old alpine 7903e pre amp hu problems - diyAudio
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Old 18th December 2008, 06:01 AM   #1
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Default old alpine 7903e pre amp hu problems

Hi I'm trying to fix an old hu i got for cheap the problems I'm having are that it doesn't out put any sound through the pre amp and it wont load Cd's i have another old alpine cd only hu that has a lot of the same parts

dose any one know where to start and what component i should be testing .

pic is the unit
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Old 19th December 2008, 02:18 AM   #2
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OK start by considering that Alpine most probably does not carry parts for that 1991-93 era HU. < just a FYI > Call Pacific Coast Parts or look them up online and ask to be for sure.

Then as I recall this HU has a common problem of needing the CD mechanisms switch's replaced. It won't load could be dirty rollers, and bad switch's on the mechanism that sense where the CD is as it loads into the position to drop into play mode. Dirty rollers can be cleaned with alcohol and clean wipes, and operating the load servo and allowing the rollers to rub themselves clean on the alcohol wetted wipes. and or Q-tips.

As for no sound out, well that's a good one but here again the HU might not be able to decide which source to use (i.e, radio or CD) due to bad sensors in the CD unit, or the CD Radio selector circuitry has failed or is confused possibly by incorrect signals from the CD mechanism.

With a HU this old I would be asking if the CD drive motor and the Laser assembly are still available from PCP. As these parts along with position sensor switch's were the big failures I saw on these long ago...Also ask PCP if they have the service document on this model still as your gonna need it to order and get parts you might need..Hope this helps....
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Old 19th December 2008, 02:26 AM   #3
anatech is offline anatech  Canada
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Hi weesatron,
That brings back memories for sure! I did warranty service on those.

1moreamp is correct. Standard service for these were switches and clean the CD feed rollers so your CD's don't get scratched. This may solve all your problems.

-Chris
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Old 19th December 2008, 02:59 AM   #4
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I did repair on at least 50+ of the 7903/4's . The most common problem that I remember is the worm gear getting trash on it. Since the 7903 is the pullout model, it would get turned sideways when pulled out. Any specs of trash, grass, dust balls, ect. would get stuck in the worm gear and cause a switch to malfunction. This was not always the case, but was the most memorable of that unit. I remember aligning the optical pickup. Bad vol-pot's. Soda under the buttons, and LOTS of burned traces. Being a pullout made this model go through a lot of problems with the dirty worm gear. Clean it, and you might get lucky.
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Old 19th December 2008, 03:08 AM   #5
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Quote:
Originally posted by anatech
Hi weesatron,
That brings back memories for sure! I did warranty service on those.

1moreamp is correct. Standard service for these were switches and clean the CD feed rollers so your CD's don't get scratched. This may solve all your problems.

-Chris
Hey Chris, 1more amp, ect. I was just wondering. (or any former service techs). Do you or anyone else remember the Sony CDX-77 ? Did anyone do service work on those? 3rd CD unit Sony made. Worst CD unit ever. I remember wondering about the poor tech that had to do warranty work on these. Horrible design ALL-OVER... I did what I could for that model, but wondered what the return rate was on them. I stopped working on them. Could not get the gremlins out. Fix one problem, and another would start. Awful units... Was it just me, or did anyone have the same experience with the CDX-77 ?
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Old 19th December 2008, 03:43 AM   #6
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Thanks for the info ill give it a good clean i also have a old cd player out of a honda that has the same cd mechanism so i mught have some good parts.
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Old 19th December 2008, 04:15 AM   #7
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Also forgot to say that when i loads cd's sucks in the Cd fine then after a few seconds it spits it back out disk dosn't spin up or anythink.
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Old 19th December 2008, 06:39 PM   #8
anatech is offline anatech  Canada
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Hi tomtomjr,
Those Sony units were no fun at all. Luckily, I didn't do warranty on Sony, but had many out of warranty. One major problem is that the Sony Service manager up here did not tell the truth. Then there was Sony Corp. They would never admit when they had a problem - ever! Everything was swept under the rug. Like most Japanese companies of that time, they were too proud to admit to their problems. Some, like Teac, would come out with bulletins like " Hey, we've discovered <problem> and here is the fix we have worked out". This after you've been dealing with this fault and been told they don't experience that problem. Oh, and their fix was something you or another shop had suggested.

Alpine was much better about service issues, at least in Canada. I only saw a few worm gear issues up here though, switches ruled even in their cassette mechanisms.
Quote:
Bad vol-pot's. Soda under the buttons, and LOTS of burned traces. Being a pullout made this model go through a lot of problems with the dirty worm gear.
How do customers get most of a cup of coke (or coffee) inside a dash mount unit??? Happened a lot. Then the destruction caused by installers, or worse yet, owners friends.

I still deal with the old service manager from the Alpine days. Super guy that distributes Cyrus and Creek in Canada, possibly all North America for Cyrus. We went through a lot, but he was always honest and fair.

-Chris
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Old 19th December 2008, 06:44 PM   #9
anatech is offline anatech  Canada
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Hi weesatron,
Quote:
Also forgot to say that when i loads cd's sucks in the Cd fine then after a few seconds it spits it back out disk dosn't spin up or anythink.
That means it didn't read the TOC. This could be due to switches, there are a couple in the CDM itself also. Could be a loading switch (probable) or a dead laser assembly. If you continuously hear the loading motor running, you have a problem in the CD loading mechanism for sure. If you hear it stop, then the fault is in the CDM. It is possible there are more than one fault. Heck, that is very likely.

When I used to get these in out of warranty, I would quote for all switches and a complete clean. A setup was also done as the unit would always perform better afterwards. The factory setup was okay, but not great. That was true with all machines really, including home machines.

-Chris
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Old 19th December 2008, 08:15 PM   #10
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Quote:
Originally posted by anatech
Hi weesatron,

That means it didn't read the TOC. This could be due to switches, there are a couple in the CDM itself also. Could be a loading switch (probable) or a dead laser assembly. If you continuously hear the loading motor running, you have a problem in the CD loading mechanism for sure. If you hear it stop, then the fault is in the CDM. It is possible there are more than one fault. Heck, that is very likely.

When I used to get these in out of warranty, I would quote for all switches and a complete clean. A setup was also done as the unit would always perform better afterwards. The factory setup was okay, but not great. That was true with all machines really, including home machines.

-Chris
Anatech is very correct with what he has posted..... been there, done that, got the T shirt
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