Alpine 7803S CD head unit not reading CDs

[Bruce A Haugh]

The lense is cleaned, the tracking motor repositions the laser pickup
properly (not a sticky slide mechanism, will reposition itself to the
inner limit switch), there is output from the laser (can see the red
light), the laser pickup attempts to focus on the CD (lense moves up and
down about 2mm), the CD spins up properly at what seems to be a proper
speed (might be fast but I still have to confirm this).
Are there any other checks I should make before attempting to replace the
optical pickup? I would like to test the photodiode array if possible
bu,t without schematics, I can not be entirely sure which leads to test.
I don't want to accidently short the Laser if it will be a simple fix.

________________________________________________________________________
| Bruce A Haugh B. Sc. M. Engineering Talented Amateur |
| yrp...@freenet.mb.ca Japanese Anime Fan Club Member |
| VE4 VFR |
|________________________________________________________________________|

[Sam Goldwasser]

In article <Pine.SOL.3.91.96072...@winnie.freenet.mb.ca> Bruce A Haugh <yrp...@freenet.mb.ca> writes:

> The lense is cleaned, the tracking motor repositions the laser pickup
> properly (not a sticky slide mechanism, will reposition itself to the
> inner limit switch), there is output from the laser (can see the red
> light), the laser pickup attempts to focus on the CD (lense moves up and
> down about 2mm), the CD spins up properly at what seems to be a proper
> speed (might be fast but I still have to confirm this).
> Are there any other checks I should make before attempting to replace the
> optical pickup? I would like to test the photodiode array if possible
> bu,t without schematics, I can not be entirely sure which leads to test.
> I don't want to accidently short the Laser if it will be a simple fix.

Does the focus lock on - or just continue 6 or 8 or more times to focus?

If you have a scope, checking the RF test point would be instructive.

See the FAQ if you haven't already.

http://www.paranoia.com/~filipg/HTML/REPAIR/ (in the USA)

mirrored at this URL in Italy:

http://ftp.cised.unina.it/pub/electronics/REPAIR/ (better for Non-USA)

--- sam (s...@stdavids.picker.com)

[JrTech]

On Sun, 21 Jul 1996 13:06:17 -0500, Bruce A Haugh
<yrp...@freenet.mb.ca> wrote:

> Hi, Bruce
>
> I've replaced many pick-up on this and many other Alpine units, and from your post , I'm pretty sure
>you will need to replace them. You can try to realignment if you wish. The test points are on the bottom of the unit,
>thru the drilled holes. They are: VR , RF , and TE. There are others , but these are the one you need, they are labeled.
>Carefully solder test leads thru these holes, watch out for shorts! There are 3 pots on the the right side of the pcb.
>they are VR101- VR103, only one is labelled, I believe., its been a while. VR101 is for Tracking Balance, VR102 is
>Tracking Offset, VR103 is FE Bias( Focus Bias). Alignment Procedure is similar to other CD players. If you need step-
>by -step, repost then I will reply. Hope this helps. Sorry I couldn't reply sooner because my computer was down for a week,
>
>- - - - - - - JrTech- - - - - - -

I would like to test the photodiode array if possible
>bu,t without schematics, I can not be entirely sure which leads to test.
>I don't want to accidently short the Laser if it will be a simple fix.
>