Mega ST 2 DMA port problem / will not see hard drive

[MR*Atari*]

hi all

 

ok i acquired this mega st 2 a long time ago in a bad way to put it mildly (dead floppy chip, 2 dead roms out of the 6 and 3 dodgy sockets for the blitter, MMU and Glue, all now replaced

 

anyway after spending many hours on it i finally have it working almost 100% except for 1 thing

 

it will not see or work with a hard drive and before anyone says yes the hard drive does work and is set to auto boot and yes it does work with TOS 1.02 that's in the mega (basically the hard drive works with a 1040STFM with TOS 1.02) so it should work with the mega

 

whatever i try and do it will not see the drive or work with it, this mega did have some water damage to the rear corner of the motherboard by the DMA port

(i have changed the port as the original had corrosion in the pins) and as far as i can see the tracks are ok on the board but i guess you can never be sure..

 

can anyone advise what else i can look at?

 

i HAVE changed the DMA chip

 

according to my service manual the MMU could be an issue? why would this affect it? anyway i shall change this...

 

any help would be appreciated, i'm determined to get it back to full working condition!

[MR*Atari*]

ok i also have an STFM test cartridge, but only part of it, ie: the cartridge that fits into the cartridge port

 

when i test the DMA i get "D0 - DMA timed out" error and according to my service manual this is what it says...

 

D0 - DMA timed out, no DMA occurred due to faulty DMA controller, Glue or memory controller, or the HDINT interrupt was not processed by the MPF, the failure can be isolated by seeing if the DMA controller respondes to HDRQ from the test fixture with ACK. Verify the MPF by seeing that the HDINT input causes an INTR output from the MPF.

 

sadly i don't have the rest of the test kit to verify