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fredag den 12. juli 2019


Allright ... here we go again.

Wanted to play a game of dodonpachi daioujou black label (converted cartridge), and got a dead screen. Now I have two PGM motherboards so i went on to test the cart in the other PGM motherboard and the cart worked fine?

Some of these PGM boards are equiped with the dreaded varta battery from the factory, but mine where already removed. I therefore where a bit confused as to what the issue might be. Apart it came!
(By the way, this is a rev. 5 board . You want the rev. 14 - as it has the coin-cell battery and not the leaky varta one).




From the picture above I already added the fix (the big wire). The fix is documentet a couple of places on the interwebs and apparently fixes the issue. It patches a broken track running under the connector for the additional players (3 and 4 i think).For me it's not a big issue that the additinal player's connector does not work, but if the track is not connected - you'll be greated with a black or green screen upon boot. I checked continuity with a multimeter and sure enough - no beep.


It's not my best solder work, but it's running now. Those small via are not easy to get solder to stick to.



Now all working again

lørdag den 29. juni 2019

Sega STV - Repair log



Today we are going to look at a Sega STV board. I bought the PCB of some italian guy on the Arcadeotaku forums and i were listet as working. I wanted a cheap board for a game i had on the way from Japan. (more about that later).

The STV board is practically a Sega Saturn in arcadeform. I never saw this, back in the day - but the hardware intriges me. It uses cartridges like the MVS / AES system, but as the hardware is of newer date, the carts are a lot smaller in size.


Now sometimes when you go "cheap" and working - you just get cheap shipped to your door - if you know what i mean :-). Well the board were working, picture wise, but sound where all messed up. It sounded metallic and the sound where cutting out intermittently while playing. I did some research on STV sound issues and found that it's almost allways about the Caps and / or DAC.

I then went on aliexpress and ordred some Caps and a DAC for the board.

Fast forward 3 weeks and I got the parts in.I then proceeded to desolder the Dac from the board.


Used a Heatgun to remove this part from the board. Still learning how to use it.




The new Dac had some different designations on the IC but it also identified as a TDA1386T. The package seemed a bit smaller in hight (if that makes sense). I cleaned the pads after removal and soldered the ned Dac in.




After testing it seemed better as the metallic'nes of the sound went away, but sound where still muffeld and intermittent. Guess it's time to recap the sound section.


Recapped the sound section and now the board is working again :-)

https://www.youtube.com/watch?v=EFu_ivdTUTA






tirsdag den 18. juli 2017

Truxton - repair log




I picked up a Truxton PCB a while back on Arcadeotaku. The Board were advertised as working, which it was but had serveral repairs done to it. Mainly trace rapairs with wires. They are alle done neatly, so no need to re-visit them.

However the game did have wavey line during the first minutes of gameplay, which I at first did not notice. As time went on they did get worse until you could not help but notice the fault.

I thought to myself that the fault might be associated with out of spec capacitors and proceded to exchange them. Also, - this repair log on Jammarcade (http://www.jammarcade.net/truxton-repair-log-3/), where the same fault where fixed by replacing out of spec capacitors, seemed to confirm my susspision.

So off they came...



And new Panasonic Caps where installed in their place. "16V 470uf"





The other capacitors will have to wait as I do not have those in stock.

Just for fun I used my cheap chinese tester on the caps and at leat one is completely out of spec. They should both have been 470uf caps. But not bad for around 30 years I guess.... :-)







Now all fixed and working! 





tirsdag den 5. juli 2016

Thunder Fox - repair log


I picked up a Thunder Fox on Fleabay advertised as not working or rather without sound. Seller stated that a missing cap might have something to do with it. Well ... not so much. Besides the sound issue the condition of the PCB is ok.




Now Thunder Fox is one of those PCB's that needs -5 volt from the edge connector. I hooked it up and sure enough the sound where missing for the most part, but some peeps and beeps could be heard. I put in the missing cap but nothing changed.

First thing i then did where testing the amplifier to see if it where dead. Running a finger over the pins and turning vol up and down, - noise could be heard. All this means the amp is properly ok.


I decided to shotgun the repair for an easy fix and changed the two quad op amp's in the amp section, but no such luck. Instead I began probing the Z80 responsible for the sound section. A nice clean 4 Mhz signal where reaching the Z80 and most of the address lines where active. hmmm...

Instead i turned my attention to the eprom / maskroms in the sound section and where able to verify that they where all good.


I decided to replace the Z80 anyway since i had a spare lying around. Off it came and some nice machined pins where installed.



Unfortunately no change after having fittet a known working Z80.

My attention then turned to the DAC and I noticed that when probing outputs they where dead silent, but the input where very active (when coining up). The game is setup for no sound in attract mode. A new Y3016F where ordered on Aliexpress.

Fast forward 4 weeks and the part arrived ... Yay ...:-)

New part allready fitted

Youtube Video of working game

Now all working!!

tirsdag den 24. maj 2016

Gladiator: Road Of The Sword - PGM IGS

Bought this game some weeks ago. Found the game very fun in mame and found it for cheap at a UK reseller. Not all was well with this game and something needed to be done about it. Now I have heard about the PGM games being suspeckt to battery acid damage, but never thought about it buying the game. Oh well ... time to do stuff...

No permanent damage where done to the PCB, but a good cleanup was needed.