TweetFollow Us on Twitter

ADB Repair
Volume Number:5
Issue Number:11
Column Tag:The Electrical Mac

Related Info: ADB Manager

Repairing the ADB

By Eric Schlienger, Champaign, IL

ADB Repairs

[Eric Schlienger received a BSEE at the University of Colorado at Boulder in 1979. He was in charge of the both the control system design group and the software group of Retech Inc. of Ukiah CA. He has worked primarily with Hewlett Packard computers until he went back to school at the University of Illinois at Champaign-Urbana. He is currently working towards a Ph.D. in Materials Science and Engineering.]

Several months back I was doing some work on my brand new Mac II and started experiencing a “scritchy” mouse. Considering myself a clever fellow, I decided to clean it during a particularly lengthy recompilation of all my code. Since I was being clever I decided I might be lazy as well and so I did not unplug my mouse. Similarly I used whatever implement was at hand for the cleaning operation; in this case a pair of metal microscopy tweezers. Well to make a long story “short” I slipped....OOPS! Both keyboard and mouse took an immediate trip to Lala land, terminating my programming session rather abruptly. Terminal ADB failure.

While reading February ’88 MacTutor, I noticed that several other folks have experienced the same ADB symptoms, and although their method of generating an ADB failure would appear to be less certain than mine, I am convinced that they may be able to repair the situation with a $0.79 fuse in 15 minutes. ( or have their service man do it) As a new motherboard is probably more expensive and less readily available, I believe that some people might find the repair procedure interesting.

Before attempting a repair, do be certain that you have checked all cabling and preferably tried a different mouse and keyboard. If you have verified that the problem is indeed with the ADB, you are then ready to Open The Box.

The Tools

First off, you will need a few tools. These are an ohm meter, a Phillips screwdriver, small needlenose pliers, small diagonal cutters, a small soldering iron with solder, a felt pen, a container for screws, and 1 ounce of ethanol (you may choose the flavor). It is also best to buy the fuses you need before you open the box. These fuses are referred to as PICOFUSES, and they are rated 1A 125V. They are roughly the size of a 1/4 watt resistor. The manufacturer of the ones I bought is Littlefuse Tracor.

Finding The Fuses

To begin, clear a large area for storage of the Monitor, Keyboard, Mac II top cover, the Drive platform (drives still attached) and the cables. Please note that the floor does not qualify as a storage area; neither tennis shoes nor carpet fuzz are items that are regularly found in properly functioning computers. As such it is best to avoid circumstances where they might be introduced.

If necessary park the heads on your hard disc. Unplug the CPU and remove all cables. Move the keyboard, mouse, monitor and cabling to the designated Storage-Area-Not-On-The-Floor. Pick up the CPU and turn it 180° such that the back is facing you. Remove the screw located in the top center of the back panel (Fig 1.).

Then turn the CPU back around. Reach around back and depress the two cover latches and swing the top up. Continue to swing the top up and give it a jiggle to free it from the front of the CPU case.

Behold the inner workings of the Mac II. If you become nervous, sit down and consume the ethanol while reminding yourself not to touch any of those neat chips. With the felt pen, mark the outside of the floppy disc cable where it plugs into the mother board. (This is so you are confident which way it goes back in.) Write down the number of the socket that the cable is plugged in to on the cable itself. Gently grasp the plug where it goes into the socket and pull it out; DO NOT PULL ON THE CABLE! If you have a hard disc (you probably do), mark the power plug and the SCSI ribbon cable and remove them in a similar fashion. Verify that all devices on the drive platform have been disconnected from the motherboard.

Remove the four platform mounting screws and lift out the Drive platform (Fig. 2). Place it gently in the Storage-Area-Not-On-The-Floor.

OK. Now look at Figure 3. With the aid of this drawing you should be able to locate the devices labeled F1 & F2. The “F” stands for fuse. (Clever these Apple folks, huh.) In my case, F2 was blown.

It may be that F2 is the ADB fuse, and F1 is the fuse for the Serial Ports, but I haven’t verified this one way or the other. With your ohm meter you should be able to test the fuses. The basic procedure is to measure the resistance of the fuse. If the resistance is greater than one ohm, it is bad. (Actually it should be zero.) If both fuses test good, put everything back together, obtain more ethanol and prepare to pay big bucks for a motherboard.

Fixing The Fuse

If a fuse is bad you have two options. The first is to find a static free workstation and remove the motherboard to replace the fuse. In this case you desolder the old fuse and install the new one. The second method is something of a kludge, but functional, safer and easier. Basically what you are going to do is to piggyback the new fuse on top of the old fuse. Since a blown fuse is an open circuit piggybacking is the functional equivalent of replacing it. However for those who regularly give tours of the inside of their computer, it should be noted that this repair may be esthetically deficient. The procedure is fairly simple:

Take one of your new fuses (they come in a box of 5) and using the needlenose pliers, bend the leads 90° on either side of the fuse body. About 1/4 inch below the fuse body bend the leads 90° such that the leads are now at a right angle to the fuse body (Fig 4).

Trim the leads so that the distance to the last bend to the end is about 1/4 inch. Slide the leads under the old fuse at either end, and grasping each lead in turn with the pliers, pull it through until the new fuse is over top of the old one. Bend the leads up and solder them into place on the old fuse. When soldering don’t use too much heat as you do not want to remove the old fuse from the mother board. When the new fuse is securely fastened to either end of the old fuse trim off the excess leads.

Reposition the drive platform, replace the 4 mounting screws, replace the drive cabling. Put the front of the cover in place and swing down. A gentle tap may be required to get the front to seat properly. Replace the rear screw and the cables. Your ADB should be repaired.

Please note that the presence of a piggy backed fuse will almost certainly void your warranty, so if your computer is fairly new consider having an authorized service man do the repair. If it is out of warranty and the alternative is a new motherboard, you might give it a look see. Please remember that while the box is made to be opened, the circuitry is not hardened against standard computer room contaminants such as coffee, donut crumbs or peanut butter sandwiches. So don’t leave the computer disassembled so that everyone can see your handiwork and comment on how clever you are.

As a general rule, do not mess with the ADB or associated devices when the power is on. This should hopefully eliminate the need for ADB repairs.


Community Search:
MacTech Search:

Software Updates via MacUpdate

Between 2 Taps - Tap for Tap interview M...
Hello, and welcome back to Between 2 Taps, Tap for Tap’s Indie Dev interview series. [Read more] | Read more »
Facility 47 (Games)
Facility 47 1.0.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.1 (iTunes) Description: You wake up alone and freezing in an icy cell. You try the cell door but it’s locked, it seems that you are stuck with no... | Read more »
The best Photoshop alternative on iPad
Instagram and Lightroom are great and all, but sometimes people need to get extra creative with their image editing.Like, Photoshop creative. If you're one of these people, take a look at our pick for the best mobile Photoshop experience on iPad... | Read more »
The Walking Dead: No Man’s Land guide -...
A new update for The Walking Dead: No Man’s Land was released last week, making it the perfect time for you to head back to your base and take out some walkers. Here’s the lowdown on what’s new to the game, and how to take advantage. [Read more] | Read more »
Goat Rider guide - Tips and tricks to st...
We've all been there. One second, we're riding high on a crazed goat, and the next, we've been tossed off it like someone who's no good at goat ridin'. [Read more] | Read more »
Real Boxing 2 CREED: How to become a gre...
Just in time for Rocky fans who can’t wait to see CREED, the latest movie, we have the official tie-in game,Real Boxing 2 CREED. It builds on the success of its predecessor and there’s lots to take in so we at 148apps thought we’d run you through... | Read more »
CoinOp Heroes 2 guide - How to build an...
CoinOp Heroes 2 justlaunched and, like all clickers, it's dangerously addictive stuff. You have to furiously tap your screen to defeat wave after wave of foes and earn an insane amount of cash to spend on character upgrades and an army of minions... | Read more »
Dr. Panda Firefighters (Education)
Dr. Panda Firefighters 1.0.1 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0.1 (iTunes) Description: FIGHT FIRES AND SAVE THE DAY!Work together with Dr. Panda and his firefighting team to rescue his trapped... | Read more »
Puddle + (Games)
Puddle + 1.0 Device: iOS iPhone Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Puddle is back in a new "+" edition featuring enhanced graphics, new videos and Apple TV support ! No IAP and No Ads. Dive into Puddle... | Read more »
Football Manager Mobile 2016 (Games)
Football Manager Mobile 2016 7.0.0 Device: iOS Universal Category: Games Price: $8.99, Version: 7.0.0 (iTunes) Description: Football Manager Mobile 2016 is designed to be played on the move and is the quickest way to manage your... | Read more »

Price Scanner via

Adorama Black Friday deals: Up to $400 off Ma...
Adorama has released their Black Friday deals for 2015. Save up to $400 on MacBook Pros, $200 on MacBooks and MacBook Airs, and $270 on iMacs. Use code RYBFDEAL during checkout to see these prices.... Read more
B&H Photo Deals: $200 off 12-inch 1.2GHz...
In addition to the B&H Photo Black Friday week sales we posted yesterday, B&H has lowered their price on two products to $200 off MSRP: - 12″ 1.2GHz Gray Retina MacBook: $1399 save $200 - 13... Read more
Best Buy Early Access: Today only, Up to $125...
Best Buy has iPad Air 2s on sale for up to $125 off MSRP and Apple Watch models on sale on their online store for up to $100 off MSRP with special codes through midnight CT tonight. Choose free... Read more
UPPERCASE DESIGNS Premium Ultra Thin Keyboard...
UPPERCASE Designs today announced its new Premium Ultra Thin Keyboard Protector and its Palm Rest Protector Set for the 12-inch MacBook. The accessories provide durable protection for the 12-inch... Read more
Al Jazeera Launches New iOS And Android Mobil...
Doha, Qatar based Al Jazeera has launched new mobile and tablet apps on the iOS and Android systems bringing the latest Al Jazeera news and programmes live together with on-demand personalisation.... Read more
B&H Photo Holiday Sale: Up to $250 off Ma...
B&H Photo has all new Macs on sale for up to $500 off MSRP as part of their Holiday sale including free shipping plus NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off - 15″ 2.... Read more
Free Aura ‘Ultimate’ Mac App For Gmail Update...
Miami, Florida based Crosscoded has announced Aura 1.2.0, an update to the Mac app for Gmail. Aura mixes the power of a native client with the flexibility of the Gmail web app with support for up to... Read more
Apple Will Edge Closer to Samsung in Smartpho...
Total smartphone shipments for 2015 are projected to decline by 9.7% to 1.286 billion units, according to the latest report from global market research firm TrendForce. Though Chinese vendors have... Read more
Sidefari – Split Screen Multitasking In Safar...
Francisco Cantu’s Sidefari is a simple web browser designed to act as a companion to Safari on the iPad. With multitasking in iOS 9, Sidefari uses the new Safari View Controller to show an extra... Read more
12-inch MacBooks in stock for up to $120 off,...
Adorama has 12″ Retina MacBooks in stock for up to $120 off MSRP including free shipping plus NY & NJ sales tax only. For a limited time, Adorama will include a free Apple USB-C to USB Adapter,... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Merchant Operations Manager: *Apple* Pay -...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more than Read more
*Apple* Pay QA Manager - Apple Inc. (United...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more than Read more
Sr Software Engineer *Apple* Pay - Apple In...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more than Read more
Hardware Systems Architect - *Apple* Watch...
# Hardware Systems Architect - Apple Watch Job Number: 38449977 Santa Clara Valley, Califo ia, United States Posted: Apr. 16, 2015 Weekly Hours: **Job Summary** The Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.