MDR 7506 repair help request

[BrandtW]

Hello all!

I the left driver on my 11 year-old 7506's has failed. It passes a multimeter continuity test. I noticed that the right driver crackles a bit when continuity is established, but the left driver remains silent.

My suspicion is that I simply need to replace the driver, but I want to confirm with people more knowledgeable than me. Is it possible with these drivers to pass through a signal from left to right, but the left driver still be silent? Or is it the driver at all that's failed?

Also, the surround foam on the drivers have deteriorated into foam paste. Is there a replacement product for the foam ring?

I appreciate any feedback.

 

[cinemakinoeye]

I the left driver on my 11 year-old 7506's has failed. It passes a multimeter continuity test. I noticed that the right driver crackles a bit when continuity is established, but the left driver remains silent. My suspicion is that I simply need to replace the driver, but I want to confirm with people more knowledgeable than me. Is it possible with these drivers to pass through a signal from left to right, but the left driver still be silent? Or is it the driver at all that's failed?

Sounds like a wire is broken or a driver is blown. I assume it passes the continuity test for one channel but not the other, but it could be one of three things.

If you are able to measure resistance, the resistance measured at the connector between tip and ground (L) and ring and ground (R) should be about 66 to 69 ohms each. Given the manner in which these are wired, it is possible for the signal to feed the right channel when the left driver is not working. The problem with your left channel could be either a) a broken wire in the cable or b) a bad connection (due to a poor solder connection in manufacturing that is easily fixed) or c) a blown driver.

The first step is to verify the integrity of the cable from the connector to the inside of the left earpad. Easier to replace the cable than the driver!

The second step is to test the drivers by doing a low voltage continuity test of the driver after opening up the headphones. If you don't hear anything and you are not getting 66 to 69 ohms resistance, then the driver is blown.

As far as the foam on the driver, I removed the crumbling foam from mine, cleaned off the residue, and left it at that. I'm sure the foam helps with high-frequency diffusion but I did not worry about it.

I replaced my original earpads with the Brainwavz Micro Suede Earpads, making them far more comfortable to wear.

 

[BrandtW]

Sounds like a wire is broken or a driver is blown. I assume it passes the continuity test for one channel but not the other, but it could be one of three things.

If you are able to measure resistance, the resistance measured at the connector between tip and ground (L) and ring and ground (R) should be about 66 to 69 ohms each. Given the manner in which these are wired, it is possible for the signal to feed the right channel when the left driver is not working. The problem with your left channel could be either a) a broken wire in the cable or b) a bad connection (due to a poor solder connection in manufacturing that is easily fixed) or c) a blown driver.

The first step is to verify the integrity of the cable from the connector to the inside of the left earpad. Easier to replace the cable than the driver!

The second step is to test the drivers by doing a low voltage continuity test of the driver after opening up the headphones. If you don't hear anything and you are not getting 66 to 69 ohms resistance, then the driver is blown.

As far as the foam on the driver, I removed the crumbling foam from mine, cleaned off the residue, and left it at that. I'm sure the foam helps with high-frequency diffusion but I did not worry about it.

I replaced my original earpads with the Brainwavz Micro Suede Earpads, making them far more comfortable to wear.

Thanks for the detailed response, Cinemekinoeye. I've performed continuity tests with these findings:
Left red to right red 70 ohm
Left copper to right copper 70 ohm

Tip to red 1
Tip to copper 1
Tip to green 3 ohm
Ring to red 3 ohm
Ring to copper 70 ohm
Ring to green 1
Sleeve to red 70 ohm
Sleeve to copper 3 ohm
Sleeve to green 1

I'm a bit baffled by this outcome.

 

[cinemakinoeye]

Thanks for the detailed response, Cinemekinoeye. I've performed continuity tests with these findings:
Left red to right red 70 ohm
Left copper to right copper 70 ohm

Tip to red 1
Tip to copper 1
Tip to green 3 ohm
Ring to red 3 ohm
Ring to copper 70 ohm
Ring to green 1
Sleeve to red 70 ohm
Sleeve to copper 3 ohm
Sleeve to green 1

I'm a bit baffled by this outcome.

Can you clear up where are you making these measurements? On the drivers themselves? Looks like there is a short somewhere but not totally clear. Can you post a photo?

 

[BrandtW]

The plug to colored wired tests were performed by alligator clipping the pos probe to the tip, ring and sleeve of the plug, and touching the neg probe to the pads that the wires were soldered to on the left driver.

The left to right tests were performed on the pads of the two drivers.

This interface doesn't appear to allow for the attachment of photos from the computer library. Let me know what conditions you'd like to see an image of. I'll see whether I can DM them to you.

 

[earmonger]

This interface doesn't appear to allow for the attachment of photos from the computer library. Let me know what conditions you'd like to see an image of. I'll see whether I can DM them to you.

Between the chain/link icon and the smiley face is an "insert image" link.

 

[BrandtW]

Ah, thanks. Oddly, only the option to attach from a URL was visible before. I'm not sure whether you can tell anything useful from this image of the drivers, but I'll use it as a starting point.

 

[cinemakinoeye]

So the next thing I would do is take an audio source and use alligator clip jumpers to see if each driver works or not. This would help determine if the problem is blown drivers or an electrical connection. I had a pair of MDR-7506 headphones where one driver was blown and this is how I determined if it was the wiring or the driver. I made a special cable to test the drivers. Now I have a handy 3.5mm plug to three alligator clip testing cable rig I've kept handy for future use. The key thing to determine is if the cable is damaged or a driver is blown.

 

[BrandtW]

This makes sense. I used a similar setup to test home speaker drivers. I'll try on the headphones.