Power problem on my SMR4 mkii - near 0 voltages

Hi, first of all I have to say i’m very new to this. I was very excited when I read that I could build my own synthesizer so I ordered all the parts needed and hired someone to print the drawings in the PCB. I’m planning to fabricate 5x of this and I’ve already tried to make 3 filter boards and none of them have given me the right values when I measure them. They’re in different progress stages
At first, I will just focus on the third one:
In this one i’ve soldered just until the power part, that means the 16 100 uF capacitors, diode, voltage regulators, etc.
The thing is the following: When I measure the blue dot with the red and green dots, I get 0V.
I don’t know where is the problem, but i’ve been measuring some parts which could give you an idea
I’ve measured the diode from leg to leg and they give me 9V. Then from the end of the diode to the lt1054 and it gives me some small miliVolts value, the same from diode to positive leg of C12.
Then i also get like 0,003 mV between the legs of IC9 7805.
I’ve replaced already the diode once. Despite I think the problem might be this new diode again, i won’t replace it until i’m sure that’s the problem, because it’s really fresh one. I’m using N 4004, is that fine?
This is it

I really appreciate your help!!
P.S: Sorry for my noobness

Are you sure of the polarity of your power supply jack? In particular, if you’re using a power supply for guitar pedals, it won’t work!

omg really?
im using this

which one should i use?

From the user manual:

https://mutable-instruments.net/archive/shruthi/manual/

“2.1mm DC power jack. The Shruthi can be powered with a 7.5V-9V unregulated supply, or with a 9V battery adapter. Make sure that the connector has a center pin (or tip) positive / outer collar (or sleeve) negative pin polarity. Most universal power supplies allows the polarity to be selected – the polarity being often represented by a diagram like this: - (o +, or by the indication tip: + . The power supply has a reverse polarity protection.”

Your power supply has the wrong polarity.

1 Like

Woooow thank you very much!!! I just tested with a reverse polarity power supply and it worked!
I just tested my other shruthi which was already finished and it turned on!!
The thing is i just see leds and screen turned on but nothing else happens… do you know what to do now?

It looks like I’m not the person who sold you this kit, so there’s of course a lot of mystery surrounding it – where and how you obtained the parts… To start with, is the ATmega chip programmed?

I’ve been searching these famous kits just for soldering and didn’t find, it seems a very old and discontinued project, but im glad there’s this forum for asking all this things. Most of the parts i got them from mouser/newark/farell, as described on the list.
I don’t know if ATmega chip is programmed… how can I know it?
I was checking other threads and found out that if I turned around the trimmer I got some contrast on the LCD. So now I have this single line, and all the leds are turned on.
Can you please help me? :smiley:

Did you just order it from Mouser?

Or did you buy it from a site telling you the chip contains the Shruthi-1 code?

yes, I just ordered it from Mouser, I followed this list: https://docs.google.com/spreadsheets/d/11WKMWPtxPBN4BW76uDtzTzKF8XDOC9zIeIdGT7QqJD0/pub?output=html&widget=true
Is there some step im missing?

The chip is blank, it doesn’t know anything about sound synthesis :slight_smile:

You need to write these two .hex files to the chip.

hexfiles.zip (75.0 KB)

And set the fuses to this:

LOCK           = 2f
LFUSE          = ff
HFUSE          = d6
EFUSE          = fd

You’ll find tutorials online about using an AVR ISP mkII programming adapter, or an Arduino board. It’s not specific to the Shruthi, but applies to any ATMega project.

Maybe some sites are still selling pre-programmed chips with the Shruthi code, it might be cheaper to just buy that.

1 Like

Oh now I understand…
Thanks for informing me.
So if I make it on my own first I need to buy an AVR ISP mkII programming adapter, right?


Is this fine? Where do I plug the ATmega644 here?
Is there a tutorial on this forum to make this step by step?
Thanks a lot

This is the correct adapter.

You have to plug this adapter to the 2x3 connector on the control board.

There are no step by step tutorials since I used to sell the pre-programmed chips with the kits.

1 Like

Thank you! I’ll do the homework and let’s hope I can get it done :slight_smile:

1 Like

Hi! I just wrote the .hex files to the atmega644p chip.
I had an error while setting the lock fuse to 2f:

And I have a little question also. Im using atmel studio and I’m not very sure if i’m writing both of the .hex files, since there is this one by one writing and I’m not sure how to write them both.

I feel i’m very close to finish this!
Thanks a lot