May 212019
 

Quick update here.

One small bug fix with the byte sum not clearing when reset.
The analysis routine has been updated to check if alternate bytes are stuck high, low or are all the same.

I think that’s all. There may be other things too but its been a while and I’ve forgotten what they might be.
I’ve since started using source control for my projects so will be able to keep better track of things

 Posted by at 5:51 pm
Apr 302019
 

A friend of mine sent me a couple of Vanguard pcbs which didn’t sync at all on all monitors I tested.

The only difference I saw was that his pcbs were Centuri versions while my pcb which synced good was SNK version.

Centuri versions on the video board have a factory mod with some flying wires which are not documented on the schematics and which are related to the sync circuit.

 

SNK version has no flying wires on the video board:

offcourse undoing the factory mod on the century board fixes the sync problem but I wanted to learn something more.

It seems that Centuri versions were modified to use the positive sync monitor supplied in their cabinets and probably they also improved the sync

signal in comparison to the original circuit.

Anyway , if you want to keep the mod but invert the sync for common monitors or TVs, you have only to solder the wire which goes to pin 3 of the 74LS05 marked in red

to pin 4.

 

Apr 302019
 

While cleaning the storage I found a very interesting power supply made by Sanwa and marked SNW-7E which works with 110 or 220V

The model SNW-7F is the same model working with only 110V

It’s a very nice and compact power supply ( with a tendency of getting really hot!) and I learned that it was used on the most famous japanese superguns .

When I powered it up it worked but on the -5V line I got -7,5V .

I decided to try to repair it and fortunately the -5V was given by a 7905 regulator with few parts around.

I immediately noticed that the regulator didn’t regulate at all since it passed exactly the same voltage on the input on its output.

Replacing it with a new 7905 fixed completely the problem

 

Note:

it turns out that this power supply is just a rebadged version of the RT-85A model made by Taiwanese company Meanwell

https://www.meanwell.com/webapp/product/search.aspx?prod=RT-85

 

 

Robocop repair log #4

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Jan 112019
 

I recently aquired a few Robocop PCBs, and this particular one seemed to be working fine at first glance. Eventually however, I realised that certain sounds seemed to be missing from the attract mode.

In particular I noticed Robocops speech as he rolls off the Prime Directives was not there. A closer look playing the game revealed further sounds missing, like the groans from the enemies as you kill them and others.

I then realised that is was just the ADPCM samples that were missing.

So I looked at the CPU board where most of the final digital and analogue circuits are. First I checked the DACs and found no samples present, so went further back to the large YM2203 sound chip. I probed pin 19 of the IC and would have expected to hear the samples here, however I heard nothing except static.

Pin 19 circled in red
Pin 19 circled in red

I was able to determine that the ADPCM samples are stored in the EN02 ROM, so I popped this into an eprom reader and checked the content.

The eprom was corrupted, so I burned a new one and the samples were restored.

Another Robocop saved.

BINman program update

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Jan 022019
 

Today I’ve uploaded the latest version of my BINman software.
This version is v4.3.2 and has had some rewrites and a few extra features added.
First is the ability to deinterleave the bytes of a file into nibbles.
Second feature added can be found under the “Special” menu. It was added as a request from a user. This swaps the nibble values from one byte and the adjacent byte then deinterleaves that file. For example an original file of: “12 34 AB CD” will output two files, one containing “13 AC”, the other “24 BD”.
Its not something I’ve ever had the need for but obviously someone wanted it so here it is.

As usual it can be found in the “Downloads/PC Software” section.

 Posted by at 7:04 pm