Boss DD-3 (b) Problem

[Unluckyfett]

Bypass works, direct out works. Delay signal is not right. 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, just bothering me as I sit at home with it on my bench at work waiting to be fixed. If I'm reading correctly pin 7 on IC5 should be ≈ input signal. And pin 7 on IC8 should be delayed waveform? So if I have clean delayed waveform on IC8, the problem is somwhere on the bottom right of the scheme correct? Or in the feedback circuit?

Schematic:
https://www.freestompboxes.org/downl...e04d6bdf7033e8


Thanks for any insight

[Unluckyfett]

The problem is the DRAM. I replaced the IC and its fixed now. Hopefully this helps someone in the future.

[Unluckyfett]

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

[Unluckyfett]

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

[Unluckyfett]

The problem is the DRAM. I replaced the IC and its fixed now. Hopefully this helps someone in the future.