No Bootloader screen


when I start my Shruti I can´t see Mutable Instruments and the Logo too.
After I turn the Power on, its Jump in the Filter edit Page.
The four Encoder under the Display are without funktion. I can´t edit the Pages or any Parameter with the Encoder.

I´ve Updated the Shruti from v0.94 to 0.95
PCB Version is: v0.7

Assembling Problem?
Bootloader Problem?

The bootloader is what allows the firmware of the synth to be updated. I don’t see how this could be related to the problem you experience. Unless you press the 6th button when powering the unit the bootloader is not invoked.

Someone had a problem like that and it was due to a bad power supply. What is the voltage on the +5V pin on the control board?

Another possibility is bad solder joints or bent pins (during chip insertion) on the MCU. Or just a section of the MCU having been damaged by an electrostatic discharge.

Can you tell exactly what is shown on the screen when you start the unit?

Another possibility is a bad Oscillator/Quartz connection, so the ATMega gets no signal and is stuck…

Another interesting thing is, can you see something on the Display (try turning the Trimport the whole Range left and Right 25 Turns - you must at least get some Black Squares…)???

Sorry i was AFK…

on the ControlBoard PCB I´ve measured 4,97V.
When the MCU was damaged, can I change this with another MCU like this:

On the Screen ican see after the Start:

Cut res env lfo
127 63 63 63

Encoder right from the LCD and the 6 knobs under the Leds works fine.
With the one Encoder I can scroll in the Menü push and set the Parameter.
With the Knops S1-S6 I can Jump in the Menü.
When I will Play the Shruti it Sounds like a Bassdrum. It is the only preset.
The Firmware Update with a EMU 1x1 an MIOS Studio works fine.

I will look @ all the solder Points. and search for Bad Solder.

Yes you can buy this part, but you’ll need an AVR programmer to flash the firmware on it.

What is the voltage on the middle pin of each pot when you move it from left to right?

Do you really think a blank chip from Atmel knows anything about MIDI and detecting a press on the 6th button of a Shruthi-1 board? That it knows it will be used in a board with a 20MHz crystal? The Shruthi is updatable by MIDI and works on the digital boards because I flash the fuses and a bootloader on all the chips in the kits!

the Firmware flash via Midi does not go???

:slight_smile: ok no.
I´m new in the DIY Synth and Controller Flash Community. I help a Frind with its 3 Shrutis.
The first Shruti works really Fine. This is a Awesome little Box. (I love it.)
The second and the third makes little Problems.

the voltage on the middle pin is left = 0V and right 5V

I have checked the solder pins from the Quarz and the MCU. It seems to be ok.

Fix a Solder bridge @ 330k and 2.2k Resistor (Filterboard down left)
Fix a Solder bridge @ C15 100n (Filterboard)

My bet is that there’s something wrong near pins 30, 31, 32 of the MCUs. These are the AVCC / AGND pins, so something wrong here is going to mess with the ADC.

The Voltage on the Pins 30/31 = 4,91V.
tomorrow I will check the Shruti with another power supply with more Power.
the current power supply I use have 9V 200mA.

Are you sure there’s 4.9V on pin 31? It’s supposed to be grounded!

ohh Sorry @ Pin 31 = 0V
and @ Pin 30 =4,9V

OK that’s fine… I strongly suspect a problem with the MCU itself then. You can send it back to me and I’ll check it, or you can directly buy a replacement on the store.

OK! thanks.
I will show your offer my Buddy.

The voltage regulators LM7905 have a Voltage on the metallic plate. Can it be true???
between Pin 1 and 2 = 0,55V
between Pin 1 and 3 = 0,68V
between Pin1 an Metalic Plate = 0,55V
between Ground (Circuit) and metalic Plate = 0,55 - 2,27V Random variable voltage

Yes, the metallic plate of the LM7905 is not grounded! don’t connect it to ground!

If you read +/-5V at the points described in the assembly instructions there’s no need to worry about the regulator.

@ pichenettes

No, on the -5V Points I measure 4,93V or 8,34V random variable voltage.

We doesn’t shipping back the atmega Chip. To much shipping fee’s.
Can we buy 2 new atmega chips with the replacement option?
Are the chips reflashed too??? We do not have avr programmer…

There’s a serious problem with the -5V rail then, thought it might not be related to the ADC lockout… What is the voltage at pin 5 of the LT1054?

I have after soldered the 3 pins from LM7905 the voltage is stable @ -4,93V
@ pin 5 of the LT1054 = -12,13V

The problem it seems to be Fixed.