Repair Logs – Page 69 – JAMMArcade.net

Psychic 5 repair log #1

May 192016

Last year after a lot of research I succeded to buy at a good price an original board of Psychic 5 , one of my favourite game of all time, which was really in mint conditions.

psychic5

Some days ago I picked it up for a play and after some minutes the game developed this problem during attract mode:

psy5

psy3

psy2

After some more time the game was total yellowish:

psy4

Game hasn’t any schematics available and there are not any games known to me which have similar hardware and schematics available.

I could only go blind and try to find the reason of the fault.

So I started to short some signals of srams looking for palette changings and I found a couple of them at pos.6N and 6M, 16kbits.

The one at pos.6N had the first 4 data pins low and I was pretty sure either it was faulty or the 74ls245 connected to the data bits.

After desoldering, the sram 2018 was tested good in the programmer. That meant that the programmers didn’t use all data pins of the palette rams. The 74ls245 was good because it could drive correctly the signals without the ram installed.

I tested some TTLs nearby looking for strange signals but found nothing.

Decided to go brute force using my logic comparator and testing everything on the video board but starting with FUJITSU parts which are known to be very unreliable.

The logic comparator found a 74ls08 with all the outputs faulty

psy6

I double checked the outputs with a logic probe and they were all in the grey area (no good logic signal).

After changing it I fix the problem 100%

psy8

psy1

So FUJITSU brand proves once again to be really unreliable!

Dangun Feveron repair log

PCB Repair Logs Comments Off

May 132016

More than a repair a quick fix.

I got this Dangun Feveron PCB :

Dangun_Feveron_PCB

The owner said that most of sprites were scrambled and I could confirm the issue upon powered up the board:

Sprites data are stored into two 42 pin 32Mbit MASK ROMs @U25-U26:

sprites_ROMs

When I went to probe them I noticed a broken jumper @JP3:

broken_jumper@J3

Checking with a multimeter the connections of this jumper relevealed that point ‘2’ was connected to pin 32 of the two MASKs ROMs, therefore the higher address line A20.So, signal coming from point ‘3’ was not reaching this pin due this broken jumper and this caused the sprites issue.Once restored it:

RSCN2919

all came back to normality.End of job.

Batsugun Special Ver. repair log

General, PCB Repair Logs 1 Response »

May 122016

Received this Batsugun Special Ver. PCB for a repair:

Batsugun_Special_ver_Japan_PCB

Game played fine but colors were all dull and washed-out, take a look at this comparison with a MAME snapshot on the left:

colors_comparison

or this video:

This was a clear sign of some troubles in colors palette circuitry.After studying the hardware, I was able to locate this section by shortcircuting some address/data lines of two CXK5816 SRAMs @U39 and U40 and at the same time observing color changes on screen:

palette_circutry

Besides the two mentioned SRAMs, you can see some 74LS245 and two 74HC273 involved in data bus (the first ones in exchanging data from/to the two RAMs, the latter in latching).When I went to probe the two 74HC273 I found that input pin 13 of the one @U43 was stuck low and its corresponding output pin 12 showed only weak signals:

74HC274@U43_probing

So confident I went to remove it:

74HC274@U43_removed

When I tested it out-of-circuit it failed:

74HC273@U43_failed

Once fitted a good IC and powered up again the board, the game played great with no further issues.

fixed

End of job.

1941 : Counter Attack repair log #1

General, PCB Repair Logs 3 Responses »

Apr 252016

I had on the bench this mint 1941 : Counter Attack CPS1 boardset:

1941_Counter_Attack_PCB

Board played fine except for a minor sprite issue on some objects on backgrounds which manifested only on first level:

sprite_issue

The game use the ‘CPS-B-05’ ASIC on C-BOARD which acts as a GPU generating all the graphics:

CPS-B-05_C-BOARD

so I swapped a good known one from a Street Fighter II : The World Warrior boardset:

CPS-B-05_C-BOARD_SFII

All the sprites were restored so I had confirm the ‘CPS-B-05’ ASIC was bad (probably an address line was ‘spitting out’ wrong address).I could swap the entire C-BOARD but appearances count too so I decided to transplant only the IC on the original C-BOARD.

CPS-B-05_SF2_removed

I used an hot-air rework station covering the plastic connectors with tin foil as protection against heat:

CPS-B-05_reworking

To solder the chip I used the ‘drag soldering’ technique:

I succesfully tested the reworked C-BOARD and declared board as 100% working :

Undercover Cops repair log #2

PCB Repair Logs Comments Off

Apr 242016

Recently I received this Undercover Cops PCB for a repair:

Undercover_Cops_PCB

Before power it up I inspected the board and found that the resistor array @RA3 was replaced by an homemade one, very ugly solution:

resistor_array_RA3

Since the original part is not a common resistor array (it’s a mix between 4.7KOhm and 220 Ohm resistors) I replaced it with an original spare part :

4.7K_resistor_arrays

Powering up the board, all was working fine except for the PCM samples that were scratchy:

The chip which plays the samples (fetching data from a MASK ROM located on VIDEO board) is the ‘GA20’ ASIC:

GA20

Probing some pins with an external amplifier I had confirm that sound came out already corrupted from it so most likely its DAC section was faulty. So I played the card of replacing it taking a good chip from a GunForce donor PCB:

GA20_removed

And this was the winning move since voice samples were restored:

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