DBX286 with an 8Khz whine from the de-esser

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Nathaniel Steele
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DBX286 with an 8Khz whine from the de-esser

Post by Nathaniel Steele »

The other DBX post reminded me I have a 286 at home which works fine except when the De-Esser is engaged you get an approx 8Khz whine in the audio. I suspect an op-amp is oscillating in the De-ESSER circuit but I havent been able to track it down. Anyone ever have this happen or have some advice? They arent my favorite processors, but it would be nice to have it fully functional....

Thanks!

grich
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Re: DBX286 with an 8Khz whine from the de-esser

Post by grich »

WAG, since I never worked on one...look for dried-up caps on the power supply rails.

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Bill DeFelice
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Re: DBX286 with an 8Khz whine from the de-esser

Post by Bill DeFelice »

You don't mention which version of the 286 you have. I do recall something similar to what your speaking of with the original Project 1 version, which has the separate wall-wart power supply. I have a few of the updated 286a units and have never had that issue, although I found them a bit too transparent for my tastes.

If you have the original Project 1 version here's the archived schematics for the early versions: DBX 286 Project 1 Schematics
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Nathaniel Steele
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Re: DBX286 with an 8Khz whine from the de-esser

Post by Nathaniel Steele »

It's not the project1 version, and It's not the new "s" version, so maybe its the "a" version. It has an internal PSU, and a black case with grey/white lettering (IIRC, havr to dig it out of the closet again...)
Bill DeFelice wrote:
Sun Feb 17, 2019 12:47 pm
I have a few of the updated 286a units and have never had that issue, although I found them a bit too transparent for my tastes.
It's not my favorite either but it would be nice to have it fully working.

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Bill DeFelice
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Re: DBX286 with an 8Khz whine from the de-esser

Post by Bill DeFelice »

I have the 286a versions. I can't find my copy of the schematics at the moment but it's possible the ones I previously linked to may be close enough for troubleshooting. I don't recall what I did to the one I repaired and it's no longer available to me to examine which components I replaced. Does the oscillation change when the threshold or frequency controls are manipulated?

I hate to blindly suggest that you shotgun caps in that section of the board but I don't know if you have a o'scope available to trace the problem or not.
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Nathaniel Steele
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Re: DBX286 with an 8Khz whine from the de-esser

Post by Nathaniel Steele »

AS I recall, it came and went with the bypass of the de-esser section, the de-esser controls didn't affect it. I do have a scope and remember trying to track it down, but it seemed to be everywhere. I could probably shotgun caps, nothing looked bulged or leaking. Time to dig it out and try again, since I don't plan on moving again this year......which was why it got shelved back in august...

Thanks Bill.

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