Need help to revive Senn HD555

I was given a pair of HD555. Since it didn't cost my anything, I decided to explore on "modding" here in this forum.

Here's what I did -

Removed inner grilles - success

Removed stock cables/PCB/headband wires - success

Drilled hole in the right cup for dual entry - success

Soldered new cables to the drivers - FAILED!!! (My 1st experience with soldering)

The new cable is a Daiyo brand 2xRCA to 1x3.5mm stereo plug. The reason I chose this off-the-shelves cable were solely due to convenience since I only need to solder the wires to the drivers. The stereo plug came pre-attached.

I cut off the RCA plugs & prepare the exposed wires for soldering to the drivers. Each channel has 2 strands - signal & ground. I ensured that right channel went to right driver & vice versa. When I'm done with the soldering, I plug it to my Nano & hoped to hear something. There was no sound at all. I hope I didn't damage the voice coils.

I'm in Singapore. Is there any expert who may wish to help me out? Or perhaps recommend some service centres I should visit.

I don't think Sennheiser would want to solve my problem. Or am I wong here?

Before I end my soldering session yesterday, I desoldered 1 driver & left the other driver intact. This morning I thought I should just plug the hp to my mobile for testing. I thought even if it is only 1 side soldered there should still be sound. There was silence.

Then I picked it up & drop it on the table twice (just few inches off the table). I heard music after that. I quickly put it over my head. At max. vol. it wasn't loud & then it slowly faded away.

I'm quite sure I identified the channel & ground correctly (online guide supports my deduction).

It's a case of poor soldering, I think.

I'm going to have another go at soldering.

Just had another go at soldering. Failed again. It's hard to apply solder to bond the wire onto the specific contact point of the driver.

Now I noticed that the silver pattern on the driver has faded away. Does this means irrepairable damage?

Not going to do anything until someone in my area offer to help or point me to some service centre.

Out of curiosity I rang Sennheiser to see if they would entertain an end-user who took the liberty to modify their products. They said they would look at it on a case-by-case basis.

When I visited the service centre, they fixed my problem on the spot (for a reasonable fee). However, they made me understand that they will assume no liability on their works done to modified products. This is a fair policy I can accept.

In fact, I find their service quality excellent. Whilst waiting for my gear to be fixed, a couple walked in with a PX200 (1 driver not working) still covered under warranty. They received a new set instead. Such practice is not common in this part of the world I'm in.

Happy Chinese New Year to all (Year of the Rabbit it is).