I recently aquired a Supersonic that played, however no sound (AS-2518-32 board), I replaced the header pins on the board, and I now have it somewhat working. There is a constant high pitched tone(this tone starts once the machine boots, and changes pitch slightly when you start a game) – I can adjust the volume pot up and down, as well as mute it by adjusting the sustain down – however when I do this, none of the other switch sounds work (they do when its loud/sustained enough, but the other annoying tone is still constant).

I have replaced all the elctro caps on the board, as well as U1 and U8 the 2 x 4049 chips.

Are there any other specific caps and or chips you would recommend I replace that would remove the constant tone that increases and decreases when you adjust the volume?

Also just replaced the 4526 ICs and not much change - although i did notice that during gameplay, the tone stops for a second or so when a switch is hit, then goes back to continuous

Not much progress. I'm not awesome with understanding chip functions but are the outputs all on one side of the chips (odd numbered legs?) and I assume test these with the logic probe and see if it goes from low to high or high to low?

Thanks

Rob

Quench Thank you so much - that is one of the most useful posts ever! Really appreciate the detailed information.

So i got my logic probe and during sound test got flashes from high to low on J1 pin 12, U2 pins 4 and 7, however nothing at all on pin 13 and only high on pin 14. during the sound test, i do get the high pitch constant tone, but every few seconds it drops down pitch and generates what i assume is a sound test beep, so its almost like a siren sound during sound test, (ie going up and down), as opposed to the constant tone which is on out of sound test mode.

Given these are not as expected, i assume i start by replacing U2 (4042 - will have to see if my local supplier has one)- OR, since these are the input legs (ie 13 and 14 that are not getting as expected signal), does that suggest a problem on pins 3 and 4 of J1 or the MPU. One thing i have not done is replace the header plug on J1 (i did the pins), maybe i should do that 1st?

Thanks a million again

Rob

Replaced j1 header plug with no change.

Only other update is I tested again and accidentally shorted pins 13 and 14 of u2 and noticed it changed the tone a fair bit when I did this

I get a little bit of a background hum with the sound board connected to backbox and this quietens down when it's isolated however the constant tone stays there.

Thanks heaps to all the super helpful replies - i have learned quite a bit. I changed a few more IC's with no luck. I had to send another board off to be tested in a test fixture, so chucked the supersonic sound board in as well - hopefully the repair guy will test and sort for me - i will let you know how i go.

I did replace the 555, and adjusted the sustain pot quite a few times.

Hadn't thought about changing dip switches on MPU, but will once the board is returned

No the tone is constant, then interuppted by other sounds when switches are hit.

The tone starts upon power up, and changes slightly when a game starts

Just got the repaired board back. A 7339 and 741 chip were replaced and all is good.

Now te to give the machine a proper play!

Yep, 7493 sorry