# Old school Alpine 7909L repair thread



## sbeube02

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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## sbeube02

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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## sbeube02

Next problem is with the QRB connector.
Someone has cut and swapped the wires, I don't know why 



















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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## jeffp

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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## jeffp

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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## sbeube02

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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## sbeube02

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...


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## jeffp

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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## sbeube02

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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## jeffp

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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## sbeube02

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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## jeffp

You can power the unit up without the DC converter. The CD player must be connected in order for the unit to power correctly.


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## sbeube02

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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## jeffp

Make sure the cable is 6" long 16 conductor 1.5mm pitch and connector/connection on the same side of the cable and you are good.


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## sbeube02

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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## jeffp

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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## sbeube02

Hi,
The bulbs were found on ebay, they are rated at 6V 60 mA if I remember correctly.
If you need a ribbon cable I might try to source you one here in Europe.


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## jeffp

I thought you may have gotten the Ebay bulbs. Didn't they want 10.00 USD per bulb? I have sourced a number of the ribbon cables and have a good supply.


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## sbeube02

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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## sbeube02

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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## jeffp

Ok, the caps for the circuit board for the cd player MUST be replaced. The cd player will not work reliably if they are not replaced. You can find what you need from digikey, they are Panasonic parts. Or if you really want to spend some time go to aliExpress and get the elna parts, but it will cost you.
Where did you get the bulbs from on ebay again. I would like to buy some of them myself. The 2mm bulbs really are not the correct parts, you need a bulb that is about 10 ohms, otherwise you will over heat the resistors on the back side of the display board. 

Don't do anything else to the mech before you replace the caps. You may have a bad laser, but that can be determined after the cap replacement. My guess is that if it is original it will need to be replaced. I have replaced a number of lasers that worked, but the were sensitive to vibration and jolts. The problem is the rubber suspension for the focus lense, the rubber sags and forces the cd player to force a focus of the lense. A new part has the optics positioned almost perfectly, so the focus circuit has to do very little to focus the optics, the focus circuit basically becomes a stabilizer of the optics to take the bumps and jarring if an install into an automobile. 
Good work, you really tore down the mech, you did not have to go so far, but it is good experience I suppose.


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## sbeube02

Dear Jeff, for the bulbs just search on ebay for item # 400097661094
They are $7 for a lot of 100pc. They are 6.5V 68mA so about 10 ohm.

I have de-soldered the 20ish capacitors from the CD board, only 2 are within specification.
All the other are leaking and out of spec by 90% !! I think this might be a problem 
If this doesn't work, I will try to buy a new laser lens.


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## jeffp

Thank you for the lite link on ebay. I bought the lights, Alpine wanted a lot of money for them, I bought all the parts they had left in stock. The ones off of ebay will work perfect. Just double check the solder on the 1/4 watt resistors on the back side of the front panel board and resolder the component if the solder looks gray and dull. 

The caps, are BAD! LOL. I have never worked on a 7909 that did not have bad caps, unless it had a replaced mech from Alpine. 

The cd player as you have figured out will not work correctly until the caps are replaced. I have seen a unit that would not even load a cd due to the bad caps. Be careful removing the components, a good number of people end up damaging the board in the process of removing the components. 

So if a cap does not want to come off, use your solder iron and put a solder blob on the leads to remove the cap, then you can clean up the solder on the pads after the part is removed. The key here is not to damage the board.

I use a old type writer eraser pencil to clean up the component landings. So wick, or remove all of the solder off the pads, then use the eraser to clean the pad with some alcohol on the erasser. Clean the pad with a kemwipe/cloth and alcohol. 

Then what I do is solder the pad and make sure all of the pad accepts the solder, then I wick off the solder, and apply the solder to one pad, solder the new cap in place, then after it is located correctly on both pads, solder the second leg of the cap, and it is done. 

You have to clean the pads good, as the leaking caps make them so they will not accept solder, and the part of the pad that was not soldered to begin with is still dirty, and will continue to corrode the solder joint after you resolder the new cap in. 

Piece of cake right  or like the Russian said in one of my favorite movies space oddesy2010 piece of pie, easy as cake LOL, still makes me laugh.


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## sbeube02

I started working on the recap of the CD mechanism.
I removed carefully the 20 old cap, only 2 were still OK. Cleaned with solder wick and flux cleaner.
I have ordered a full capacitor set from Mouser, including all the cap for the main board and audio board.
I now have to wait for my order to come.


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## jeffp

Don't forget about the 220 and 470 leaded caps on the board


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## sbeube02

The two leaded caps were tested with ESR meter and they are good.
I have received all new capacitors:









And recaped the CD board:


















I have reassembled the head unit but the CD doesn't read / spin.
The laser lens goes up and down with a small cliking noise a few times and then the CD ejects.
I don't know if:

The laser lens is dead
The trim pots needs to be adjusted
A chip is dead on the board

The DCDC is still missing on the audio board but I think it has nothing to do with my problem?

I have to check the RF signal with an oscilloscope.


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## jeffp

That is a difficult one to advise you on. The focus, is what you hear clicking. So go to all of the adjustable pots on the board. Set each pot to the mid point, fortunately Alpine did a very good job of making the pot to be just about perfect adjustment at mid point.
The Tbal pot is the one to make slight adjustments to, so chuck a (Store bought CD), and before it ejects the cd, try the adjustment and make the adjustment slightly clockwise and counter clockwise on the pot. You are trying to get the cd to spin. So if you are successful at making the cd spin, you just may have a good laser.

You need to put an oscope on the RF test lead-landing on the circuit board. I solder a wire to that point, when the cd is playing adjust the Tbal and Fbal to maximize the PEP waveform on the scope. 

Also, you can tweak the resistor on the laser slightly counter clockwise to the corner of the resistor (it will be a cut off the corner of the resistor, and if you look at the resistor wiper, you position the wiper on that part of the corner. Make that adjustment ONLY AFTER the circuit board adjustment does not work to get the cd to spin and play. 

Either way, the oscope will show you what the waveform looks like, and you will know if what you are adjusting is improving the amplitude (PEP) of the waveform envelope or decreasing the waveform PEP amplitude.
If that does not work, then the laser is dead, and since it is a L model, chances are it is dead, but do your adjustments first, the unit could easily be out of adjustment and calibration.

Also, regardless of how the two leaded capacitors tested, realizing the components are 25 years old or so, and in light of all of the restoration work you have done, does it not make sense to replace those two components also? We are talking what .75 EURO for both components. Additionally, the majority of the RCL test instruments don't really stress test the component. So unless you are using a Phillips 6303 or better, the test is cursory at best. Just my O2 on that point.

hope that gets you going and your unit starts working.


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## sbeube02

Update. I checked some signal with an oscilloscope.
So, I connected and labelled few wire to the required test points.








I followed the adjustment procedure provided in the service manual:









The test point are the following:

TP1 PLCK
TP2 TE
TP3 RF
TP8 FE
TP11 VCO ?
TP12 VR

Test 1: 
Connect TP11 with TP12
Check signal between TP1 and GND. Frequency must be 4.32 MHz +-0.005 MHz. If not, adjust with VR1701.

Here is the result:








Accuracy of scope is not as good as a frequency counter but anyway the frequency is quite good at 4.326 MHz.

Test 2:
Connect TP8 with TP12
Measure signal between TP2 and TP12.
The signal must be centered on 0 V. If not, adjust VR1001.

Result:








Waveform is odd, peak to peak level is low. I don't know if the values are ok. Anyway, I moved the VR1001 pot to center the waveform.

Test 3:
Don't connect anything.
check signal between TP3 and TP12.
Check the eye pattern for max amplitude. Adjust with VR1002.

Result : 








Waveform is difficult to capture on a digital oscilloscope. Don't know if the peak to peak voltage is OK ?
The VR1002 pot don't change anything.

Additional test :
I checked the laser diode current between the two LP test points (10 ohms laser feed resistor).
Measured 0.488 V which corresponds to 48.8 mA laser current. It seems to be a good value.

Next :
Try to adjust laser current with the very small pot.
If not, change the laser module (they are still available on aliexpress).

I maybe have a bad sled or spindle H bridge driver ? I have to check if the servo send a command to spin the motor.


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## jeffp

go to the RF test point on the board, connect your oscope to that point and observe the wave form. 
It is good that you could adjust the various pots on the board. most of them should be just about mid point. 
the RF wave form will tell you everything you need to know. 
You say you hear the unit clicking, the cd does not spin? correct. 
You can try to tweak up the laser, but that will be only somewhat effective. 
I have just read my last post. Your laser is dead, replace the laser.


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## sbeube02

Hi Jeff!
The lens click as it goes up and down.
The spindle doesn't spin at all.
RF point is TP3. You get the RF waveform on my previous 3rd picture.
Could you tell me the vertical deviation of your RF signal in volts?
Anyway, I have read somewhere that RF signal must be about 1 V pkpk.
So you are right, my laser must be dead.
What about the laser current ? Is 48.8 mA a good value?


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## jeffp

rotate the laser counter clockwise to the corner of the resistor pot. if you have already tweaked the resistor then rotate it to the center of the resistor side, just don't tweak it all the way counter clockwise. Then you can tweak the resistor on the main board, the tBal first, and tweak it for maximum pep of the RF wave form, then tweak the fBal to maximize the RF wave form. You accomplish this by chucking the cd, and before it is ejected attempt the adjustment. Maybe you will get he cd to spin, but either way, I am banking on a defective laser. Obviously the focus is working, so that would indicate a low level laser output.


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## sbeube02

OK, I have tried to rotate counter clockwise the small pot on the laser head.
I now get a laser current of 55 mA. Even with that, the CD does not spin.
You are right, my laser must be dead. I have ordered one brand new and it must arrives soon.
I will let you know as I will change it.
Thanks for the help Jeff!


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## sbeube02

New laser is arrived 

Here is some pictures of the replacement.
It is a painful job to do 

First you have to disassemble the CD mechanism the get access to the laser block:


















Hard job is to get the solder out the ribbon flex:









New KSS-163A laser:









Notice the laser current is written behind the block, 46.3mA for the new and 46.8mA for the old laser:









Them glue with the double sided tape the ribbon over the metal bracket:









Don't forget to remove the small solder bridge before to continue (ESD protection for the laser diode).

Solder the rest of the ribbon:









Again don't forget the solder bridge before switching on the head unit.

Everything back in place:









Et voilà ! The CD started to spin and works perfectly: 









The RF amplitude is far better than before (700 mV vs 200 mV):









I now have to adjust the potentiometers accordingly the adjustment procedure.

Jeff, you were right about the laser health! Thanks for helping me :bowdown:


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## jeffp

Now you need to reassemble the unit, with the top cover installed and burn-in the unit for about 5-7 days continuous play let it get hot and just run. Then go back and readjust the cd player.
The last thing you will need to do is install the cd mech into the radio, the four corner leg screws and see how the cd is chucked into the player. hopefully it will pull the cd into the mech correctly. Note the action of the clutch, and make sure that when the cd hits the back of the mech, the clutch slips, and the cd drops into place on the spindle motor platter.
If the clutch does not slip, you will start to destroy every cd you play, as it will leave hash marks on the cd from the roller doing a burnout on the cd. Don't fall into the trap of making the clutch not slip to chuck a cd, and DON'T screw with the clutch, other then adjusting the spring tension. 
Almost every unit I have worked on needed lube grease, and tweaking to get the mech to work correctly. Make Sure it is mounted into the radio all the screws tight to finish up the adjustment of the clutch, additionally, run the unit until it is up to temp, the L unit and 7909 units run hot due to the power transistor on the right side of the main board behind the display pcb. So let it get hot and make sure the unit still chucks the cd properly. I have noted that as the unit gets hot the clutch more often times then not needs readjustment. 
I think it has to do with the temp if the rubber roller changing and it grips the cd differently, but don't quote me on that LOL. Every time I think I have a set procedure down to adjust the mech it proves me wrong and I end up screwing with it to get it to work.


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## sbeube02

Yes you are right, the clutch is a little bit loose and I think some lube grease is needed on certain part. Because the CD chuck but I have to help it with fingers.

I have made some measurement of the current on the + 10 V and - 10 V rails from de DC/DC converter.










I have bought this unit with a missing DC/DC so I suspected something wrong on the audio supply rails.
I put a symmetrical regulated power supply on both rails and measured the current.
I checked current at about 68 mA on both rails.
I think this figure is correct.
I have received a new DCDC converter from the Alpine spare parts service.
I now have to resolder it and change all the capacitors on the main board.


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## jeffp

The current seems a little off. I consistently read 67ma +/- 2ma and 107ma +/- 2ma on the one rail. 
The thing is that I get a bigger drain on the one rail.
The part you bought, is that an actual alpine dc/dc converter? They have the part listed at 195.00 USD


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## sbeube02

Jeff, do you have a link for the DC/DC listed at $195 ?
I have bought it from Alpine spare parts in Europe for about $45.
This is the revised unit.
Original ref was 50T16438W01.
I got 50T16438W02.





































Now I can at least hear the sound of my 7909L head unit :laugh2:

But ... this is not the end of the problems 
I don't have sound on the left channel, unless I put the unit in CDS mode where all works perfectly.
I may have a bad OP amp or another broken track near the balance potentiometer.
I also have to change the caps on the main board. I have started and some are leaky...


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## jeffp

I thought you listed a link in one of your posts. 
Do you have a link, or contact email for Alpine spare parts or the outfit that sold you the converter? I would like to see if I can get a few converters myself. 

REGARDS:

Jeff


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## sbeube02

Jeff,

This is the French Alpine service center that sold me the converter. I now they have ordered form the Alpine Service center in UK.
You could try to reach them: https://www.alpine-service.co.uk


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