JAMMArcade.net – Page 165

Lightning Fighters repair log #2

Jan 062015

Found this Konami Lightning Fighters PCB buried somewhere in the pile so today I decided to take a look at.

I know quite well this kind of hardware since I repaired two of them in the past and I can say it’s not really complicated, the use of graphical ASICs simplify a lot the PCB layout and troubleshooting.

Once powered on I got a solid black screen.Probing the main 68000 CPU revealed that watchdog was active and board was resetting endless.Dumped the two program ROMs gave me bad dump of the one @E15.Once reprogrammed a 27C010 EPROM, board succesfully booted but all colors were clearly wrong:

Schematics of this game were available so looking at them revealed that color RAMs were two 2018 @D18 and D19.Probing these two static RAMs I found some addressing lines not pulsing fine.All of these were tied to the four outputs of a 74LS157 @F19 (whose inputs were connected to address lines of 68000 CPU and ASIC marked ‘053251’ so this was how the two colors RAM were being addressed) .

Piggybacking a good 74LS157 restored all colors.Using my HP10529A logic comparator was a further proof of my suspects that were confirmed definitively testing this multiplexer out-of-circuit where it failed miserably:

Fitted a good 74LS157 brought back the PCB to 100%.

SEGA NAOMI multi BIOS

General Comments Off

Jan 042015

P1pkin has released his NAOMI/NAOMI2 multi BIOS for everyone.

By changing the dipswitches you can change the region of your system
DSW2 DSW3
OFF OFF Japan
ON OFF USA
OFF ON Export
ON ON Korea

Original thread can be found here

Thanks very much to P1pkin for this.

ABI Chipmaster Pro – FAIL!

General Comments Off

Jan 022015

Here is a sad fact and its one I picked up on quite a while ago when I compared the Chipmaster Pro to my Boardmaster 4000.
Both of these devices test the Z80 CPU out of circuit yet the Chipmaster Pro seldom gives a PASS result where as the Boardmaster always gave me a true PASS or FAIL result.
I bring this up now as Andrew96 reminded me of this issue and has even made a short video of it here
https://www.youtube.com/watch?v=GCA_KPoa18I&feature=youtu.be

As he states, ABI refuse to fix this problem and that is just unacceptable.
Be warned before you shell out a good amount of cash on one of these devices. You can’t even add your own test without spending another load of cash on the extra software.

Im glad I never paid much for mine.

Vendetta repair log #2

PCB Repair Logs, Repair Logs Comments Off

Jan 022015

Got this original Konami Vendetta PCB from a batch of faulty boards I recently bought:

Board was really brand new as it was come out from the factory but once powered on I was greeted by a flashing white screen sign that the watchdog circuit was active and the board kept to resetting:

Usually the watchdog is on because there is some troubles in the main code execution.So I started with my multimeter the check the main CPU (a custom marked ‘053248’) area and found an high resistance between ‘D1’ (DATA LINE 1) of the CPU and the program ROM:

Obviously, for the proper CPU operation, all its address and data line must be daisy chained with the main code ROM as confirmed also by schematics:

So I used a provisional patch wire and board booted fine:

But external appearance matters too.So, following the path of this data line, I found the point where the track was interrupted (picture on the right was taken with USB microscope) and I patched it with some AWG30 wire:

Job done.

Oric repair log

Computer Repair Logs, Repair Logs 4 Responses »

Dec 312014

today I got a couple of Oric computers.
Ive been after one of these for some time now but prices have shot up of the last 12 months.
I couldn’t resist buying these two, both of them which required repair, as the price was right.

First is red/black one.
I first started by removing the ULA and powering up to check voltages. I do this with Spectrum’s too as these early voltage regulators have a habit of going wrong with disastrous consequences.
With everything looking OK I refitted the ULA and power up. I was greeted with this screen.

Ive read enough about the Oric over the years to know that the ULA is very hardy and the RAM is very poor. Ive also read that a fried ULA will usually result in nothing on screen at all.
I opted to desolder the RAM first.
There are 8 x 4164 RAM chips and on testing two of them failed.
I socketed and replaced the faulty RAM and I now have this

The random writing is my doing as the keyboard is flat on the bench when testing.
Happy with this. I think the second unit has the same fault too.

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