Porchy

Aug 232019
 

Today I received this Arkanoid PCB from Rich.

I was told the fault was with the sprites not being visible.

Visual inspection showed a pretty grubby looking PCB that has clearly had some work done before by the looks of it.

It also had this wiring harness soldered directly onto two pads of the edge connector. It was only 2 but I really hate this.

I fired the PCB up and sure enough I had the exact issue

Before receiving this board I had decided where I was going to look for the fault. After probing for a few minutes I was sure I was in the right place.

All these outputs were barely toggling so I went ahead an removed it.

As I had similar issue on my last Arkanoid repair I had a decent stock of spare 669 IC’s. New one fitted and another Arkanoid fixed.

 Posted by at 6:54 pm

SSL switch

 General  Comments Off on SSL switch
Jul 272019
 

The site has now been switched to use SSL. Hopefully this works for others and not just myself.

Thanks

 Posted by at 4:42 pm
Jul 272019
 

Some time ago Team Europe has had success in resetting the security fuse on 8751 MCU’s.
See these posts
Post 1
Post 2
Post 3

While looking for something else among my own hoard of stuff I came across an old Choplifter PCB that has been used over the years for parts but the MCU was still present.
Inspired by the work of Team Europe I decided to give it a go myself.
Removing the cap was a bit tricky because I don’t really have the tools required for the task. I ended up using a small file and making a lip so I could fit a screwdriver under it and pry the lid off.

Adding some nail varnish generously donated by my daughter and we have this familiar sight.

I threw it in the UV eraser for 15 minutes and tried reading.
I got data back but was it good?

Comparing to the one currently in MAME I had 1 byte different at address 0x100.
Now, looking at the MAME source we can see that it applies some software patches.

The byte at address 0x100 is indeed on of the patched areas.
Not sure why address 0x27b is also patched. Without this one applied there is no need to compensate by patching address 0x2ff.
Anyway I removed these patches from MAME and booted with my dump and all seems to work just fine. Hopefully the MAME team will agree its a good dump and add it too.

Thanks to Team Europe

 Posted by at 4:18 pm
Jul 222019
 

One drunken day at the excellent Revival event I offered to look at a Nintendo Space Firebird PCB.
Initially I was given the eBay link which had a few pictures of the fault.

When I got the board I did my usual visual checks and found a few things I didn’t like the look of.
First up both main RAM chips are socketed. I removed these to check out of circuit and found this

I fixed that up by removing a leg from a donor chip and soldering it on

Next up was the 8212 Input/Output port. It too was socketed with a single wipe socket but what really got me suspicious was the state of the soldering

I wasn’t a fan of this so desoldered it. When I desoldered it I found this

A bit of trace has been lifted there. I can only assume this has been removed before.
I fitted a new socket and moved on.

Found a burnt looking resistor on the sound PCB

The resistor still reads 20 ohms but i will replace that once my parts order comes in.

Lastly there were a few areas with the solder mask removed and solder on it. Not a huge problem but it needs addressed.
I cleared the excess solder from these places and covered them using a Chemtronics pen.

Not pretty but it does the job.

Firing up the PCB for the first time confirmed the original fault was still present.
As the fault was with the video I looked there first.
I started by reseating the two socketed RAM chips

To my surprise this fixed up the graphics. Not sure what effects the previous fixes would have had but Im not removing them to find out.

New problem now. The game hangs at the title screen at the same point every time.
Whenever I get issues like this I always think RAM or ROM issues.
I had already confirmed the RAM so went on to dealing with the ROM’s.
All of them were a match for Space Firebird according to MAME’s ROMident but the ROM at location 5J was for a different version of the game.

It should have been this

I erased and reprogrammed the 2716 EPROM and now the game plays fine.

While comparing gameplay against MAME I realised some colours were missing

This should look more like this

I chased this round for quite a long time only to realise that the 74LS04 inverter I was using (as stated in the manual) to invert the colours was my problem. Switching to the proper Nintendo inverter PCB made everything look right again.

All that’s left now if to replace all those capacitors on the sound PCB and that burnt looking resistor and this board is done

 Posted by at 6:18 pm
Jul 072019
 

Today I’ve uploaded the latest version on my BINman software to v4.5.0
The main addition here is the inclusion of Fluke 9010 signatures to the checksum area.
Not only does it have support for the 8 bit signatures it also supports the 16 bit signatures.
For 16 bit signatures, it will only support single files so if your hardware has the files across 2 EPROM’s then these will need interleaved or whatever is required to merge them.

Enjoy

 Posted by at 8:04 am