Asteroids - Sound fault

[Equites]

Symptoms

All sounds on the Asteroids PCB were present except for the rock explosions, which did not work but would occasionally.

Solution

Found that the counter (LS161) at P8 had all five outputs stuck, replaced with a fresh counter and now sound is 100%

 

[Nes4life]

Symptom
Heart-beat thump sound has gone

Solution
Replaced IC (SN74LS174N) at N7 and sound retuned.
Initially thought it was the .22uf mylar cap (C33) and also replaced the 555 next to it as other threads suggested these often fail but had no affect. Socketed the new IC.

 

[Battlezone]

Symptom

Heart-beat thump sound has gone, but little clicks

can just be heard at (what is presumably) the start of

each thump.

The clicks speed up during the game (implies the 4 bit speed control is good).

There are no clicks out of game (implies 555 enable control is good).

Dead end

Socketed and replaced the 555 (no change).

Solution

Oh yes the .22uF mylar cap (C33) has been broken off.

Wish me or my lad had spotted that earlier. Cannibalized

a board with a missing saucer sound for the time being.

 

[Equites]

Nice fix, the C33 cap is nearly always the culprit when the heartbeat is missing. They are so easily torn off and easily missed as that area is dense with components.

I had to replace one only last week. I'm sure I've got spares I'll have a looksie. Equites2016-04-06 22:42:18

 

[Monstermug]

Symptoms: Board had failed and saucer sound stuck on when powered up together with constant pulsing reset line.

Fix: Fixed address seconding circuit which stopped the constant saucer sound loop but saucer sound was now missing. NE566 had output stuck high. Changed NE566 with LM566 and saucer sound came back. Thing to note is that with a LM566 saucer sound now oscillates at a slightly different frequency making it sound more like police sirens with a varied ramp up time. Borrowed NE566 from spare board bought back correct sounds. I quite like the new saucer sounds though so tempory put back the LM566 until I can source an original made by Signetics.

 

[Nes4life]

Symptom
Ship fire sound is pathetic and short but Saucer fire sound is fine.

Solution
First check 555 timer at L9. If no joy then check capacitor at c50 and then resistor at r61. For me it was a previous repairer putting a 6.8k resistor at r61 when it should've been 680 ohm! Other significant components for this sound are: r65, c47, c48 and q5 transistor.