# Alpine 7909 NEW dc converter



## jeffp (Jan 18, 2015)

I have been working on these two decks/head units for some time now, and it has been a long haul with these two units. I am beginning to believe they have been floating around for some time, as they have been totally taken apart, attempted repair, including one processor replacement on one deck. 
So both units had bad dc converters, one unit took some time to disassemble and repair, but overall it turned out good. The second converter had the top removed with a dremel I would guess, and that part was questionable weather I could get it up and going again, there were lifted pads for the components, all of the solder connections were corroded. I managed to salvage the major components like the transformer and inductors, the two transistors and diodes. All of the caps and resistors needed replacing, so I bought those parts and installed them. 
I was able to get the part working, but there was a imbalance of the + and - 10 volt outputs. The + 10 volt output was 9.85 VDC and the - 10 volt output was 10.06 VDC. Not to bad, but I was having problems with the cd player, and getting it to read without noise with a not so good burned cd, so I decided to build the new converter to even up the output voltages and see how that did in the unit. The thing that concerned me somewhat was the 9.85 VDC output as it could be a factor for noise and total output of the preamp, or line out.

I built the new converter and it is working very well. The voltages are within .08 VDC of each other. The converter is very quiet, and I can't see any noise coming from the outputs on the scope. The audio quality is VERY clean and noise free.
The deck now operates down to 9.6 VDC dc source voltage, so your battery can be just about dead in the car and the deck will still play, forget any amp operating at that voltage, but the deck still will work.
The prototype is not all that pretty, but it fits in the same location, and it will fit just fine in the deck fully assembled. There doesn't appear to be a need for the case like with the stock converter, so I am saying this is a success.
I will burn in the converter for a day or so and see how it stabilizes if it has not already, but at this point everything is looking very good, and well within noise specifications and stability.


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## cajunner (Apr 13, 2007)

great work!

did you compare it to a stock converter for performance testing?

how much did it cost you in parts to refurbish?

is it ready for pictures, or you will just wrap it in electrical tape and call it a day?


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## jeffp (Jan 18, 2015)

Really, I did not even bother, the new part specs are 9.6 VDC to 36 VDC operation. Current output is 9 watts @ 10 volts on the input. The voltage regulators are good for 1/2 Amp without heat sinking. The noise floor is negligible @ 20 millivolts.
I still have to design a new PCB for the part. I am not sure how much that will cost me, but it is worth the time and effort. 
As I first thought, the part does not need RFI/EMI shielding to do its job. The outputs are Very stable and I am happy with the results. 
The deck has been going now for about two hours, the components of the converter are running very cool, I can hardly feel the heat difference when I touch the components. I guess I could get an infrared gun on it to get an exact temp, but that is not necessary.

The total cost with a circuit board made is looking at about $60.00 not to bad I don't think. I sure like this part much better then the stock converter for sure.


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## Robb (Dec 5, 2008)

That is cool man.
If I ever need to repair my 7909 (if it ever comes out of the box), I know who to send it to !


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## Kriss_Kross (Feb 29, 2016)

Hello from Italy,

I have the chance to get a 7909 from a friend but the DC DC converter is simply missing... removed it for another unit!
I would like to try the challenge to put it back to life but I would like it flush when remounted so no external converter.

Would it be possible to have one built for my unit? How can I contact you ?
Many thanks!

Best
Chris


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## iyamwutiam (Nov 20, 2006)

There is a guy name Jeff ..who specializes in restoring 7909s . I will pass it on , he comes on the site on occasion.


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## stantri (May 9, 2015)

Hello from France,

I am in the same situation as Chris in Italy; I have two 7909L but one has its dc dc Converter missing. 
Jeff seems to have found the magic formula: restore the life to 7909...
And I think that it interests many 7909 owners.
Did Jeff think of producing other converters ?
Thanks Jeff for your information and you help

Best regards
Tristan


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## ryanr7386 (Feb 21, 2011)

What are you guys referring to as missing? The black box on the Power supply wire? If so that's the noise filter, not the dc to dc converter! The converter is inside these units, you would have to open them up to get to them.


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## jeffp (Jan 18, 2015)

Ok Christian was considering selling me one of his 7909L units, however he wanted to much money for a unit that was not complete and had the incorrect QRB connector and wire harness for the L model. 
As I said to Christian, I have the components for the converter, but I have not made a circuit board.
So are you saying there is a market for the dc converter, and if so how much would one pay for a unit I designed, being exactly the same component electronically, with my custom case?
Also Ryan said something about the black box on the wire harness, is this what you are referring to the dc converter?
email me at [email protected] if you like, maybe we can work something out. I do need an L model for a customer in Germany, so if you have one you would one willing to sell let me know. 
I will require a complete unit, cage wire harness, and the deck complete, missing the dc converter is alright, but I am not going to pay 400.00 for a unit with shipping and trash a 600-700 dollar J model I have to repair the unit I bought from you, if you want to sell.
I can also do the retrofit to the J model to work as the L model for the tuner, so right now that seems like my best bet.


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