11.25khz weee sound on aux/cues

[unitedreco]

out of nowhere the gremlins came out. Scoped out the auxs/cues and i see and hear an 11.25kz weeeeeee almost like digital giberish or a mouse getting strangled on the aux/cue master sends although its oscillating at much much higher levels, dropped all the dls not outboard gear, pulled all the modules and killed all the buckets all clean there as well, program out is clean, aux/cues direct out at patch is where ive narrowed it down to ....recapped the aux/ cue cards in center section noise is still there, im lost and its late , if anyone has any ideas or experienced this let me know. Thanks

[michaeldtech]

The mix bus does not have the noise?
One common thing causing oscillation on all buses was bad decoupling caps on a channel dynamics card, but you say you had both channel buckets powered down and modules removed.
Check all of the fuse resistors on the cue/aux cards for 1 ohm exactly.  Anything higher than 1.5 ohms should be replaced.
Mike

[unitedreco]

got the meter in hand and ripping out cards in 5 minutes

[StefanNowak]

Do you have the centre CRT/TV installed? could it be related?

Stef.

[unitedreco]

hi stefan

I ripped that thing out eons ago, and unfortunatly that weeeeee is still here, wasnt the resistors, im cancelling sessions on friday to do a full check up ....when you think all is going right i lost the monitoring 20 minutes before my session today ...quick thinking had me route thru the sls side ...looks like a long techie weekend...uuuggghhhh

[waltzingbear]

I once had a 6k start to dump something around that freq into the audio, turned out to be a logic circuit in the center section oscillating because of a dead lamp!!!!

good luck

Alan

[unitedreco]

alan

funny you mention lamps, this should be added to a journal , always always change blown lamps especially in center section, i had that happen once when the program lamp went out, little extra voltage not getting sucked up by the components makes other stuff freak out, sounds weird but its happened to many( signs of an emerging bigger issue? who knows). Unfortunatly for me thats not the case, il let you guys know later il have it figured out sometime today.

[unitedreco]

Ok this is going to sound crazy but then again ...here it goes....ive always said bargraphs seemed to add a little noise to the bus, that weeee sound is coming off the 73 card back by the meter board, it was dumping on the aux/cue ...still cant figure from where though, i recapped it again even though it wasnt due for one and the meters are and have been working perfectly so unless its an ic or rectifier transistor im stumped for tonight...i did notice a miniature cap a 22pf had a slight crack to it but i dont think thats the issue and i dont have one to swap it out with either...il go thru my ic bank and start swapping ics and see if its that

[waltzingbear]

you need to find the source of the oscillation to really cure it.

a 10X probe on a scope makes a good antenna for finding oscillations, just "wave it around" til you see the oscillation on the scope, then find the actual source. It has to be large somewhere.

Alan

[unitedreco]

fixed...a friggin ribbon that connects the buckets somehow got loose....DOH!!
its always the littlest things and i try and remember that all the time.