CD Drive Repair HPC-3LX

[JoergR]

Hi all,
I'm trying to repair my inlaws Sharp XL-T300H stereo - a compact thing of only emotional value. It appears the CD Pickup is broken. CDs were turning and read, but the audio was distorted. Audio on FM works fine, so I think it's not a problem with the audio system itself.

The laser pickup is a HPC-3LX 20N which appears to be a standard part. I got a replacement part HPC-3LX 30N (note the difference) from eBay that looks identical to the part I removed from the unit. Upon putting it in, CDs would not even start to turn anymore and the display shows "No CD"

So now I have two questions forum members may be able to answer:

1) Does anyone know if an HPC-3LX 30N should work in place of the original HPC-3LX 20N?
2) If it should work, how can I test conclusively, if the replacement part I got is actually working?

Thanks a lot for any help.

Best,
Joerg



   

[fzabkar]

Laser assemblies are shipped with a solder blob to protect them against ESD. You need to desolder this blob before installation.

[JoergR]

Thanks for the reply, that is interesting. Could you be more specific as to where such a solder blob is to be found / removed? I've attached an image of the pick up unit I removed and the new one looks identical - also on the solder side - the only differnence being the 30N instead of the 20N on the sticker.

[fzabkar]

I don't know if all laser pickups are shipped with a blob these days, but here is one example:

[JoergR]

Thanks  so much - one really needs to know what one is looking for to actually see it!
Removing the blob and the unit works again.

Do you know why these blobs are there? I suppose they shorten the laser diode. Are there any other typical components that feature this kind of protection?

Thanks so much, my inlaws will be thrilled ;-)

[fzabkar]

I don't recall seeing these blobs in other scenarios, but I haven't seen everything. :-)

I assume that the blobs straddle the laser's terminals, but I've never examined them closely. All I know for certain is that the blobs protect against ESD during shipping and handling.

[JoergR]

Well, still some mysteries to explore. Thanks again anyhow!