MagicianLord77
Enthusiast
Hi guys, I find myself with this Sega Naomi board that has let me down. It's my first and only Naomi board, I know it used to work, then was stored at a not very dry place for around 2 years, then came to my hands to seem to perfectly work for a couple of hours then hang in game - screen froze all of a sudden, and never turned on again.
It's an early revision with an amount of factory wire patches, resistors, etc., came with Virtua Tennis.
When I disassembled it, it seemed like it had never been opened before, it was very dusty, cleaned it up.
Filter board looks fine, no traces burnt.
Took out the old CR2032 and the supercap just in case, no leaks found. I left the case fan disconnected.
So, current status is no boot, no video, no audio
. Leds turn up, fan spins, and emits the square wave at its yellow pin (around 160hz).
Verified the contents of its EPR D 21577 BIOS chip with mame -romident, all good.
Checked voltages at the filter board: 3.38, 5.05, 12.42. Good values right?
Also at the test points the board: 2.05 (SH IN), 2.54 (2.5V), 3.35 (3.3V), 5.02 (5V), 12.40 (12V).
Some few capacitors used to look a bit swollen or with a white kind of rust, so ordered a full set using the retro hardware capacitors list and replaced them all, found that almost all had quite high VLoss % / ESR compared to the new ones, an average of 8 times the value of the new ones. Only the big "ELNA" ones were in very good shape. Anyways, after the effort of replacing every electrolytic capacitor, nothing changed.
So now I find myself not knowing what to do next, I've got a 200Mhz scope but I'm not sure what could I measure. Could the RAM be the culprit? should I go and replace the 4 cpu SDRAMS or the 8 graphics ones too? if not, what else?
Any suggestions appreciated! Attached front and back pics of the current state of the board
Thanks!
It's an early revision with an amount of factory wire patches, resistors, etc., came with Virtua Tennis.
When I disassembled it, it seemed like it had never been opened before, it was very dusty, cleaned it up.
Filter board looks fine, no traces burnt.
Took out the old CR2032 and the supercap just in case, no leaks found. I left the case fan disconnected.
So, current status is no boot, no video, no audio
. Leds turn up, fan spins, and emits the square wave at its yellow pin (around 160hz).Verified the contents of its EPR D 21577 BIOS chip with mame -romident, all good.
Checked voltages at the filter board: 3.38, 5.05, 12.42. Good values right?
Also at the test points the board: 2.05 (SH IN), 2.54 (2.5V), 3.35 (3.3V), 5.02 (5V), 12.40 (12V).
Some few capacitors used to look a bit swollen or with a white kind of rust, so ordered a full set using the retro hardware capacitors list and replaced them all, found that almost all had quite high VLoss % / ESR compared to the new ones, an average of 8 times the value of the new ones. Only the big "ELNA" ones were in very good shape. Anyways, after the effort of replacing every electrolytic capacitor, nothing changed.
So now I find myself not knowing what to do next, I've got a 200Mhz scope but I'm not sure what could I measure. Could the RAM be the culprit? should I go and replace the 4 cpu SDRAMS or the 8 graphics ones too? if not, what else?
Any suggestions appreciated! Attached front and back pics of the current state of the board
Thanks!
