Caps list for BIG channel & Center section

Graham Langley founded Amek in 1973 with Nick Franks. Since then, AMEK and TAC recording consoles have been the choice of demanding audio professionals for over 25 years.

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Re: Caps list for BIG channel & Center section

Postby swor27 » Mon Oct 19, 2015 5:40 am

also good advice, ill not spend the time to recap the modules im sending (which looking for the path of least resistance, i would have done anyway... haha).
Interesting some caps are in the wrong way... is this something they did on purpose? or just a factory/tech mistake?
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Re: Caps list for BIG channel & Center section

Postby Jim Williams » Mon Oct 19, 2015 10:24 am

It's more than common, it's standardized in most gear. Designers assumed DC offsets would be low so they didn't care. Electrolytic caps can tolerate up to 20% of their rated voltage with a reversed DC polarity. That doesn't make it acceptable as THD also rises. It's a matter of convienience.

Even if the same opamp is used throughout with it's tendency to have DC offsets at either positive or negative polarity, run an inverting stage and you just reversed that offset. As long as the el caps don't blow, most designers don't care about the increased THD.

In order to correct that oversite, you must select the opamp used first, then measure the DC offsets and polarity on each opamp output pin. Then re-orient the cap the correct way and be done with it. Usually after 'correcting' a few thousand caps in a LFC, you realize that it should have been done and marked correctly during manufacturering. You end up being the manufacturer yourself as you are completeing the design long after sale.

Selecting low offset trimmed opamps allows the after-sale 'designer' to remove most of those caps.
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Re: Caps list for BIG channel & Center section

Postby swor27 » Thu Mar 09, 2017 6:59 am

Hey Guys, im JUST NOW getting to this project... life happens. haha
as im setting the desk up and going through it, its not too happy...

Im having issues with the console passing signal through any center section “components"

The center section was modded by Jim Williams almost exactly a year ago.

I DO get signal out of the buses on individual channels
I DO get signal to pass thru to the speaker outputs WITHOUT the center section seated in its connector (but ribbon cables are connected)
I DO NOT get signal passing out any of the aux sends
I DO NOT get stereo bus to pass signal from channels routed to ST bus etc.

Im not seeing 5V light on the desk light up and have found the battery to be leaky on the CPU card, which I’ve removed (see pictures)

Im not sure if this would be an issue within the BIG 3 module, a 401 PSU issue (which all outs are testing correct with DMM), or an issue with the CPU card causing other issues?

Thank you for any insight!

Regards,

Dylan
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Re: Caps list for BIG channel & Center section

Postby swor27 » Thu Mar 09, 2017 7:06 am

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