Yellow Magic works then freezes

Hi All,

I finished the Yellow Magic build and decided to take the LM13700N chip out of my other Shruthi and put it in my Yellow Magic to see if it worked OK (as I broke my other one and am waiting for a replacement) it all worked fine for a few minutes, sounded great etc…the the unit just froze the sound stopped and no buttons work. If i power down and back up again it works again but then after a minute or so freezes? Any ideas what the problem could be here?

Speculating here: There seems to be something in the power supply overheating/thermal throttling. Either you have a weak PSU that is marginal, or your Shruthi draws an unexpected amount of power. Did you measure the current draw? Try another PSU? Check the socket of the replaced chip for shorts?

Bad connection somewhere. Likely between the two boards. Check the joints on the connectors.

It could the rare optocoupler / 644p problem. Try swapping the 6N137 and the ATmega644p with the other unit. Is the problem still present?

and when i plug it in it makes a weird sort of warping noise?

That’s normal, the “Star Trek” sound as it is called.

tried it with the other chips and there was just loads of horrendous noise. put the other chips back in and it played for 30 seconds fine then just froze up again?

Any LED/LCD activity upon freezing up? Following up on Jojjelito, do the 7805/7905 get particularly warm?

> tried it with the other chips and there was just loads of horrendous noise

What do you mean? Was the unit booting correctly?

> put the other chips back in and it played for 30 seconds fine then just froze up again?

Can you make the freeze happen faster by sending heavy MIDI traffic to the unit (for example shaking the pitch bend lever).

the leds just freeze and so does the lcd put they stay lit and on and the 7805 and 7905 are cool?

What do you mean? Was the unit booting correctly?

Yeah it booted fine but it was just gurgling and making elongated notes.

Can you make the freeze happen faster by sending heavy MIDI traffic to the unit (for example shaking the pitch bend lever).

Yeah if i tweak the pitch bend lever on my controller it freezes straight up?

as soon as i pitch bend it actually ?

You have a working unit and a freezing unit.

What happens when you put:

  • The 6N137 of the working unit in the freezing unit?
  • The ATMega644p of the working unit in the freezing unit?
  • The 6N137 and ATMega644p of the working unit in the freezing unit?

You said that in some condition the unit was not even booting correctly and emitting weird noises… What happen when you try to power it WITHOUT the MIDI cable connected to it? Same problem?

The 6N137 of the working unit in the freezing unit?

Freezes as soon as i touch touch the pitch bend

The ATMega644p of the working unit in the freezing unit?

Unit boots but horrendous elongated warping noise, which wont stop like the startek noise but it carry’s on and on!

The 6N137 and ATMega644p of the working unit in the freezing unit?

Boots up but freezes as soon as you touch the pitch bend lever.

You said that in some condition the unit was not even booting correctly and emitting weird noises… What happen when you try to power it WITHOUT the MIDI cable connected to it? Same problem?

It has been booting up but emmiting weird noises with the chips in that work in my other shruthi, when i try the chips from my other shruthi with no midi cable same elongated warping startrek noise.

Plus the functioning unit works fine with whatever combination of those chips, but if i plug the control board of the malfunctioning yellow magic shruthi into the good shruthis filter board i get the mad elongated screaming warp type noise!

> Unit boots but horrendous elongated warping noise, which wont stop like the startek noise but it carry’s on and on!

What happens if you go to the system settings and set the filter board to “dly” instead of “lpf”. What’s happening here is not a bug - it’s just that the chip in the control board has not been configured to drive the delay filter board.

It’s a bit difficult to explain, I’ll try to make this clear.

I suspect there’s something wrong with your ATMega644p.

I want you to test your board with a working ATMega644p. You have one - from the working board. But this ATMega644p doesn’t “know” that it is going to be used with a delay filter board, and thus, it is not sending any particular information to the delay chip - that’s why you get this horrible noise - it is not related to the bug at all.

So please take the ATMega644P from the working unit; put it in place of the Yellow Magic control board; go to the system settings page and set the filter type de “dly”. Then, try the MIDI in…

Just in case it might help diagnose my problem please see my pics, its minus the LM13700N chip that has gone back into my functioning Shruthi.
I’m off to bed. Good night people.

Unlikely to be a soldering problem; More likely to be a damaged chip.