EE / Tech riddle re: Mackie board

Archived from groups: rec.audio.pro (More info?)

Ok, I'm dumbfounded. Can someone help me troubleshoot this one?
I had a session the other day recording drums through our Mackie 24-8
bus. While setting up and getting levels I ran into several dud
channels. I switched the mics to other channels, did the session, and
decided to test the board later.
So today I plug a dynamic mic into all 24 channels one by one and
discover that channels 3, 7, 8, 10, 11, 13, 15, and 16 allow little to
no signal in and the gain knobs have almost no effect.

THEN... I turn all the phantom power on and plug a condenser in. It
works perfectly on all 24 mic pres.

THEN... I turn phantom off and plug the same dynamic mic that I used
initially in to all 24 channels again and get perfect results on all
channels.

What gives? Why would cycling phantom power like this have this
effect? And why didn't certain channels work with the dynamic
initially?

Thanks in advance for any help,

Daniel Fox
ZUMIX, Inc

Archived from groups: rec.audio.pro (More info?)

"Daniel Fox" <upryz1@gmail.com> wrote in message
news:1121296164.129650.300190@g47g2000cwa.googlegroups.com
> Ok, I'm dumbfounded. Can someone help me troubleshoot
this
> one?
> I had a session the other day recording drums through our
> Mackie 24-8 bus. While setting up and getting levels I
ran
> into several dud channels. I switched the mics to other
> channels, did the session, and decided to test the board
later.
> So today I plug a dynamic mic into all 24 channels one by
one
> and discover that channels 3, 7, 8, 10, 11, 13, 15, and 16
> allow little to no signal in and the gain knobs have
almost no
> effect.
>
> THEN... I turn all the phantom power on and plug a
condenser
> in. It works perfectly on all 24 mic pres.
>
> THEN... I turn phantom off and plug the same dynamic mic
that
> I used initially in to all 24 channels again and get
perfect
> results on all channels.
>
> What gives? Why would cycling phantom power like this
have
> this effect? And why didn't certain channels work with
the
> dynamic initially?

Having just shed a Mackie SR32 with bad ribbon cables, all I
can say is been there and done that.

Steve nailed it in the other post.

Archived from groups: rec.audio.pro (More info?)

Daniel Fox <upryz1@gmail.com> wrote:
>Ok, I'm dumbfounded. Can someone help me troubleshoot this one?
>I had a session the other day recording drums through our Mackie 24-8
>bus. While setting up and getting levels I ran into several dud
>channels. I switched the mics to other channels, did the session, and
>decided to test the board later.
>So today I plug a dynamic mic into all 24 channels one by one and
>discover that channels 3, 7, 8, 10, 11, 13, 15, and 16 allow little to
>no signal in and the gain knobs have almost no effect.
>
>THEN... I turn all the phantom power on and plug a condenser in. It
>works perfectly on all 24 mic pres.
>
>THEN... I turn phantom off and plug the same dynamic mic that I used
>initially in to all 24 channels again and get perfect results on all
>channels.
>
>What gives? Why would cycling phantom power like this have this
>effect? And why didn't certain channels work with the dynamic
>initially?

Intermittent ground. Call Mackie and ask them for a replacement internal
ribbon cable.

You probably had a poor connection that was "sealed up" by the 48V
phantom. If so, it will go bad again.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

Ok,
I plan on opening the board up and dealing with ribbon cables. I'll
try and report the result. Some tips I picked up from a tech who has
done a ton of these:

1. Use a small vise to squeeze the ribbon cable into the plastic
connectors.

2. a *tiny* bit of deoxit and seat and reseat connectors several
times.

3. very slightly bend the pins with a pair of pliers so that upon
seating there is more pressure and better contact inside the connector.

Thanks to everyone for the help,

Dan Fox
ZUMIX, Inc

Archived from groups: rec.audio.pro (More info?)

In article <1122870537.998076.61580@g44g2000cwa.googlegroups.com> upryz1@gmail.com writes:

> I plan on opening the board up and dealing with ribbon cables.

> Some tips I picked up from a tech who has
> done a ton of these:
>
> 1. Use a small vise to squeeze the ribbon cable into the plastic
> connectors.

That's rarely where the problem lies. Usually you get a failure at
that point when you've tugged on the cable too many times. This isn't
really a problem inside the console.

> 2. a *tiny* bit of deoxit and seat and reseat connectors several
> times.

That can work. Since the pins and sockets are gold plated, Caig ProDif
Gold is probably the best thing to use that's readily available.
Stabilant 22 may also be good for this as it actually improves
electrical contact when the pins are properly mated, but it doesn't
solve a mechanical problem, which is what you have.

> 3. very slightly bend the pins with a pair of pliers so that upon
> seating there is more pressure and better contact inside the connector.

You could get lucky, or unlucky. I'd go with #2 only.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo