MXR 114 Equalizer Feedback question

[Archvile]

I checked out some of the forums on here and didn't see anything specifically related to my issue, if there is, please fwd me to it and apologize if I doubled a thread..

Anyways, I got a vintage MXR 114 10 band graphic equalizer from a garage sale. Paid $10 for it. My dad had one back in the day so I know about it. It was in pretty bad shape, the slides were all caked with junk and seized. I took it apart, deoxit'd it, lubed it up cleaned it up and it does work. I have it going to a tape monitor input and when the monitor is on there is a horrible feedback/high pitch squeal going back to my speakers(music muted). But when I shut off the monitor( or unplug the mxr) the prob goes away.

I've tried the mxr on a carver amp, a sony es amp and my kr-9600 amp and its doing it on all of them. Even my wireless mouse causes some weird feedback into my speakers when this thing is on.

Is there anything I can check out inside this thing or something I should be looking at. I've tried diff amps as I mentioned, diff patch cords and it's still doing it. I even remember my dads 114 doing the same thing, but not nearly as bad as this one.

Any help is appreciated. Thanks much!!

 

[ryuuoh]

Are you certain you have it hooked up right?

 

[Archvile]

Not 100% sure. I did try diff combos, resulting in either feedback or it not working. Currently its setup using the line and out of the eq into the tape in/out on these receivers, using the monitor function. I want to say thats wrong, but it works. Just got a bad feedback. Its just the eq and a receiver. Theres no mixing board

Whats the correct way to set this up? Do u use the line in/out into the tape in/out of the receiver or do u use the tape rec/mon into the tape in/out on the receiver? I have an ipod hooked up to a cd input of my carver or to the aux input of the 9600.

 

[Markw]

These things need to be inserted into the signal path.

That is to say that they have to intercept the signal path, take the signal, feed it to and from the eq, and right back into the signal path exactly where it left it.

I don't know how all the manufacturers labelled their ins/outs but the basic idea is thus:

On the receivers tape monitor loop, the "tape out" goes to the eq's input.

The eq's output goes back to the receivers "tape in" on that same tape monitor loop.

Hit the "tape monitor button on the receiver and you should be in business.

At least, that's the way it should work. Dunno what controls you have on the eq.

 

[Archvile]

That's the way I have it set up then. The EQ out is going to receivers tape in, and EQ in is going to tape out. Sounds fine with the mon off(regular signal) but when I hit the tape mon button, there is a bad feedback sound happening(when it's going through the EQ). Tried diff amps/receivers and it's the same deal.

That's why I was curious if it was a bad ground in the EQ or bad caps or what? Or maybe its just a bad EQ that I picked up.

 

[RCenteno]

The MXR 114 is a nice EQ. I have two of them for which I have replaced every single component, resistors, capacitors, film capacitors, tantalum capacitors, OPAMPS and they are working great. A complete refurb of both for little money. Underneath the EQ there should be a diagram on how to hook it up. I am sure you're doing it right, it could be an OPAMP problem, an elect. capacitor, internal wiring. Check the ribbon cable to make sure it is connected correctly to the board or perhaps the back switch is bad. PM if you like.

 

[Archvile]

Thanks. I will have to take it apart and go though it. I know these EQs are selling for alot on ebay, my $10 investment isn't so bad at the moment, lol. I may have to "refurb" it and hopefully my problem goes away. It sounds great when I have it cranked. But when I hit pause, I have to turn it down as the feedback/distortion is annoying. Thats why I thought maybe I was missing something. Is there a service manual online for this?

 

[Rasputin]

The MXR 114 is a nice EQ. I have two of them for which I have replaced every single component, resistors, capacitors, film capacitors, tantalum capacitors, OPAMPS and they are working great. A complete refurb of both for little money. Underneath the EQ there should be a diagram on how to hook it up. I am sure you're doing it right, it could be an OPAMP problem, an elect. capacitor, internal wiring. Check the ribbon cable to make sure it is connected correctly to the board or perhaps the back switch is bad. PM if you like.

I’m thinking of modifying mine also. Do you remember the type of opamp you used for the replacement? How did it perform?

 

[DemBonnies]

I checked out some of the forums on here and didn't see anything specifically related to my issue, if there is, please fwd me to it and apologize if I doubled a thread..

Anyways, I got a vintage MXR 114 10 band graphic equalizer from a garage sale. Paid $10 for it. My dad had one back in the day so I know about it. It was in pretty bad shape, the slides were all caked with junk and seized. I took it apart, deoxit'd it, lubed it up cleaned it up and it does work. I have it going to a tape monitor input and when the monitor is on there is a horrible feedback/high pitch squeal going back to my speakers(music muted). But when I shut off the monitor( or unplug the mxr) the prob goes away.

I've tried the mxr on a carver amp, a sony es amp and my kr-9600 amp and its doing it on all of them. Even my wireless mouse causes some weird feedback into my speakers when this thing is on.

Is there anything I can check out inside this thing or something I should be looking at. I've tried diff amps as I mentioned, diff patch cords and it's still doing it. I even remember my dads 114 doing the same thing, but not nearly as bad as this one.

Any help is appreciated. Thanks much!!

I'm having the same issue with my MXR-114 which I just started using again after ten years of just plain not listening to my stereo [shame on me]...I was running it through the EPS inputs on my Onkyo TC6500 MKII...I changed it to TAPE 2 inputs and same issue, terrible feedback so I've pretty much eliminated the receiver as the issue.
Given that my MXR-114 is original to me and it has no power switch, I'm thinking that the fact it was powered on for basically 3 decades from the late seventies to the early 2000's and now has sat dormant for close to ten years, it may very well have a bad pwr supply.
Anyone have any thoughts on this?