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Old May 22nd, 2018, 08:37 AM   #1
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Sound Devices SD302

Does anyone have any tech knowledge of the SD302?

The mixer has developed self-noise which is most severe when CH1 mic is selected. It sounds like the sort of noise you sometimes get with old amps when a carbon track builds across a circuit board. In this instance it is a background low crackle with intense crackle over. The noise does cross over faintly into the other two channels.

I bought it used with an uncertain history. It worked fine initially then gradually has developed the self noise.

It is of doubtful worth sending it back to the US from Australia to be fixed, that is assuming the parts support remains. A look inside revealed it may have been in a hostile environment in the past with some white bloom corrosion inside the case. Some of that had dusted off onto the PCBs.

I opened it out completely, gave it a good careful thorough clean with PCB cleaner, fine art brush and blow out, a close look for any crud that might be conducting between joints, then a good long rest to disperse any residual solvent. This seemed to fix the problem for about 20 minutes then it came back.

There are three transformers which are mounted flush to their PCB and impossible to clean beneath. Before I go through the torment of unsoldering and pulling those off to clean beneath with the attendant risk of heat damage, does anyone have a clue as to how that self noise might be caused.
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Old May 22nd, 2018, 11:13 AM   #2
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Re: Sound Devices SD302

Hmmm. I've owned a 302 for 15 (or more?) years now. It's held up pretty well, despite my abuse and neglect (and rain, and beaches with salt-water mist, etc). So if some corrosion got into yours, it may have really faced some tough situations (as you say).

I hear you about the probably-not-worth-it sense of shipping it back to the US for a spa visit; I just saw one for sale for $500US. But you know, I've gotten REALLY GOOD email and phone support from Sound Devices over the years (I own a bunch of their stuff). As in: they factor in the technical expertise of the particular user.

I used to build equipment for recording studios (I didn't design the stuff, but I did solder, test, etc), so I'm OK with pulling and replacing components on PCBs. But modern surface-mount stuff is beyond my current skill set.

So drop SD a line and they'll probably help out. Considering how many 302s are out there, I'd guess they've come across just about every situation and possible failure.

https://www.sounddevices.com/support/inquiry

An obvious suggestion, but really I find SD's support (and the knowledge of the people on the support desk) to be pretty damn good.

Good luck and let us know what happens!
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Old May 22nd, 2018, 12:27 PM   #3
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Re: Sound Devices SD302

I use that mixer. There is a small chance you could have accidentally flipped a switch on the side (line/mic/phantom power/Tpower/48/24v). Like Jim said its still worth a lot of money, SD is a good company if it was me Id send it in or talk to a tech.
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Old May 22nd, 2018, 02:29 PM   #4
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Re: Sound Devices SD302

As others have stated, the lowest cost pre-owned 302 we've seen is $500 usd, so even sending it to the mother ship would most likely be a lot less than replacement, unless you can find someone down there to work on it.
In any case, I'd talk to someone at SD.
I've had a 302 since 2006 and would not part with it.
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Old May 22nd, 2018, 07:19 PM   #5
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Re: Sound Devices SD302

Workday is over, so I checked on something I remembered and found some records.

Three years ago, after a dozen years of problem-free service, my 302 wouldn't power up from either internal or external power. GAH! But luckily I had a backup mixer.

So I contacted Sound Devices. They said to send it in, and said their repair rate for out-of-warranty 302 mixers was $150US per hour. They suggested a pre-authorization fee of $300US to fix the thing. At the time, used 302s were going for about $850US or so, so that seemed reasonable.

I can't really exactly what the problem was, but SD charged me $175.22US plus shipping for the repair.

So today, even if their labor rate hasn't increased, I wonder if round-trip shipping from Australia + labor + parts is worth it....especially with the corrosion you've already found.

But again, SD support may be able to say something like "oh, that's just sound dust; don't worry about it" or maybe "sounds like your 302 went scuba diving; it's probably not worth the effort to ensure reliability."

I'm not trying to be negative...more that SD may be able to tell how serious the issue you're facing is, and what the exact (or likely) cause it, and how hard it would be for you (or a local tech) to repair the thing.


OK, I'm getting redundant. Hopefully the numbers I provided here are helpful.

Good luck!
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Old May 25th, 2018, 04:39 AM   #6
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Re: Sound Devices SD302

Quote:
Originally Posted by Bob Hart View Post
It is of doubtful worth sending it back to the US from Australia to be fixed, that is assuming the parts support remains. A look inside revealed it may have been in a hostile environment in the past with some white bloom corrosion inside the case. Some of that had dusted off onto the PCBs.
Sound Devices is quite good with support, even for older units, but the costs of shipping plus the costs of parts and repairs, means I am very doubtful it is worthwhile with the very low cost of what the 302 is worth today.

I'd just write it off (assuming that just ringing/emailing them doesn't turn up any worthwhile leads) and buy something better/newer instead.

What exactly are you using the 302 for, and what are you using it with?

The Zoom F4 is an insanely crazy deal now at only US$450 (or if you're happy to wait a little longer and spend a bit more then the Zoom F8n is only weeks away from being launched officially).
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Old May 26th, 2018, 04:29 PM   #7
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Re: Sound Devices SD302

So here's my suggestion, Bob:

Drop a note to Sound Devices.
Could be this is something you could fix (since you seem pretty handy with a soldering iron), or something a local tech with more skills could fix with a little input from Sound Devices.

If it looks like your 302 is beyond repair, maybe convert it to studio use. You still have two good channels right? So you could:

-Use it as a nice preamp for voice over.

-Use it as a stylish, accurate, and useful meter bridge under your main editing monitor.

-- Even build a fun case for it so it looks extra slick...maybe even cut off the strap/protector wings so your cabinet will be a bit more flush.

But I hope you can resurrect your 302. I still use mine; it's a great piece of kit!

And let us know how your repair/repurposing is going!
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Old May 28th, 2018, 01:49 PM   #8
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Re: Sound Devices SD302

Thank you for all your responses. Yes it is a great mixer. The noise issue arose after about 12 months.It also became a bit finicky about turning on in cold weather.

I've gone through all manner of combinations with the phantom power switches. I use phantom powered mics. The noise is significant on one of the channels but does cross over into the others at a very ow level.

I had it rigged for recording from a Decca tree outdoors for some events, a strange and different way of doing things. The Decca tree is normally used indoors.

The three channels and their switched assignment into two output channels was handy for feeding a two channel recorder. Without three clean channels I can do this no longer.
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Old November 1st, 2020, 11:15 PM   #9
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Re: Sound Devices SD302

Well win some and lose some. I sent myself slightly wild trying to make the phone work and was not in a fit state to sleep. Some years back I bought a field mixer off the eBay at what was then a bargain price. It turned up okay and fully functional except there was a fault within the fancy lights which tell you the levels which had been disclosed.

However, within a few months it developed self-noise in the form of a loud crackle in the audio. The cost of sending it to its home was not worth the value. I have had a few goes at fixing it. There are signs there may have been a seawater splash onto the top as patches of white crystal were inside. I cleaned and swabbed those out thoroughly but the issue did not go away.

I finally found the source of the crackle. There are a bunch of little slide switches on the side. They did not make a crackling sound when moved, so I left sleeping dogs to lie. However this time they seemed a little baulky as slide switches do become over time. I gave them a good shot of WD40 and then a blast from the lens air can to move the WD40 around inside them.

Noise gone.

It seems that conductive but resistive tracks may have developed inside the switches across insulation between contacts due to damp drawn by nearby salt. These little audio mixers have such high efficiency that a small current going across would be strongly amplified. We shall see if I am right but so far so good.

The construction inside is really remarkable. The circuit boards and all their little components are encapsulated. It is things which are attached like switches and plugs which are vulnerable.
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Old November 3rd, 2020, 11:37 AM   #10
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Re: Sound Devices SD302

As a long shot question, does anyone happen to know the product name and brand of the small LEDs in the audio levels chaser display in the Sound Devices 302 mixer.These or the sub-assembly PCB are not available from Sound Devices as a user-installable part.
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