Nord User Forum

Hello,

My hobbies are music and electronic, and sometimes they dance together.
I've a Nord Lead 3. Suddently it does not boot. The LCD shows nothing (see picture), no response from any key, no sound.
It's out of warranty of course, so I dissassembly it.
I've found the "Nord Electro 2 Service Manual", both the synth shares some hardware. The power supply is the same. The main board has the same main MCU and some other IC are the same.

What I've checked/done
Clean all the board: no success
Visual inspection under microscope: nothing seems wrong
Re/Solder main board ICs, not desoldering them, just heating the pins agains. No succes
Power supply
rails are ok, no ripple with oscilloscope, voltage feets. It draw 15mA almost from 5V and just 3mA from 3.3V line. Caps are all good. I've replaced caps, and checked it out of the board, but this happens to be a no luck try.
Main Board:
I've checed all, and my attention goes to the main MCU: MC68331
RESET PIN signal is ok, always HIGH, it means SP705CU is doing is job.
Crystal output is OK on 32.76Mhz almost
At startup something happens on various pins output, then all keeps stopping.
What I've notice is that BERR pin (Bus Error pin) is HIGH, from the datasheet this it the Bus Error PIN, I suspect something is wrong with other IC.

Do someone have a clue of what I can try?
It could be some DSP broken, they are out of production I know.
I'm starting thingking my Nord is ready to the junk paradise.

Thank you!

//EDIT
Find the solution here: nord-lead-rack-forum-f12/nord-lead-3-pr ... ml#p143872

Some suggestions:
See if the CSBOOT (active low) asserts after reset. This is the boot chip select pin and it selects the Boot ROM. During reset this signal should be high.
If you see CSBOOT go low after RESET de-asserts, look for DATA activity.
If you see CSBOOT go low, but no DATA activity, I expect the Boot ROM is either corrupt or damaged.
If CSBOOT remains high, the MCU cannot boot, so the MCU is likely damaged.

Note, BERR is active low, so if it's high, there's no error.

23skidoo wrote:Note, BERR is active low, so if it's high, there's no error.

Fair point. I remain uncertain the BERR applies to the boot though. It's not listed in the troubleshooting section of https://www.nxp.com/docs/en/application ... 332TUT.pdf:

Some things to look at from this document:
5.1 Critical Signals to Check
• RESET should stay low for at least 512 clocks during a power-on reset. If using the internal PLL, RE-SET will remain low for a little longer because the VCO must lock first. RESET should then go high and remain high.
• CLKOUT should be at the system clock frequency. If MODLCK is held high at the release of reset,CLKOUT should be 512 times the frequency going into EXTAL (8.389 MHz for a 32.768 kHz crystal). Make sure that the frequency is exact, as a measurable error may indicate limp mode and oscillator faults. If MODCLK is held low at the release of reset, the frequency on CLKOUT should be the frequency going into EXTAL.
• Immediately after reset, CSBOOT should pulse low five times for a 16-bit port and nine times for an 8-bit port.
• FREEZE should be low and HALT should be high. Otherwise, the MCU is halted, or is in BDM.
• BR and BGACK should be high. Otherwise, the external bus is granted away. (These are bus request and bus grant acknowledge - I think they only apply when at least two bus masters need to arbitrate bus access - not the case here).
• Make sure that the data bus pins are configured correctly during reset.
• Make sure that IRQ7 is high during reset.

Thank you.

Find attached the CSBOOT after a reboot. Just after reboot it outputs a weird signal (see zoom image) - but that's maybe due to my RIGOL DS1052E - then stays HIGH.

While running CLKOUT is like the image, also find attached XTAL (32.768 kHz almost). CLKOUT is 25.1655Mhz (almost 3 times 8.398Mhz, what?)
While running RESET is always HIGH
While running HALT always HIGH
While running BEER always HIGH
While running FREEZE always LOW
While running BG and BACK are always HIGH

If no other idea comes out, I can try to setup an environment to check the signal after RESET happens.

Thank YOU!

The weird CSBOOT image might indicate a measurement setting or method error:
Please check these two suggestions and re-capture the CSBOOT if either applies:

1. Minimize the ground loop:

I assume your probe has a loop like the one on the left. -This "flying lead" style ground connection sometimes creates a large loop antenna that captures radiated high-frequency noise. To improve the quality of the measurement, connect the ground clip to a PCB ground point as near to the CSBOOT measurement point as you can find. If possible, twist the ground lead around the probe to reduce the loop area.

For best measurement fidelity, some probes provide ground "spring clips" like the image on the right to get the smallest possible loop area. These are difficult to use without correctly-spaced test points on the PCB, so I don't recommend these for diagnostic measurements.

2. Check the Acquire>Sampling mode of the Rigol DS1052E:

For non-repetitive signals (like CSBOOT) this must be set to "Real-time".

Thank you. It makes no difference the sampling mode, I was in "Real-Time" mode yet.
I was able to acquire even with the short ground loop method, but makes no difference. About this CSBOOT, I think it's my scope or probe. Cause the
Maybe looking at the eprom lines? Although I prefer not to fall in the rabbit hole

CLKOUT at 25MHz concerns me...
https://www.nxp.com/docs/en/application ... 332TUT.pdf indicates that noise at VDDSYN might cause clock frequency errors.
Please check VDDSYN for DC voltage value and noise.

The schematic shows a large capacitor on VDDSYN. I suspect this is an aluminum electrolytic capacitor. These are known to wear out. If possible, share a picture of this part of the circuit board.

Seems ok to me.
Two picture, out from XFC (trace pointed by scope), and 100uF connected to the via.
I've replaced C3, C4 and C2. Nothing changed still 25Mhz
MODCLK is HIGH
Replaced also the caps on the 5 and 3.3 lines of power supply, no success. Even it i think that was not the problem cause i try to inject 3.3V and 5V from another supply.

Thanks.

Maybe it has nothing to do, given the detailed problem search you made and since you say that you tried also to supply the 3.3V from an external PS (hopefully stable enough), but in this old thread on Gearslutz they suggested to add a capacitor to the 3.3V regulator http://www.gearslutz.com/board/so-much- ... ost6515383 so it seems that stability of 3.3V line is critical on NL3.