Author Topic: Taito Space Invaders PtII 3-Layer PCB Repair Log #2  (Read 2172 times)

Kaizen

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Taito Space Invaders PtII 3-Layer PCB Repair Log #2
« on: March 01, 2017, 06:43:51 AM »
I picked up this PCB recently and finally got around to plugging it in and testing it.
It fires up and runs the attract screen okay but has a few issues:

Issue #1 - Upon Player 2's turn the base immediately shoots a missile.

Issue #2 - Upon Player 2's turn the base goes all the way to the right.

Issue #3 - The 'thump...thump' invader noise is very soft, adjusting the pot (VR6) makes the noise disappear when you turn it all the way down but turning it all the way up, you only get a faint sound.


https://youtu.be/DdzcRfjto7o



I decided to look at the control issue first.
First thing to do was to see what was happening with the 7414's at [2] and [3].
Number [3] was behaving correctly, inverting the signal from a HI to a LOW and vice versa when you press the corresponding switch.
The outputs at pins 8 and 12 on [2] were stuck high.
I removed the chip at [2], socketed and refitted a new 7414 and the Player 2 controls are now working correctly.









Issue #3  was just a case of the master volume was a bit sticky.
After turning it a few times all other sounds rose to ear piercing level.
Adjusted the rest of the sounds as required and the board is now 100% working.  :)