Nothing happening (kit shruthi 1 + SMR 4 mkII) (FIXED)


i ve build the whole kit except the LCD.
when i tested the power on the filter board i had theses results:


i decided to carried on and nom the led are not lighting.
I’ve check all the solders and electronics components are in the right place.

it is the first time i’m building something in electronic
i don’t know anything about electricity…


What is the voltage on the +5V pin of the control board?

when i check the red and green point on the filter board

these results are

  • 0,60 on the red point
    -4,31 on the green point

is that right when the filter board in entirely build ?

hello pichenettes

the voltage on the +5V pin of the control board in -0,61

i’m using a 7,5 v power supply center pin positive …

No, these should be +5V and -5V.

Do these voltage change when you plug in the filter board? If so, there are two options: either your power supply is too weak (try setting it to 9V and check that it can source at least 300mA) ; or there is a short on the control board.

What are the voltages on each pin of the regulator?

See this

the power supply I’m using Is 500 mA.

on the 9v I’ve got -0,62 and -5,36
on the 12v i’vz got -0,64 and -7,11

sorry, but do you mean the Voltage regulators on IC 9 and IC 5 ?

If you are reading constantly negative voltages on the Stacking connector you don’t point the black probe to GND.
See here for a tutorial on how to make correct measurements - you stated its your first build so maybe its your first time you try to use a Multimeter. So far your Measurments are either mysterious or (because you didn’t measure right) meaningless.

BTW the voltage regulators are IC 6 and IC 2 and both have 3 Pins. Make shure you didn’t swap them as these are 2 different types in the same package, labeled 7805 and 7905. IC 5 and 9 are LM13700 double Transconductance Amplifiers, the have nothing to do with the conditioning of the Power.

on the IC9 regulators i’v got

face to “o” -0,63
face to “-” 0
face to “1” 15,19

on the IC5 regulators i’v got

face to “o” -7,11
face to “1” -14,17
face to “+” 0

It looks like the 7805 is fried. You should read +5V on the “O” pin. Another thing worth trying: with the board not powered, is there any continuity between +5V and GND?

i’ve exchange the regulators i’v put the 7805 on IC 5
and 7905 on IC 9…

i’ll change and see

If your Wallwart supplies 7,5V (or 9V) and you are measuring ± 15 Volts (thats a potential of 30V) you have a Perpetuum Mobile…

@fcd72, sometimes I think the marking on some wallwarts, like “9V 300mA” means “has the internal redresser and cap sufficiently large so that it can power a 7809 under a load of 300mA” ; ie, “output voltage has a huge AC component and doesn’t drop below 11V as long as less than 300mA is drawn”. Silly but that’s the only way I could make sense on the labelling of some samples I have…

15V is not unusual for a 9V unit. The -15V comes from the LT1054.

shouldn’t be a fully stuffed SMR-4 Board sufficient load for even a tinyweenyshitty WallWart?

i’ve got 2 power supply…
a universel

a 9v but with negative center pin

First one should do with either 7,5V or 9V Settings

YAOUHHHHHHHHHHHH ! It’s working… i’m f…king boy who mistook 7905 and 7805… but that’s the way we learn.


Glad it works now…have fun with it and welcome to the Shruthiversum™