Topic: Any electroncs/preamp wizes out there?

[Swampy]

Hey everyone. So I started to gain mod my DMIC-20 and got to a point that I kind of got over my head. A board member here agreed to finish the mod out of the goodness of his heart, for which I am very grateful. So I got it back tested it out on the home system, and ran it for a show. Eveything seemed to work great. I ended up selling it and the person who bought it said that they had a problem with one of the channels dropping 30dB. I got it back at home and Im doing some testing and Im showing idenitical levels. Im not accusing the person who bought it of anything, I have every reason to believe that he was telling the truth, so I definitely want to get to the bottom of this becuase I really can afford to not sell this thing... Now, I had put the burr brown IC chips, and he said that he switched them (left channel chip to right and vice versa) and it worked for a little bit and then it dropped back down again... I really need some help, becuase Im not much of electroncs guy.. Do you think that this could be because of the IC chips or do you think it would be because of the gain mod? Can anyone help me out? If anyone needs more details, please please let me know! 

[pfife]

sorry can't help... +t for the troubles, hope everything works out.

[leegeddy]

alex;
i would highly doubt that the BB INA217 chips are the culprit. i have those chips in both my mv100 and the dmic and they work fine.

marc

[Swampy]

hmm, ya, I guess its the gain. I guess Im just gonna have to eat it and just deal with it

[chase]

i'm assuming you used those burr brown ICs for continuous gain between the resistors?  i would do some testing on the chips, not to make sure the chips arent busted but to make sure that Vin, Vout, and Vcc are at what they are supposed to be.  got a schematic?

[nic]

I was the person who bought it from Alex.

I'm fairly positive it isn't the Burr Brown chips as when I switched them L>R, R>L, the dropping signal didn't move with the chip.

if I had to guess, it's something in the gain pot-mod, cold solder joints or possibly a ground loop.
when I tapped the box, the signal would drop in/out

[chase]

well if you open it up and take a look at it and can't see anything visibly wrong with any of the solder points, i would get a schematic and do some testing to try to pinpoint the problem and possibly resolder something.

[Swampy]

Its not the chips, Ive tried replacing them, and it still dropped. All the solders look to be good. i really dont know anything about schematics or electronics really for that matter so I dont know how much that would help me. I guess Im just under qualified to fix it. Thanks for the help so far everyone!

[F.O.Bean]

alex, if yoyre THAT bad off, and have schematics, i will take a look at it for ya i guess, i wont do ANYTHING to it unless you tell me too

did al not help out w/ telling ya his did the same thing till he cleaned it

[Swampy]

did al not help out w/ telling ya his did the same thing till he cleaned it

Where?

[F.O.Bean]

did al not help out w/ telling ya his did the same thing till he cleaned it

Where?

http://taperssection.com/index.php?topic=36279.0

[dklein]

If tapping the box makes it go in and out then you're dealing with a physical connection issue.  Hook up some mics, monitor on headphones while you play around, find the loose thing and fix it!

[Swampy]

I shook it every once in a while for like an hour and couldnt get it to go out...