Voltage test failed - step5 smr4mkii

Hi everybody,
I’m David from Nantes, France.
I have started to build my first SDIY with a Shruthi. I am a beginner in electronics.
And “of course” I am blocked at step 5 for the filter board: I have +5V at red dots but no -5V at green dots.
With the help of a facebook friend (who repairs synths) I have tested continuity at several places.
Everything seems fine but I still have only 0.15V at pin5 of the LT1054.
Capacitors are placed like on the pic. Tantal cap installed too.

I am blocked on this since last week end and I am desperate.
I’ve tried another LT1054 but nothing changes. I’ve tried at 7.5V, 9V (positive at the center).
I don’t know what to do :frowning:

Have a good week end !
David

PS: someone around Nantes ?

Check the polarity of all capacitors near the LT1054.

Hi Olivier,
Already checked several times.
Am I missing something ?
On the pic below I have removed the 7905 to change it (maybe…).
But I don’t have the right voltage out at pin5 of the LT.

Does the LT1054 get super hot?

What is the value of C3?

Is C1 correctly polarized?

1/ no
2/ C3 is labelled “100” so I guess it’s the good one
3/ C1 tantalum (labelled “10”) has the + mark at the bottom on the pic above

Hmmmm… Show the soldering under the LT1054?

He he, my friend said the same “Hmmmm” :wink:
I’ve done many continuity tests.

It was a joy to start my first SDIY project but now after one week blocked on this power supply problem I don’t know what to do to fix it.

What is the voltage on pin 8 of the LT1054? pin 5? On each sides of the diode? Could you post a photo of your PSU?

Hello/bonjour Olivier,
Before the diode : 9,02V
After the diode : 8,35
Pin8: 8,35
Pin5 : 0,15

Hard to tell… ESD killing the LT1054?

Otherwise search for shorts or damaged traces on the PCB?

Beyond this point, there’s not much - first time this problem happens.

Same thing with another LT1054 I have bought :frowning:
Do you think the PSU is ok or do I have to buy another one ? Which one do you advice ?

It’s possible the PSU is a bit limp. While it claims to output 0.1amp more than you need they often lie.

Try getting one that outputs 500mA or more at 7-9v (7v is better as the regulators run cooler).

I don’t think your PSU is a problem. If it was, the problem would show later when powering the entire circuit.

At the moment your circuit consists only of a 7805 and the LT1054, you don’t even need 10mA to make it work.

> Same thing with another LT1054 I have bought :frowning:

If your work environment generates a lot of ESD you might have fried both.