Amiga 4000 Repair Part 1: Recapping and RAM issues galore!

[@georgechambers3197]

After my lame attempt to clean the motherboard I gave up on the project. The battery was replaced not long before you came and hauled it all away. The battery in the 2500 was also replaced at about the same time. I'm really glad to see you getting the 4000 working again, it was a great computer and I did many hours of graphics work with it. I hope to see you get it working with all the cards that were loaded in it. Thanks Adrian, for the videos!

[@kennethschultz6465]

Great respect

[@OzRetrocomp]

This might sound weird coming from a fellow ADB viewer, but thanks for the donation. I'm looking forward to seeing how Adrian brings this A4000 back to life.

[@only257]

George Chambers ☺️well you give it a good try

[@ChaosHusky]

If you sold it cheap you're a git as i'd almost kill for one.. Or would have, except when i had to repair it for a friend and...god they were poorly made and designed! My 1200s are more reliable and easier to work on, that's for sure.

[@gallgreg]

Love the Napoleon Dynamite T-Shirt!!! TRULY AWESOME!!!

[@jorgecuelar3391]

I dont know why saturdays is always a nostagia trip & enjoy these kinds of videos😇 so a big thanks👍👍👍for uploading

[@GGruba]

Great video! I remember the days when Amiga 4000 hit the market. That was something great, like dream machine for most of us. And It seems like it was yesterday... Oh, just realised, that your full house must smell with that lovely vinegar.😊

[@only257]

G. Gruba 🤩

[@little_fluffy_clouds]

By the time Amiga 4000 was launched in 1992, we had 66 MHz 486 PCs with VGA graphics and SoundBlaster sound, so it was too little, too late. All my friends abandoned ship. I kept my beloved Amiga for another year, but eventually gave up and made the switch as well when Doom came out in 1993. I’ll always be upset that Commodore had the early starter advantage and the technological lead, yet screwed it all up by failing to develop & evolve the platform rapidly enough to remain ahead of the competition..

[@johnperkins3935]

That 8MB jumper was for a future upgrade that was never released. You should leave it in the other position. 2MB Chip RAM is the maximum.

[@jonnymyrberg3180]

Yes for the never realised AAA chip :) (Advanced Amiga Architecture)

[@PrimalNaCl]

Correct. Even with a > 2MB SIMM, it'll never register/use more than 2MB of chip ram.

[@jjdigitalvideosolutionsllc5343]

Yes, CHIP RAM is limited to 2MB, ignore the 8MB jumper. There are some hacks that will let you put more than 16MB of FAST RAM on the motherboard. Instead of 4x4MB sticks, you can use 4x16MB sticks for 64MB. Even if you don't attempt a 64MB hack, you can install a single 16MB stick of RAM in one socket for a full 16MB. This is useful if you have broken plastic clips on your SIMM sockets.

[@only257]

John Perkins 😇

[@captainandrew016]

@@jjdigitalvideosolutionsllc5343 Hey I am an Amiga Noob; and was wondering about an Amiga 4000T. What setup is better; using the fast ram upgrade or ignore that for Zorro 3 ram upgrade on the motherboard? Because I think I read that using both would not be optimal.

[@GadgetUK164]

Great to see another A4000 on the way to recovery! Yellow screen, could be lots of things =/ rule out the RTC by removing the chip. If you still get a yellow screen, my money would be on glitchy 245's on the Super Buster side. Could also be the F86 as it was on the Yellow screening A4000 I fixed a few weeks back. Check Super Buster socket too.

[@eDoc2020]

Yes, it's easier to remove a socketed RTC than to desolder and replace a logic chip. I hope he wasn't actually going to replace the logic chip first.

[@nadeembackus2741]

I read your comments in your accent 😆😆

[@basvanharen2904]

@@nadeembackus2741 haha

[@brotheredward06]

It could still just be that it doesn't like the RAM too - when I tinker with the Minimig FPGA core any time I screw up the SDRam controller I get a yellow screen with asymmetric power light blink.

[@BrianRRenfro]

When I clicked this in my subs I didn't pay any attention and thought it was another RetroManCave video! Amiga 4000 KZbin-A-Thon! I am going to become an expert!

[@lycanananas_sq5fox]

I also thought that it's RetroCaveMan video :D

[@beetooex]

Go on Neil. Leave a comment and show us you're watching too.

[@adriansdigitalbasement]

Heh and I actually recorded this video a few weeks ago before RMC’s video came out. Funny timing.

[@davefarquhar8230]

I bet some of Neil's baking powder for fluffy muffins would work wonders on the front faceplate.

[@BrianRRenfro]

@@adriansdigitalbasement So weird too since I NEVER expect to see Amiga content from the US and especially a 4000 although I suspect the PC enclosure style Amigas were the more popular models here since I only know one person who ever owned one but have seen a few in person in professional hands put to video toaster duty.

[@georgestyka6088]

Adrian, never apologize for your HVAC or similar, you are making a video, life does not stop and you are not in a multi million dollar studio, and backgroud noise, setup, mistakes are life and why I like to watch. You are doing what you love, the best you can, by yourself. Ignore those who critique or offer criticism. It is easy to tell others what they are doing right and wrong, much harder to be the one actually doing it. Keep up the great work, and I know this is an older video, but it is the 5th time watching, you are top notch, thank you for keeping it real.

[@MBDB666]

I love your troubleshooting methodology and attention given to researching known issues in the forums. These videos give great examples of how to approach the restoration of any brand of computer. Thanks for being so detailed in these, its entertaining and educational. 😁👍

[@JamesPotts]

I went for years with a piece of Scotch tape holding a SIMM taut in my 386.

[@daishi5571]

That's disgraceful, use wooden toothpicks!

[@seanys]

I cheered, too, when the Kickstart screen came up. That washing in water bit had me nervous as hell.

[@2dfx]

Adrian - that replacement battery is the newer 3/V80H replacement. It's NiMH instead of NiCd and will not leak! They are a great OEM-style replacement for the NiCd leakers.

[@otopico]

That's a fine A4000. I wish I could justify buying an A4000 or A1200. I loved those machine back in the day. Great work.

[@WY.C64-Guy]

2:30 - "Sorry for noise, AC kicked on...." Multiple other videos - "Sorry for noise, furnace kicked on..." - To tell you the truth, I don't notice. Are you doing some post-recording audio adjustments to minimize it? 4:30 - MT RAM... *GASP!* . Great video, Adrian. Looking forward to how this turns out!

[@kimidri]

This video randomly popped up for me , found it very intresting i broke the bank to buy a 4000/40 back when i ran a BBS but it was far too much power so i sold it for about £1000 after about a year and got a a2000 which is still in my loft about 30 years later and a a500 this video has made me thing of digging them out lol

[@jdryyz]

Now this should be interesting. AGA Amigas can be challenging when it comes to repairs. Glad to hear you will still replace the battery.

[@animatewithdermot]

Watching you take out those RAM chips was like the "cut the red wire" scene in a bomb disposal movie. great stuff! God my old 4K was rickety like this.

[@animatewithdermot]

Oh, BTW, regarding the wretched battery: my friend was a great tech admin wizard. He cut all the batteries out of my 4K and two 3Ks (saving them in the process). Solution in adding a battery back, if needed, without risk of future damage: he soldered two wires a few inches long to the motherboard and attached them to the battery, which was now inches away from the motherboard and sensitive parts. Just a thought for anyone who really needs a clock.

[@gallgreg]

So excited about _another_ repair video!! Looking forward to you getting the Amiga fully working and upgraded!! Thanks for the steady flow of new content, Adrian!!!

[@kooziesan]

I could watch board fixes every day. So relaxing

[@MrSatellitehead]

Adrian your efforts and videos are greatly appreciated. I could watch these all day long.

[@ThePCPitChannel]

I love how happy you get when something works :D

[@basvanharen2904]

Congratulations for so far! I'm sure you are going to fix the rest and I'am anxious to see the next part. Hopefully you show some more Amiga repairs in the future, there are some true repair experts on KZbin but your video's are understandable and clear. If this video would have taken 2 hours, I probably sat it out haha. Great effort, thanks!

[@sircompo]

I didn't know those PCB socket pins existed. Very interesting. Thanks for introducing us to the Amiga PCB Explorer as well; that'll come in handy diagnosing the SCSI issue on my A4000T.

[@AmstradExin]

PCB Explorer for the win!

[@Codeaholic1]

Fantastic video. Adrian your music selection was top tier!

[@JARVIS1187]

I really want to know, why people downvote such great videos over and over 😱

[@darkstatehk]

32:41 Slight and careful application of your de-soldering heat gun onto to the plastic whilst manipulating it, will get them back into a compliant position (memory removed of course!). By the way, this is the best retro themed channel in my opinion. It's not just the fun things that you do, it's your personality. Everyone wants a friend next door just like you!

[@CoreyDeWalt]

You're correct. I love when creators post longer, more detailed videos

[@markrhine5809]

I think these video's are very, very interesting, I enjoy vintage electronics and I am a first time viewer, but will continue watching these video's. Have a nice day..

[@hmbpnz]

Great videos; thank you. You teleport me back to when I was a kid but show me stuff that I understand now as a EE. Your channel is really unique. Keep those old machines running, man.

[@Halterung01]

Man, I love that intro. Music is just perfect but the thing I enjoy most is that VHS filter. So many of these filters just overdo it whit destabilizing the image and adding an unrealistic amount of noise. This looks bang-on exactly like the results of my own NTSC VHS recordings when using my setup to generate analogue video signals from digital sources for recording.

[@LesKingBNE]

My only channel that has notifications on and i watch immediately.

[@Dukefazon]

4:50 - that music is so nostalgic! It's not an OST from an old game I guess but it hits just the right notes. Reminds me of Traps and Treasures on the Amiga I guess.

[@jetsonian]

Console5 is the best. I have never received a kit that's short and they're ALWAYS high-quality components. I'm glad to see you've skipped the Digikey search and are just going with with best now. :-)

[@seanys]

Thank you for letting us know about Amiga PCB Explorer. What an amazing resource!

[@ThomasSIversen]

40 minutes of pure nostalgia. Thanks for providing quality content for a saturday evening!

[@cablecartman]

don't leave us hanging... bring on part two. (amazing work)

[@OzRetrocomp]

They say these things happens in threes: first RMC, now Adrian ... at this rate The 8-Bit Guy will have an A4000 restoration video out by the end of next month. What are the odds? :D

[@basvanharen2904]

Its a late Commodore marketing stunt.

[@jefbed212]

I've noticed that too. Its also common in the 3D printing community.

[@otopico]

I'm OK is that happens. Amigas deserve all the love.

[@MikeDUtah]

That board is GORGEOUS after you cleaned it

[@koushiroizumi0]

Hey Adrian! Here's a tip on how to clean corrosion. Take a toothbrush, dip it in vinegar and GENTLY rub the area. Repeat if necessary. It really works wonders. You can also use this with regular short bristles paintbrushes, for cleaning corrosion or cleaning of dirt in general, although for dirt you'ld idealy be using some other substance.

[@10MARC]

Great stuff, Adrian! Glad you found a chip that would work for CHIP RAM. Just leave that jumper at 2 MB. This will make a really nice A4000 - and the Toaster that was in there will be great! The A4000 is what I use for probably about half of my videos.

[@gertsy2000]

Putting caps back on the same way you took them off trusts that they were on correctly in the first place. I think you put C105, C106 & C107 from the A3640 CPU Card on the wrong polarity. Known issue with the silk screen. Could cause problems over time. That obviously isn't the issue though. You seem well on the way to fixing that. Great video!

[@gbowne1]

at 17:37 the 74HCT174 chips are hex positive edge-triggered D-type flip-flops with individual data inputs (Dn) and outputs (Qn). The two 74HCT166T chips are an 8-bit serial or parallel-in/serial-out shift register.

[@BollingHolt]

Cool! At least you're making progress! I've never owned an Amiga before, and the more of these videos I see about them, the more I want one.

[@electronash]

You've been doing some great restoration work on this channel. Very methodical, too.

[@myownalias]

I love seeing some Amiga content on the channel. In my mid to late teens, I had an Amiga 1200 and absolutely loved it. I always lusted after the Amiga 4000, but it was way out of my price range, I saved my allowance for the best part of 2 years to buy an A1200, and then saved again for a 68030 upgrade with 4MB of fast RAM, then saved up again to get a 340MB 2.5in HDD. When I got my first PC, PII 350, I handed my niece the A1200, which swiftly got broken, much to my annoyance. I really wish I held onto it, I'd love to break out Geoff Crammond F1GP on the original hardware.

[@mrcassioo]

Oh how familiar this sounds. The guy I bought my A1200 from had only moments earlier unpacked a brand new A4000. Sure I was super happy about the A1200, but at the same time I couldn't help but feel a lil envious as I carried my new baby home. :P

[@parrottm76262]

I sure love me some Amiga! Looking forward to the A4000 working fully again.

[@crowbarviking3890]

Thank you for uploading each saturday. Love your repair videos.

[@aqualung2000]

I absolutely love your channel. You should have a patreon. If you did I would definitely be one of your patrons. I love your technique for cleaning those old motherboards, but I would feel so much better if you were using distilled water for that very last rinsing step (or if not distilled, then tap water run through a reverse-osmosis water filter.) I used to live in Oregon so I know you guys have _pretty_ soft water (which is great!) And I seriously doubt there would be enough mineral deposit to do anything to that motherboard. Buit...it would make me *feel* better :)

[@ScoopexUs]

Nice that you got the A4000 booting! Winced a bit as you plunged the motherboard into water with not even IP rated components left on it. There are also lots of crannies and especially spot under chips that can trap moisture for a very long time. I also recommend snipping caps with cable stripping pliers (not wedge-shaped normal pliers), if you have no desoldering station. Twisting is a method that guarantees that you put a great force on the traces, which is bad.

[@kaczan3]

Soldering montages so relaxing.

[@JimLeonard]

Congrats on your success. It can be difficult trying to troubleshoot a system you're not familiar with. I had a Rev C. motherboard that wouldn't work no matter what until someone clued me in that the Rev C. has no onboard crystal osc. which accelerator boards require.

[@koushiroizumi0]

So you can't use a Rev C. with an accelerator board? Or does it require a special one?

[@AndyDavis007]

Awesome repairing video, Adrian. I must say the music soundtrack was spot on. 🎶

[@pyography]

Yes, that is an awesome track. My question is what is it?

[@quantass]

Thank you, Adrian, for an Amiga repair. Anything C= i'm always fascinated by! Quality channel overall!!

[@enzofitzhume7320]

Adrian, your videos keep on getting better!! Like the new sound tracks.

[@aetch77]

Tuned in expecting to see another instalment of the mac repairathon. Was confused to see amiga, figured it would make a nice break, yay.

[@mrcallypso1]

Reminds me of working on my sister's Packard Bell. The layout of the memory and position of the cpu are very similar.

[@iamdarkyoshi]

I use my actual vacuum cleaner from the 70's with the hose on the output, since it lets you do that. The heat from the motor does a great job drying washed boards. Even had a CRT board survive the procedure and the board works now! Obviously I made sure it was properly dry, a widescreen CRT board is going to have some pretty nasty voltages on it!

[@CRG]

I noticed on the sysinfo screen that it was reporting ECS rather than AGA. Possible indication of something else faulty in there and maybe U976 close to the battery. Might be worth belling out traces or even removing those few ICs to be sure you've got all the rot out.

[@adriansdigitalbasement]

It's a bug in SysInfo. Does that one NTSC machine even in WinUAE...

[@zaooo]

Good to know that my ears still capture high frequencies well, that CRT at 2:06 is super audible :D

[@dj9volt]

I have grown to love Raindropsies I remember hearing it for the first time in your Commodore 64 repairathon video series and it’s AMAZING I know it’s not releated to the video topic but I thought I would share

[@pawe3130]

Moje marzenie z dzieciństwa - Amiga 4000. Świetny sprzęt !

[@RetroReviewYT]

Enjoying this so far. Watched Retro Man Cave’s video on the Amiga 4000 as well.

[@rdxdt]

Finally someone who don’t say “battery acid” and say what the substance that leaked really is.

[@timrb]

True. Car batteries have an acidic electrolyte, most other batteries use an alkaline solution.

[@ZTK-RC]

One time I let a car battery spill on me and I didn’t know what it was but I felt some burning on my lap and took my clothes off and went for shower. Fast forward to the next morning, my clothes were a shredded mess setting on my bedroom floor. I had never seen anything like it but I am a simple man.

[@rdxdt]

@@ZTK-RC Well car battery is called Lead Acid battery, it is made from diluted sulfuric acid and a lead composite, and sulfuric acid is quite good dissolving organic tissue, NileRed has a really nice video showing the effect of acids on his skin and paper. Usually those old "barrel" battery are Nickel and Cadmium based, and newer versions are Nickel metal hydride batteries. NiMH cells have an alkaline electrolyte, usually potassium hydroxide, which are corrosive too.

[@chrisprice4287]

Love these videos.Would have loved an Amiga back in the day but had my Zx Spectrum during the 80s and had so much fun with it, yes i know it no C64 but it had its charms. Thanks for making my day Adrian in these troubled days stay safe from one type1 to another:-)

[@biblebadcopycatofcuneiform8210]

It's odd to hear "super" being used vs "very" and "really". It's great to see another Amiga restoration.

[@pipschannel1222]

Excellent work again Adrian! Getting more professional by the hour ;-) This beautiful 4000 is definitely worth saving 👍

[@hackbyte]

FINALLY; Adrian got an Amiga 4000 in his Digital Basement. Love it ;)

[@brianv2871]

I think he's actually had that Amiga 4000 for a few years now.

[@andreassjoberg3145]

When testing computer boards out of their case, make note of if the screw-holes are part of the grounding or not. About at the time of the A4000 system-grounding through mounting-screws became industry standard. The Amigas usually work anyhow, but things can get flakey. Good luck in the repair.

[@warrentb1]

If you're worried about brittle plastic breaking it often helps to warm it up slightly, a hair dryer or warm water will work depending on the application.

[@willierants5880]

Great episode Adrian. Why not reflow all those crusty solder joints? If they aren't nice and shiny they aren't good. Some good flux and solder tip (I prefer an SMD flow tip for reflowing) and a few minutes of time is all it takes. Of course reflowing the solder joints isn't a guarantee, but it will help. Cold and cracked solder joints can pass a continuity test, but fail when under load or at temp or even cause intermittent issues under operation.

[@giffimarauder]

Don't know if anyone mentioned it previously, but one of the smd caps on the processor card has wrong plus minus marks on the pcb and was wrongly mounted too because of that. This only comes into effect under certain software routines, can't remember when, but I fixed it when I recapped all smd caps and all worked out of the box as before. I desoldered the smd's with an air blowing solder station and guess what? Two or three of the caps got too much heat and exploded, man that smell You'll never forget! Can't compare it with anything I know, maybe thats how hell smells...😄 To stop the sims unlocking I pragmatically honed them down on both sides a bit without any issues, always walking the hard road...

[@nicwilson58]

WOW Adrian, there I was watching this repair and what do i see? My old SysInfo program I wrote in Assembly language many years ago and is still being used, that is kinda cool :)

[@thisnthat3530]

The "power" light on Amigas actually indicates whether the audio filter is active. If it's on, frequencies above 5kHz are filtered out to reduce the aliasing of the 8 bit audio. The filter can be enabled or disabled in software and probably gets turned on after the initial tests so the light may have been off even if connected. Some Amigas have a resistor so the light only dims when the filter is off, but for others the power light turns off completely.

[@TheSulross]

And this video is a good illustration for why I don't bother to buy vintage computers. Wouldn't have any recourse for anything that is failed or starts to fail. I only look to modern recreations of vintage computers for a means to get a retro fix

[@HaveYouTriedGuillotines]

I seem to remember something about either the 3000s or the 4000s actually having one of the caps in the audio circuit _on backwards_ in the schematics themselves. You might want to look into that.

[@NJRoadfan]

Some of the caps on the A3640 68040 CPU card were installed backwards at the factory. SIlk screen error on the board. Hopefully Adrian is aware of that!

[@theannoyedmrfloyd3998]

I will be super impressed when you finally do some Atari ST / TT / Falcon repairs.

[@FlopsPL]

Is worth to check CPU card revision. Some revisions had wrongly placed (I think) two capacitors (wrong direction - polarization). In my Amiga, when I replaced capacitors, I always try to use tantal one.

[@hobsonbeeman7529]

Whenever I need to make changes to the mobo’s, I typically take a picture of it before I do anything to it, especially since it may be put aside while waiting on parts or other projects.

[@LuxorVan]

I finally had to buy a new roll of desoldering braid, I only use the chem-wik #4 10-50L and that roll lasted me 5 years! It is readily available for around $19 on ebay and works like a dream.

[@Tommyinoz1971]

Even before I watched this video, I saw people on other forums losing their shit about the twist method Adrian used to remove the surface mount electrolitic capacitors. I say it's fine and Mr Carlson is proponent of this method too. I'm sure Adrian is able to evaluate and assess the boards condition and judge the likelihood of damaging the traces using the twist method. It's not as high risk as some people say it is.

[@MrRobbyvent]

check resistor network too. I found some that have failed a couple of times.

[@lexpee]

i'm glad you think on the viewers. 40 minutes is al ready long. 30 minutes or less is more common, If it is interesting then time flies. People drop out if the videos are too long.

[@KrishnaDraws]

Console5 is a good place to buy replacement caps. I've purchased from them before when replacing caps on my Mac SE FDHD.

[@weepingscorpion8739]

What is it about KZbinrs, especially Adrian, Neil from RMC, and Jan Beta fixing up so many Amigas these days (or in RMC's case pretty much since he started his channel)? Yes, I know that I have an Amiga 500 that I need to repair, and I will get to it! :) Great video! :)

[@SimonSays-Techtalk]

Hi Adrian, I was just watching this (older, I know) video. I saw you twisting of the smd caps. Give it a try to cut these caps just above the plastic base first. These caps usually fall apart leaving only the metal feet. These can than be soldered off.

[@RogerWilco486]

FYI there’s a very strong possibility that A3640 has the capacitor silkscreens reversed for several of them, causing the replacements be installed with reversed polarity.

[@dragonhed123]

I really enjoyed this video I especially love the end where you do most of the motherboard troubleshooting keep on making awesome videos and looking forward to the next one!!

[@DevilishDesign]

Love the T-Shirt!! :)

[@hucky29]

Nice t-shirt Adrian. Gotta love Napoleon dynamite

[@UpLateGeek]

Just checked the datasheet for the LS174, and as long as clear is high (it's pulled high on the schematic), and you're seeing activity on the CLK pin, then that should be working. If the clear pin were low then you'd be seeing low on the outputs, so the fact that you're seeing high on the output suggests the chip is bad. If the outputs were shorted to ground when the original battery leaked, that would have killed it. Also, seems a little wasteful to use 16MB SIMMs when 4MB sticks would suffice. But then again, I just had a quick look around for my spare SIMMs, and the only ones I can find are 16MB, so I guess they're common enough that it's not a great loss. Now I'm wondering what I did with the rest of my SIMMs. I know I pulled them out a couple of months ago to go through them and find the 16MB sticks for my 4MB 30 pin SIMM project, but I'd really like to know what I did with the rest of them!

[@cesarferrari3385]

Great work!! thanks for showing and teaching so well how to repair theses machines.

[@keithwhisman]

I remember right you have to have two banks populated with SIMM Memory modules and it has to be Banks 1 and 3 or Banks 2 and 4 or all 4 banks populated at once. I’ve broken so many 30pin and 72pin SIMM retainer clips on the memory sockets and that’s when the sockets were new. I can only imagine how destructive I’d be with old brittle plastic memory socket retainers.

[@bobingabout]

The A500 has a varta battery in it too, but no real time clock (unless you install one), I have no idea what the battery is even for, so I just got a pair of wire cutters and snipped mine off last time I opened it up.... pretty much like you did.

[@SparksNZeros]

for potentially old brittle plastics like that i just pre heat them with a hairdrier on low, helps make them that tiny bit more flexible to get things apart

[@connorofarrell7215]

One tip my dad gave me when I was little with the older plastic ram sockets hit them with a hairdryer or heat gun on low for a little, makes the plastic a little more pliable and there less chance of then breaking

[@fred_derf]

re: Removing SIMMs with plastic clips. I've had the most success by unclipping each side separately. Choose one side, pull forward (medium lightly) on the end of the SIMM, and then pull the clip back until there is a click, this will get the clip past the leading-edge of the SIMM but it will be holding the SIMM from the side. Repeat on the other side, then just pull the whole SIMM forward (without touching the clips). I find this a much safer procedure. When you try to pull both clips out at the same time it's very easy to apply unbalanced pressure, or to continue to apply more and more pressure on a side that is actually free without you noticing.

[@duderobi]

I am always reminded on star wars episode 1 "It's working, it's working"

[@sRetroReviews]

Part 3 of your trs-80 model 4 please

[@a4000t]

Nice Video! To remove the face plate is easy, just hold pressure out on the top center of the face plate while you push the clips bottom and top with a screwdriver until they all pop free. its sounds a bit confusing but is easy in practice. the audio caps are notorious for leaking,since the 22uf were supposed to be npo's iirc. The a3640 has several known errors on the board,the polarity is wrong for 3 caps iirc. the board + is mis-marked. the 74xx part nearest the battery is notorious for going bad or having traces eaten under it from battery leakage. It does take forever to get to a workbench prompt on the 4000 w/o ide and floppy attached :) Glad to see it was only bad chip mem,in 20 years and 100's of a4000 repairs,i never encountered a bad chip simm lol. 8MB simms work as 2MB chip simms fine.

[@adriansdigitalbasement]

Ah yes I positioned the caps on the 3640 looking at the photos instead of the PCB markings so didn’t notice them being reversed.

[@eDoc2020]

At least the Amiga case is better than my Gateway 2000 where the front face is also held captive by the CD tray faceplate. To get the drives out of that you need to eject the CDROM, remove the tray front, remove the plastic front of the PC and remove the drive bays. Hopefully that drive doesn't get stuck closed; then I would have a chicken and egg problem and would be unable to get to the drives.

[@bnice7]

It's worth noting that any capacitors on the -12v rail will (correctly) appear to have their polarity reversed.

[@eDoc2020]

Nice video as always! Something I suggest doing is using some spare wire to bring the battery off of the board. Then you can place the battery where leaks won't matter. It also makes future replacement much easier. Also, why did you go straight to recapping the board? Since the symptoms led you to replacing chip RAM, I would've done that before looking at recapping. It is better troubleshooting practice to only change one thing at a time. I also suggest probing suspect capacitors with an oscilloscope and looking for excessive ripple. It won't catch everything but can still be helpful, especially on newer equipment with buck converters on board. I've measured 600mV of ripple on a 5v rail before!