Critical Fixes
Every vintage computer has specific things that fail, especially portables. It is not a small feat to design a portable computer, and IBM in the 80s and 90s was one of the best when it came to the quality of engineering and manufacturing. Even so, every model has weak points.
Whether you have just acquired a new 701C or are diving head first into an extensive restoration, there are common issues and, more importantly, critical things you’ll want to take care of as soon as possible. This is a list I have built from my own experiences and research. It is by no means complete and will continue to evolve.
The “Sleep” Battery
The Sleep battery is used to place the machine into a suspended state, keep power to critical memory, and shut down unused devices. This battery, unfortunately, is often the cause of damage to the main board. Its electrolytic fluid can leak and damage components in the surrounding area, causing the main battery not to charge or, in severe cases, preventing the laptop from turning on.
It doesn’t help that the other main contributor to electrolytic leakage and damage is also close by in the main battery terminals.
Note: The replacement of this battery is mainly seen as optional as this is just one more battery to have to be concerned about, and modern NiMH replacements in the correct size are hard to come by.
Regardless of if you plan on replacing this battery, at the very least, you should remove it and remediate the surrounding area to prevent further corrosion and damage.
To remove the battery, make sure you’ve gone through my disassembly guide on iFixit and have separated the main board. While it may be possible to remove the battery from the square panel on the bottom of the machine, doing so may do more harm than good. There is usually yellow Kapton tape securing the battery that can get quite stuck to the coils.
Steps to Remove:
Step 1. Complete the disassembly using my disassembly guide on iFixit.
Removing without disassembly could cause damage to the board. As this battery is prone to leakage you may inadvertantly pull up or damage the components the tape is stuck to, or be unable to disconnect the battery connector if your try to do so via the hole in the bottom of the case.
Step 2. Remove the Kapton tape securing the battery.
As some components underneath may be damaged, be sure to do this carefully.
Step 3. Use a pair of needle-nose tweezers to disconnect the battery.
The best case scenario, the battery connector will come away freely.
If there has been corrosion, spray IPA on the board near the connector and carefully try to wiggle the tweezers back and forth to coax it loose.
In the case on the left, the connector came away from the wires. The corrosion was so severe the connector was welded together.
Final Step: Cleanup
Use IPA (90%+) and an anti-static brush to clean the surrounding areas of the board. You want to get as much corrosion out of the connectors and off the components as possible.
You can now move on to the battery terminals.
The Main Battery & Terminals
The second major issue the 701 series experiences is the failure of the main battery. Most of the original 701 series batteries were NiCd (NiCad) or Nickel Cadmium. These batteries were notorious for leaking, expanding, and damaging the case and surrounding components. If you’ve purchased a 701 or pulled one of our storage recently, the very first thing you should do is check the battery. Often it will be “stuck” in place and cannot be removed until the laptop is disassembled.
Forcing the battery to be removed may damage other components or the terminals. If the battery resists, move forward with disassembly.
Step 1. Complete the disassembly using my disassembly guide on iFixit - if you haven’t done so already.
Step 2. Remove the large chunks from the copper terminals.
Spray the area with IPA (90%+) and using one side of a pair of needle-nosed tweezers, gently scrap away the large pices of buildup.
You will want to do this carefully and take your time, you may find that the corrosion has eaten through the plastics or copper on the terminals.
Step 3. Flip the board and continue.
Turn the board over and continue on the underside. Make sure to get inside the loops of the copper terminals as well.
Every so often, you’ll want to apply more IPA and brush off the loose buildup with an antistatic brush.
Step 4. Cleanup.
When you’re done the terminals should be free of the blue corrosive material and you should hopefully have not encountered any damage.
Step 5. Check continuity.
Before calling it good, you’ll want to check the continuity to make sure there hasn’t been any issues inside the connector itself.
You can do this by turning the board over and testing the continuity between the 4 copper terminals and their respective through-hold solder joints on the underside of the board.
This will help you diagnose other issues in the future.
The CMOS Battery
The most common error codes that you’ll see booting up ANY IBM 90s-era laptop point directly to a dead CMOS battery:
161: Bad CMOS Battery
163: Date and Time Incorrect
This can be remedied by replacing the CMOS battery with a new one. These are luckily still in production and readily available at most electronic suppliers.
Some choose to replace these batteries with a coin cell holder or other compatible types with leads. However, I always go for the direct replacement. The coin cell holders never made much sense to me as those are designed to reduce the work needed to replace, but based on this battery's location, you’ll need to do a full disassembly every time anyway.
The other thing to note is that the internals is incredibly compact. The slightest change to height or pressure on the wrong component could cause a short or other damage.
The replacement part I use is the ML-1220/F1BN.
Let’s get started.
Step 1. Complete the disassembly using my disassembly guide on iFixit - if you haven’t done so already.
Step 2. Locate the battery on the bottom of the CPU board near the HDD connector and the RAM expansion slot.
It may already have some corrosion, so do a quick cleanup with some IPA before continuing.
Step 3. Clip the first lead.
Using a pair of flush-cutters clip the lead that connects the top of the battery to the board. It will be the lead on the right.
Step 4: Apply Flux.
Bend the battery up and away being careful not to put too much strain on the second lead still connected. Apply a good amount of flux to the connections.
Step 5: Desolder the battery.
Using a pair of tweezers, hold onto the battery while touching a soldering iron to the lead still connected. It should come away freely.
Step 6: Desolder the first leg.
Use your tweezers to grab hold of the first leg that was clipped. Using your soldering iron, touch the pad and remove the leg from the board.
Step 7: Align the new battery.
Align the new battery on top of the leads making sure you have the proper justification. If you are using a different model of battery, remember to check the polarity!
Step 7: Solder in the new battery.
Gently press down on the battery to make sure it stays in position. Using your soldering iron, press down on each of the legs until the solder flows underneath. The goal is to have the solder flow around the leg so that the leg makes contact with the pad underneath.
Step 8: Check your work.
Using a multimeter, always check for shorts and that the battery voltage is within the normal range. For a brand-new battery, this is generally between 2.5 and 3 volts.
Complete!
The fixes above should make you comfortable enough that no further damage will occur when in storage. It should also give you a good baseline to troubleshoot any additional problems.
