Amiga 2000 Video & Audio Issues

[TmaxElectronics]

About half a year ago I started repairing a badly battery damaged A2000 which had some memory issues. After a looong time of letting the project settle I finally got somewhere in the repair. The problem was a almost rotted trace for _UDS, just outside the area which I cleaned. It was still good enough to sometimes work but bad enough to not do so reliably. Also broken was the Even CIA and probably some ram chips (I just replaced all because I started being frustrated lol). I Fixed those issues and now Diagrom boots up without any memory errors and the memory test and the CIA tests succeed.

Now however I'm faced with another Problem:
Although diagrom boots I can only use it with the serial terminal. Nothing is ever displayed on the screen except for some flashing green bars at startup and then some random colors as the rom is "forcing stuff to run in fastmem if avaible".
Running any graphic tests also yields nothing but a slightly differently color-filled screen, except in "test raster" where I get some purple-green lines across the screen. I've verified that the color value output from Denise is actually what the display shows (so eliminated the Vidiot as a possible fault) and tested the monitor with my working a500.

And another issue I noticed is that the audio tests are non functional. They do play a tone but it is interrupted (sounds just like morse code). No idea if the two faults are related though.

I'm once again out of ideas for what to try as I've swapped around All chips between another A500 and the A2000 and none make any kind of a difference. Has anybody maybe seen this issue before?

[TmaxElectronics]

Ok so I just played around with the DiagRom a little more and noticed that running the 320x200 Screen test makes the system hang indefinetely until a hardware reset. I'm still not sure what that tells me though. I've just re-swapped all chips (except buster of course) with my other a500 and that boots into workbench without problem. All very confusing to me.

Oh and I forgot: I'm using diagrom 1.2.1 as thats what I have, and I don't own a programmer to upgrade to 1.3.

[Castellen]

Given the symptoms, it's very likely that there is at least one open circuit line in the register address bus (RGA), or possibly the DRAM data bus (DRD).  Refer to the schematic for details: http://amiga.serveftp.net/Schematics/A2000_schematics/A2000_R6_schematic.pdf

Both of these buses are common to U200 (Paula) and U201 (Denise); use a scope to check for activity on all 8 address lines at either U200/201 and 16 data lines, and it should quickly be obvious what's not working.  From there you'll be able to work backwards to pinpoint the open circuit track/via.

The register address bus is created by U101 (Agnus), so an open circuit line can be also caused by one or more bad contacts in the PLCC84 socket.

[TmaxElectronics]

Ah yes man thank you soooo much. Apparently there was a slightly bent pin in the plcc for agnus that I didn't notice before. So far I only checked for continuity from the top of the plcc pin to the other ICs (and perhaps actually bent the pin in the process  ). But after bending all pins straight again the A2000 is back up and running again ^^

Interestingly enough I didn't notice any missing data on the bus where the bad connection was, probably due to activity from the connected ICs or cross-coupling.

Now I have to think what upgrades to do to the thing to make it most useful for me. I already have a harddisk and am thinking about doing one of the HDMI output mods. Any suggestions on other things I could do?

[Castellen]

But after bending all pins straight again the A2000 is back up and running again ^^

I'd suggest replacing the entire PLCC socket unless you're very confident it's perfect.  IC sockets are notorious for causing all sorts of horrible intermittent problems.

Any suggestions on other things I could do?

Depends what you want to do long term.  There are plenty of interesting options in terms of the PiStorm and Vampire expansions.

[TmaxElectronics]

I'd suggest replacing the entire PLCC socket unless you're very confident it's perfect.  IC sockets are notorious for causing all sorts of horrible intermittent problems.

Yeah probably not a bad Idea. I'll order one for when I have some free time to work on the amiga next.

Depends what you want to do long term.  There are plenty of interesting options in terms of the PiStorm and Vampire expansions.

In the end the machine is likely going to be used for running some demos for 80% of the time and the rest for games. So the more capable it is the better