Corrado Tomaselli

No background in electronics. Learned everything by reading pdf books and expecially Video game logic Vol 1 by Atari and in general early Atari and Williams arcade manuals

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

 

 

Apr 282019
 

Some weeks ago I bought this game for my collection in really great conditions.

While playing, I messed up with the external potentiometer of my supergun and menaged to detach it for a brief moment . Result was that the power supply jumped to 7V on the 5V line and 18V on the 12V line.

With my surprise, the game was not totally fried, sprites were still good but all the background was totally black

Also the game had no sound ( but the amplifier was still good)

For the graphics problem, 2k sram @H15 and H16 had all the data lines in the grey area.

Changing them restored completely the graphics.

 

 

The sound had also another UMC 6116 sram and the data lines were completely in the grey area.

 

Changing it led to no improvement but after checking the connections I found out D6 line was not connected to the Z80 but only to the YM2151.

I probably broken it during the exhange. Restoring the line led to a fully working game.

In the end it appears that UMC parts were the weakest devices of the pcb , I replaced all the ones which were present on the pcb

 

Defender repair log #3

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Mar 112019
 

Again my Defender boardset had developed another fault.

I had already repaired here:

Defender repair log #1

and here:

Defender repair log #2

This time after the screen “Initial tests indicate all unit OK” it rebooted in an endless loop.

The diagnostic LED were flashing two times correctly before resetting, so I thought it was the ribbon cable.

After spraying and moving the cable , game still reset itself after the initial test but after a while it didn’t produce anymore the classic startup sound and all the LED were always stuck lit.

The 6821 PIA on the romboard should send an \IRQ signal to the main CPU after the ram test but the signal was missing, that’s why the watchdog kicked.

Also the 4 LED stuck lit is an evidence that the PIA died.

It’s known to be not very reliable, so I decided to desolder it , put a socket and test the only one PIA I had for spare which luckily made Defender to boot again.

Game was  fixed without any problems ( for the moment )

Outrunners repair log / pinout

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Jan 272019
 

Got this game from a friend who took out the board out of a rusty cabinet.

The game needed badly a clean, so I dismounted everything before attempting to turn it on and washed everything carefully.

The game has two jamma connectors for player 1 ( Monitor A,left connector looking at the above picture) and player 2 ( Monitor B, right connector looking at the above picture). The connectors share same power lines, so you can connect wherever you want to play as P1 or P2.

Unfortunately board was not working correctly, it showed from a brief moment a garbled text about network connection and then nothing happened.

I decided to start dumping the program maskroms and found immediately one branded SEGA MPR-15539 which had some internal connection problems.

The other one , same type and capacity was dumped good.

After burning a new program rom on a 27c400 ( 4mbit maskrom pinout eprom), game booted perfectly although without any sound.

There was not even a noise coming from amplifier so I decided to desolder it and found immediately the problem

The amplifier was litterally blown

From Mame source I could get the right one to order, a TDA1518AQ, replaced it and finally the game had sound.

Unfortunately some tracks sounded bad with wrong samples.

There were other SEGA branded maskroms used as PCM samples, I read both of them ( 16mbit maskroms) and one of them , IC1, had A16 internally broken.

After buring a new 27c160 eprom with IC1 data, game sounded perfectly again.

No other problems were found

I will share the pinout of the board to play it on a different cabinet than the original one with a filter board ( the manual has only the schematics of the filter board unfortunately).

Game is Jamma as stated, so all power, video and audio pins are the same.

Board is using the following digital pins: on component side pin 22 is for shift up and pin 22 for shift down. On solder side, pin 22 is to select DJ Music or radio, pin 22 and pin 23 to move forward or backward the selection of musics. This is valid for both P1 and P2 connectors

There is an AMP connector in the middle used to drive lamps but I haven’t yet figured out the pinout and to me is not very interesting.

The most interesting part is the analogue controls which is handled but the daughter board 837-7636 which is in common with all Sega System 32 driving games.

I found a partial pinout on a japanese website and decided to expand it with Outrunner pinout


Last Duel repair log

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Jan 272019
 

Bought this game for personal collection but despite having declared working it had some graphic faults.

In particular the intro had blockly graphics and generally lacked shade of colours. The gameplay was in general fine at least for the first two levels.

I started to check maskroms and found LD13 and LD15 which handled the tiles of the intro. Maskroms were tested good on the programmer.

Data pins went to a 86s100 custom chip which usually is not very reliable ( see bottom right of the pic below)

At this point I decided to put a socket and change it with another one I took years ago from Poker Ladies.

Unfortunately the defect was still there but after another look underneath the board and I saw some borken traces which connected the custom to a 74ls273.

There were 3 traces severed but still the graphics were not fixed at all without a sign of improvement.

At this point I started to probe all the other ttl of the video board until I noticed a floating data pin of a 74ls273 which led again to the custom.

The trace interrupted at some point but I could not see any visible scratch until I noticed it near a silscreened text H1, not easy to find at all


After repairing this track the game was fully restored