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Started on another forum, posting here because the other forum doesnt seem very active.
Schematic: https://www.badcaps.net/filedata/fetch?id=2255465
Video:https://youtu.be/HrLFl7cKsnM
Pink label Square chip made in Taiwan. Bypass works, direct out works. Delay signal is not right. Another person described it as " constant a noise that can be clearly shaped by Delay Time, Volume and Mode, but very subtle by Feedback" Clock seems to be working. I replaced all 10uf electrolytics just because. No change. Based on sound and experience, should I be looking at the AD part or the DA part? I found a breakdown of how the microcontroller samples 12bit audio, I have a scope, I plan on doing more probing.
Update 1:
I pulled C049 to help isolate the problem, and that killed the ticking garbage noise but no delay (obviously). So I used the tone probe back to IC8. I am not sure how the whole DA thing is accomplished but I know it's done by RA1 and IC8b. Looking before IC7, pin 3 of IC5 has clean signal. If I understand correctly, pin 7 of IC5 should be serial pulses, which it seems to be. So now I'm wondering if its a problem with RA1 and IC8b or if theres a problem with the micro controller. For shiggles I checked the adjustment of the clock as shown in the documentation and it says the pulse should be 5v and 12.5us rising edge to rising edge. I only had the cheap chineasieum scope today, the clock signal is present but it was only reading .5v P-P. I double checked all the voltage rails and everything is close enough 8.8v 4.2v and 4.8v. I'm sure the battery is weak after all the troubleshooting. I checked the memory chip and there is clean serial bitstream on the scope. another thought I had was the compander. Is all the noise "normal" and the compander removes it in normal conditions? I checked the tants attached to IC2 and both check good, usually they let the smoke out so Im not surprised that they test fine.
Lots of testing and no real progress.
I apologize for the scattered thoughts. My brain is a series of Robot Chicken Sketches.
Tomorrow I am going to break out the Tektronix if I have time and double check the clock. Besides throwing components at it, I am running out of ideas
Please someone let me know if my thought process is entirely wrong
Update 2:Again, not on the whole AD-DA process but it looks like things start to breakdown at IC8. I ordered one and we'll see what happens. With IC8 removed there is no noise (but no effect obviously).
Anyone have any thoughts on the wave forms?
Schematic: https://www.badcaps.net/filedata/fetch?id=2255465
Video:https://youtu.be/HrLFl7cKsnM
Pink label Square chip made in Taiwan. Bypass works, direct out works. Delay signal is not right. Another person described it as " constant a noise that can be clearly shaped by Delay Time, Volume and Mode, but very subtle by Feedback" Clock seems to be working. I replaced all 10uf electrolytics just because. No change. Based on sound and experience, should I be looking at the AD part or the DA part? I found a breakdown of how the microcontroller samples 12bit audio, I have a scope, I plan on doing more probing.
Update 1:
I pulled C049 to help isolate the problem, and that killed the ticking garbage noise but no delay (obviously). So I used the tone probe back to IC8. I am not sure how the whole DA thing is accomplished but I know it's done by RA1 and IC8b. Looking before IC7, pin 3 of IC5 has clean signal. If I understand correctly, pin 7 of IC5 should be serial pulses, which it seems to be. So now I'm wondering if its a problem with RA1 and IC8b or if theres a problem with the micro controller. For shiggles I checked the adjustment of the clock as shown in the documentation and it says the pulse should be 5v and 12.5us rising edge to rising edge. I only had the cheap chineasieum scope today, the clock signal is present but it was only reading .5v P-P. I double checked all the voltage rails and everything is close enough 8.8v 4.2v and 4.8v. I'm sure the battery is weak after all the troubleshooting. I checked the memory chip and there is clean serial bitstream on the scope. another thought I had was the compander. Is all the noise "normal" and the compander removes it in normal conditions? I checked the tants attached to IC2 and both check good, usually they let the smoke out so Im not surprised that they test fine.
Lots of testing and no real progress.
I apologize for the scattered thoughts. My brain is a series of Robot Chicken Sketches.
Tomorrow I am going to break out the Tektronix if I have time and double check the clock. Besides throwing components at it, I am running out of ideas
Please someone let me know if my thought process is entirely wrong
Update 2:Again, not on the whole AD-DA process but it looks like things start to breakdown at IC8. I ordered one and we'll see what happens. With IC8 removed there is no noise (but no effect obviously).
Anyone have any thoughts on the wave forms?
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