Nord's classical Virtual Analog Synth Nord LEAD 1/2/2x/3/4/A1 and Nord Rack versions

Re: Nord Lead 3 problem, does not boot

Postby hozone » 21 May 2021, 14:48

Thank you.
I've checked the pin1 of 27SF010. It's 0.30ohm (so directly connected) to 5V line, that is 4.985 read on my UT61E.
Italian suppor tells me they have to check the board, and if they are not able to solve the issue they will ship to Sweden.
I'm starting thinking this is the only way. I can replay the MCU, but the more i touch, the more the support will not take this board in consideration, this is just a supposition.
Attached high resolution board picture.
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Re: Nord Lead 3 problem, does not boot


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Re: Nord Lead 3 problem, does not boot

Postby 23skidoo » 21 May 2021, 18:17

I would absolutely send it to support, let's see what they say. If they can't fix it and Sweden for whatever reason won't or can't, then we'll look at more invasive actions. But it may be as simple as "whoops that chip somehow got erased during a failed upgrade" or whatever, and they can restore it using a simple re-program. I can't find a supplier for the SST27 series anymore, and you can't drop an SST39 in place (well you theoretically maybe could if you pre-programmed it and then cut the pin 1 connection, basically making it a ROM, but that's just theory from a quick skim and I'm not certain that in practice it would work).
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Re: Nord Lead 3 problem, does not boot

Postby pterm » 21 May 2021, 19:56

23skidoo wrote:I would absolutely send it to support, let's see what they say. If they can't fix it and Sweden for whatever reason won't or can't, then we'll look at more invasive actions. But it may be as simple as "whoops that chip somehow got erased during a failed upgrade" or whatever, and they can restore it using a simple re-program. I can't find a supplier for the SST27 series anymore, and you can't drop an SST39 in place (well you theoretically maybe could if you pre-programmed it and then cut the pin 1 connection, basically making it a ROM, but that's just theory from a quick skim and I'm not certain that in practice it would work).

The blank part is availablehttps://www.findchips.com/search/sst27sf010. A blank part is not helpful though.
hozone's measurement shows the Vpp pin connects to 5V, so their NL3 lacks the capability to update it.

@hozone Thanks for the photo but I do not see anything obvious to try. I agree with 23skidoo - it's time to send it to Support.

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Re: Nord Lead 3 problem, does not boot

Postby 23skidoo » 21 May 2021, 22:57

Oh nice, thanks for the tip on that part. I might get a few and see if I can't whip an Arduino into programming them. Just in case, you know.
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Re: Nord Lead 3 problem, does not boot

Postby hozone » 28 May 2021, 11:54

The repair will not be cheap, I'll try myself. I'm not so sure it's the ROM, It may be the SRAM chip, that are cheap and relatively easy to change.

First of all, I've to understaind the behaviour of my RIGOL (see my post here: https://www.eevblog.com/forum/testgear/ ... -question/), it makes me not aquire a good input. It's "strange" to me, of course I'm not a pro :)
I've acquired images also with the logic analyzer, see attached.
Using the analyser it seems CLKOUT goes from 8Mhz to 5Mhz, but I'm again not sure about this instrument at that speed, I've never use at this frequency.
One again thank you.
Attachments
Capture_boot.PNG
Capture_boot.PNG (31.51 KiB) Viewed 2431 times
Capture_afterfirstCSBOOT.PNG
Capture_afterfirstCSBOOT.PNG (44.78 KiB) Viewed 2431 times
Capture_duringCSBOOT.PNG
Capture_duringCSBOOT.PNG (51.97 KiB) Viewed 2431 times
Capture_running.PNG
Capture_running.PNG (51.26 KiB) Viewed 2431 times
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Re: Nord Lead 3 problem, does not boot

Postby 23skidoo » 28 May 2021, 15:31

Well the skips on your LA show me that it's not reading the signal right, if that's a clock signal it should be perfectly regular. When you're dealing with signals in excess of a few MHz you need short traces and good grounding to get a clean signal. You also need to set the LA threshold correctly for the signal being analyzed and the only way to do that is to have worked with it on known signals ahead of time. Troubleshooting a piece of gear without knowing your LA and how it behaves on similar signals is a recipe for confusion.

I assume you're familiar with the Nyquist theorem relating sample rate to bandwidth, right? Bandwidth on an oscilloscope is the -3dB down point from an analogue perspective, so your 50MHz scope is 3dB down at 50Mhz. It has nothing to do with sample RATE which is how fast new samples are acquired, which as pterm mentioned must be more than twice the frequency you wish to measure or you will get aliasing. The same principle applies with your LA - you need to check the sample rate - and in the window of your screenshots here it looks like it is 16MHz which would give you a maximum bandwidth of 8.0MHz. Anything over that will alias. Note that digital pulses (square waves) typically need about 3-10x the bandwidth depending on how precisely you need to see the edges, so if you want to properly see a pulse on a logic analyzer you need AT LEAST 3x the bandwidth of the signal you want to measure and that's cutting it very close by most lab definitions. I prefer to have closer to 5x as a low threshold.

From the 3x perspective you'd need >50MHz sample rate to observe the 8.389MHz clock correctly, and a 150MHz sample rate to observe a 25MHz clock or digital datastream correctly. Anything lower and you won't be seeing the true signal.

For instance, when dealing with 50MHz SPI signals, I use a Rigol MSO5104 which has up to an 8Gsa/sec sample rate (spread across all the active channels; with 16 active channels that still leaves me 500MHz of sample rate and 250MHz of bandwidth, 5x the 50MHz signal I want to observe). That's about the minimum speed I'd use for signals that high. Remember for scopes and logic analyzers that (in all equipment I'm aware of and have used, at least) you must divide the current "scope sample rate" by the number of active channels to get the channel sample rate. Thinking about it, you had 2 channels active on your LA, so perhaps you only had a true per-channel BW of 4MHz... hmmmm. Again, the only way to know for sure is to use it on real, known, signals first and see how it behaves.
Last edited by 23skidoo on 28 May 2021, 15:37, edited 2 times in total.

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Re: Nord Lead 3 problem, does not boot

Postby hozone » 19 Jun 2021, 09:26

Thank you @23skidoo,
I've miss your reply, sorry about that.
I'm a IT developer, so I'm not a pro in electronic, that's just hobby for me. Thios is the reason of my mistakes. Anyway I really approciate your help. I know the Nyquist, but forgot about that :facepalm: Also, the 3x rule o thumb will help me.
I'll keep you updated as soon as I get time to work on this synth again. Unluckily my job takes me most of my time those period.
Again, thanks!
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Re: Nord Lead 3 problem, does not boot

Postby hozone » 04 Jul 2021, 19:40

It's alive! THANK YOU ALL!
I finally had the time to replace the components I've buy, and the broken thing was...
...
suspense...
...
one of the SRAM CY7C109B IC, It was not the first one I've replaced, It was the second one, but I was lucky!
It costs me a few hours and couple of Euros.
The most important thing is that I've learn something thanks to you, and also I've salvaged this keyboard from his end.

:keyboard2:
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Re: Nord Lead 3 problem, does not boot [SOLVED]

Postby Mr_-G- » 04 Jul 2021, 19:44

:thumbup: Excellent!

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Re: Nord Lead 3 problem, does not boot [SOLVED]

Postby maxpiano » 04 Jul 2021, 22:51

Good job! :clap: :thumbup:

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