Galaga sound question

ckasek

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So a month ago I picked up a galaga that had no sound except the ship explosion. I was gonna try to get the sound issue fixed, but then a week later, i picked up a second galaga that is fully working. The non-working one has been sitting since, so I'm trying to unload it now.

I figure though, since i have two of them here, are there any hints on what I could do to try and troubleshoot? I know it could be the custom chips, or the ram chips, or something else alltogether.

Anyone able to tell me what socket the chips are in? I could try swapping them between boards to see if that's the problem or not. Anything else worth trying that won't involve de-soldering and re-soldering stuff?

Part of me says leave it be and not risk damaging one or both, but the other part says, hey, if I can figure out the problem and fix it, it makes unloading it that much easier.

Thanks!
 
The 54xx is the one that makes the boom sound and I don't think this is the problem. I would check first that the chips are getting power and ground on the pins first. I have been swaping a lot of chips recently and have bent broken pins. I don't think just swapping chips is the way to go. If I had more patience I would not have several chips to repair. Here is the custom chips and what they do. If you have the flat resistor packs you might want to replace them. I think I have seen this problem in a repair log and if I remember right it was a resistor pack.

54xx Sounds Generates Explosion Sounds (possibly a custom Z-80?) [Mux 4 Channel Audio Generator]
53xx Steering Input [Custom 4Bit Micro/Handles Steering/sw/read]
52xx Audio Processor [Audio Processor 4 Bit Voice]
51xx Input Player controls, DIP switches, etc [Custom 4 bit I/O - Coins]
50xx Sound Sequencer [Sound Sequencer]
13xx Horizontal Scroll [Horizontal Scroll]
12xx Sprite Position [M.OBJ. Position]
11xx Playfield Shift Register [Datashift Playfield Register]
10xx Micro Buffer Data [Micro Buffer Data]
09xx Sprite Ram Buffers [M.OBJ Ram Buffers]
08xx Bus Controller (basically the same as Pacman's "285" Sync Buss Controller) [Multi-CPU Bus Controller]
07xx Clock Divider (generates horizontal and vertical timing pulses divided down from master clock) [Sync Generator]
06xx Bus Interface [Custom 50's Controller]
05xx Star Generator (tapped pseudo-random feedback shifter-- makes scrolling starfield)
04xx Bus Interface Motion object and scratch RAM to CPU bus interface [M.Obj Controller]
03xx Buffer, Playfield Data [Buffer, Playfield Data]
02xx Custom Shifter Custom shift register for data from graphics ROMs [Shift Register]
00xx VRAM Addresser (basically the same as Pacman's "284" VRAM Addresser) [Video Ram Addresser]
 
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from when i was reading about the sound issues before, I saw that it could potentially be resistors, the 7489 RAM or the bipolar roms.

Seemed like the roms were the only thing I could try swapping (without getting into soldering), but as you said, I'd hate to bend/break a leg and then have to start replacing chips. May be that it's just not worth it, and to just sell it as is vs. trying to find the problem.
 
from when i was reading about the sound issues before, I saw that it could potentially be resistors, the 7489 RAM or the bipolar roms.

Seemed like the roms were the only thing I could try swapping (without getting into soldering), but as you said, I'd hate to bend/break a leg and then have to start replacing chips. May be that it's just not worth it, and to just sell it as is vs. trying to find the problem.

Let me know if you want to sell this.

It is a lot of work if it has the crummy resistor packs and ic sockets. That means one thing to me, Galaga Renue kit.
 
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