Archos AV4X0

Back in early 2000 dedicated media players (and recorders) where all the hype, and Archos was a big player (puny pun intended). The AV series where  Audio/Video players and recorders with colour TFT displays, recording capability and small IDE hard drives. The  4X0 series was the second generation, sporting 3.8" screens and capacities from 20GB to 80GB.
Among them the AV420 is a bit special, as it uses a 1.8" drive instead of a 2.5" one its build considerable smaller and lighter. It also has exchangeable batteries, which all the other models do not have.

Heck, why?

I like dedicated devices. That was not always the case. A few years back i was completely hyped by the prospect of having one device for everything. Nothing i ever had was quite the right thing, and i thought that maybe the technology was not up to the task. Later i thought my budget was up to the task. Then i started to realize that "one size fits everyone" is the size that fits nobody right.
Modern player are either dirt cheap bullshit or dirty expensive audiophile bullshit. Not all, there are some with quite good ratings and decent prices. But most. And old ones, like this, can go for an absolute bargain. I got mine for 12€ from eBay. Battery was half-dead, workarounds discussed later.

Batteries (AV420)

Replacement batteries for these devices are not made anymore, not even third-party. That's not too bad though. For one, the original pack (at least the one i own) is really easy to open and replacement cells are easy enough to obtain. Alternatively any cell can be soldered directly to the PCB (if necessary non-destructive).
Note: There is apparently one shop selling those:  akku-markt

Replace the cells in a bad pack

My Pack had no bottom side, just a sticker that can be removed easily. The two cells as well as the protection/connector Board can the be removed. The Cells measure 48mm x 30mm x 6mm and can be found on Ebay, Ali, Bestbuy and the like via the term "liion 603048" for prices ranging from 2€ to 10€.

Connect different Cells

The simplest way is to solder wires directly to the spring contacts in the battery compartment, but that will more or less interfere with actual battery packs. Its not to hard to open the case and solder wires to the PCB. This way one can either remove the wires when a real pack turns up, or just shove the wire (isolated!) under the pack.
Open the case by removing all the screws on the side. Then remove the sticker in battery compartment and remove the screw hidden behind it. The back plate can the be pried apart (i used a slim jim from ifixt, i think its called "iSesame", but any pieace of very thin spring steel with rounded edges will do). Left and right from the battery contact springs are good points to solder, the wire can then be guided through the many holes in battery compartment. I simply glued my cell into place using hot glue, so it can be removed without remains. Be careful, the original battery pack has battery protection, you should use one too (search for "liion 1s protection", should cost less than 2€ delivered).

Batteries (not AV420)

The single LiIonCell is fixed and not meant to be changed. As if we care! Remove all six screws and pull off the back cover (it needs a bit of prying, but be careful not to break anything). Then gently remove the hard drive. Gently! The flat flex cable by which it is attached is made of pure unobtanium and breaks easily. The battery is soldered directly to the PCB. Similar Cell can be bought on eBay, Ali, suchlike. As the original Cell does not have a protection board the replacement Cell ... should have one anyway. Doesn't hurt to have one extra.

HDD (AV420)

The spinning HDD is probably the main power hog (the display backlight might be worse, but only if its on). And its to small anyway. The best option for replacement is a decent sized compactflash card. As the disk is a 1.8" PATA one, SSD's are, although existing, hard to come by and quite expensive. A CF adapter cost next to nothing and a decent card can be obtained for a good price. I got a used 32GB SanDisk Extreme for 17€. A used SanDisk extreme is a good choice, as those are expensive when bought new, and cheaper cards tend to have abysmal writing performance.
The player will initialize the new disk on its own, simply format it as FAT32 with LBA. Do not try to mirror the old drive, i tried and it set the player off. I had to reformat the disk and simply copy the data (which worked fine). Remember, make sure to either copy your data before you replace the disk or make sure to have a way of connecting the old drive by its own.
Open the case by removing all the screws on the side. Then remove the sticker in battery compartment and remove the screw hidden behind it. The back plate can the be pried apart (i used a slim jim from ifixt, i think its called "iSesame", but any pieace of very thin spring steel with rounded edges will do). Then the side panels can be removed with a bit of wiggle, followed by the top plate. Be careful, the LCD is hold only by the fragile flat flex cable.
Now the two screws holding the HDD can be removed. Replace the disk with the Adaptor/CF card and put everything back together. The player initializes the card by itself.

HDD (not AV420+)

The 2.5" drives are even more power hungry, but at least offer more storage capacity. It is easier and less expensive to get 2.5" PATA SSD's, although compactflash cards might be cheaper anyway (see above). Replacement is simple, same process as for the batteries. Except that you can let the batteries alone when exchanging the disk. But even if your battery is fine, it might be a good opportunity to replace it anyway.

Power supply

Has 5V, 1.2A, center positive. Hate me, eBay sellers, for i shout out the secret you so carefully blur out on every product photo!