buildafriend
Well-known member
You should try pulling the channel cards. Divide and conquer is the name of the game
Noisy circuit, can a PCB trace or solder joint cause it? stumpped...
- Thread starter pucho812
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Help Support GroupDIY Audio Forum:
Brian Roth
Well-known member
Looking again at the Elan I/O module schemos, I can now see how a rogue channel could inject noise into a channel of the stereo bus. To try and isolate:
1. Go through each I/O strip and push the "Monitor On" switches to off position while listening to the noise.
2. If No Joy (and with the "Monitor" switches still off) then walk through the modules and press the "Rev" switches.
Bri
1. Go through each I/O strip and push the "Monitor On" switches to off position while listening to the noise.
2. If No Joy (and with the "Monitor" switches still off) then walk through the modules and press the "Rev" switches.
Bri
pucho812
Well-known member
Brian Roth said:
Yes went there the first time I was out looking at the desk. No joy.
If the noise is intermittent, try wiggling wires/cables while listening. Tapping around with a pencil eraser can sometimes identify a flaky solder joint.
Semiconductors can fail gradually but generally go from bad to worse, not good/bad/good again.
JR
Semiconductors can fail gradually but generally go from bad to worse, not good/bad/good again.
JR
Brian Roth
Well-known member
pucho812 said:
And you also muted the Echo Returns on the master module? Hmmmm...
bri
pucho812
Well-known member
Brian Roth said:
yes... I know it's a separate path but if I solo something, no noise.
Brian Roth
Well-known member
Approx. 1-1/2 years ago I installed a 48 input Elan. Clues indicated it was built mid 1990's before Sytek bought the product line. The schematics I've managed to scrounge are fairly close to the actual desk, although the master motherboard/"ribbon chaos" is quite a bit different since the master section sits between I/O modules 24 and 25.
However, earlier comments in this thread seem to imply the noisy desk is MUCH newer, so perhaps the schemos I have don't apply.
So, I'm also stumped. Have you looked at the noise with an oscope?
Bri
However, earlier comments in this thread seem to imply the noisy desk is MUCH newer, so perhaps the schemos I have don't apply.
So, I'm also stumped. Have you looked at the noise with an oscope?
Bri
pucho812
Well-known member
Yes... I scoped out the noise. With a sine wave present in a channel going to the stereo buss, I see a nice clean sine wave when I measure at the ribbon output of the master, however it does bounce around like d.c. Slightly.
ruffrecords
Well-known member
What kind of sol is this. Is it solo in place (destructive) where it mutes all the other channels or is there a separate solo bus which feeds separately into the monitor via a relay/FET switch?pucho812 said:
Cheers
Ian
pucho812
Well-known member
ruffrecords said:
Yes separate solo bus, so when you solo it is a different set of chips feeding the monitor path. Yes it is destructive, solo in place
solo each channel one at a time... until you find the unhappy one.pucho812 said:
If none problem is in L/R bus
JR
pucho812
Well-known member
JohnRoberts said:
that's the conundrum, went through every channel and no noise. so yes I would agree it is L/R buss but that was swapped with a known good replacement and the noise persisted. which has me now thinking a faulty ribbon off the mother board.
pucho812
Well-known member
so sytek thinks it's a grounding issue and it's caused at location. I have never heard a grounding issue ha results in that kind of noise. I also would think if it was grounding that it would be in both sides of the stereo bus.
pucho812
Well-known member
Well haza haza. After a much back and forth with the manufacturer, mainly me insisting the fault is the motherboard and the manufacturer insisting it was not, they sent out a replacement motherboard.
Took several hours to remove the old motherboard. Unsoldered every wire. Then soldered the same wiring to a new board. Once I did that, everything was working as it should. All the noise and everything went away. Could it have been that I touched up a bad joint? No, I had already went there on the old motherboard. Since the motherboard is traces and a few passive components, I can only assume at this point that a trace cracked with a hairline fracture causing problems. The ribbon cables were reused and ok. No failed passive components, no active components. But anyway is all working 100% now.
Took several hours to remove the old motherboard. Unsoldered every wire. Then soldered the same wiring to a new board. Once I did that, everything was working as it should. All the noise and everything went away. Could it have been that I touched up a bad joint? No, I had already went there on the old motherboard. Since the motherboard is traces and a few passive components, I can only assume at this point that a trace cracked with a hairline fracture causing problems. The ribbon cables were reused and ok. No failed passive components, no active components. But anyway is all working 100% now.
A partial short from a bus to ground like from a solder blob or splatter, could cause an elevated noise gain, but they are usually visible.pucho812 said:
Academic at this point with it fixed, congrats.
JR
pucho812
Well-known member
Thank jr.... onto the next thing
So that's how this worked out. I was just as stumped the day we went out and looked at it together, but also came away from that visit thinking that the motherboard had to be defective.
pucho812
Well-known member
Cracked trace perhaps
