Alright i have been doin the tests that have been suggested to troubleshoot a H4 motherboard ( viewtopic.php?f=78&t=2362 ). I'll post the results here if someone maybe see something obvious that im too new to see.
Something i noticed was that som Dx and Ax adresses didnt go to 5v when reset is hold as can be seen in the FIRST POWER UP VOLTAGE TEST.
PULL UPS OHM
Pin 1 ↔ D4 2190
Pin 2 ↔ D3 2190
Pin 3 ↔ D2 2190
Pin 4 ↔ D1 2190
Pin 5 ↔ D0 2190
Pin 6 ← AS 4310
Pin 7 ← /UDS 4300
Pin 8 ← /LDS 4300
Pin 9 ← /RW 4170
Pin 10 → /DTACK 1000
Pin 11 → /BG 4250
Pin 12 → /BGACK 2340
Pin 13 → BR 4630
Pin 14 → Vcc 0
Pin 15 → CLK 7550
Pin 16 → GND 120
Pin 17 ↔ /HALT 4530
Pin 18 ↔ /RESET 940
Pin 19 ← /VMA 4230
Pin 20 ← E 6260
Pin 21 -> /VPA 4620
Pin 22 -> /BERR 4610
Pin 23 → /IPL2 4650
Pin 24 ↔ /IPL1 4640
Pin 25 → /IPL0 4680
Pin 26 ← FC2 2190
Pin 27 ← FC1 5360
Pin 28 ← FC0 5350
Pin 29 ← A1 2190
Pin 30 ← A2 2190
Pin 31 ← A3 2190
Pin 32 ← A4 2190
Pin 33 ← A5 2190
Pin 34 ← A6 2190
Pin 35 ← A7 2190
Pin 36 ← A8 2190
Pin 37 ← A9 2190
Pin 38 ← A10 2190
Pin 39 ← A11 2190
Pin 40 ← A12 2190
Pin 41 ← A13 2190
Pin 42 ← A14 2190
Pin 43 ← A15 2190
Pin 44 ← A16 2190
Pin 45 ← A17 2190
Pin 46 ← A18 2190
Pin 47 ← A19 2190
Pin 48 ← A20 2190
Pin 49 ← Vcc 0
Pin 50 → A21 2190
Pin 51 → A22 2190
Pin 52 → A23 2190
Pin 53 ← GND 49
Pin 54 ↔ D15 2200
Pin 55 ↔ D14 2190
Pin 56 ↔ D13 2190
Pin 57 ↔ D12 2190
Pin 58 ↔ D11 2190
Pin 59 ↔ D10 2190
Pin 60 ↔ D9 2190
Pin 61 ↔ D8 2190
Pin 62 ↔ D7 2190
Pin 63 ↔ D6 2190
Pin 64 ↔ D5 2190
BUS SHORTS
Pin 1,2 4.39K
Pin 2,3 4.39K
Pin 3,4 4.39K
Pin 4,5 4.39K
Pin 5,6 6.89K
Pin 6,7 9.21K
Pin 7,8 9.22K
Pin 8,9 9.22K
Pin 9,10 5.23K
Pin 10,11 5.69K
Pin 11,12 6.73K
Pin 12,13 7.04K
Pin 13,14 4.64K
Pin 14,15 9.77K
Pin 15,16 7.42K
Pin 16,17 4.75K
Pin 17,18 5.5K
Pin 18,19 5.64K
Pin 19,20 Infinity
Pin 20,21 12.48K
Pin 21,22 9.38K
Pin 22,23 9.38K
Pin 23,24 9.38K
Pin 24,25 9.38K
Pin 25,26 6.89K
Pin 26,27 12.26K
Pin 27,28 17.41K
Pin 28,29 8.12K
Pin 29,30 4.39K
Pin 30,31 4.39K
Pin 31,32 4.39K
Pin 32,33 4.39K
Pin 33,34 4.39K
Pin 34,35 4.39K
Pin 35,36 4.39K
Pin 36,37 4.39K
Pin 37,38 4.39K
Pin 38,39 4.39K
Pin 39,40 4.38K
Pin 40,41 4.38K
Pin 41,42 4.38K
Pin 42,43 4.38K
Pin 43,44 4.38K
Pin 44,45 4.38K
Pin 45,46 4.38K
Pin 46,47 4.38K
Pin 47,48 4.38K
Pin 48.49 2.19K
Pin 49,50 2.19K
Pin 50,51 4.39K
Pin 51,52 4.39K
Pin 52,53 2.25K
Pin 53,54 2.24K
Pin 54,55 4.39K
Pin 55,56 4.39K
Pin 56,57 4.39K
Pin 57,58 4.39K
Pin 58,59 4.38K
Pin 59,60 4.39K
Pin 60,61 4.39K
Pin 61,62 4.38K
Pin 62,63 4.38K
Pin 63,64 4.39K
Pin 64,1 4.39K
LS11 SHORTS
U60 DM74LS244 Pin 1 and Pin 19
U61 DM74LS244 Pin 1 and Pin 19
U57 T74LS373B1 No Connections between pins
U58 T74LS373B1 No Connections between pins
FIRST POWER UP VOLTAGE TEST
Pin 1 ↔ D4 5,05
Pin 2 ↔ D3 0,06
Pin 3 ↔ D2 0,06
Pin 4 ↔ D1 0,06
Pin 5 ↔ D0 5,05
Pin 6 ← AS 3,46
Pin 7 ← /UDS 3,41
Pin 8 ← /LDS 3,41
Pin 9 ← /RW 3,43
Pin 10 → /DTACK 3,56
Pin 11 → /BG 3,62
Pin 12 → /BGACK 3,47
Pin 13 → BR 3,44
Pin 14 → Vcc 5,06
Pin 15 -> CLK 1,02
Pin 16 -> GND 0
Pin 17 ↔ /HALT 0,15
Pin 18 ↔ /RESET 0,24
Pin 19 ← /VMA 3,49
Pin 20 ← E 1,86
Pin 21 -> /VPA 5,03
Pin 22 -> /BERR 5,03
Pin 23 -> /IPL2 0,03
Pin 24 ↔ /IPL1 2,98
Pin 25 -> /IPL0 5,04
Pin 26 ← FC2 3,5
Pin 27 ← FC1 3,45
Pin 28 ← FC0 3,43
Pin 29 ← A1 3,5
Pin 30 ← A2 3,5
Pin 31 ← A3 3,5
Pin 32 ← A4 3,5
Pin 33 ← A5 3,5
Pin 34 ← A6 3,5
Pin 35 ← A7 3,5
Pin 36 ← A8 3,5
Pin 37 ← A9 3,5
Pin 38 ← A10 3,5
Pin 39 ← A11 3,5
Pin 40 ← A12 3,5
Pin 41 ← A13 3,5
Pin 42 ← A14 3,5
Pin 43 ← A15 5,04
Pin 44 ← A16 3,5
Pin 45 ← A17 3,5
Pin 46 ← A18 3,5
Pin 47 ← A19 3,5
Pin 48 ← A20 3,5
Pin 49 ← Vcc 5,06
Pin 50 -> A21 5,05
Pin 51 -> A22 3,5
Pin 52 -> A23 3,5
Pin 53 ← GND 0
Pin 54 ↔ D15 0,04
Pin 55 ↔ D14 0,04
Pin 56 ↔ D13 0,04
Pin 57 ↔ D12 5,05
Pin 58 ↔ D11 0,05
Pin 59 ↔ D10 0,05
Pin 60 ↔ D9 0,05
Pin 61 ↔ D8 0,05
Pin 62 ↔ D7 5,05
Pin 63 ↔ D6 5,05
Pin 64 ↔ D5 5,05
CLOCK TEST
M68000
Pin 15 (DEFAULT 8Mhz) 7.813 -8.065 Mhz
Shifter
Pin 2 (DEFAULT 32Mhz) 32Mhz
Pin 39 (DEFAULT 16Mhz) 16Mhz
MMU
Pin 5 (DEFAULT 16Mhz) 16 Mhz
Pin 20 (DEFAULT 8Mhz) 8Mhz (some fluctuation)
Pin 19 (DEFAULT 4Mhz) 4Mhz
GLUE
Pin 34 (DEFAULT 8Mhz) 8Mhz
Pin 54 (DEFAULT 2Mhz) 2Mhz
Pin 43 (DEFAULT 0.5Mhz) 0.5Mhz
DMA
Pin 39 (DEFAULT 8Mhz) 8Mhz
WDA1772
Pin 18 (DEFAULT 8Mhz) 8Mhz
ACIA
Pin 3 (DEFAULT 0.5Mhz) 0.5Mhz
Pin 4 (DEFAULT 0.5Mhz 0.5Mhz
Atari 520 STFM faulty - Project
Re: Atari 520 STFM faulty - Project
Alright, it seems that i have this issue https://exxosforum.co.uk/atari/last/STF ... /index.htm (among others). Im using a scart cable that works (tested with other ataris). My question is if i cant just redirect HSYNC to pin 2 (pin 20 on the scart) and skip CSYNC ?
/zChris
/zChris
Re: Atari 520 STFM faulty - Project
Hi @zChris if your /halt is still low then you’ve still got other issues as well to be honest.
The ST should run regardless of a monitor connected or not.
The ST should run regardless of a monitor connected or not.
If it ain't broke, test it to Destruction.
Re: Atari 520 STFM faulty - Project
Yeah that i know 
i just wanted to have a clear white picture atleast
/zChris
i just wanted to have a clear white picture atleast /zChris
Re: Atari 520 STFM faulty - Project
You have checked the MMU for hsync and vsync right? Should be 15khz on one and 50 or 60hz on the other. You usually don’t get 50hz on a PAL machine until it’s started to read the rom etc.
If it ain't broke, test it to Destruction.
Re: Atari 520 STFM faulty - Project
Yeah the signals look fine to me atleast, except for csync. Csync is between -1v to +1v.
The screen is rolling vertically and are displaying different shades of black/grey.
/zChris
The screen is rolling vertically and are displaying different shades of black/grey.
/zChris
Re: Atari 520 STFM faulty - Project
Alright. As it is now is that there is a white screen and a double buss error so the CPU goes into a halt.
Ive tested with a Atari Diagnostic cart but it does not show up on the screen or output anything on the serial.
Ive read the Atari 520st - 1040st service manual (the motherboard is a stfm) and it says that if the diagnostic does not work and that the CPU is halted with buss errors being asserted right before it halted it can be that the CPU are unable to read from ROM or that one chip is not responding to a read / write, probably DMA chip or MC68901 chip.
To test for this it says to check that DMA chip is responding with a RDY assertion when it is /FCS, and it does just that. After that the manual says to check that MC68901 responds with a DTACK when it is /CS, which it does not.
So my question is if its more plausible that the MC68901 is broken and needs to be replaced or if the HALT happens before the process to initialize MC68901 has happened?
Ive tested with a Atari Diagnostic cart but it does not show up on the screen or output anything on the serial.
Ive read the Atari 520st - 1040st service manual (the motherboard is a stfm) and it says that if the diagnostic does not work and that the CPU is halted with buss errors being asserted right before it halted it can be that the CPU are unable to read from ROM or that one chip is not responding to a read / write, probably DMA chip or MC68901 chip.
To test for this it says to check that DMA chip is responding with a RDY assertion when it is /FCS, and it does just that. After that the manual says to check that MC68901 responds with a DTACK when it is /CS, which it does not.
So my question is if its more plausible that the MC68901 is broken and needs to be replaced or if the HALT happens before the process to initialize MC68901 has happened?
Re: Atari 520 STFM faulty - Project
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