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Alpine 7909 dc to dc converter info needed

17K views 96 replies 10 participants last post by  jeffp 
#1 ·
Hi all, I just got this deck and it is a mess. I believe I can get it up and running again. One big problem, the dc to dc converter has been hacked into. No problem there, but one component is missing, a capacitor.
Do any of you have a blown unit, or the information so I can verify the missing cap. Also, if someone out there has a blown component, I can reverse engineer the unit, complete a schematic and come up with full documentation provided I have the unit complete, unmolested.
Hope someone can help.
 
#62 · (Edited)
You are funny guys, I worked hard on the schematic of the dc converter, and the diode was the last part I needed to identify.
So with that done, now I have a complete parts list for the converter.
I was thinking of making the circuit board, but after working on some of the worst converters, I have not had to do a new board. I have been able to repair all of the converters, and some were smoked real good. The power transistor is the trouble area, and fortunately, that is easy to do the repairs to.
So here is the completed schematic, now verified.
 

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#65 ·
I do have allot of time and effort in these units. Currently, I am looking into the bobbins for the transformer.
I got a repair unit in and did my normal repairs to the converter powered it up an let the unit run for a while. When I got back the unit was dead, the power transistor was toast again. So I went about to trouble shooting the problem and that was the transformer. I checked it with a LC meter and the readings on the secondary windings were not so good.
I tried to disassemble the transformer but I knew that was not going to fly, and I was right, the ferrite core broke, so I disassembled the part anyway, and I was right, the windings got hot enough to burn up the wire insulation and short between windings, so it was toast along with two transistors. Really bothered me a little blowing two transistors, but that lead me to a new problem, how to replace the transformer.
I found one that may work on alibaba I have to buy 2000 pieces, not to bad they ended up costing 28.00 if I can get them paid for and shipped. The company does wire transfer, and I am hoping they will do credit card as well.
so if that goes good I will be able to build new transformers, what pain right?
 
#67 ·
Tat is correct they are small. I do have a transformer turning fixture that I will modify to chuck the small transformer.
I can do a better job winding the transformer then the original vendor, and who knows maybe they will be more robust.
The whole thing is a PITA as you mentioned.
 
#68 ·
I finally got the transformer bobbins and Ecores on order. I was able to get a sample of 20pcs of each part. I also sourced the wire for the build.
Now I will wait and see how long it takes to come in.

The transformers are becoming a problem. I have had two failed parts in the last two weeks, so since there are no replacement parts, this is becoming an issue with repairs.

I did build a dc converter, and it does work very well, but I am not happy with the heat the regulators are making. The part heat soaks the deck after about 5-6 hours of operation.
I have looked at a alternate dc converter that has the outputs @ 12 VDC in stead of 15 VDC and that just may be the answer to stop the heat issue with the 10 volt regulators. I will order the part and see how it goes.
 
#70 ·
Well that is one way of dealing with the issue, but I don't think most people will take care to install the unit with the separate PSU for the amplifiers in the unit. I know Alpine did the 7990 unit that way, but it is a much bigger unit then what is need for the 7909. The 10 volt negative rail only draws 66-67ma and the positive rail draws 105-107 ma so we are talking very low wattage.

I did receive the transformer bobbins today, an they fit the current cd converter board pinout perfectly. I have the wire on order and it is on its way to me. Now I can build the transformers and hopefully make improvements on their build.
I think this is still the easiest way to repair the converters. But maybe I am hard headed LOL.
 
#71 ·
Ya, and one has to question how far to take these upgrades to not destroy the original design intent as well I suppose. What you have accomplished here Jeff is astonishing, at least to me anyway. I have owned several 9's through the years, not so much here lately due to the aging process of these units. Assuming you'll offer service for these units it is peaking my interest to purchase another. And I think I know where to look by the way :)

Keep up the excellent work Sir!
 
#72 ·
I enjoy doing the restoration on these units. I am pretty good at it now LOL. I have had very positive responses to the units I have sold and have repaired a number of units as well.
But you always get that one customer, no matter what happens they are the biggest PITA customer. I just finished up one such customer, and at the end of the day I lost out on 20.00 or so in shipping because he had to ship through the post office, and he ran the costs yada yada yada and he cant understand why I am not to pleased with the transaction, and my abrasive email did not help according to him. So there you have it Rick, I am just difficult to work with LOL. Good riddens dude, I HATE THE POST OFFICE, its right up there with the DMV!
I'm better now LOL.
anyway, back to the transformers. I cant wait to build one of them. I have all the equipment to build them, pot them evacuate all of the air out of the windings, and go for it. I have had to build the transformer for a high voltage power supply I market to a customer, so I am just wondering how much my part will change from the original part and how it was made. When I unwound the bad one I could see the part was made very sloppy, so I am thinking the adjust resistor on the converter will have to change also. Thank god for the decade resistor.
Now all I have to do is figure out how to hold the little sucker LOL, the bobbin is so small, amd without the Ecore it is even smaller. Should be fun.
 
#73 ·
I received all of the components for the transformers. I had to reorder the wire as the first wire I bought was JUNK. The insulation was not to my liking. So I decided to use the wire I had on hand and turn two wires in parallel on the primary. That worked out good. I then used the same wire on the secondary.
The first transformer I turned just like the original transformer, and I had a higher then wanted voltage on the positive rail of the output, 11.7 VDC a little higher then I wanted.
I turned a second transformer and this time I turned two wires in parallel on the secondary winding and it turned out good. the negative rail was 9.99 VDC and the positive rail was 9.86 VDC very close. I still would have liked to se 9.99 on the positive rail. The issue is that the positive rail current draw is about 40 milliamps more then the negative rail, a little hard to overcome with such a small transformer.
I spoke to my engineering buddy, an he seemed to think I was splitting hairs. I asked him if he thought two or more turns on the positive winding would get the voltages closer, and he laughed, smarty.
I am happy I was able to get the components to go this work on the converter. Otherwise I would have to tell people Sorry, I cant repair your deck. I did do a new converter, and it works well, but it gets a little to hot for my taste over about 8 hours or so.
I have new wire coming in to try on the next transformer, so we will see how that goes.
 
#75 ·
Hi rick, do you just want the recap only? I have found most of the units have problems with the transport and need some work on the laser and other work.
I have been charging 400.00 to do a restoration of the unit, so it is good to go, and reliable, not to mention making the improvements on the audio out. Give me a call (714) 907-6318
 
#76 ·
What to do about a missing cd converter can????

I have built the transformers for the converter and they have turned out perfect. I am seeing 1/10th of a volt difference in the +10 volt and the -10 volt outputs. I talked to my engineering buddy about it and he said I was splitting hairs, and that was an excellent matching of the two outputs.

Anyway, so the next big problem was I got a unit someone hacked to death, and the RFI can was missing all together. So I went to work on that problem as well.
I could think of only one thing to do, build an new can. So I just finished up my dies to bend the can with today. Here are a few pictures of the finished product. I made the can from brass shim stock. I will find a source on the copper sheet I need and that should be easier to bend then the brass sheet, but both are perfectly acceptable to use to shield the RFI from the converter. I have to finish it up and drill the holes for the power leads, then assemble it, solder it and seal it with RFI tape, DONE DEAL!
 

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#78 ·
I understand what you are doing and why but I have to ask.

Have you explored using a premade unit? I have had really good luck using these.




The one with the heat sinks will to 12amps stock and will do 24amps if you put a larger heat sink on it or a fan.

The second one is rated for 2 amps. The voltage display on this unit is not to be trusted. It is close but does not read the same as my Fluke says, which I trust.

These units are not even expensive at $10 and $6 respectively. I have not gotten any feedback or noise out of the ones I have used.
 
#80 ·
I guess you missed the first sentence of my post. That or you fail at reading comprehension.

I understand restoring one for whatever reason one chooses. It was more targeted if someone who just wanted one to work and not spend hundreds of dollars on an inherent poor design from the beginning.
 
#81 ·
Sorry that your a little sensitive there dude but what he is reconstructing actually is a component that is attached to the audio pcb board, inside the unit. I'll let him explain why what your suggesting won't work!
 
#82 · (Edited)
ok I did not get back to this until now. So I have looked into just buying a component to replace the "poorly designed" part. I in fact did design construct a regulated unit and the part worked very well.
One problem though, the regulator was running hotter then I wanted it to, and I still had to build an RFI can for the part, or use an old can from a stock converter.
The components you have listed here are from what I can see, are not isolated grounds. The requirement is a +10 and -10 volt supply voltage for all of the op amps in the unit. The ground isolation is for the noise factor, and even still there is some motor noise I see on just about every unit, way down in the mud, and you cant hear it in the speakers, but my instrumentation has found it.
I did build the part, but in the end it turned out easier to simply repair the stock part, no heat related issues over time, and the part works.

So there you have it, the deck is repaired exactly as Alpine built it, and from its history, apparently many many people did not seem to think it was to inferior to buy and compete with.
I realize there are "Higher Quality" head units out there, all digital, 24 bit processing, yada yada yada, but this unit has the antiquated analogue outputs, the features that make the unit very easy to operate, and features you cant get from most all other units.
I don't find that I need to enhance, correct, or modify the audio output in any way, other then using the bass and treble controls on the deck, and that for me is just to cool. I tried a number of alpine components, 3347, 3348, fosgate PA2 and NONE of the components made the unit sound any better.
So I will stay with my "old school" unit and be very happy doing so rocking down the road with a Fosgate power 650 amp. My hotrod currently does 130dB of crystal clear audio, that WILL make you go deaf, oh the sound of Eric Clapton unplugged like he is sitting right in front of you playing, good enough for me.
 
#85 ·
Your comment earlier about an inherent poor design is partially true with these 7909"s. The capacitors inside these sealed boxes he is reconstructing were prone to overheating and shortening the lifespan considerably with these converters.
 
#88 ·
The confusion is the plastic black box with one yellow, and one black wire in the wire harness. That box (on the J model) is a noise filter that provided the dc converter 12 volts. The difference with the J model (and 30th anniversary) from all of the other models is that box. The dc converter is powered by that dedicated power source in the wire harness. The 7909 and 7909L power the dc converter with the single yellow switched power wire in the wire harness.
The second power source feed was done to cut down on any internal noise that may have been generated by the unit itself, like the cd spindle motor for example.
hope that clears it up
 
#89 ·
Transformer components Finally!

I was able to source the transformer bobbin and ecores through one company. I got 30psc and 30 pairs of ecores. Then I started using a number of them, so I tried to get a new order, company is gone, that sucked.
Well I finally was able to find a new company with the components. I bought 100pcs and pairs of ecores.
I can build 100 transformers now, So now I have every part to build a dc converter from scratch. I haven't made the circuit board, but haven't need to replace a board yet. I have been able to work with every unit and get it working again.
 
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