nutballchamp
Well-known member
I'm helping a friend fix his Zookeeper and took his boardset home to test in my machine. I got his boards running except for the sound and I'm stuck. Here's what I've done:
Reflowed solder to header pins
Replaced the 4 big caps (C22, C23, C57, and C58)
Replaced the 2 2002 sound amp chips (U29 and U30).
Swapped all socketed chips one at a time from my working sound board.
Replaced U18 LM324 Op Amp Chip (realized later this is for speech that doesn't exist)
Check Volume pot with my meter.
Checked +5v at the board and various chips. There is +12v at the sound amps (U29 and U30).
Checked one SIP resistor pack. Didn't check the others as they don't test in circuit and I only de-soldered one to test.
What's weird is that the sound is kind of intermittent. Once I got his boardset working the sound was on for about a few minutes and went dead. I powered on and off and it came up again for about a minute. After that it didn't work for a week. Last night for some reason the sound worked again. Went back to not working after I turned it off.
I've been testing the sound with my rom and video board. I also have been using my cables that work on my sound board.
Where do I start from here? I have a logic probe and scope. Should I start probing all the logic chips or check the analog amps with my scope? Wish I could understand how the circuit works more. Seems like the sound starts at the 6821 chips and is controlled by the processor? I'm kind of hell bent on figuring this out.
Thanks.
Reflowed solder to header pins
Replaced the 4 big caps (C22, C23, C57, and C58)
Replaced the 2 2002 sound amp chips (U29 and U30).
Swapped all socketed chips one at a time from my working sound board.
Replaced U18 LM324 Op Amp Chip (realized later this is for speech that doesn't exist)
Check Volume pot with my meter.
Checked +5v at the board and various chips. There is +12v at the sound amps (U29 and U30).
Checked one SIP resistor pack. Didn't check the others as they don't test in circuit and I only de-soldered one to test.
What's weird is that the sound is kind of intermittent. Once I got his boardset working the sound was on for about a few minutes and went dead. I powered on and off and it came up again for about a minute. After that it didn't work for a week. Last night for some reason the sound worked again. Went back to not working after I turned it off.
I've been testing the sound with my rom and video board. I also have been using my cables that work on my sound board.
Where do I start from here? I have a logic probe and scope. Should I start probing all the logic chips or check the analog amps with my scope? Wish I could understand how the circuit works more. Seems like the sound starts at the 6821 chips and is controlled by the processor? I'm kind of hell bent on figuring this out.
Thanks.