5150 fx loop problem - the brown note

[Neeklaus]

I traded for a 5150 head that I got knowing it would need some work, but I'm stumped on this one.

pretty much anything I've put in the fx loop results in this extremely loud terrible sound which in no way resembles a guitar. it's like a giant fart - a brown note if you will.

here's what I've done for troubleshooting:
i just put new power tubes in there and they function as expected
i swapped preamp tubes with a known good tube for v3 which per the below chart is the fx loop tube
http://www.fjamods.com/5150Models.html
swapped cables, tried multiple single stompboxes that I know function correctly

this leads me to believe it's a component problem

any help fellas?

PAGING JERRYP!

 

[mchn13]

What series is it?did you try contact cleaner in the loop jacks? My old blockletters' effects loop got funky all the time, til I had it hardwired out...

 

[Neeklaus]

it's a signature model, original 5150

yeah, I hit it with contact cleaner.

I actually put a short jumper cable in there after cleaning it (and making sure there was no moisture in there) to make sure no debris could get in it.

If i have the jumper cable in the loop and switch the loop on, it works perfectly, no hums no loud noises just good ol fiddyonefiddy

 

[Neeklaus]

posted this on HC as well....seem to be getting some responses.
http://acapella.harmony-central.com/sho ... brown-note

here's some additional info:

cleaning the fx, so far, seems not to have solved much.
it's odd, like when I use my looper pedal each successive loop/repeat gets more and more muddied and terrible, if i boost ANYTHING on the EQ pedal it immediately goes into terrible loud screeching/farting

also - if I just have the FX loop on and a pedal in the loop, there's a faint low wooing sound added once I click on the loop

 

[Neeklaus]

fx loop on, but no cables plugged in - everything works fine, even with the loop clicked on no whooshing.

 

[Neeklaus]

problem found?

 

[JerryP]

Someone has the jacks jumpered internally. Remove that little bare wire connecting the two jacks.
Jerry

 

[soc_monki]

i never liked the effects loop anyway...so i never used mine. then again, i dont really use time based effects, except for the chorus i used to have. still sounded better out front than in the loop! good luck in getting it fixed!

 

[Neeklaus]

Someone has the jacks jumpered internally. Remove that little bare wire connecting the two jacks.
Jerry

i noticed that, but just assumed it was stock.
wtf
why would someone do that?

 

[Neeklaus]

PS....i owe you a beer JerryP