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by zChris
Thu Feb 08, 2024 12:42 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

Re: Atari 520 STFM faulty - Project

20240204_173303.jpg
20240204_173303.jpg (192.71 KiB) Viewed 209 times
ps. Not sure why the forum rotates the image?
by zChris
Thu Feb 08, 2024 12:36 pm
Forum: ST536 030 ST ACCELERATOR
Topic: ST536 - Build in progress
Replies: 10
Views: 648

Re: ST536 - Build in progress

Nice setup with the camera. Which model is it ?
by zChris
Thu Feb 01, 2024 9:47 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

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 ...
by zChris
Wed Jan 24, 2024 10:28 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

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
by zChris
Wed Jan 24, 2024 9:54 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

Re: Atari 520 STFM faulty - Project

Yeah that i know :) i just wanted to have a clear white picture atleast :)

/zChris
by zChris
Wed Jan 24, 2024 9:28 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

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
by zChris
Fri Jan 19, 2024 10:43 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

Re: Atari 520 STFM faulty - Project

Alright i have been doin the tests that have been suggested to troubleshoot a H4 motherboard ( https://www.exxosforum.co.uk/forum/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 adre...
by zChris
Thu Jan 18, 2024 10:09 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

Re: Atari 520 STFM faulty - Project

Here are the CLOCKs measurements. EDIT: Made a misstake and measured the wrong Pin on GLUE 8MHZ. The correct pin measures correctly M68000K Pin 15 (DEFAULT 8Mhz) M68000Pin15.png SHIFTER Pin 2 (DEFAULT 32Mhz) ShifterPin2.png Pin 39 (DEFAULT 16Mhz) ShifterPin39.png MMU Pin 5 (DEFAULT 16Mhz) MMUPin5.pn...
by zChris
Thu Jan 18, 2024 8:08 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

Re: Atari 520 STFM faulty - Project

The oscilioscope im using is DS1052E 2channel 50Mhz 1GSa/s.

/HALT goes high then low on a power on. It react on RESET.

OE (Pin 22 on the roms L0-L2, H0-H2) is always low.

/zChris
by zChris
Thu Jan 18, 2024 7:41 pm
Forum: NOOB QUESTIONS
Topic: Atari 520 STFM faulty - Project
Replies: 17
Views: 1257

Re: Atari 520 STFM faulty - Project

Ive measured what you suggested @stephen_usher and here is the results:
Pin 49 VCC 5.2V
Pin 14 VCC 5.2V
Pin 15 CLK 7.813 -8.065 Mhz
Pin 17 HALT Logical Low (240mV)
Pin 18 RESET Logical High (4.08V)

Here is an image on the CLK and it doesnt look good? Never got a stable curve.
clk.png
clk.png (507.48 KiB) Viewed 633 times
/zChris

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