warm:  either uncomfortable for a finger placed on top, or
> noticeably hotter than the other chips on the board. If so, disconnect
> power immediately. It indicates a short circuit.

It can also indicate a backwards chip.  I've done it.

-- 
David Griffith
dgriffi@cs.csubak.edu

A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

On Thu, 10 Nov 2011, Welton Barker wrote:

> Thanks, those are exactly the kind of suggestions I need! I am very green at this. The chips and capacitors are all oriented correctly. How exactly do I measure the power rail voltages? Pretend you are explaining it to a kindergartener :-)

First, MOTM has its own yahoo group so you might want to
subscribe and ask there:  motm@yahoogroups.com.

If you have the assembly manual/user guide, there's a
troubleshooting section which gives you some things
to do and voltages to measure.  Do those along with
the general troubleshooting pointers handed out.

And I'll repeat what someone else asked:  in what
way *exactly* is it not working and how did you set
it up for this test?

m

--
Monty Brandenberg