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Pengo repair log

PCB Repair Logs Comments Off

Nov 062015

Some days ago I bought on Ebay for cheap an untested original Sega Pengo PCB, today it arrived:

Buying a board as untested is always risky, you could ended up to have a not working one on hand and indeed mine was.I was greeted by a solid black screen when I powered it up, the main Z80 CPU didn’t reset properly.As schematics suggested the /RESET is generated by a counter 74LS161 @IC23 so I went to probe it and found it was missing clock signal.At this point I started to suspect some trouble in the timing signals generation.The Pengo manual has a troubleshooting section which suggests to check some iC in case the picture will not appear:

When I went to probe a 74LS74 @IC66 :

I found its outputs pin 5 and 6 were stuck high.I put a my fingers on it and it was really burning hot.Also comparing it against a good one with my HP10529A logic comparator confirmed my suspicions:

Once removed, the IC failed the out-of-circuit test:

Fitted a good IC fixed the board completely, no further issues were found.

Sengoku Ace PAL dumps added

PAL Updates Comments Off

Nov 052015

Today our member Corrado sent in the PAL dumps from a Sengoku Ace PCB.They are all tested into GAL16V8 targeting device.Thanks to him for this contribution.

New PAL dumps added

PAL Updates Comments Off

Nov 052015

Today some addition to our PAL database.With courtesy of user ‘tinhead’ on the EEVBlog forums we can host his recreations of registered PLDs found inside the Hi-Lo Systems ALL-07A EPROM programmer (which I personally use).You can read more about here:

https://matthieu.benoit.free.fr/hilosystem_all-07_universal_programmer.htm

Speaking about arcade PLDs, I successfully reversed into a GAL18V10 targeting device the dump made by Porchy from the PLS153 marked ‘315-5298’ found on some Sega System16B ROM boards (171-570 and 171-5521).

Ken-Go repair log

PCB Repair Logs Comments Off

Nov 052015

I had this rare Irem Ken-Go PCB (an undumped version included in latest MAME release) from my friend Joachim for a repair:

The board played fine except for an issue where all sprites were formed but missing all colors appearing like black shape:

Sprites generation circuit is located on top board where some customs lie:

Documentation for this specific game was not available but luckily I could know function of the various customs by looking at the R-Type schematics and so identity the one involved in the sprites palette generation:

The custom itself was marked ‘KNA91H014’ in 60 pins QFP package:

Probing it revelead that inputs were fine but outputs had irregular signals:

So I opted for replacing this custom (taking a good one from a dead Vigilante board) :

This was the right move since sprites were correcly restored:

End of job.

Haunted Castle repair log #1

PCB Repair Logs Comments Off

Nov 042015

Got this Konami Haunted Castle PCB for a repair:

When I powered it up for first time, two were the faults I noticed : sound and sprites were missing.So I started to troubleshoot first issue.The sound circuitry of this hardware is made of an Z80 CPU,a 6116 SRAM, a 27256 ROM and YM3812 DAC plus a couple of custom for PCM samples and music generation (K007232 and ‘K051649’).When I went to probe the Z80, I found that most of data lines were stuck LOW or HIGH.The ROM containing sound code was good as well as the relative RAM.With the help of schematics I figured out that sound code data were latched by a 74LS374 @G11 :

Probing its outpus revealed they were stuck and piggybacking it caused playing some random samples.So I decided to remove the IC :

It failed when tested in my programmer:

Sound was fine but, as I said, sprites were missing (except for some):

Since I already repaired in the past a couple of Haunted Castle boards with identical issue, I knew where to look at.Hardware uses for sprites and tiles some 4464 DRAMs in ZIP package.In particular the two related to sprites are the ones @H3 and @H4:

So I ordered some spare parts from China.When they finally arrived , I could successfully finish my job by replacing them:

Another great game preserved!

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