Porchy

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.

 Posted by at 3:57 pm
Sep 082019
 

Please note that there are multiple contributors to this site and each has their own individual views and opinions and they are NOT necessarily the views and opinions of other contributors.
Each persons work shown on here is their own.

 Posted by at 11:10 am
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