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Discussion Starter · #1 ·
Hello all,
I am quite new on this forum.
I am from France and recently acquired a famous Alpine 7909L headunit.
I bought this unit as not working.

This thread will be showing an inventory of the things that need to be fixed and the repair procedure.
Any help will be appreciated.

Here are some pictures.

General view of the head unit:




The face-plate is in really good condition as well as the switches.

The QRB cage is in great condition but I was told it is not from the correct model (probably a cassette unit) :



The top cover paint is poorly scratched but I think it could be painted over.


The volume button is broken and had been repaired with black tape.
It will be a challenge to find a new one in good shape.


The foam thing on the treble and bass cursors have seen better days:


That's all for the cosmetic description. I will follow later with internal inventory.
 

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Discussion Starter · #2 ·
First surprise when I opened it up: the DCDC converter is missing.


The top cover is engraved by hand with an odd number:


I can find the same number on the CD mechanism:


Big surprise: the ribbon cable between the CD mechanism and the main board is missing!


A track on the audio board PCB was cut:


The CD mechanism has already been serviced. There is a message in Danish language dated from 1999:


The ground pin on the small ribbon cable is not soldered anymore:


Presence of soldering job on the laser test pad RF, TE and FE:


More to come soon!
 

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Discussion Starter · #3 ·
Next problem is with the QRB connector.
Someone has cut and swapped the wires, I don't know why :confused:





Basically, the CD changer line out and Front out are swapped.

I think I have to re solder the wires in the correct order.
 

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I have looked at al of your pictures and it looks as though you have the 7909 cage and QRB connector. I maybe could not see the AUX input RCA from the o]picture. The 7909 L unit should also have two pink/white wires on the QRB connector audio interrupt input and audio interrupt out wires.
That really is not a problem though. Most people don't use the AUX input to the radio, or the audio interrupt either.
Seeing the board connectors and apparently the heat shrink on some of the wires shows the inexperience of the person that worked on the unit. They did not need to cut an solder wires but simply remove each terminal and install it where they wanted in the position on the connector they wanted.
The main board looks ok to me from what I could see. The CD circuit board was removed, obviously they were having problems with the cd player, very common. The biggest thing I can see is that the DC converter is missing, now that is problematic, finding a replacement part will be difficult. I have passed on a sale of units if it was missing the dc converter.
Anyway, I can get the unit up and running if you like. I do the restoration for 400.00 and it will be new again. You do need the dc converter though.
or if you want to sell the unit, let me know. I just opened up an Lunit, at least the front panel said it was an L and the case said it was an L, but the main board is a 7909, slight differences there, so I was not to happy about that seeing I had two guys in Europe that ordered a radio and now I am short one. anyway, give me a call if you want (714) 907-6318

REGARDS:

Jeff Priddy
 

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Where did you find your unit, just out of curiosity. Most of the Ebay units that are sold look to be in the same state of dysfunction or worse, but according to the seller they don't know what is wrong with the unit and it is untested. From the things that you find on the unit when disassembled, obviously they were not fully disclosing the state of the unit to get a better selling price.
 

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Discussion Starter · #6 ·
Dear Jeff, thanks a lot for your helpful reply.
On the QRB connector there are the 2 pink/white wire for audio interrupt in and out. But there is not the Aux input RCAs. The seller told me the QRB cage comes from a cassette model but I don't know the exact model number.

I agree with you regarding the poor soldering job that has been done inside this unit. The wires could have been easily swapped without cutting, just pulling the little plastic tab. Anyway, I have re-soldered the wires in the correct order.

For the missing DCDC converter, I am thinking of using an of-the-shelf module, like Traco power or something else.
I have been for this unit for years so I will first try to repair it myself before considering to sell it.
Anyway, your help is really appreciated. :)
 

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Discussion Starter · #7 · (Edited)
This unit was found localy here in France, from a DIYMA member here that have tryed to deal with you before.

I have found others problems in this unit and a good one at that.

Burned track on the Front and the Rear Line Output ground:




And a lot of strange wires and cut tracks:




That are mostly the GND track or +10V that are cut.
I think at some time the DC/DC burned and someone tried to use only GND and +12V to power the audio part... :eek:
 

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Hello, the burned trace is from shorting out the RCA ground wire(rca connector outer part of connector) to 12 volts. The trace is a ground trace.
The pictures you have shown me regarding the wires are correct. The cut trace, the capacitor, the 5.6K ohm resistor, and the two black wires on the AUX relay on the bottom side of the board.
You need to find the components you need and I think the only way to do that is to buy a second unit and build one good unit from both units.

REGARDING the volume control knob, use super glue on the cracked part of the knob, make sure you get the glue in the crack, then put the knob in a vice to close the crack and let the glue dry. After the glue has dried, you can scrape the excess glue off the outside of the knob. FIXED, just don't put to much glue on the cracked part. Try to use a small bench vice that has a the notch cutout in the jaw to locate the knob shaft and clamp it in two places with that type of jaws. Clamp the part just enough to close the cracks that are filled with glue. let dry over night.

The cut trace on the Audio board, if it is the one I am think of, will be cut for the cd converter + 10 volt line, a 200 millihnery inductor was used in line but it is not required if you don't have the part.

Also given the age of the unit, you are really going to be required to recap the whole unit, the cd mech board, and the main board. The tuner generally does not need to be recapped. You will NEVER get the cd player to work correctly if you do not recap the unit.

REGARDS:
Jeff Priddy
 

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Discussion Starter · #9 ·
Dear Jeff, thanks for the useful information.

The capacitors change will be done of course. All the capacitors are dated from 1990, I think they have seen better days.

I have checked on the service manual and you are right, some wires, capacitor and resistor added on the bottom looks genuine.
I still have a doubt on the 2 small black wire under the AUX amplifier.
I have found there are 2 resistors (R49 and R50) that were removed on the IC4 OP amp low pass filter (amp for the tuner section). This is strange.

The 2 cut traces on the audio board ar on the +10V section, just after the DC/DC converter output and just before the CB602 connector.
Also there is a black wire added on the GND??



First cut:


Second cut:


This might be a problem!
 

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The two black wires on the main board are there to make the AUX input work. ONLY the 7909L unit has the wires on the board. The 7909J model mainboard was reved to fix the problem that the L model had. also if you look at the back of the unit around IC4 you will see two 1/8 watt resistors on the board.
The black wire on the audio board is standard, you may also want to add the ground wire from the filter choke on the main board as well, that is standard also.
REGARDS:

Jeff Priddy
 

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Discussion Starter · #11 ·
I have tried to power up the unit without de DCDC and without the CD player.
Only two bulbs and one green LED on the faceplate power up then blink.
When I switch ON, the two bulbs and led stay on but there is nothing on the VFD screen.

Could this be caused by the CD mechanism not connected?
 

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Discussion Starter · #13 ·
Oh yes, I understand.
On startup, the main micro-controller send a initialization command to the CD mechanism. If not connected, the main micro-controller doesn't receive the acknowledgement command and put the unit in standby.
I have found a ribbon connector that will work on the unit. It is a Fujikura brand ribbon cable.
 

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Discussion Starter · #15 ·
I have ordered the ribbon cable at Alpine spare parts department. It's amazing this part it still available.
I have followed on the board track repair and the front board.


So I changed these 3 10ohms SMD resistors that look burned (VFD filament power supply).


I changed 2 tact switches that were too soft when pushed.


And changed the bulbs that were all burned or with broken leg.
Unfortunately the original bulb 2mm are not available, I had to replace them by 3mm bulbs that are a little high.


On the main board I repaired the burned traces with some thin wire, solder and nail varnish to protect and isolate:

 

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where did you source the 3mm bulbs? They are 6 volt parts correct? The reason the resistors on the front panel are burned looking was due to the small 2mm bulbs. I have come across this problem a number of times and it is due to the small bulbs. Combined in the circuit, the smaller bulbs draw to much current, and cause the over heating of the resistors on the front panel. The bulbs you have bought should be around 10 ohms +/- 2 ohms and you will be good to go.
I am surprised Alpine still has the cable also, I tried to source the cable through them and could not get the part. I had to go through alibaba to get the cable.
Regarding the burned ground traces, you just may want to go with a small gage wire to do the repair. I have tried both methods, and found I was more confident with the small gauge wire method of repair then trying to do a trace repair.
good work.
 

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Discussion Starter · #19 ·
The bulbs were really cheap: 10 cents each.
I finally received the ribbon cable from Alpine:




Et voilà ! The unit powered up correctly:




The DC/DC converter is still missing so I can't even test the radio audio output.
The CD mechanism won't load a CD correctly. The mechanic parts are completely stuck with dirt and old grease.
I have to dismantle and clean everything!
 

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Discussion Starter · #20 ·
I completely dismantled the CD mechanism and carefully cleaned all parts with alcohol. I then put some new grease where needed.

Removed the main and auxiliary PCB :

Opened the loading rubber roller :

This part was full of gluing oil? Very strange and totaly stuck:

The lens shows a blue coloration but not in the center:

Rest of the parts:

All cleaned and re-assembled:


Now the CD mech works near OK. It loads CDs but need some help near the end of the loading because the clutch is a little tired.
If I help with my finger the CD will load correctly.
Anyway, the laser lens goes to the park position and then starts going up and down trying to focus. It try few times, fails and eject the CD.
I think I have to check the RF signal with an oscilloscope or do a serious recap on the capacitors.
 
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