J1power supply no power when testing

Sorry very newbie question, but does this part get soldered on too? The holes are massive and it will take a lot of solder?

Yes, this part is soldered. Heat the leg of the DC connector, heat the “ring” on the PCB a bit, and let molten solder flow into the hole. It’ll fill the ring, not fall through it…

Also, start by soldering the middle leg. You can reheat the join and move the part until it is correctly aligned. Then solder the other legs.

yes every component has to be soldered in order to make a secure connection. just hold it in place and fix one of the lugs and adjust it while reheating until it’s ok. make sure you keep touch to both the board and the comnponent lug to make a firm connection.
then solder the other pins.

Thank you. Unfortunately I’m not getting any readings on the. Multimeter … I must have gone wrong some where

I seem to have the capacitor orientation correct. Could it be my power supply?

Hi Nevadine!

That pic is slightly too low resolution to read the power supply polarity - are you sure it’s +ve on the tip?

It’s also slightly underpowered at 9-volt 200mA (300mA capability is recommended), but as long as still get at least +7 volts at the input of your Shruthi you should be fine.


Hello sorry about the pic. How do you tell if the tip is positive? Sorry for the newb question

It’s plus . Minus so I guess it’s negative? Balls.

there is a little graphic like this:

  • —( o— + (= center pin positive/ this is what you want for shruthi)


  • —( o— - (= center pin negative)

edit: it is on the lower right corner of the psu in your pic

if you got the wrong one, the protection diode should have saved the other components from damage

if you have a multimeter connect the black cable to the ring and hold the red one to the tip. if you have positive readings it’s ok, if the voltage is negative you’ll have to get something else

Well that’s good news at least. I just checked my other ac adapters ( for my mopho and blofeld ) they are all negative polarity. Looks like I might have trouble finding one with positive polarity.

The Shruthi-1 uses the same power supply polarity as most keyboards / modules - the polarity is the same as on the Mopho…

Please post a clear photo of your PSU, on your pic I can’t clearly see the polarity logo.

If it is wrong, you don’t need a new one. Just cut the wire and resolder them the “correct” way :wink:

The psu on the left is from my mopho, it’s also labeled as negative polarity, the one on the right is the 9v I bought for the shruthi .

Sorry for straddling forums btw, I can’t upload pics on the iPad from here.

right one is center pin negative, the left one is center pin possitive

Ok so it appears to love the mopho psu, despite the large voltage. Readings came out fine all +5s and -4.95s in the correct places. Guess I will have to use the mopho supply for the time being.

Also just want to add that the support here and in the electronic music community in general (regarding the shruthi) is fantastic.

Thanks to everyone for all their time. I look forward to becoming a bit more knowledgeable and contributing myself.

Sorry one final question so that I don’t need to start a new thread the 7805 and 7905 things protrude quite a bit from the bottom of the board. Should I cut them or leave them?

The PSU you were originally trying has a center tip negative.

Warning! Don’t use the Mopho PSU. It seems to output 15V, which is

  • above the max voltage rating for the LT1054, so there’s a risk you’ll blow the LT1054 up.
  • well above the voltage regulator output of +5V. This is not a problem per se, but the voltage regulators will be awfully hot when the rest of the synth will be soldered (at the moment the circuit is not drawing much current so the regulators won’t heat). Linear voltage regulators convert any excess power given by the power supply (in your case 15V - 5V times the consumed current) into heat. The Shruthi draws ~ 150mA (0.15 A) on the positive rail. The regulator will thus dissipate 0.15 x 10 = 1.5W into heat. From the datasheet of the regulator we find that this correspond to an elevation of temperature of 93°, so your 7805 will be scorchio at 110° or so…)

Please try to find a center-tip positive supply ( + —o ) ----- - like on the mopho), with a 9V or 7.5V output, capable of delivering at least 300mA (to be on the safe side).

Don’t cut, they are supposed to protrude for better cooling.