Nov 152017
 

Maybe many of you will recognize this IC and throw up hands in horror:

This is the ‘infamous’ ‘HB-41’ used on several arcade PCBs (from Seibu/TAD Corporation but not only) :

  • Raiden
  • Blood Bros
  • Legionnaire
  • Sky Smasher
  • Toki
  • Dynamite Duke
  • Olympic Soccer ’92
  • Cabal
  • Heated Barrel
  • Operation Wolf

This analog component (20 pin SIL package) is used in sound circuit to mix background music and sound FXs as well as it acts as as filter of both.From my experience (maybe also others can confirm it) it’s a prone to failure part.Let’s take a look at what is inside it:

As you can see from above Hi-Res scan the custom is built around two ICs :  a 4560 dual operational amplifier (8 pin component on the left) and a 2060 quad operational amplifier (14 pin component on the right), both from JRC manufacturer.All the rest are resistors (also printed film ones, the black squares), ceramic and tantalum capacitors.In order to reproduce, after removed the epoxy, I pulled all the parts and metered them then I drawn schematics  :

Then I routed them ending up in a 5.3 x 1.8cm PCB:

More or less same dimensions of original part:

Here is how it looks assembled:

I used an LM358 and LM324 for my testing which maybe are not the best solution since the original OP-AMPs have both high gain bandwith (10MHz) but the replacement works well on all PCBs I tested so far.Here is testing on a Cabal, Blood Bros and Toki PCBs:

See you all to next reproduction project!

 Posted by at 10:28 am
Nov 102017
 

I had on the bench this Thunder Cross II PCB by Konami:

Many components were removed from the board : one WORK RAM @12D was missing and the other one @11D cracked in half, also the ER5911 serial EEPROM was not there :

The two tilemap RAMs @17H and 18H:

Some electrolytic capacitor in audio section:

The 3.58MHz oscillator @9K (it generates clock for whole sound system)

Also the RAM in sound section was almost desoldered, indeed it came off easily:

With patience I installed all the mising components and powered up the board :

At closer inspection the above error was caused by a broken trace between pin 21 ( address line A10) of the two 6264 WORK RAMs, I promptly patched it:

Now the board went to intial self-test showing two bad devices, both related to sound system.

The one @4F is the ROM containing code of the Z80, the one @5F is its 2K x 8it RAM (previously replaced by me) 

Both were verified as good so problem was elsewhere.Sound system is made of a Z80 which commands a YM2151 FM synthesis chip (used for music) and custom marked’053260′ which plays ADPCM/PCM samples.Lalsty BGM+ samples are sent to a YM3012 DAC which outputs analog sound them amplified by OP-AMP and amplfier.When I probed the YM2151 I found that PIN 21 was dead:

This pin is the serial data output :

I pulled the chip:

It was really bad but also replacing it I still got the error @4F and 5F on self-test.YM2151 datasheet says that in typical application pin 21 is tied to YM3012 but on this board it’s tied to the custom ‘053260’ and then from this to serial data input (pin 4) of the YM3012 DAC.So the ASIC was likely bad.Time to remove and replace it:

Finally board got past the self-test and entered in game with full sound:

But, as you can see from above video, sprites were all garbled.MASK ROM check reported two bad 4Mbit devices @3K and 7K :

Using a logic probe revealed that two address line (pin 6 ‘A3’ and 39 ‘A9’) of both devices were stuck high:

These devices are directly addressed by the ASIC ‘051960’ (working in pair with ‘051937’ which reads data) which from my eperience is not really reliable.So I replaced it:

But I was wrong.At this point, after check as good all connections, it was clearly obvious that the two MASK ROM were bad.Indeed, once removed them, they both failed in same address lines when I read them in a programmer:

 

I replaced them with two pin to pin compatible 27C400 EPROMs and MASK ROMs check no more complained:

Hence board 100% fixed!

 Posted by at 6:56 pm
Nov 092017
 

This project started when, during my repairs, I came across these two PCBs.

Blood Bros:

Raiden:

Both were faulty.Blood Bros played blind :

While Raiden lacked of the BLUE color:

The culprit was the same in both boards, the ‘UEC-52’ (sometimes silkscreend on PCB as ‘HB-52’):

It was clearly faulty in Raiden and missing at all in Blood Bros:

This custom in SIL package is an RGB DAC  responsible to convert the digital signals of color palette circuit into analog, it’s used on some Seibu/TAD Corporation PCBs like :

  • Raiden
  • Blood Bros
  • Sky Smasher

Some time ago I partially figured out the pinout and schematics/parts after removed some of the epoxy resin that encapsulate it:

As you can see it’s a 15 bit DAC whose design resembles the Taito ‘TC0070RGB’ : two octal D-type flip-flops , some printed film resistors (with typical values of 4K, 2K 1K, 470 and 220 for the 5 bits of each color) forming resistor ladders before the output to JAMMA RGB pins.But there was also a third IC that I could not identify.At first glance I thought about some kind of darlington array to amplify the signals so I made a post on EEVblog asking for some help:

http://www.eevblog.com/forum/projects/how-to-amplify-ttl-logical-levels/

The user ‘stj’ (thanks again to him) pointed me in right direction suggesting that the unknown IC could be a 74LS367 used for video blanking.So I removed the IC from a working custom and was able to identify it as a 74HC368:

At this point I had all the info to complete my schematics in order to design a replacement, obviously I first made some prototyping on breadboard which went fine.Later I sent my project files to China for manufacturing and got the bare PCBs after some weeks:

Time to populate (in my design I used 74HC574 since it has more logical pinout compared to 74HC374)

Here is a side-by-side comparison:

Testing was successful on both boards (excessive brightness of recordings is an issue of camera, video levels are exactly the same of original part)

See you to next reproduction project!

 Posted by at 4:36 pm
Nov 092017
 

I bought a faulty Pac-Mania mainly for spare parts but I gave him a chance and tried to repair it

The game was missing sound roms, after replacing them, game booted and you could play but the screen was totally a mess.

After some blind testing I started test all socketed custom chips and rams against new ones and I eventually found the culprit

in the “text” ram @L5!

It was so bad that it totally covered the screen with junk graphics

Replacing it fixed the game 100%

Nov 092017
 

Got this Pacland, Sidam version, in mint conditions  for a repair

The game had some color bitplanes of the sprites shifted to the left as you can see from this pic

The sprites are handled by CUS29 and there are two 2149 rams connected.

Piggybacking a good 2149 ram on top of the one @3T restored good colours

Testing it out of circuit confirmed it was bad

The game had no other faults and was 100% fixed