Wanted: 318069-11 (Agnus 8375 2MB NTSC)

[Tavis]

Hey all, on my journey to repair my Video Toaster, I have isolated one of the issues down to the MegaChip. In order to figure out what is wrong with it, I suppose the easiest thing to try is swap out the Agnus chip.

If you, or anyone you know can provide me with an 8375 Agnus (318069-11 2MB NTSC) chip that would help me out.

Name your price.

In the meantime, I have a logic analyzer and oscilloscope I can use to troubleshoot if I knew what I was doing So if anyone has any tips on how to approach that, please let me know. Thanks.

[alexh]

I don't think a Video Toaster (2000?) needs a 2MB Agnus. Just take it out and put the 1MB (or 512KB) Agnus back in?

I don't think you'll find a 318069-11 Agnus for sale from retail outlets ever again. The new replacement 16-bit Amiga PCBs enthusiasts designed all take 8375 2MB Agnus chips and so all supplies are gone as users bought them all to make new A500++ and A1000+ motherboards.

Also Individual Computers bought lots and lots for the ACE2B

https://icomp.de/shop-icomp/en/shop/product/ace2.html

[cpiac64]

first check without megachip with original fat agnus
second i suppose you want change the fatagnus on megachip
3° i need verify in my lab if i have a 318069-11 for sale

[Tavis]

Ok so here’s my current condition:

I found an 8370 on eBay and took the MegaChip off the board and replaced it with the 8370.
Now the Amiga will boot off a floppy with workbench on it but whe I click anything on the dish (clock, utilities, etc) the computer freezes. I can resize windows and move the window around but as soon as I tried to launch anything on the disk the machine locks up.

Also the computer is no longer booting off the hard drive.
It has a Trumpcard with two hard drives. When I power up without a floppy inserted, I can see it access the first (boot) drive and both the disk light LED fro the card and the led on the actual disk light up but stay solid.

It never boots up unless I use a floppy.

I am wonderig if at least one of these problems is related to the 8370 since it can only addres 512k and I read some where that it has an 8 bit refresh and the ram on board (256x4) has a 9 bit refresh…

So I guess what I need are both an 8372A to see if I can at least get the computer to work properly period. And a nice to have would be an 8375 (318069-11) to see if there’s any hope for my MegaChip.

** The GVP O30 Combo accelerator board has onboard ram and two sims in it as well. How does this get accessed? I know very little about Amigas.

This Amiga has the following cards:

Video toaster 4000
gvp g-force combo
megachip
blue ribbon sound works card (one stop music shop)
sunrize industries ad516
trump card disk controller
2 hard drives
Syquest drive and disk

[alexh]

Battery damage to the motherboard?

[cpiac64]

rev of mobo?
if rev 4.x need 8371 (with modify, work with 8372a)
if rev 6.x need 8372a

[Tavis]

Originally Posted by alexh

Battery damage to the motherboard?

Well I’ve removed the battery scrubbed it clean and went all over it with my scope and my multimeter and haven’t found anything wrong. It boots up ok. Every time. Just can’t do anything else.

I was thinking, if not the 8370, then maybe a faulty RAM. I swapped the two CIA chips and no change. If I move the J300 to the right then I get cycling grays from black to white in a loop and the power LED flashes 6 times. Not sure if that’s normal or not. J300 is the CIA clock sync selector I think. Something to do with timing between 60/50hz. I’m NTSC so I need 60.

[Tavis]

Originally Posted by cpiac64

rev of mobo?
if rev 4.x need 8371 (with modify, work with 8372a)
if rev 6.x need 8372a

It’s the 6.x with 8 256x4 rams.

[alexh]

There are numerous ROMs or programs to get you an exact chip location for RAM failures.

Have a look at this video from 23:50 Gadget uses the Logica Diagnostic ROM Plus there is DiagROM (but I think the memory test on that ROM is not great).

[ Show youtube player ]