Hi,
I know you said early on that you tested and recapped the power supply
but this still sounds like a power supply problem to me. The loss of a
single diode in the bridge or a filter cap before the regulator might
not completely disable the supply, but would render it noisy under
load. I suggest checking the supply voltages (and ripple content if you
have a scope) ahead of the regulators. Also look for cold solder joints
or even improperly installed (polarity reversed) or improper values in
the main filter caps for the supply. If this noise is living in the
power busses, it would explain why it increases as additional sources
are added to the buss.
Jim Mikles
On 7/20/2011 6:23 AM, Matt Syson wrote:
Hi
Bar graph circuits tend to make a noise only when switching led
levels, especially LM3915 type systems. Not many have an oscillator
running so I am doubtful that it would be the metering.
I think you should be chasing poor power and connections around the
master sections.
You could try unplugging external gear to see if it is a 'ground loop'
problem attempting to appear when the desk internal grounds are
disturbed but this could be a different problem to the 'noise',
(assuming this is a crackly type of sound).
Matt S
On 20/07/2011 03:09, Doug Easley wrote:
Continuing the chase of aux noises, I noticed today that when I press
the monitor on in the meter select I get a funky ripple buzzy crud
added to a hummy sound. This is the first thing I've found that has
affected my noise. By pressing the peak/rms switches I can make the
optional phase meter go back and forth sometimes and hear a click
noise for every LED movement. So maybe I'm on to something. Then I
thought well disconnect the meter power and it will go away but no
such luck. With meter power disconnected the same sound would happen.
There are some meters that only have a few sections working which
hasn't been too much of a problem so far. I can meter in pro tools
and I have analog VUs on the master. Is there some way to bypass the
bargraph meter circuit to see if that's my problem. Are there caps in
there that are supposed to keep it quiet?
thanks for the responses, doug
On Jul 18, 2011, at 4:09 PM, Ike Zimbel<[email protected]> wrote:
Hi Doug,
Following on Matt's suggestions, I would agree that the
oscillator section could be suspect. I would also check that all of
the logic chips are well seated and that their leads and sockets
look good. Replace them if they don't. Also make sure that all of
the ground connections, including mechanical connections to the
front panel (pots, switches etc.) are clean and tight. It is
unlikely that the Aux sends are creating this noise, but more likely
they are amplifying noise that's coming from something common to
them, again as Matt said. I am away from the shop for a couple of
weeks so I don't have access to my Elan drawings to give you
specific chip names, locations etc.
Best,
Ike
On 11-07-18 8:54 AM, Matt Syson wrote:
Hi
You are looking for something 'common' as it adds up when listening
to more stuff on Solo.
It could be supply noise (check with an oscilloscope) or a module
which is seriously noisy or even talkback or slate tone circuitry
that has access to aux busses although may be nominally 'switched
off'.
Double check all possible outputs and look for any 'common'
circuitry (the 'block diagram' should get you close). Ultimately,
pull modules or 'break up' the mix bussing if it is available on
plugs.
Matt S
On 18/07/2011 13:35,
[email protected]<mailto:[email protected]> wrote:
Hello, I think this is the way to post here.
I have a 15 year old 40 channel Elan I bought new. It's been very
reliable. It was in a fire 7 years ago. I got it back in
commission after a couple of idle years of storage and
cleaning/repairing. It was recommissioned and has done pretty
well, everything works except some partially working l.e.d. meters.
Lately the master section has a small ripply sound when cranked
all the way up without channels turned on. Small annoyance, but
irritating. However when you solo the auxes you get a really
intense version of hiss noise ripply trash, sounds like a
combination of computer interference meets bad caps/junk. As I
said it's appeared of the last few months. Soloing A,B,1,2,3,4,
just adds to the crap incrementally. When using the track busses
to pro tools, it's fine , goes to pro tools good and quietly.
I recently tested and or replaced all the resistors in the power
supply and recapped the power supply. I also disconnected the
Elcos for everthing except the monitor one to the amps to make
sure it wasn't from another piece of gear.
I still have the trashy sound in auxes. Any suggestions? Any
logical procedure to locate the source of my noise?
thanks , doug
--
Ike Zimbel,
Zimbel Audio Productions Ltd.
Toronto
416-720-0887
"Studio House Calls". Authorized Warranty service for Allen&
Heath, Clear-Com, Drawmer, Soundcraft, SPL and Yamaha. Repairs and
upgrades to analog audio equipment including: AMEK, dbx, Neve,
Neotek, MCI, Soundcraft and more. Ask about our RF frequency
co-ordination services!
www.zimbelaudio.com
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