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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!!

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