Duo Power Supply Fix 97/03/05
I was one of the unfortunate ones to have the Duo Dock Power supply start ticking on me. I know several people that this has happened to; even heard rumors of Apple fixing docks years after they went bad. Anyway, even after the tech guy described my problem, when I mentioned that they must have some kind of repair policy on this, after talking to someone, he denied ever hearing about this problem!
Warning! Do not attempt this unless you are good at working with electronics! I recommend you get a new power supply from your local dealer! I will not be held responsible for anyone's misfortune if they try anything on this page!
Here's a great place to buy Powerbook parts from and to get repairs done:
DT&T
720 E. Evelyn Ave
Sunnyvale, CA 94089
Wk: (408) 747-1555
Hm: 800.MAC.7977
Fx: (408) 747-1110
Anyway, here are some suggestions on fixing the ticking power supply:
Tools:
Torx T-10 wrench. I got mine from Sears ($4.49). You need this to remove the circuit board from the metal base of the power supply. Get a fairly long one as you need to reach a torx screw that is buried.
Size 8 X 1/4" tapping pan head screws for putting the dock back together (49 cents). You could use rivets if you wanted to. Rivets and the rivet gun are available from Sears or your local hardware store. (approx $14-$30).
Small drill bit (1/8"???) to drill out the rivets on the power supply. There are four rivets and you can't miss them. Drill them out to open the Power Supply.
Capacitor to replace the bad one at location C28. Radio Shack Cat. No. 272-1028 RADIAL LEADS 100 MFD ELECTROLYTIC CAPACITOR 35 WVDC maximum. 99 cents.
Pliers to bend metal ( you need this), Phillips screwdriver (to put new screws to put it back together). Flat blade skinny screwdriver to take the Duo Dock apart.
Solder and solder wick (to remove the solder from the capacitor leg holes).
Suggestions and Procedures:
From the Duo FAQ:
I feel your pain -- my dock started ticking last week. Anyway, a ticking Dock is a sign of a bad power supply. It usually starts after leaving the dock unplugged for a period of time. Let it tick for a few hours, and it may stop by itself once the faulty capacitor is charged. Eventually, however, you will have to either get a new power supply, or try to fix it by replacing the faulty capacitor. Here's how:
(these instructions are from Murray Pickard)If you are at all uncomfortable working with electronics and/or switching power supplies, don't try this repair yourself. Even though the power supply might be disconnected from the AC power, the capacitors in the power supply can still have deadly charges left in them.
For those of us with Duo Docks, that suddenly find the power supply ticking, A very cheap fix appears to be replacing the capacitor at location C28 in the power supply. There are two of us that have been able to 'fix' the power supplies by replacing that capacitor. (a 100 uF 25VDC electrolytic capacitor. $.99 from Radio Shack) This is not to say that other components in the power supply might eventually fail in the near or far future.
To take the Duo power supply out, first follow the directions in the duo manual to install a new nubus card. After you follow these directions, you'll have your dock in three pieces: base, cover and logic board assembly. The base will contain the power supply. To remove the supply, you need to push both tabs that are towards what used to be the dock opening for the duo. Do this while you
have the base slightly inclined towards you, and the power supply will just slip out.
I've received some e-mail asking about the next step: You have to drill out the rivets in order to open the power supply. Don't worry too much about screwing up your power supply by drilling it open; it's the only way to fix it without buying a replacement. Putting the PSU back together when you're done requires a bit of improvisation. Let me know what you use to hold it together (unless you use new rivets, of course.)
Of course you know what to use... the size 8 X 1/4" pan head tapping screws. They will secure your power supply after you have fixed the capacitor.
Hint: Hold the power supply so the fan is to your left and the power jacks are pointing toward you. Look downward by the jacks, slightly to the left of them. There will be the word CAUTION printed on the circuit board. Capacitor C28 is slightly below and to the right under the CAUTION. (Actually the N),
TAKE NOTE! Record the polarity of the fan, polarity of capacitor C28 and which direction the fan is blowing!!!!
You do not want to put them back in backwards!!!!
Take out the 3 torx screws.
Take out the Fan. (To take out my fan, I bent the retaining metal on top of the fan that holds it in. I just bent it back later.)
Once you have the fan removed, you will have to separate the power supply clip that is tethered to the metal wall like a C. I just pried it loose.
Once you have the Torx screws, Fan and power supply cords separated from the metal wall, you can look at the circuit board to inspect it and replace capacitor C28.
Reverse the procedure to put everything back together and use the tapping screws to put the power supply back together.