Good Morning, here is an interesting issue!

I was not going to post till I replaced the caps on the sound board and switches (kits due Thursday) but after poking around last night thought I'd get the ball rolling.

Bally Star Trek- Works fine but the slingshots at the bottom have no sound effects or weak sound effects and sometimes garbled/wrong sound effects.

Pins on MPU, lamp driver board, solenoid board have all been reflowed, ground mods done to solenoid board and it has a new main cap, the sound board has a new main cap and the bridge rectifier board is brand new.

Tried different sound dip switch settings with no change. Now here is the interesting part.

I have sling shot sound effects if I disconnect the slingshot coils or even hold the coils manually with my finger so they can't move in the fully open or fully closed position. The sound effect only goes away when the coils are allowed to move full stroke. Its hard, it doesn't go away totally but you can still hear it faintly. I have looked close at the switches to make sure nothing is being grounded out and everything looks fine.

The MPU is clearly seeing the switches as the slings are firing and there is a "call" for the sound effect, what would cause the sound to drop out or lose 90% of its volume which the coil actuator goes full stroke? Not an issue with any other switch or the pop bumpers.

Other Bally Star Trek games they work, I can hear them in videos off Youtube. The machine scores off the switches as well with no problem.

When this happens you can hear the sound effect play but the volume is reduced by 90% and even then not all the time. 1 shot in 10 will sound normal. I noticed this last night when I had the playfield up for testing. Faint, but you can hear it.

The slings are working so therefore the MPU is seeing the switches as the MPU is firing the coils and increasing the score.

It only happens when the coils are allowed to go full stroke. Holding the coils in and the sound effect works perfect even with a quick ball strike. I'll do a video later if you like.

Very odd.

Tonight I removed the LED lamps behind the slingshots and the problem is virtually gone. Most strange.

The large 100uf one has been replaced, the others will be done when the kit comes in from Great Plains on Thursday.

Also changing out the other 2 caps on the solenoid board, the 160uf 250V one is almost impossible to find in stock, ordered a radial 150uf 350v instead.

I'll make it work.

Hey! Status update shows kit parts arriving today, I know what I'm doing tonight!

Board has been recapped now, interesting results.

1) So the first thing I did was replace all the missing switch caps under the playfield, this seemed to make little difference in sound issue. Much nicer to play now that it picks up the quick ball strikes!

2) Second thing done was to "unbolt" sound board from back cabinet. This made speaker hum at idle go away, much more pleasant.

3) Third thing done was to re-cap sound card. This seemed to have some effect. Reverb seemed better. Still at least a 1/4 of the time no sound effect was noted and sometime "garbage" or the wrong sound effect would occur.

4) Tried adding cap to slingshot switch on left side and played. No shot gunning. Added one to right side, also no shot gunning.

At this point the slingshot sound problem seems to be 99% gone with the only remaining issue being occasional "garbage" sound being played randomly as the ball strikes targets around the playfield. Not even sure how I could diagnose that. Sound card is recapped, connectors are good, solenoid board has new main cap and minor caps will be changed out in a few days. MPU sending mixed commands to sound board? No idea.

EDIT: I did try checking gaps on switches and rapping on the playfield to see if gaps were too close and vibration was causing a switch to trigger causing the random sound effect when slings/pops were activated, nothing noted.

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I did notice that once the ball was slipping down the "A" roll over lane at the top and made the wrong tone. It did it somewhere else too but can't recall where. Need to record some plays and see if I can catch.

ok, I'll double check. Most of the connectors have been gone over and anything that looked off re-pinned and reflowed. Hell, everything was reflowed just because.

EDIT: Another sound quirk- The power on "tune" has normal volume but the credit up tune is very quiet. Try and make video tonight.

Here is a video of gameplay; you can hear me credit up the machine a few times in the beginning, it is very soft compared to the other sound effects. Is this normal?

The "mixed up" sound happened once or twice while playing, seemed to happen this time while the ball was in the pop bumpers so hard to pick out. I'll try again this weekend to see if I can get a better example. Thanks for the help!

EDIT: yes the 2x insert is flickering, I was trying a LED there to see how bad it would be, pretty bad!

All pins were reflowed with fresh solder.

There is four possible dip switch settings for sound (positions 8 and 32) mine are set different than yours.

I have attached the information from the Bally Star Trek manual.

What are yours set at in positions 8 and 32?

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I have the sustain pot set at around 12 o'clock, the other tunes have strong volume. Just the credit up tune sounds like it fades in and out.

Yes, already at 12:00, if not a touch more.

I'll do another video showing position and various switch effects after work.

Interesting maybe.

1) Sound board is AS-2518-32 as the manual states it should be.

2) Sustain is roughly set at 1:00, any less, like say noon position and the tones are so soft you almost can't here them. Any more than 1 o'clock and the tones continue to play after being triggered.

3) I have attached short video- I start the machine at 12 o'clock position and you can here how quiet tones are (all but silent) but effects are very normal volume. Half way into video I start adjusting sustain so you can here tones again. I then restart machine so you can hear start up "bloop" and start tone, credit tone and game start tone. Credit tone a do a few times as it "fades" in and out. I then drain ball so you can hear ending tones.

4) I replaced the last caps on solenoid board, no difference.

5) Started installing 1k resistors to sockets, most excellent to run LED! Thing has already gobbled a half dozen 47's, I swear the new ones are all junk that have a lifespan of minutes at best.
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Good Morning all- Found the Bally repair manual this morning and going to do some voltage reads and other tests today. I'm thinking while reading the problem is going to be related to the sustain circuit of the sound board and not with the MPU. The MPU is clearly triggering the sound board and it is playing the correct tones. If I get the chance, I'll post another video.

Very interesting, more clues!

Voltages are as follows

TP1 5.13 (5V expected)
TP3 11.66 (12v expected)
TP4 42.8 (43v expected)

Looks decent with the 12V being a touch low.

What I found curious this morning- I set the sound to off/off on dip switches S8 and S32 of the MPU so it is in chime mode which is not to my taste.

If something is "a noise" like credit up or add player button, the volume is good and strong. If I trigger a chime like the far right outlane rollover it is very, very quiet. However if I tap the switch several times rapidly, it ascends in volume pretty quick till it is at the same level as "noise".

The same "chime" is used for the outhole. If I drain a ball the first two of the countdown of bonus is quiet and then rapidly goes to normal volume.

So what is the difference between the two when the sound board is processing each event?

Had the same issue before changing caps.

Going to take a break for a few days. Shorted out a lamp socket and popped corresponding transistor. Changed that and got light back but suddenly sound stopped working. Sound board voltages good. Turning sustain knob high gets you "hmmmmmmmmmmmmmmm" out speaker but nothing else.

Time for a nap.

Ok after nap feeling slightly better.

Power supply check- TP 1 & 3, good
Frequency Generator check .9 volts, good
Audio amp test tap pin 2 at U9, good 2 volts and ticking noise heard.

Tone trigger generator test- with jumper from 5V to U2, pin 5 nothing is heard when a slingshot or bumper is actuated. Sound card still has no sound output.

Voltage controlled attenuator test- short between pin 1 and 2 of U8, hit switch, still no sound.

Checking pin 1-4 on the connector 5.0 volts is present. If you trigger a playfied switch it rapidly drops and then returns to 5.0v

Turning the suspend up till you get a hmmmmmmmmmmmmmm (3 o'clock) you can faintly hear signals/tones when the playfield switches are activated.

I'm going to ASSUME this means the MPU is signalling as it should and something has failed on the sound card?

I feel a little better if that is the case.

It is 2.2uf 50 volt, factory is 2uf 25v I think.

Thank you and Quench for your help but I'm at the point where it is best if I replace the board with one of yours as it looks like I'm dealing with two sound related problems now. Working with the manual this morning in regards to no sound I'm at the point where it states "check U2 if x happens replace U2 and if that doesn't fix it replace Ux" when chasing down the problem.

If I'm going to start throwing random parts at it I just assume buy one of your excellent new boards. Perhaps when I have more time and a bit more experience with solid state machines I'll come back and revisit the board and see if I can fix it for my own education.

1) I have a logic probe which I used to make sure 1-4 on the connector were getting high/low signals when a playfield switch was set.

2) Amp is working, speaker good.

3) I did check one of the U chips for 2.5 volts on a leg, can't recall which one as I'm at work and not at my notes

4) Solder joints are all good.

New board was ordered yesterday, I'll revisit the old board when I have more free time. Thank you very, very much for your assistance. I need to learn more of the theory of operation so I can troubleshoot better but time is running out this summer season and many other projects aside from pinball to work on before the good weather ends.

If you are inclined and have the time send me a list of tests you wish me to do, I have a few minutes free tonight as the webbing is drying fully on my other project. I cannot swap chips at this time but can do voltage readings and use logic probe to check activity.

Oh and of great annoyance- I was going to check all resistors and diodes on board the other day and manual does NOT list correct values. Board is clearly original and several values do not match what is published in factory manual.

I think this pin is going to be the death of me.

Good news- Sound board came in promptly and works great! All sound related issues are gone.

Bad news- Think I lost a Motorola MC14514B U4 IC on the lamp driver board.

Since the sound was functioning I went back to installing 470 ohm resistors on the lamp sockets to run a few LED bulbs. I'd install 2, check the machine and proceed further. What I failed to notice after installing one was the resistor was sticking out and caught a side rail and was bent over into the lamp power.

So when I dropped the playfield and powered up the machine it was locked on (in this case middle lane, outer, transistor Q60) whoops.

I fixed the bent resistor and replaced the transistor at Q60 and now the lamp doesn't illuminate at all. New Q60 transistor was moved to a different location (Q37) and works fine and the transistor that was at Q37 does nothing at the Q60 location. The resistor for Q60 is fine and I can make the light flash by grounding the pin at the header.

Did I just lose the U4 latching decoder IC? I'm having the worst luck.

1) Thank you on U3/U4, was tired when I was entering info last night. You are correct and I have amended the post.

2) Will try tonight and let you know.

3) I tried comparing activity between Q37 (inner lane) with Q60 (outer lane) both at the transistors, resistors and latch chips. I'm thinking it is how the Bally mpu and driver board activates them I'm seeing odd signals. I get a very fast buzzing from both when tested, it is not a clean high/low indication.

It could be an artifact of the design in all fairness, the early solid state stuff was/is pretty crude in some respects.

On the other hand (which is my position) if the switch does actually trigger a noise, therefore the player should be able to hear it during play. All works as it should now so all is well.

I think people give Bally Star Trek a bad rap for nothing more than the sound which could certainly be better. Hard for people to imagine what things were like then though, we have the benefit of hindsight and modern stuff has spoiled us. I use the analogy of 80's PC's that could barely play games like Quake at reasonable framerates and 3dfx burst onto the scene and doubled the framerate, resolution and color depth overnight.

The game is actually pretty fast and fun once you start working a play strategy. Getting the upper orbit shot to build an extra ball bonus and get back into the saucer area to try and build BALLY not as easy as it looks. Once it is full touched up, mylar'd and waxed should be a pretty fun game.

It really does benefit from LED lighting too.

No, if I jump Q60 it does not illuminate.

I know that I'm doing it correct as if I jump Q37 the other lane lamp illuminates.

Grounding pin 3 at the header causes the Q60 lane lamp to light and the transistor now at Q60 was taken from Q37. The new transistor I installed once already at Q60 was removed to Q37 and works perfect there.