Taito 3 board Space Invaders - Click sound after player hit

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Taito 3 board Space Invaders - Click sound after player hit

Just picked up a Taito Trimline SI with the 3 board set.

Everything seems to play correctly. Only issue is that immediately after the player hit sound completes, there is a click/thump/tick--whatever you want to call it; almost like you've just powered up your stereo receiver and it sends an uncontrolled surge to the speakers before warning up.

The sound is there completely so the generator, amp, volume control is all there. Just that it ends with a significant 'click'.

Any ideas where to start? Thanks!
 
Looking forward to the answer. I have the same problem.
 
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Chances are electrolytics near the final OP-AMP are shot, or any that filter the power busses to the op-amps(3900s). To be honest I haven't seen the 3 board stack in person yet but I know its modeled very closely (or vice versa) from the l-shaped set.
 
I think this'd be the board in question: the 7 3900s are mixed in with the resistors in the middle-top.

Only 4 electrolytics on this board:
2 axial 10uf25V (blue near top/left)
2 silver 100uf16V on the left side.

Question: does the silver casing on the 100uf16V mean anything? can these be replaced with normal-looking caps?
 

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Yes - this will be either a bad cap in the audio generation circuitry or a bad op-amp - similar problem on a Zaxxon board I fixed lately. A single bad cap and a knackerd LM324 quad op-amp chip. Silver casing is just the old style, doesnt mean anything special.

Just posted my Zaxxon repair log thread that might prove useful as a guide.
 
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Thanks for the info. Just replaced the 100uf16V caps and it did not make a difference.

Now to wait for a shipment of caps to arrive before i continue.
 
I replaced all the caps and the sound remains.

Pac-fan, were you able to get your's to go away?
 
Not electrolytics, only in game play not in test; also missing UFO travel sound

I replaced all the caps and the sound remains.

Pac-fan, were you able to get your's to go away?

Sorry, been 8 months and now just getting back to this project/thread and thought I'd provide an update.

I added the Braze multi-kit to the board and this allows me to individually test each sound separately.

So far, all sounds from this menu work perfectly fine with the exception of the UFO traveling sound (missing). There is NO clicking sound after the end of the player explosion sound. However when playing the game itself there is.

Chances are electrolytics near the final OP-AMP are shot, or any that filter the power busses to the op-amps(3900s). To be honest I haven't seen the 3 board stack in person yet but I know its modeled very closely (or vice versa) from the l-shaped set.

Also I checked the board and found that all 7 of the 3900's were replaced with sockets and new chips, and I swapped every one around multiple times to no fix or worse behavior. Also the primary audio amp was socketed and relaced. It's heat sink gets very hot (> 125 degrees as I cannot touch it more than a sec); but all other sounds work so doubt it is that.

Finally, all of the electrolytics were recently replaced by whoever did the socketing work as well; so I suspect they are not an issue -- especially when it doesn't make the sound in test mode on the multi board -- just when normally playing.

So what's the difference between normal trigger vs. test?


Onto my other issue .. UFO sound is missing. I have traced back that pin 9 on the 26477 goes low when activating the sound. I also measured the resistors and pot coming back out to the primary amp and they all are okay. I haven't measured the frequency control resistors yet. Does anyone have any tips on testing the 26477 (without an OScope--just a DMM and Logic Probe)?


I think this'd be the board in question: the 7 3900s are mixed in with the resistors in the middle-top.

Only 4 electrolytics on this board:
2 axial 10uf25V (blue near top/left)
2 silver 100uf16V on the left side.

Question: does the silver casing on the 100uf16V mean anything? can these be replaced with normal-looking caps?

Yep.. that is EXACTLY my layout of board with the exact same wire hacks on the chip on bottom right and across the connector and 2 extra wires.

I noticed that besides the wide (.6" wide / .1" pinspacing) 26477 UFO sound chip actually has what appears to be a narrow (.4" wide / 1/16" pinspacing) unpopulated chip holes under and to the side of the existing one. I haven't metered the pins but suspect that must be a place for the smaller version of the chip?

I may need to replace the full size chip with the smaller one (if it is indeed at fault) as only one source for the full size at $14+ship, but a couple sites have the smaller chip at $10+ship. Does anyone know for sure if they are interchangable on the board?
 
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Another update. -- I replaced the 4 electrolytics again (even though they had been replaced once) but it didn't make any difference.

Also, I noticed that the only time I notice the large 'click' is during game play after your base is hit it clicks, as if it's turning off and then back on the sound amp. This does not occur using the Braze multi setup test menu. Also, regardless of the setting of the volume on the control for base hit it still clicks the same volume level. Therefore I dont believe it has anything to do with that circuit. There must be some secondary control signal to do something to the audio amp after that hit that causes it.

I did notice that a previous owner did a horrible job socketing the LM377, in fact pin 9 is missing the pad and not even soldered to anything on the socket. In the schematics I see it is crossed over to pin #6 as well as leading to some shared circuitry common to both. I wonder if that is what is causing it. I am hessitant to cross it over in case there was a design change and I damage something worse. It seems weird that it only is in the case of this one sound but then again the game does 'reset' the play after this unlike any other sound it makes where it will continue playing , so perhaps there is extra instructions to do something with the amp after that point.

Also, for the missing UFO travelling sound, I verified that it has both the 26477 .156" .6" wide pinout (with one in place) and the smaller .100" .4" wide version under it... everything connected the same--so they could populate either socket.
 
Positive progress

I remembered that I had gotten a Bally/Midway SI-II sound board in a lot of misc boards off eBay a few years back. Found it and it had a SN76477 chip soldered in.

I dug out my desoldering station and 56 stubborn 35 year old solder pins later, I had both chips free. Installed 2 sockets and then moved the B/M one over to the Taito.

Fired the game up, went into test mode and TADA... UFO Saucer sound working :)

Now, to continue to attack the clcking sound. I noticed that whoever had it before me had socketed the LM377 and pin 9 was floating and in fact when I pulled the chip, the socket leg pulled with it. I put it back in and there was nothing to solder it to as they had lifted the pad on the bottom. I checked the schem's and it showed it was crossed over to pin 6. So on the bottom, used some 22 gauge wire and crossed it over pin 9 to pad 6.

Put it back in and suddenly the game was twice as loud! I had to readjust the bias of each sound to not overtake each other as much, and tweak the master volume. At least this now lets the background thumping to be louder that was really quiet before.

Finally, annoyed that the clicking sound only happens when the base is destroyed in gameplay but not test mode, I fired up a game, but accidentially hit 2 players. Interestingly enough it did NOT make the sound when I went between player 1 and 2 dying. However after the last player 2 death, it DID click then after player 1 depth (I had got a free base there so played longer on that player) it clicked! It also clicks once after initial boot.

Therefore clearly it is not something specific to the caps/sound board -- some instruction is causing the sound to go through. All other sounds are fine. Since it is related to player death/game redraw, or final one, it must be some mode the CPU puts the board in to power off and back up the sound chip or somehow affecting the voltage to it and therefore may be more of a power supply issue instead of sound board issue.

That's all the info I have now.. I don't know if I will spend any more time debugging the click--everything else works. If anyone has any more info to share on that, it would be great to help me and the other person here with the same problem of clicking.
 
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