Harrison Ford Filter 500 series overtone problem

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Martan

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Nov 9, 2019
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37
Hi! Sort of:) 1st problem is that my cable plugged into the output was shorting the output to ground. I have one of those Mogami snakes that someone on ebay had put together. While I was trying to see if the cables were the problem I switched from one line to another. Random grab of line 5 turned out to be bad luck. It shorted the output to ground and seems to be why my DRV chip got hot and burned out. I had already desoldered the IC socket before figuring this out.

BUT, my -16V is still continuous with ground.....yet still measures -16V to ground and 32V to the +16. This is happening at the card edge connector at the back of the lunchbox. It seems like this should be a problem, but I've been running preamps in that slot prior to this with no problem. This is not supposed to happen, correct?
 

Martan

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Joined
Nov 9, 2019
Messages
37
Will do, but this happens at the 500 series lunchbox card connector. I'm wondering if there is just too low of resistance in the power supply that my multimeter thinks is continuity. I think below 100ohm it reads continuous (Fluke 87V)
 

jensenmann

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Oct 10, 2004
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2,634
Location
Karlsruhe, Germany
You have to pull the card out of the frame. Still the onboard smoothing caps will get charged through the meter´s current. That will show a short at the beginning of measurement. But if you measure for a while then you´ll see that the voltage drop (or resistance depending on which mesurement mode you´re using) your meter shows will rise (if there´s no short). In case there is a short on the PCB the meter will not change.
 

Martan

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Nov 9, 2019
Messages
37
With the card out and no ic's I get no continuity between ground and -16V. With the card in the slot and no IC's there is continuity, but I measure 16V. With no card in the slot the slot has continuity between ground and -16V
 

Martan

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Nov 9, 2019
Messages
37
AARRRRRGGGGGHH! So, that weird overtone series is also there if I run the signal through my FET/500 in the same lunchbox, and also there if I run the signal through a standard racked 1073 clone :( So, looks like its more of a Logic Pro or Apogee Symphony overtone problem (which sounds much more expensive).

Thank you to all of the kind people would made suggestions on how to fix things. Looks like the filters were just fine (despite me un-soldering and resoldering most of the components) and I can get on with making faceplates.

All the best,

Marty
 

Martan

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Nov 9, 2019
Messages
37
Switched to the other i/o card on the apogee and no overtones. The filters work fine. Mixed emotions :)
 

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