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"Buzzing" EMIMs

kmanusa

kmanusa

AK Subscriber
Subscriber
I have a problem with one of my Infinity RS-4.5s. One of the EMIMs makes a "buzzing" sound when playing certain kinds of music like vocal music with lots of midrange. Now I know what you are thinking, the EMIM diaphragm is bad and needs to be replaced. But not so fast.

When I jiggle the two push-on connectors that attach to the back of the EMIM (plus and minus) the "buzzing" goes a way. I tried first DeOxit, then metal polish followed by DeOxit, on the push on connectors of all the EMIMs in this particular speaker. After that the problem seemed to go away but it reappeared again today. Again, jiggling the connectors seemed to re-establish a good connection and the "buzzing" (actually more like distortion) went away.

So my question is this: has any else experienced this problem with EMIMs? Another question is whether there can be a bad connection inside the EMIM that might contribute to this problem. I don't seem to have this problem with the other EMIMs, Also, I have cleaned the big rheostat that varies the EMIM level on this speaker so this part is not causing the problem.
 
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could be a bad solder joint between the tab and the diaphragm. i haven't cracked open an EMIM before, but on EMITs it's very easy to access and remelt that joint.
 
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Looks like I will be building an EMIM jig so that I can take it apart to check for bad joints. In the meantime, I might try subbing one of my "on deck" EMIMs for the troublemaker.
 
Check the fuse that is controlling the emim, if there is one. I have found that if the fuse-holder thingie that screws into it's slot is loose or not making good contact, it will cause distortion.

bill
 
siramazing said:
Check the fuse that is controlling the emim, if there is one. I have found that if the fuse-holder thingie that screws into it's slot is loose or not making good contact, it will cause distortion.

bill
Click to expand...

Hi Bill, only the EMITs are fused in my 4.5. The usual suspect for EMIM problems is the rheostat but I have really worked over mine and it is noise free.

Keith
 
Interesting tidbit-- I measured the DC resistance of each EMIM in this speaker and they all measured 3.3 or 3.4 ohms including the "troublemaker".

I do notice that the push-on connectors and the EMIM contacts are slightly oxidized and some parts are covered in a sort of soot or whatever (who knows what kind of 'air pollution' these speakers might have been subjected to :smoke: !) This even after multiple cleanings with DeOxit and metal polish.

This indicates that 30 + years of age can add an unwanted "patina" to the electrical contacts of these drivers that can be hard to remove.
 
Could be a loose connection from the tabs to the brass screws internal to the EMIM Keith, that is where I'd look first.
 
Army said:
Could be a loose connection from the tabs to the brass screws internal to the EMIM Keith, that is where I'd look first.
Click to expand...

Hmmm, Army, you could be on to something there! I'll have to take it apart and find out for sure. It measures 3.2 ohms DCR but I wonder if this is intermittant.

I went through my "on deck circle" of EMIMs last night to look for a substitute while I work on the buzzer. Most are of what appears to be the RS-II type; that is, a slightly different color middle diaphram and different kind of damping material in the rear. I do have a couple of RS-4.5 era EMIMs, one measures 3.7 ohms DCR and the other 3.2 ohms. These are the ones I would choose from first.
 
kmanusa said:
Hmmm, Army, you could be on to something there! I'll have to take it apart and find out for sure. It measures 3.2 ohms DCR but I wonder if this is intermittant.

I went through my "on deck circle" of EMIMs last night to look for a substitute while I work on the buzzer. Most are of what appears to be the RS-II type; that is, a slightly different color middle diaphram and different kind of damping material in the rear. I do have a couple of RS-4.5 era EMIMs, one measures 3.7 ohms DCR and the other 3.2 ohms. These are the ones I would choose from first.
Click to expand...

I had to take all of my emims out and replace all the brass screws and clean all the contacts with deoxit. Also took brasso brass cleaner to all the tab connectors, once I got all that done, I haven't had a problem since :thmbsp:

Hope you figure it out; I know how annoying this can be :yes:
 
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