Amiga 500 A501 RAM Board Battery Replacement - Unnecessary Surgery Guide

Amiga 500 A501 RAM Board Battery Replacement
Unnecessary Surgery Guide

*Alphabetical list of writings
*Helped along by this Jan Beta video

These past ten years my Amiga has been (blissfully?) unaware of the true date and time. As far as that Spanish girl was concerned, it has been 1991 this entire time. The longest year ever has recently come to an end, and I've brought her back into the 21st century. Ten years prior, when getting back into real Amiga hardware, one of the first things I learned when looking online was the essential need for one to get out their stored Amiga's, take it apart, and throw the battery out of it.

While some Amiga's did not come out of the factory with a real time clock (RTC), the ones that lacked this all had an option to add one, either from 3rd party sources or directly from Commodore. For the top selling Amiga model, the 500, the official RTC offered from Commodore was in the form of the A501 RAM expansion, which added 512k of slow or chip RAM (depending on configuration/hardware support), along with an RTC with a rechargeable battery. While the Amiga was running, it would trickle charge the battery, so while the machine was off, the battery could provide just enough juice to keep the time and date stored.
^What you'll need, top left. Encased, top right, bottom Rev5 and Rev6

Unfortunately Commodore did not design the A501 to be consumer friendly, opting to take several measures to hopefully require the need to get your dealer involved. Number one, the A501 was completely encased in steel and soldered shut. This meant that despite this piece of hardware being installed in the 500's trap door slot, which was easily accessible by the owner, most consumers would not have the tools required to take a look inside. So in the event the battery died for some reason, well, back to the dealer you go, for even if you had the ability to access the innards, the battery itself was uncommon and soldered directly to the board. In my case, the battery itself worked just fine going into this century, so replacements due to failure probably were not common. The problem lies with the original's tendency to leak out acid as it ages.

As the battery acid leaks onto the board, it's very possible that your A501 will be rendered useless to you. Luckily, due to its steel case and location, damage would likely be rendered only to the memory board itself in such an instance, leaving the Amiga 500 fine. Other Amiga's may not be so lucky, with boards attached without a case directly onto the computer's motherboard, meaning leaked battery acid may spell doom to the entire machine. Hence; Take your Amiga's apart and get that original cylinder looking rechargeable battery as far away as you can. I have a revision 5 and revision 6 A501, both of which had started to leak slightly when I took them out, though thankfully the acid had not touched the boards. ^With coin cell battery holder in hand, we line it up on the Rev5 A501, and solder it in

With the battery removed, the board itself will still work perfectly fine. All the battery did was keep the current time accurate while the machine was off. If you're okay with not having an accurate time, then forget about replacing the battery, as I have done that very thing for a decade. Even back in the day, the clock was not exactly useful. Like most Amiga owners, I did not have a hard drive originally, running everything off of floppies. Games were unlikely to want an accurate time, leaving only applications and Workbench itself to enlist this  function. Workbench did not show a time on screen by default, meaning you had to take an extra couple steps to show one. I actually did bring up the built in clock application while typing away in word processors, so indeed it would have occasional use for me.

These days I do have a hard drive for my Amiga, and I spend quite a bit of my time in Workbench. So while still not exactly necessary, I did become curious about bringing this aspect of my A501 board back to life. Replacement rechargeable batteries are available online through various Amiga related stores, but those will likely face the same eventual leaking fate. Why not just do what almost all PCs did for their clocks? Use a simple coin cell battery? For several years I've read up on the topic, skimming the material for the most part, seeing if anything grabbed me to the point I would want to do this myself. Most material did not make clear the "why" of certain aspects of using a coin cell, like the need to solder a diode. It's one thing to say I need to do it, but you really need to tell me WHY I need to do it if you want me to follow you. A video by Jan Beta was finally able to explain that to me and make me want to do this for myself, though I found a couple aspects of his video confusing, which is why I wanted to explain the process I took. ^Top - Solder diode to those points on Rev5 board and you're done. Bottom - The same to these points on a Rev6

To convert the A501 to use a coin cell battery, we'll need a few supplies. You'll need a coin cell battery holder of the standard PC variety. To go along with that you'll need a battery, a CR2032 lithium button cell. You'll need a single 1N4148 diode rated for 75V, and finally you'll need a solder gun and probably a small amount of solder. This could theoretically be performed using things you have around your house, and thus for free, though most of these materials will prove rather inexpensive if bought.

With a coin cell battery holder in hand, and your A501 board taken apart, line up the battery holder so the positive end is closest to the end of the board with the two battery terminals, though using the point more inward (see pics) due to clearance issues. The negative terminal will be lined up near a single battery terminal which is going toward the bulk of the board. Holding this in place, use your solder gun on the other side of the board as you push the coin cell through the solder points. If your board does not have solder here anymore, you'll need to add some, mine still had enough. ^Rev6 board complete, putting it back together and into the Amiga

With the coin cell battery holder soldered in place, this is the point you'll need that diode. The diode is needed to resist the charge the Amiga is going to want to put into the battery when it is turned on, thinking it is dealing with its original rechargeable battery. The 1N4148 diode rated for 75V is more than enough resistance to make sure the Amiga is never able to charge your non chargeable battery. On the bottom side of the board, solder the diode to both the positive and negative battery terminals. That's it for the hardware aspect, put a battery in and put her all back together! ^Setting it all up on the software side of things

With the A501 back in your Amiga, load up Workbench (or any application type program which would likely boot into Workbench and have a preferences program) and navigate to the preferences program. I will note that I have an upgraded version of preferences for Workbench 1.3,  which is version 1.3.10, distributed by Amiga, Inc. in 1997 to make the preference/setclock commands more compatible with the year 2000. An interesting read on the Amiga and its unique Y2K issues (and beyond) can be found here. In a nutshell, the battery backed up clocks are capable of telling the Amiga the correct year up until 2078, where it will upon resetting the machine reset to 1978. Despite this, preferences for Workbnech 1.2 and 1.3 will not properly set the time after the year 2000, so the above version 1.3.10 will be required for that, unless you're using Workbench 2.0 or higher. And even with these issues considered, issues with all Amiga operating systems will cause dates to be inaccurate after 2046.

And beyond the operating system and its date problems, programs themselves might exhibit issues if not coded for thinking beyond the year 2000. If you find a well liked program suddenly starts to crash after properly setting the date, this could very well be the reason why. With this in mind, you may want to settle for simply having the proper day and time, and set the year back into the 90's so you won't have to deal with these issues. For the moment I'm enjoying my Amiga knowing not only  the correct day and time, but also the year. Perhaps in the future some of these aspects might be updated (Where are you Hyperion?!), if not, eventually I'll be returning to the 90's yet again! But at least I'll have the proper date and time, if not the proper year. With a coin cell battery inside the A501, it should last several years if not more, and when it dies it will be rather easy to replace again. If Commodore had gone with this method, like most PC manufactures, many Amiga's might not currently be on death row.
^Sure looks mighty fine backlit

Please check out my video where I show the processes, like soldering, live on camera, and walk you through the software aspects of it all as well. I certainly owe a thanks to this Jan Beta video which allowed me to think I could do this myself. Please be aware that there are a couple aspects of his video that may be confusing, an example is he soldered the coin cell in the opposite directions, negative to positive, check his description while watching.

Location: Detroit, MI, USA

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