Another Data East board on the bench today, it’s the time for an Heavy Barrel one from my collection :

As you can see from picture above, CPU board was in bad state, very dirty and dusty (besides it missed a couple of RAMs) so I decided to clean it washing with soap, toothbrush and warm water :

Since drying the board under the sun would take some days and given that I have two Robocop PCBs which share the same CPU board of Heavy Barrel, I decided to troubleshoot at least its ROM board:

The first visual inspection revealed a broken IC @18F:

Thanks to schematics (but after removing its pieces I found also  the silkscreening under it) I could identify it in a 74LS08:

So was time to power it up for the first time getting this result:

Game was fully playable but with wrong backgrounds graphics.MAME source reports two set of tiles ROMs for each layer so I went to dump the first one to do a compare.When I tried to read the ROM ’24’ @17F, my programmer gave me a warning:

I pulled the 27512 EPROM device off the programmer and some pins started to fall off in my hands:

I burned a new device and this fixed the backgrounds issue:

I was thinking board was 100% fixed but while I was testing it, an horrible sound came from speaker:

Sound FXs was barely audible replaced  by the noises above.PCM samples are played by the usual OKI MSM6295 located on the ROM board.Diverting the OKI analog output (pin 36) to an external amplfier I could hear clear all the sound FXs but then the signal was lost along the way before it hit pin3 of 1458 OP-AMP and then be carried to CPU board to be mixed with the music (I circled in red the exact point) :

In this small part of circuit there are few discret components so I went to test them with my multimeter set for continuity test.When I put probes on the 100nF mylar capacitor @C3 the multimeter buzzed:

I desoldered it and had confirm it was really shorted:

Fitted a good capacitor restored full sound.End of job.

 

Got this Irem X-Multiply PCB (actually a conversion from an Hammerin’ Harry M81 board) from my friend Josef for a repair:

It showed a graphical issue where some sprites (like enemy shots) were blocky during gameplay and backgrounds missing during attract mode:

Sprites and tiles data are stored respectively in eight 1Mbit EPROMs on video board for a total of sixteen devices.

Original devices were 1Mbit 28 pin MASK ROM:

https://pdf.datasheetarchive.com/datasheetsmain/Datasheets-X2/DSA62700099.pdf

while who made this conversion used ST M27C1000 :

https://pdf.datasheetarchive.com/indexerfiles/Scans-065/DSA2IH00172244.pdf

Video board has some jumpers which must be closed according to the type of adopted devices :

In this case the jumper configuration was set to  ‘EP’ so not suitable for 27C1000 but required the use of JEDEC devices like 27C1001 or 27C010 (while the ‘MASK’ setting can work straight only with the original 28 pin 1Mbit MASK ROMs and not with 27C1000 which, although the similar pinout, have some extra pins to deal with, so some modifications are needed)

Reprogramming all the data for sprites and tiles into 27C010 1Mbit JEDEC EPROMs fixed graphics completely.

 

Got two Undercover Cops PCBs (a native and a Alpha Renewal version converted one):

Both had sound issues.

The first one had all music but sound FXs were missing.In this kind of hardware (IREM M92) music is generated by YM2151 sound synthesis chip while audio samples from a “NANAO GA20” ASIC custom chip (QFP 80)

Probing the pins of the latter revealed no activity on its DATA/ADDRESS bus (it addresses and read data from the MASK ROM ‘W42’ on ROM board)

I dumped this device and it matched the MAME ROM set so problem could be elsewhere.Tracing back the connection from GA20  to the MASK ROM  I found that some address lines were not in continuity like the other.I could pinpoint the break in interconnect ‘CN3’ which carryes signals from/to the two device:

A simple reflow was enough to restore the full sound.

The second board was totally silent, no audio at all.All the analog audio circuit was fine.I started to test ICs with my HP10529A logic comparator and when I put the clip on a 74LS74 @IC24 on CPU board, suddenly I got sound.So I inspected the solder side of this IC and found some evident dry joints , in particular pin 16 was not soldered on its pad, (probably I restored connection when I put the clip on it):

Also here a quick reflow was enough to fix the board.