Strange Wire and Clicking A4000d

[Castellen]

a strange small wire coming from the second connector at U892 which dives under the motherboard

The second pin on that IC is a data bus line.  Specifically, that IC is part of the bidirectional 32-bit bridge between the CPU data bus and the fast memory.  Without the bridge working, the computer will still boot, but the system won't see any fast memory.  Someone has probably added the wire in an attempt to fix a corroded open circuit track on the top side of the board at SIMM socket U850.  There are much tidier ways to do such a repair.

Perform the usual basic low-level checks such as: is the power LED on, does the CPU board work in another A4000, clock jumpers are correct, ROMs are in the correct sockets, etc.  If you can narrow it down to a main board fault, then I can look at this for you.
http://amiga.serveftp.net

[Castellen]

I kinda thought it may be the PSU and was about to swap that out.

Are you still taking repair jobs on motherboards. I still have that 3000T board damaged and could ship it to you ? Probably not until the spring though.

It could be the power supply, or anything else, though you'll save yourself time with a few basic checks.  For instance, if the power LED is on, the board probably has 5V, which is all that's needed to boot to the 'insert disk' screen.

The power supply ticking noise could be it going into over-current shut down.  So a short to ground on any of the outputs may be causing it not to work.  If you were to unplug all the loads, does the power supply operate normally?  You can use a meter to check the 5V output is valid.  Then gradually add the loads to the point it stops working to narrow down where the problem is.


Yes, I'm currently accepting Amiga boards for repair.  A word of caution with the A3000T; if it's the usual case of leaked battery, these are notoriously expensive to repair for a number of reasons.  Their large size and weight makes international shipping a bit pricey.  And the area of battery corrosion in this model is particularly unfortunate as it often damages the FPU and the dozens of tracks in the area which route in and out of the 4-layer board, which usually breaks various ROM and real time clock connections.  The physical layout of the tracks in the corrosion area (dense population with many vias routing to internal layers) can make it very time consuming and therefore expensive to repair, and the job can get ugly and become fragile if there are many tracks to repair.  Don't mean to put you off, this is just my experience over 15 years of repairing them.

If you can send a detailed photo showing the areas of damage, I can estimate how practical it might be to repair.

http://amiga.serveftp.net

[Castellen]

I gave up with the 4000d. I stripped back completely and swapped out the PSU. No difference, and then amazingly after a few minutes the PSU fired up. I rebuilt checking to see if I was breathing life into the computer but no joy. This machine has busted SIMS with only the last or first available.

It's no problem to replace the SIMM sockets, I have plenty of these in stock.

So did a known good power supply show the same 'ticking' problems?  If so it may suggest something is drawing excess current and causing it to shut down.  Does the same thing happen with only the main board plugged in with no floppy/hard drives?

Anyway. I have two broken and need to make a good one, so I may organise in the new year a repair on a mouseport if that is possible on a 4000D motherboard and then fit to this machine. I also have a 1200 with a broken mouse pin.

It's probably possible to fix all of them without too much hassle.  The A4000 is easy to work on as it's mostly all surface mount.

I have spare 9-way connectors for A4000, A1200, etc.  Easy to replace these.

Email me if you'd like to pursue these jobs further.

We have discussed the 3000T before and I sent you pics and I sensed then that this may be a bit of a serious challenge. I have a working 3000T so not a major issue at this time though I would like to getr it fixed some time.

Sorry, I don't recall; I get many such Emails.  Might still have the details if you can find the date you sent it.  Whatever I said at the time would still apply.  The A3000T is a nice machine, it's just a shame that the battery corrosion does so much damage.  While it is possible to repair just about anything with enough time and money, the final job is still going to get messy once you've traced and repaired all the countless open circuit tracks.