DBX FS900 Power supply

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thomasdf

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When no connector is plugged in the input (TRS jack in my case) the LEDs are off, as they should be since no GR is happening.
When I plug my TRS jack in the input, they light up depending on the range knob position (no LED when the know is CCW and all LEDs when CW).
When there's audio playing thru the unit, the LEDs are just blinking and displaying random informations. When silence : LEDs are on, and they turn off when there's sound.
Maybe my best chance to solve this is getting in touch with an exorcist now :)
 

abbey road d enfer

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thomasdf said:
When no connector is plugged in the input (TRS jack in my case) the LEDs are off, as they should be since no GR is happening.
When I plug my TRS jack in the input, they light up depending on the range knob position (no LED when the know is CCW and all LEDs when CW).
When there's audio playing thru the unit, the LEDs are just blinking and displaying random informations. When silence : LEDs are on, and they turn off when there's sound.
that suggests a huge oscillation...
 

Brinxter

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Jan 3, 2012
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9
If I were you, I would use a pair of 24V Meanwell smps and LM317/337 for the regulated rails. That would take care of the magnetic radiation issue.
The 24V rails would need additional CLC filtering. See attachment.
I have PCB's for that. PM me if interested.
Hi what inductors are you using/recommend for the filtering?
 

thomasdf

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Aug 10, 2011
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ah wait, I didnt filter the 24v rails, they are straight out of the Meanwell PSUs... Maybe that's my problem ? I assumed that since it needed unregulated +/- 24v, taking it out of the PSU would be more than good enough.
 

thomasdf

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After some testing with 100uH and all sorts of other attempts, Abbey suggested me to test with an analog source, which I did... and magic... the LEDs behave perfectly.
We came to the conclusion that my converters produced a heavy amount of ultra sonics frequencies. I'll put a bypassable LPF (35Khz) on the audio path of the 902s and will report back !
 

trashcanman

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Jan 26, 2016
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Just a general note about these modules. I've been racking up a couple of the Noise Gates that had a few problems which were all due to bad switches on the front panel so anyone with problems should take a look at those first imo, at least on the older models. They were fairly easy to take apart and clean/fix but replacing them would probably be better in the long run.
 

thomasdf

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Aug 10, 2011
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Thanks for your input !
I ended up changing C1 and C2 at the input of the 902, for 4.7nF, making a 33.8Khz low pass filter with the 1K resistors, and solving my problem.
 

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