Repair Logs – Page 9 – JAMMArcade.net

Xexex repair log #3

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Sep 222019

Got this board from Olly.

Board looks very clean and plays but has graphical issues

Initial visual inspection showed nothing. All voltages seemed fine too.
Next I started gently pressing down on the custom chips which made a lot of changes when I pressed on 053250

Found a bunch of pins on that were lifted.
I reflowed these and checked the rest of the chip which all seemed fine.
Next boot up test gave me a lot better results but there were jailbars down the whole screen sometimes.

Continuing pressing the custom chips I could make everything change again by pressing on custom 054157.

Found most of this row lifted

and few a few here

Reflowed those little guys and all is fixed in Xexex land.
Its a really nice game that I’ve never played before.

Heavy Barrel repair log #2

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Sep 212019

Received from Austria this Heavy Barrel PCB, a run and gun arcade game released by Data East in 1987 :

Board was in really good shape and game was fully playable too but lacked of sound :

Using an audio probe revealed no sound came out from analog circuit hence the fault was of digital nature.Audio system is ruled by a 6502 CPU located on top board :

Its pinout :

Checking it with a logic probe revealed that the /NMI line (pin 6) was asserted as well as two address lines were stuck low (A12 and A14)

A non-maskable interrupt triggered is usually due to some hardware failure hence for first I dumped the ROM containing the audio code (located on bottom board), it turned out to be good.Then I focused on the RAM accessed by the 6502, a 8K x 8-bit device (6116 compatible)

As soon as I piggybacked it with a good chip I got some random sounds played.The scope revealed weak signals on some data lines of the RAM (a good signal on the left of below picture for comparison)

I removed the IC :

And sure enough, it failed the out-of-circuit testing :

New chip fitted :

Sound was thus restored and another board fixed.

Muter BMR 2005 repair log

Sep 142019

Not really much of a repair log but its just something I’ve been up to recently among other things.
Saw this recently on eBay for a cheap cheap price.

I didn’t necessarily want the unit itself but more the CRT adapters it came with but the price was right.

First pass on the visual inspection showed that something wasn’t quite right.

Removing the 4 screws on top lets you get into this thing and there is a spacer post and screw lying in the bottom which is clearly from the PCB housing all those buttons.

While fixing this in place I had a look over everything else and found something a little worrying.

The crispiness aside this is not standard. There are 2 diodes missing and replaced with a transistor with the middle leg cut off, a lot of the traces are gone due to the charring and the 10K resistors have been replaced for two in series and are also the complete wrong value.
I just opted to remove all of this and replace with what it should be.

There is a schematic for this in the back of the manual so could check the values and the connections but I also have the BMR 95 which I took a look at as well

Here is what I ended up with

Its by no means a neat job but short of reproducing that little PCB its pretty much the best I could do given the amount of damage.
I checked all the other components on this and they tested good.
I have now tested this on one of my monitors and compared the readings against my other unit and they are all good so Ill consider this one fixed.

Rapid Hero repair log

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Aug 292019

Got for repair this original Rapid Hero PCB, an obscure vertical shoot ’em up released by NMK in 1994 and a very sought-after board :

The board booted up but some sprites were affected by jailbars :

Besides, an entire music track was missing or sometimes corrupted as well as some sound effects:

The board had some sign of previous repair on solder side :

This is the area of the ‘CN1’ and ‘CN2’ connectors where the ROM board, which contains all the game code and data, plugs into the mainboard:

The repairs let assume a weakness and subsequent failure of the headers connections probably due to repeated disconnections and insertions of the ROM board.So I checked with a multimeter in continuity mode all the traces from the ‘CN1’ header and found another broken one that I promptly patched :

This fixed the graphics, no more jailbars on sprites :

Now the sound issue.

The audio circuit was previousy reworked, one of the OKI MSM6295 was likely replaced and one trace was repaired but this was not the culprit :

I noticed that if I pressed the ROM board on the ‘CN2’ connector some of the missing sounds were restored.I checked traces from ‘CN2’ to mainboard and found two missing connections to the ‘NMK112’ custom ASIC (responsible of bankswitching the sample ROMs of the two OKI6295 ADPCM chips)

I patched the traces with some AWG30 wire:

Sound was totally restored and board 100% fixed.Repair accomplished.

Apple IIe repair log – bad ram

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Aug 262019

I recently received this Apple IIe PCB from the U.S to try my luck on salvaging the 60hz IOU and using it in my International NTSC board in the hopes of getting colour which I did successfully in my previous post. This board was advertised as untested, so that normally means “DEAD” and I assumed so.

Taking one look at the RAM suggests there were issues in the past and most likely still issues. We have some original mT ( Micron ) / Apple branded DRAMs mixed in with the various replacements. Micron don’t exactly have the best reputation in regards to reliability so this is definitely a red flag. These were used by Commodore, Atari and obviously Apple as well. I guess they were cheap!

Based on the excellent condition of the board I was happy and confident in firing it up. It displays some kind of RAM error but it’s not very helpful, definitely not as helpful as the reporting in the Enhanced IIes built in diagnostic. I don’t have a choice but to go through and check each DRAM individually.

My TopMax helps me find 4 bad DRAMs of the 8. Three of which were Micron ( expected! ).

Dead RAM chips on the left clearly marked to remind me that these are dead and not to be mixed up with working. These will come in useful for refining my Atari 8bit diagnostic tool.

I temporarily replaced the dead RAM chips with known good Micron pulls from my friends Atari 800xl. But I do have some NOS TMS 150ns chips that will be going in shortly.

Replacing the RAM confirms the fix.

It’s nice to have a second board ready to go if I need it, and the fact that it’s a non enhanced board with everything socketed is a plus. I’ll be looking at converting this over to enhanced at some point via a enhancement kit which involves a 65C02 and newer roms for Apple IIc compatibility.

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