Tom and Lisa's Weird Web Page

Duo Modifications

I got into a "Duo mania" a while back, and now have enough parts for several units.  It has been fun playing around with these simple sub-notebooks and seeing how they are put together.

Before I start, let me say there is a very good list server for Duo and powerbook 2400 topics that you can join by going to www.lowendmac.com and finding the correct link. The listerver has been a great source of information about Duos.

If you want to see the King of Duo modifications, I suggest take a look at this link:  http://www.liethen.com/firebook-mana/index.html

What I set out to do was much simpler. There are 6 things I will describe on this page:

- Overclocking your Duo
- Cleaning your Duo keyboard
- Changing the CAPS LOCK light to a red LED
- Adding a hard drive activity light
- Adding a ADB port in place of the modem
- Repairing the AC adapter port
 
Overclocking your Duo:  All duos either have a 68030, 68040 or PPC 603 CPUs.  While all of them can be overclocked, the CPUs in the Duo 210, 230, 250, 280 , and 280c do not have FPUs and are a little easier to overclock successfully.
With a little soldering you can get a small speed increase.  33 MHz CPUs should be able to go to 40 MHz or more (your mileage may vary though), and the 25 MHz Duo 210 is probably good to go to 30 MHz. However, it is reported that overclocking a Duo can cause the modem port to stop working.  One person reported this happening when he overclocked to 40 MHz.  My 280c duo at 37.5 MHz seems to be functioning just fine.

Here is a view of a Duo 280/280c motherboard (they are the same part):

#1 is the CPU
#2 is the CPU oscillator
#3 is the AC plug in (see later on)

Here is a close-up of the motherboard, centered around the oscillator that controls the CPU speed:

The oscillator will run the CPU at half the frequency of the oscillator, so the stock 66.6666 MHz part in the picture above runs the CPU at 33.3333 MHz.  By removing the oscillator and replacing it with another, faster part, your CPU (and bus speed) will increase. The oscillator controls the bus speed but to the best of my knowledge you cant change the bus-to-CPU speed multiplier.

Equipment:
You will need the following items:

- A 23 Watt (or so) soldering iron with a fine tip.  A 15 Watt iron might not have enough oooommph to desolder.
- A 75 MHz oscillator (www.digikey.com, part #SE3511CT-ND)*
- fine, narrow desoldering braid (copper).  I bought some at Radio Shack, part # 64-2090B.
- some solder, preferably lead-free solder containing silver.  I bought some at Radio Shack, catalog #64-025.
- A clean, well-lit place to do your work, preferably over a non-flammable surface.

* a 75 MHz part worked for me.  You may want to try a slower or faster part (70-80 MHz) depending on how lucky you feel.

Step 1:
Disassemble the Duo, taking the motherboard out and placing it on a soft (and non-flammable) surface to avoid damaging the surface components.

Step 2:
Carefully desolder the 66.6666 MHz part. Work around the oscillator one pin at a time.  This shouldn't take long. Make sure not to avoid heating the surrounding ICs.

Step 3:
Solder on the 75 MHz part, again being careful not to heat the surrounding ICs.  Also note that the oscillator has a facing, so make sure to solder it in the correct facing.

Step 4:
Reassemble the duo. Make sure to test the modem and AppleTalk ports, as sometimes the higher CPU speed renders them inactive.

Once you have overclocked the duo, I highly recommend adding some thermal paste between the CPU and the heatsink; this will help soak up the extra heat generated by the faster CPU.

Cleaning the Duo keyboard: One of the most common questions about Duos is where to buy new keyboards or how to fix the old ones you have.  All the Duo keyboards I have come across have been repairable.  The keyboards either tend to get gunk on the mylar contacts, or a small break develops in the metallic traces on the mylar sheets. Either can be fixed.

This is the keyboard as it appears in a pristine state:

Using the tool pictured above, or carefully using your fingers, it is possible to remove all of the keys.  If you remove the keys you will see that beneath the keys there is a rubber mat:

The mat is removed freely after all the keys are off.  Beneath the mat are 2 layers of mylar plastic that have metal traces on them:

In an ideal word I would show a complete keyboard disassembly, but it takes a while to get all the keys on and off.  Please note that some of the keys have metal stiffeners which are attached to the keyboard and the keys; so don't be surprised (although they are easy to get on and off).

These metal traces can get dirtied and require cleaning to get functional.  To clean them, I suggest gently rubbing along the traces with a clean eraser (use rubbing alcohol to clean them). Watch out not to knock off the green  CAPS LOCK LED; it is easily dislodged. Also be careful not to get a fold in the mylar sheet from rubbing to hard and too fast.

If keys are still not working after cleaning the traces, there may be a break in one or more circuits.
Write down all the keys that don't work, odds are that all the keys in question are along one single trace on one of the mylar sheets (visual inspection shows this).  Using a volt meter, check along the suspect trace to determine if there is a break (infinite resistance).
If you find a break, you can use either Dotite (I could never find any in stores) or the more easily found Loctite, which is used to repair windshield heating traces in cars (find it in auto stores).
Both of these are liquid conductors, and used like glue.  Spread a little of this material over the break (not too much - don't cross over to a different metal trace), and this will bridge the gap after drying.
Between these 2 remedies, all my problematic duo keyboards have been fixed.
I would also suggest  that when you have your keys taken off of the keyboard take some time to clean them with some rubbing alcohol solution. Tidiness counts !
 

Replacing the Green Caps Lock Light:  I took this idea from a Japanese page that used a blue LED in place of the green CAPS LOCK LED. Unfortunately, I can't find the appropriate blue LEDs to use (the only SMT ones I found were 4.9 V which is too much for the keyboard, which is limited to 2.5 V or so).  I did find red LEDs that work (www.digikey.com part #L62211CT-ND).

Remember what I said above about not knocking off the CAPS LOCK LEDs ?  Well it's real easy.  If you want to replace the LED, a small amount of pressure is enough to pop it off the top mylar sheet (I am assuming at this point that your keyboard is completely disassembled).
All you do then is to place the new LED where the old one was (making sure to have the correct facing, LEDs are current directional), and use some Loctite to glue the new LED in place, being careful not to use too much Loctite).  After drying, put the keyboard back together and enjoy the new color.

Adding a hard drive activity light:  This is the toughest mod I have done for a duo, and probably one the most fun.  I originally saw this idea on a Japanese web page, but unfortunately the details were very slim.  After a fair amount of time tracking parts down and getting a refresher in basic electronics, I managed to figure out how to do this.
The SCSI hard drive in a duo has pins that allow the use of a LED.  I think an IDE drive would have the same, but I cannot confirm that. Once I checked the web page for several of the SCSI drives I had, it appeared that all the drives have the same pin outs.  Get the specs for your drive just to make sure.

The lower left hand pin of the set of 8 pins is the drain, or negative point of the circuit I built.  The source, or positive point of the circuit, is any one of the 3 pins surrounding the drain pin.  These pins are also used for SCSI ID, but using them as a source does not affect the SCSI ID.
Once you know the source and the drain, I had to design a circuit.  Fortunately, the circuit is very simple, and even I could figure it out:

Pretty simple, eh ?  If you select the correct parts, you don't even need a resistor before the LED.  After some trial and error, I find that either digikey part# L62211CT-ND (red) or L62411CT-ND (red) works well.  Digikey part # L623007CT-ND (yellow) probably works but I haven't tested it.  Unfortunately, I cant find a proper part with a blue color.  These are SMT parts and require some sort of mounting surface.  I used Digikey part# 6103CA-ND (a "surfboard") to mount the parts on.
To run the circuit through the pins on the hard drive, I suggest finding an old 2.5" IDE female socket and cut it up into the proper size.
Run wires from the proper socket holes and run the wires to the surfboard.  You can either solder the wires directly to the surfboard, use some sub-D female pins (digikey part# A2089-ND) to mate to the surfboards.

When put together, the whole thing looks like this:

The item on the left is the surfboard with the LED soldered onto it, and the item on the right is the socket I cut from an old IDE 2.5" drive socket, with wires soldered to the socket.

I also like to put some heat shrink tubing on the connection to the surfboard (not shown above).
Simple and effective.  The only work that remains is to mount the socket onto the hard drive and then run the wires and LED into position.

Here is a pic of the wiring in place, below the trackball:

ADB port modification:  Again, this is not my invention, but I describe how I do this mod.  This mod takes a power on card and turns it into a ADB port.  It takes the place of the modem card, but who wants a 14.4 modem anyway ?  If you try this, go to apples developer web pages and download all the Duo developer docs (http://developer.apple.com/techpubs/hardware/hardware2.html)

The first thing I did was to take a power on card and remove the top epoxy layer that covers the copper layer (I used a dremel).  If you don't remove the copper layer, this will short the 4 ADB pins to each other.  I used a concentrated FeCl3 (ferric chloride - Radio Shack used to sell this stuff) solution to etch the copper off.  You could also use a dremel tool.

After etching the copper off (if you etch off just the parts around the 4 signal pins, you can use the copper plate near the mounting pins to solder the socket down, although this is not absolutely necessary) , and drilling some holes out to mount the ADB socket this is what it looks like:

I used some epoxy to glue the port down onto the card. Adding some hot glue cant hurt.
 

Once put together, the wiring on the backside of your Duo should look something like this:

The pins on the ADB socket are marked 1-4.  According to Peter Leithen's web page,

Pin 1 on the ADB socket goes to Pin 83 on the PDS socket on the motherboard
Pin 2 on the ADB socket goes to Pin 47 on the modem card
Pin 3 on the ADB socket goes to Pin 8 on the modem card
Pin 4 on the ADB socket goes to Pin 3 on the modem card

Don't get the numbers mixed up.
 

Repairing the AC adapter port:  A few people have noted that their Duos wont run off of AC adapter.  I had one duo that had this problem.  A careful inspection showed that the AC socket was loose and made only intermittent contact with two of three mounting pads I could see sparks when I jiggles the AC plug when connected).
To fix this all I had to do was add a _small_ amount of solder to the loose pads (there are 3 of them) to anchor them back down, and everything was fixed. You might not need any solder at all, just to re-melt the legs into place.  I also suggest turning the board so the backside is facing up.  Add some solder to the 2 anchoring legs for a batter hold.