An A2000 and an A4000 to revive?

[Jope]

Try a want ad on amibay or keep searching eBay..

The a3640 is quite a common board. Try and get at least a rev 3.1 preferably with the capacitors replaced.

[Unknown_K]

A2000's seem to sell ok here in the US. An A2000 with a 2091 SCSI card is cheaper then any HD attached to an A500 (which is quite large and takes up plenty of desk space and you can't mount a monitor on top).

[alexh]

Originally Posted by jman

Hints on where I can get a A3640?

Find out what CPU board it has which is fried.

If it is particularly interesting (i.e. not an A3630 or A3640) then I'll swap you for a working v3.2 A3640 @ 33MHz with capacitors fixed.

The board is not for sale... just swap.

[orange]

think you should check the connector once more. that CPU slot is veery fiddly.

[jman]

The old lady's home:
http://www.storiepvtride.it/amiga

As you can see it should be a standard 68040 (25Mhz? 33Mhz?) with stock RAM (2mb?), A3640 rev. 3.0, m/b rev. D, kickstart 3.x. I didn't take many pictures, you'll know this piece of hardware way better than me ;-)
I didn't clean it to show the actual state.

I checked around and the capacitors look to me ok, but the battery has leaked (ouch!) over the motherboard. I reckon that nothing's damaged though, nothing's too close to it.

Issues so far:
- no HD: which HD size is supported by standard WB3.1? And what library do I have to use for bigger ones? This is not urgent, as I can still boot from a floppy.
- no monitor: I have a spare 17" LCD and my friend told me that the A4000 can read the VGA signal. Do I need this (http://amigakit.leamancomputing.com/...roducts_id=183) or this (http://amigakit.leamancomputing.com/...ducts_id=864)?
- battery: if I'm not wrong the battery is not really needed unless I want date/hour and HD settings to be saved, correct? Is it advisable to remove it before attempting a first boot? Do I need to unsolder it?
- CPU daughter board: once I try to boot it I'll check what happens and then I'll know if the board is gone. Is there a way to understand if the board only fails and the CPU is ok?

Trivia: this computer has been regularly enjoyed by the owner until 1999. Then, when he was writing his graduation thesis, the CPU daughter board died. The shop wasn't able to find any spare part and the owner finally gave up with Commodore hardware. Finding a replacement was not worth the effort, he was a die-hard Amiga fan, but he also had to finish his thesis, so he bought a linuxbox :-)

If you want to see further photo details, please let me know.

EDIT: apparently the motherboard is a rev. B! Added photo proof to gallery.

Thanks

[Hewitson]

"Commodore Electronics Ltd"? Don't believe I've ever seen that name used before.

[alexh]

Originally Posted by jman

- no monitor: I have a spare 17" LCD and my friend told me that the A4000 can read the VGA signal. Do I need this (http://amigakit.leamancomputing.com/...roducts_id=183)

This only works in DBLNTSC mode. (i.e. not in games)

Originally Posted by jman

or this (http://amigakit.leamancomputing.com/...ducts_id=864)?

Yes, but why not just use a TV with RGB SCART?

Originally Posted by jman

- battery: if I'm not wrong the battery is not really needed unless I want date/hour and HD settings to be saved, correct?

Yes

Originally Posted by jman

Is it advisable to remove it before attempting a first boot?

Advisable. Take antistatic precautions. Best to remove the entire motherboard, desolder the battery from below and then neutralise the alkali using a mild acid and then clean with isopropyl alcohol. Some users have been known to "wash" their board in the dish washer (on its own) with no detergent. Then dry it for several days near the water tank.

Originally Posted by jman

Do I need to unsolder it?

Ideally yes. But if you are very careful and patient you should be able to use some wire cutters & screwdriver to cut the battery free from the holders. You will still need to neutralise the alkali. I can see it all over and causing rust etc.

Originally Posted by jman

CPU daughter board: once I try to boot it I'll check what happens and then I'll know if the board is gone. Is there a way to understand if the board only fails and the CPU is ok?

No you will need a spare known working board.

[jman]

Originally Posted by alexh

why not just use a TV with RGB SCART?

Yes, that is another possibility, but my only CRT TV is quite unpractical to use and I would prefer to have the Amiga near the PC I'm ususally using :-)
Or I'll push this friend of mine to give me also the A2000 and its A1060. I just don't have infinite room for my junk ;-))

Originally Posted by alexh

Advisable. Take antistatic precautions. Best to remove the entire motherboard, desolder the battery from below and then neutralise the alkali using a mild acid and then clean with isopropyl alcohol. Some users have been known to "wash" their board in the dish washer (on its own) with no detergent. Then dry it for several days near the water tank.

I checked other similar threads on EAB and now I have a rough idea of that. I'm not very familiar with soldering, I'll evaluate if I'm up to the task.
I would like to be able to completely remove the battery, clean and then attach another new battery.

Thank you so much for your help!

[jman]

@Alexh

Do I have to worry about the batteries my A600 and A1200 stored in my garage? They don't have an RTC, right?

[alexh]

They don't have one unless it is on the RAM card. Worth taking a look at them. Easy to do, quickly check if you've got one and remove it for inspection via the trap door on the underside of the Amiga.

[jman]

I'm also checking around what can be wrong with this A3640.

Apparently the most common problem is that some of the capacitors are mounted with wrong polarity. Now I understand what you mean when you offered to swap a A3640 with "capacitors fixed".
I wonder if this may be the reason why the card fails (which I still have to verify).

I think I can buy a new, fixed A3640 card and in the meanwhile try to replace the caps on the old one.

[Hewitson]

It'd definitely be worth a shot. Plenty of Europeans on here capable of doing the job if you are not confident yourself

[alexh]

Originally Posted by jman

Apparently the most common problem is that some of the capacitors are mounted with wrong polarity.

It's really the only thing which can go wrong with them. They are 99% bullet proof.

Originally Posted by jman

I wonder if this may be the reason why the card fails (which I still have to verify).

You would know instantly. The capacitors will be bulging and there will be corrosion around the base of them and on surrounding tracks and components.

[Hewitson]

It's not uncommon for capacitors to fail without bulging/leaking..

[alexh]

While I'm sure you're right, I've never come across a failed electrolytic capacitor which has no external signs of failure.

But then I've never come across an Amiga with failed capacitors at all and there are 10's of other users on this forum who claim they have been affected.

The A3640 is the only thing I've ever had to replace capacitors and I only did it because they were fitted backwards. The board worked fine before I changed them.

[Hewitson]

There's two ways capacitors can fail:

-Bulging or leaking, usually caused by poor manufacturing practices and/or incorrect mixing of the electrolyte.

-Excessive ESR (Equivalent Series Resistance) which is basically caused by the capacitor being worn out. In extreme cases this can effectively cause an open circuit, however the capacitor will appear to be perfectly good from the outside.

[Damion]

Looking at the picture showing the audio circuit, it appears some of the SMD caps on the motherboard have leaked. The solder joints are very dull with a green tinge. (This is often the only way to tell, they leak but generally don't bulge like thru-hole ones sometimes do.) Same deal on the 3640. Sorry if this has been mentioned already, and congrats - looks like a nice machine, I'm sure you'll get her up and running again.

[jman]

Originally Posted by Damion

Looking at the picture showing the audio circuit, it appears some of the SMD caps on the motherboard have leaked. The solder joints are very dull with a green tinge.

Some days ago I've completely split apart this Amiga because I wanted to check in deep all the components. I've updated the gallery (I know you can't get enough of this hardware pr0n).
I'll see if these SMD will bother somehow.

Thanks for checking the machine!

In related news, the A3640 replacement and an amiga/vga adapter should be on their way here soon.
As soon as I've dissolted the leaked battery, I'll try to turn on the baby without hard disk, I'd like to check if I can reach at least the "feeding floppy" boot logo.

Concerning the VGA adapter, I have a couple of questions, if someone can kindly shed some light:
1) Attaching a VGA LCD screen will likely limit the available resolution to standard VGA (640x480) because the h-refresh sent from the Amiga (15khz) is not fast enough on this common kind LCD monitor (that starts at 29~31 Khz). There's a slight chance that the LCD runs at the undocumented h-refresh frequency of 15khz but it is very rare. Is these all correct?
2) When I first start the Amiga with this LCD what will I be seeing anything at all or it will already start at a wrong resolution?
3) Do I risk damaging some hardware fiddling with resolutions and testing them?

Also, alexh, you suggested to plug the amiga to a TV through a cable like this one, correct? It doesn't look too complicated, it can be a good exercise for soldering.


Thank you all for your advices.

[alexh]

Originally Posted by jman

Concerning the VGA adapter, I have a couple of questions, if someone can kindly shed some light:
1) Attaching a VGA LCD screen will likely limit the available resolution to standard VGA (640x480) because the h-refresh sent from the Amiga (15khz) is not fast enough on this common kind LCD monitor (that starts at 29~31 Khz). There's a slight chance that the LCD runs at the undocumented h-refresh frequency of 15khz but it is very rare. Is these all correct?

Attaching a VGA LCD via the VGA adapter will almost certainly result in no picture. You will need a Workbench boot disk or Workbench installed hard drive PLUS a 15KHz monitor first to be able to configure the Amiga to be in DBLNTSC screen mode. Only then will you see anything on a regular 31KHz LCD monitor.

Originally Posted by jman

2) When I first start the Amiga with this LCD what will I be seeing anything at all or it will already start at a wrong resolution?

You won't see anything. It will start at the wrong horizontal (and possibly vertical) refresh rate for a standard LCD monitor. (Nothing to do with resolution)

Originally Posted by jman

Also, alexh, you suggested to plug the amiga to a TV through a cable like this one, correct? It doesn't look too complicated, it can be a good exercise for soldering.

If you can make one (and have an RGB SCART capable TV) then sure. Or use a Commodore A520 modulator (they came with most Amiga's) if you have access to one to get a picture via composite or RF.

[jman]

Originally Posted by alexh

If you can make one (and have an RGB SCART capable TV) then sure. Or use a Commodore A520 modulator (they came with most Amiga's) if you have access to one to get a picture via composite or RF.

While I can try to make one, this discussion has just reminded me of another friend of mine which had an A500 with that modulator. I just called this guy and told me that he would really like to have his Amiga back working (just a couple of months ago he tried to restart it but it just gave him a blank blue screen), so he will bring me home his whole Amiga bundle in order to be checked.

The whole thing is getting so funny, thank you for digging this from my memory, lol!