Mega ST, DMA error

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artik-wroc
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Mega ST, DMA error

Post by artik-wroc »

Computer: MegaST rev. 5.0
Symptoms: No icons on the desktop (even the trash can).
What I swapped: CPU, MMU, MMU socket, GLUE, DMA, FDC, U26, SHIFTER, U58,59,32,33,35,36 are 74F ...
I installed Blitter and Patch, turned off the memory on the motherboard and installed 4MB on MMU and SHIFTER, replaced the CPU, DMA, FDC stands.
No effect, no icons can be seen, floppy disk drive and UltraSatan not working.
There are no IMP chips on the board.
A DMA error appears during the cartridge test.
Image

the service manual says
Image
What else can I do, check, replace, etc.
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frank.lukas
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Re: Mega ST, DMA error

Post by frank.lukas »

To go for the DMA Test you need a "ATARI LOOP HARDWARE TEST" for Test Kit Cartridge.

Replace the TOS Chips ...
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Re: Mega ST, DMA error

Post by artik-wroc »

frank.lukas wrote:...you need a "ATARI LOOP HARDWARE TEST" for Test Kit Cartridge.
I know Frank. I have it.
frank.lukas wrote:Replace the TOS Chips ...
I checked with TOS 2.06 on c'tIDE, the same effect as in TOS 3.06 on PAK. No icons on desktop.
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Re: Mega ST, DMA error

Post by Arne »

artik-wroc wrote: I installed Blitter and Patch
How about removing Blitter to keep error sources low?
artik-wroc wrote: turned off the memory on the motherboard and installed 4MB on MMU and SHIFTER
You pulled /RASx and CASx to Vcc via Resistor?
artik-wroc wrote: replaced the CPU, DMA, FDC stands.
stands = sockets?

As you have swapped the MMU socket: RAM test is passing successfully?
The external Loop Kit is working on another ST?
Image
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Re: Mega ST, DMA error

Post by artik-wroc »

Motherboard did not have a blitter patch (connection between the processor pin 12 and MegaBUS). I installed it because I thought it would help (with or without blitter and blitter patch, the same effect).
I checked the memory with test programs and there are no errors.
Memory on the motherboard is slow (120 and 150). I wanted to check if it's a problem, so I installed something like this (70):
http://atari.wroclaw.pl/fotki/stram3.jpg
still not working.
Yes, socket :)
Arne wrote:As you have swapped the MMU socket: RAM test is passing successfully?
The external Loop Kit is working on another ST?
Yes, no errors.
DMA in another board passes the test without errors. FDC, GLUE, MMU, SHIFTER too.
I have a different motherboard (the same revision 5.0) and everything works on it.
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frank.lukas
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Re: Mega ST, DMA error

Post by frank.lukas »

Work Floppy and ACSI Port without the PAK?
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Re: Mega ST, DMA error

Post by DoG »

Did you remove the solder blobs on the jumpers when you attached the blitter again?
mega blitter jumpers.jpg

If the blitter patch was previously removed, was the line, that was broken by Atari, fixed undeneath the board? Did you remove the fix when you installed the blitter patch?
MegaST patch wire.jpg
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Re: Mega ST, DMA error

Post by artik-wroc »

frank.lukas wrote:Work Floppy and ACSI Port without the PAK?
No. I only installed PAK to rule out problem with TOS on the motherboard.
DoG wrote:Did you remove the solder blobs on the jumpers when you attached the blitter again?
If the blitter patch was previously removed, was the line, that was broken by Atari, fixed undeneath the board? Did you remove the fix when you installed the blitter patch?
2 x yes
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frank.lukas
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Re: Mega ST, DMA error

Post by frank.lukas »

What about the 68901 ?
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Re: Mega ST, DMA error

Post by artik-wroc »

I will have to try :?

I forgot. 4 bombs when booting under TOS 2.06
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Re: Mega ST, DMA error

Post by artik-wroc »

Success !
However, before repair was successful, MFP was replaced. Without result.
I checked all signals at the output of the DMA connector. Pin 10 (Interrupt Request) should be 1K relative to 5V (not 120 ohms):
Image
I replaced U21 (74LS02) and ... human vs Atari motherboard 1: 0 :)
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Re: Mega ST, DMA error

Post by sqward »

I need to check that. I have similar issue with my Mega ST.
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