Repairing Sennheiser 280 pro

fat_fleet

fat_fleet

Swollen Member
Hm.. I didn't quite know where to put this so maybe here?

Anyhoo, the RH side of my Sennheiser 280s fried out last night and a new pair is definitely not in the budget right now. How easy is it to fix these things? I've got it open now, but I'm not sure what I should be looking for. A multimeter across the loudspeaker terminals (where the little wire connects) shows resistance, but I haven't desoldered the connecting wire yet. Does this suggest that the speaker is ok and that my problem is with the connecting wire? I can see one spot where the wire has been kind of stretched and pinched but when the sound cut out, there wasn't any unusual strain on the wire.. there was, though, a really loud spike in the volume which I feel indicates the loudspeaker as the potential source of the problem- but again, would I still be getting resistance across the terminals if that were the case?
 
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Hi there,
There's very little to go wrong with headphones. It's a cable and a speaker, basically.

When you read resistance across the driver contacts, was the headphone cable unplugged?
I'd expect them to read 64 ohms each side but in practice mine read 55.
If you're getting that, that's a good sign.


To check the cable, set your meter to continuity. If you touch the two probes together it should bleep or read 0 or whatever.

Use the two probes to check for continuity between RH driver negative and the 1/4" plug shield, then driver positive and 14" plug ring.
If there's a break in the cable, at least one of these won't read continuity.

If the cable checks out you can prove the driver by connecting a makeshift or spare cable to it temporarily.
Salvage an old pair of headphones or solder a 1/4" plug to some old cable...whatever.

Plug it into a headphone output and touch shield and ring (or shield and tip) to the exposed contacts on the suspect driver.

Hope that's useful. :)
 
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That was great, thanks. I've got continuity all the way up to the driver, so it's got to be that.
Not great news as the 64-ohm drivers look pretty tough to find now.
 
Yeah I did. It's the driver.
There are a couple sets "for parts/repair" on ebay with one working side, and the drivers don't seem to have any l-r orientation, so I'm thinking I could just grab one of those and try my luck.. Thing is, they use that really fine guage earbud wire, and wit the +/- sides different colors (bronze + red), I can see their orientations on the driver terminals are flipped on the L and R drivers respectively. There are no markings on the terminals to indicate the proper orientation, the L and R drivers appear physically identical, and the wire +/- orientations are consistent with each other on the opposite ends where they connect to the splitter chip on the left side.. so do you think one driver was wired backwards during assembly and could that have exacerbated whatever normal stress the driver undergoes? While it may be true I'm looking to blame someone :-)D), it would also be helpful to know the proper orientation when I go to replace.
 
fat_fleet said:
Yeah I did. It's the driver.
There are a couple sets "for parts/repair" on ebay with one working side, and the drivers don't seem to have any l-r orientation, so I'm thinking I could just grab one of those and try my luck.. Thing is, they use that really fine guage earbud wire, and wit the +/- sides different colors (bronze + red), I can see their orientations on the driver terminals are flipped on the L and R drivers respectively. There are no markings on the terminals to indicate the proper orientation, the L and R drivers appear physically identical, and the wire +/- orientations are consistent with each other on the opposite ends where they connect to the splitter chip on the left side.. so do you think one driver was wired backwards during assembly and could that have exacerbated whatever normal stress the driver undergoes? While it may be true I'm looking to blame someone :-)D), it would also be helpful to know the proper orientation when I go to replace.
Click to expand...

Hey man,
Sounds like it'd be worth a punt if you're confident you can do the soldering.
Maybe de-solder and re-solder the existing wires just to be sure?

I doubt either was wired backwards at the factory. That would reverse the polarity of one of the drivers and you'd know all about it! :eek:
 
fat_fleet said:
Well yeah.. I mean, I'd probably pick up on it when the mis-wired side suddenly stopped working. It's not like I have the sharpest ears in the joint. :o
Click to expand...

Nah, trust me man. You'd know.

If you have near field monitors or feel like experimenting when your new driver arrives, wire one in reverse to see what happens. ;)

Edit: Or even just pop a plugin with polarity flip per side on your master, and flip one side.
It'll bend your head!
 
I got a for-parts-or-repair model on ebay, 28 bucks shipped.. allegedly has 2 perfect drivers, but worn pads and some structural issues with the frame. Should be here tomorrow!
 
JhCy991d


...and done (with a plug for Stewart's Orange 'n Cream soda). :)
 
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