airtech

Sorry! Another ADR Compex Question
« on: December 15, 2006, 09:40:56 PM »
Finally changed out the 220 transformer to a 110 volt on my ADR F760-RS and took a listen.  Noticed some scratchy pots right off the bat, so I changed those out and also recapped the A and B boards.  It really opened up the sound of the unit just by the recap.

The problem that I have, is that with the unit on, the individual channel input and output pots open all the way, the output pot open all of the way, and when I adjust the input pot past 7, the unit starts to flutter and pop in sound and my external vu's peg out.  I drop down the pot to below 7 and all is fine.  This happens even without any sound inputed into the unit.  If I turn up the input and output all the way and drop down the individual input pots the sound goes away.  If I take out either side, the other side still exhibits the flutter and popping sound.  Any ideas where the problem may be?  These are the problems I was trying to cure by replacing the pots, but nothing went away.  

Thanks again for all the help.

Nate

PS.  I haven't calibrated the unit since I got it, but I'm thinking it's something else. Maybe there is a tech in my area.  Los Angeles.


SSLtech

Sorry! Another ADR Compex Question
« Reply #1 on: December 15, 2006, 09:57:37 PM »
"Motorboating"... would that describe it?

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

airtech

Sorry! Another ADR Compex Question
« Reply #2 on: December 15, 2006, 10:19:12 PM »
Well yeah, now that you mention it.  Kind of like my Grandpa's 40 year old Mercury 40 horse.  Some similarities there.

Really wierd.

You were serious right?

airtech

Sorry! Another ADR Compex Question
« Reply #3 on: December 16, 2006, 01:12:24 PM »
The other F760's that I used before had the expander section in them and even though I didn't use that portion, they didn't do what the unit I just bought does.  They actually exhibited some "breaking up" that was kind of nice for my drum kit.  

Not this fluttering, or motorboating.  Something's overloading or shorting out or something.  Not real technically minded here.  All the units that I've used have been unbalanced, though the unit I have now looks like they had the optional transformers at one time and took them off for some reason.

airtech

Sorry! Another ADR Compex Question
« Reply #4 on: December 17, 2006, 09:28:11 PM »
Any tech out there that knows about these units?
Thanks.

Sorry! Another ADR Compex Question
« Reply #5 on: January 05, 2007, 12:23:15 AM »
i would say calibration. be ready.definitely one of the most tedious gear to do
Wonderland Audio Spain
www.wonderlandaudio.com

Steve Jones

Sorry! Another ADR Compex Question
« Reply #6 on: January 05, 2007, 05:59:51 AM »
I have a convoluted calibration guide around here somewhere....
Synthesizer technician
Sydney Australia.

http://synthrepairs.com

JdJ

Sorry! Another ADR Compex Question
« Reply #7 on: January 22, 2007, 10:59:48 AM »
You motorboating son-of-a *****!

Sorry- I couldn't resist!

:green:
 Good luck with it.

-Josh

SSLtech

Sorry! Another ADR Compex Question
« Reply #8 on: January 22, 2007, 12:10:28 PM »
Check the rail voltages when this happens. If they're dancing or bouncing with the motorboating (yes, I was being serious!) then you may have some rail decoupling caps (electrolytics) which could have gone low value.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

 

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