[Solved] Shruthi (kit mkII) finished but no sound or very very low

Hello again,

I’ve finished my shruthi, it does boot, everything’s seem to work but no sound or very very low level…

I did the audio test (with the jack) every points do sounds even point 8 but not the point 7…
Should this mean that the problem is on the VCA?
I did put the optional C1 Tantalum (in good the good way)
And I did put the left 1 M resistor as well…

Where should I look at the resistor on the point 7?

I don.t get how to test a connection, or shorts with the multimeter …In ohm, Imshould have a bip noise test but don’t get it…

Also I used to have 5 v and -5 V at the power test, but know I did test it again and I stil have green -5V but red is at 7.78V

Any ideas?

First of all, remove all socketed ICs except the LT1054 and do not connect the digital board. If you have a problem with the power supply you are going to damage some chips on the control board which require 5V.

Check the voltages on the 3 pads of the 7805. Maybe there’s a weak solder joint here explaining while you don’t get +5V on the red points. Don’t continue unless you solve this.

Ok but I need to plug it to check the voltages on the pads right?
But after putting the IC out … Is that it?

Your power supply is not correctly working. You need to remove all ICs to minimize the risk of damaging one of them - at the exception of the LT1054 which is part of the power supply itself.

And yes, you need the unit to be powered for the voltage check.

Ok, IC are removed and now still green -5v but red is now 12V…

So on the 7805 pads the voltage are:
1/ 11.5 v (it moves a bit)
2/ 11.6 v (moves a bit)
3/ 12.8 v (fixed)

I saw a spark on the ground (but it’s less easy to access now so I could have touched 2 pins)

Looks like the (-) pin of the 7805 is not soldered correctly.

Sorry I understood what pads means
Not the component legs but the conductive areas on the boards…right?

So on the pads the one of the middle is 0 V is that the problem, I should resolve that middle leg so?

I meant solve it again

The pad and the part leg should be at the same voltage if the solder joint is good.

Ok, it’s weird because I resolded it and now red and green points are all ok (5v and -5v) but still not the same voltage on the 3 pads of the 7805…
I will do it again on the 3 pads so…

Ok I must be too tired then, it did change the red and green points problem back to normal, but 3 times I tried and I have always 5 V, 0V, 12.8V on the 3 pads of the 7805…Maybe after 24h on this without sleeping, I don’t see clear enough…:wink:
Nothing else could influence those voltages, it’s obviously here?

Ok, so the voltages are good. So you can put all the other ICs back and resume to troubleshooting… Are you sure the pole selection jumper is inserted?

Yes for jumper I tried position 4 and 2 and nothing…
But should I continue even if the 3 pads are not the same?
Is there an other place directly linked to him that could cause 0v in the middle pad?

I did try with all IC, already when red and green points went back to normal, and I did have more level, still low, but when I tried to do the audio test (with the jack), I don.t ear anything now…
I will put back the IC again so and try again…(sorry I take your time)…

I have to mention something thought,

I have since the beginning, IC sockets 2 and 6 backward,(wasn’t mentioned in the first procedure to care about that, I realised This in the 2nd board procedure)
but I read someone who had the same thing 2 sockets backward and you say it was ok, just you have to remember not to follow what show the socket)
But IC are on the way…

it’s ok with sockets oriented backwards, as long as you put the ICs in the right direction.
Are you sure you insert them in the right direction according to the notch, and not the dot?

Yes notch for all except for IC 1 and 2 which I put the dot towards (labeled IC on the board)
Is this ok?

What changed since I have green and red points back to -5v / 5v , is that the sound check with the jack doesn’t work anymore… And If I put back filter board and midi in, I can hear a bit more the sound only if I plug halfway the jack, which was not the case before…

Is there some specific point I could check?
How can Check with my multimeter if there are shorts?