Caius

New archive for GAL replacements of bipolar PROMs

May 072016

There are not only PALs on our beloved PCBs but also bipolar PROMs!

A bipolar ROM or briefly BPROM (“BIPOLAR” stands for the transistor technology used in the manufacturing process) is a OTP memory device, which can be programmed just once and hence the data programmed can never be erased.They were used for various tasks: address decoding, state machines, and video colour palettes, for example.Like every electronic part they can fail and nowadays obtaining a blank device is really hard and expensive.And even if you find it, your EPROM programmer probably doesn’t support BPROMs as they are obsolete parts.

Someone replace them with EPROMs mounted in a custom adapter but we chose GAL devices as replacement since most of times there is no need of adaptation (if you program them in the right way, obviously).Besides, GAL devices are really common and inexpensive.Last but not the least, they can have fast access times like BPROMs require.So,today we open a new archive for GAL replacements of bipolar PROMs, you can find it under the menu ‘PLD Archive’ on main page.I hope you will enjoy it and contribute to its growth.

Sega System 1 PAL update

PAL Updates Comments Off

May 072016

Today we have some new PAL dumps from Sega System 1 hardware.

Thanks to the work of ‘Tirino73’ and ‘f205v’ :

https://www.citylan.it/wiki/index.php/Wonder_Boy_(set_3_bootleg_2)

we have dump of the unsecured PAL16R4 @IC 67, I converted it to GAL16V8 and successfully tested on my bootleg boards.Silvio Grazini confirmed that it works also on original hardware.So now set is complete along with the dump of the other PAL16R4 @IC41 already in our database.

Besides, they dumped also the devices (a PAL16L8 and a PAL16R4) on the piggyback board, I converted them to GAL16V8 and successfully tested on my boards.

Thanks again to them all.

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 :

Hammerin’ Harry (Irem M81) PAL dump added

PAL Updates Comments Off

Apr 252016

Today ‘frsj8112′ from Arcade Otaku forums sent in dump of the specific PAL @7D from an Hammerin’ Harry PCB (Irem M81 hardware).Dump has been successfully tested by him on a GAL16V8 targeting device.Thank to ‘frsj8112’ for his contribution.

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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