Junee
I have a similar experience with my Trident.
might be time to get the old mpu fixed and give it a try.
I hope my sb100 isnt stuffed, or maybe the Altek Mpu.
(Topic ID: 198035)
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Trident
Stern Electronics, 1979
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Quoted from Quench:What issues are you guys having with the Alltek MPU and the Stern sound boards?
May be a coincidence.
Working on the sb100 is a pain.
It was part working with some sounds.
I was missing some voltages Tp2 tp3 tp5 . I only had tp3 at 2.5v
Once i "fixed" and replaced 2 x 4013 and 1 x lm324. The voltages are now 2.7 2.7 and 2.7
But now i have no sound. But i can hear the game sounds very faintly from the speaker, if i put my ear against it. It has a hum in the back ground.
I have tested the poteniometer and it works fine.
I get a single beep instantly when i power the game up but thats it. This beep changes volume with the potentiometer.
This is doing my head in. I will be getting a spare working sb100 soon. But i think i may not use the alltek, just in case.
Quoted from Quench:If TP2, TP3 and TP5 are measuring mid voltage and you hear faint sounds, then you need to look downstream at where the sounds are mixed (U18 LM324), the volume attenuator (U14 MC3340) or the amplifier circuit (U20/U21 LM380's).
Are you measuring 10V power at pin 8 of U14 and 12V power at pin 14 of the LM380 chips?I am getting 9.4v at pin8 on u14
Getting 11.7 at both lm380
Check that the mute signal (pin 1) at the LM380 amplifiers is around 7.3 volts.
Getting 6.5v at bothe lm380 pin 1
You can try bypassing the U14 volume attenuator (MC3340) if you don't have spares by removing the chip and installing a 10k ohm resistor between U14 PCB pin pads 1 to 7. The 10k resistor should give you loud enough volume as a test. Note removing U14 disconnects the cabinet volume control, so adjusting the volume will have no effect..
Quoted from Quench:Could also be one of the LM380 amp chips is dead. What DC voltage do you measure on output pins 8 of U20 and U21 when the game is in attract (quiet) mode? They should probably be somewhere near 6
volts.
U20 7.25
U21 5.3
2 weeks later
Quoted from Quench:The logic probe indications I listed in post #35 were incorrect and they've been corrected.
.The volume attenuator MC3340 chip (U14) is a common failure point.
If you have a spare 10k ohm resistor, try bypassing the volume attenuator. Unsolder pin 7 of U14 so that the pin floats in the middle of the PCB hole (make sure the pin is disconnected from the solder pad). Solder one side of the 10k ohm resistor to pin 1 of U14 and the other side of the resistor to the top pad of resistor R19 (R19 is located bottom right of the board).
Do you now get any sounds?
I have tried another working sb100 in it and is doing the same thing.
So it must be cable, connector or mpu (alltek).
I have tested the cable while plugged into mpu and soundboard. i have continuity from pin to pin.
I am in the process of repairing the original mpu. Once it is fixed i will it in the game to see what happens.
If anyone has a Trident and Alltek Mpu and could they report here if their sound works ok.
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