Amiga 500 RAM Expansion Commodore A501 Resurrection
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- Опубликовано: 23 янв 2025
- Trying to resurrect an A501 512K RAM expansion for the Amiga 500. Typically, the batteries on these boards leak and damage components and traces. Often, the boards can be recovered by thoroughly cleaning them and carefully repairing the corroded traces.
Aaaand... I said "megabyte" instead of "kilobyte" the first time I mentioned the capacity of the card. Nobody noticed, right?
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Awesome! I just got to your channel through GadgetUK's video. There cannot be enough repair videos!
Nice! There's gonna be more repairs. Quite a lot of stuff piling up here already. ;)
Thank you Jan for this video. I just replaced the already leaked battery in my A501 expansion today according to this video and it just works! Good job, thanks!
Oh, thanks for the comment. Always nice to hear that my videos are helpful to someone. :)
I bought my first Amiga 500 in 1988 while stationed overseas in Great Britain. I remember looking over some software/games in the BX(base exchange department store) and a friend commented that he couldn't believe one of the programs required a full 1 meg of RAM. Things were moving fast in the those days.
Ahh the soothing sounds of an A500 floppy drive...
:)
It was a great cozy feeling to hear that sound again for the first time in many years for me. ;)
You can effectively remove leaked battery acid (and any kind of rust) with lemon juice (genuine pressed out of a lemon :D) and then clean up with isopropyl alcohol... works nicely-
I learned that in the meantime (I tried white vinegar and lemon juice which both worked very well for me). :)
I prefer white vinegar, and I just soak the entire board in it for hours (until the green gunk fades and turn mushy). I hit it with an electric toothbrush and then rinse it off with normal tap water. From there I shake the board off as best that I can (A2000 boards can hold a ton of water in those Foxconn connectors), and it goes directly into a 91% IPA bath to "dilute" the remaining water. I let it soak in there to remove any flux and non water-soluble gunk. From there I use my hot air gun set to low to dry off the board.
I've done 2 A4000s, 2-3 A2000s, 6 A501s, 2 ZX Spectrums, and various other boards. All but one of the 501s survived the process, and the amount of corrosion that it had on it (as well as having 5 spares) convinced me not to bother fixing it.
Just be sure to get the rinsed off board into the IPA as soon as you can to prevent surface rust on the metal parts. I made the mistake of waiting and now I have a nice patina on several of my A501.
Great stuff =D Look forward to the next repair!
+GadgetUK164 Thanks! There's a huge pile of broken retrocomputery things here at the moment. Hope to get a bit of it repaired (and filmed) soon.
Ep, here?
I see that you have a good taste on retro channels :-D
:D
Dare I say this - best use for a MacBook Pro ever :) - I really enjoy watching and learning from your videos Jan :)
Haha, it's a very good use indeed. Thanks! :)
Very cool. I noticed some of the keys on the keyboard were in the wrong place though.
Oh, it's the German keyboard layout actually. ;)
Jan Beta Oh wow I learn something every day. ☺
I tried to replace this battery with a button cell, but the clock does not seem to function at all...perhaps I should just remove this as well.
At first, I thought that was an A500 plus, because of the narrow Return key. Then I realised you have extra keys for those letters with umlauts. Mystery solved.
+MarkTheMorose Yes, it's the German keyboard layout. :)
Hey, Jan. You should check what pin that was hacked...it might be expansion board detect pin...Probably the previous user disconnected the pin on the expansion board because they didn't want to cut the trace on the MB for the 1MB CHIP RAM upgrade. If you put the Fatter AGNUS in and change the jumper next to the AGNUS you can upgrade the CHIP RAM to 1MB so that you can play some games that require it.
Man! We all had those für 99 D-Mark to get many advantages in Bundesligamanager Professional :D
Great video! Do you know the values of those yellow capacitors. Some on my board are in a terrible state and I want to change them. Are they Tantalium capacitors? Any clues?
I've just got an Amiga A500+ with an A501 in the expansion slot for £8 - Think I'll have to check the A501 for the battery
Update: Just checked my A501 expansion and it doesn't have a battery - Amiga did have a battery which I removed
Yeah, the Amiga 500+ has a battery buffered clock on board so the standard RAM expansions used on these didn't come with another clock/battery. In any case it's a good idea to remove/replace these batteries. :)
I found a really small board in a trapdoor of an a500 once, didn't recognize it and it had no markings. Had about 4 chips on it and a switch. Any ideas?
+craig gilchrist Most probably a 512K RAM expansion, too. There were later versions with more advanced RAM chips that needed less chips for the same amount of memory. The switch would switch the expansion RAM off for compatibility.
Thanks Jan, I suspected it may have been 512k but it didnt show anymore ram in WB so was stumped. I still know the guy I sold my A500 too with in so may have another look at it. Also Jan Is it true that Winuae will no longer read CF cards in Windows 10. Ive rebuilt many CF cards this way but recently its stopped working. CF card boots on Amiga 1200 fine and card reader is working fine i just get NO MEDIA report. Ive done Diskpart and used Partition Wizard to see if i can see the FFS partitions but nothing. At a loss. Tried looking for something in Ubuntu Linux to do it. Any ideas at all? Thanks again Jan.
In 1988, I paid literally $280 or so for this expansion...it kept me running nearly everything for several years...cheers...I recently desoldered mine and added a button cell replacement, but this does not seem to work...oh well.
Watching this was addicting.
+Dingo Ate My Dingo! Oh, thanks! More of the like coming up. :)
How did you open the Shield?
+xorben1981 Brute force. Usually you just have to bend a couple of little tabs on the sides that go through the PCB and the case. Some of these are glued/soldered unfortunately.
Is it safe to run the card wothout the shield after disassabling?
It is perfectly safe. The shielding was only added to meet the regulations for electromagnetic emissions as far as I know. I use the A501 from the video without the shield ever since and didn't run into any problems. The same goes for the internal shielding in the Amigas btw.
mine A501 ver 6C is soldered, so desoldering :) ... those shields was required by carefull FCC but it seems every unshielded switching power supply adaptor or DC/DC or PWM LED driver or so today generates so much noise that it doesnt matter anymore ... so every radio communication must have error-tolerant protocols ... sad but true
Oh my god, I hate this shitty Varta leaking battery thing. It killed my A-4000/040. Thank you for your great videos!
Oh, glad you like the videos. Yeah, the VARTAs are killers indeed.
Wait 1MB was a lot in 1987? Well Live Aid was in 1985 and they somehow managed to record it and they used digital caneras!
Why not replacing the battery with a CR battery slot? Those don't leak...
Did that in a later video (although I got the polarity wrong at first---shame on me)... ;)
NiCd is probably slowly trickle charged when Amiga runs ... by CR you mean CD2032 or so, enough voltage for RTC, but not good to feed current into it ... (low dropout germanium diode can help to block this, if you can find it these days)
Its a resistor, Jan.
What did I call it?
a capacitor
Capacitor ? looks like diode to me marked ''D912'' .....
0:36
512 Mbyte? XD
You mean Kbyte! :)
Yeah, I was a bit off there. Switching between modern and retro computers isn't always easy. ;)
Do you usw Isopropanol only or so you Mix it?
I use 99.9% isopropanol. I learned lately that soaking in vinegar for some minutes and rinsing it with water and/or alcohol works best to remove the corrosion.
Varta of death :D probably could be replaced by a goldcap capacitor???
The resistor you removed was 100k, not 10k...
Woah, you're right. It measured 10k so I obviously trusted that more than the color code and didn't think correctly. Thanks for pointing that out... (And shame on me...)
Jan, did you figure out why on earth someone went to all the trouble to hack a switch into that card? Seems silly to me.
There are a couple (very few and old) programs/games that won't run with a RAM expansion installed, so it makes sense to add a switch if you want to run those. I never needed to switch off the expansion for anything though.
yes virtually all ram expansions had this done for comparability reasons. Although I also never seemed to need to use it.. small hacks and modifications just were so common place in old systems . I had reset function hacked in my C-64 what I also rarely used.. the times...the times..
Sometimes these cards are only used for the battery backed clock and not the memory. Some A500's have 1MB Chip onboard. I got one like that and the A501 had the exact same mod done to it!
The cut trace might be the trapdoor expansion card detect pin. There was a modification to A500's where you changed a jumper near the CPU and cut the trapdoor expansion detect trace, and the extra 512kB would be seen as chip ram rather than fast ram.
@@virtualjd6824 Right on sir :-)
QWERTZ keyboard ???
Is keyboard for Germany?
Yes, that’s the regular German keyboard here.
512Mb expansion WOW my first PENTIUM 200Mhz windows 95b PC ONLY HAD 64Mb
I actually misspoke in the video... It was a 512KB expansion obviously. 512MB would have been a bit too expensive for a home computer in 1987, I guess... ;)
cut it off CUT IT OFF ..... before it breeds
Haha, yes!