Voltage test fail (step 5)

Hi all!

I’m far from the first person to suffer from this, but it appears most threads end before an answer is reached, not one that I can understand anyway!
So I’ve started building the Shruthi the other day… the start wasn’t the best as I put one of the 100n caps in the 10u slot. They looked the same so I assumed they are the same. This will serve as an insight to my electronics knowledge I guess. (Also the reason why one of the 100n caps is blue - had to get a replacement because I broke the original lol)
Having spent an age and a half fixing this mistake, I got excited to reach the voltage test. Expected everything to go smoothly, given that after the initial rocky start I made sure of values and polarity of each component. Well, nah.
No voltage on the green test points. The red ones are perfectly fine, 5.01V according to the multimeter.
I’ve gone through a few similar topics and wrote down voltages at the critical points of the power supply… here they be:

PSU Socket - 9.13V

After diode - 8.45V

1054 Pin 1 - 0.77V
Pin 3 - 0V
Pin 5 - 0.13/0.14V (oscillates)

7905 Pin 1 - 0V
Pin 2 - 0.13/0.14V
Pin 3 - 0V

7805 Pin 1 - 5.01V
Pin 2 - 0V
Pin 3 - 8.45V

I’ll add that the power supply I bought is a decent one from Maplin, 9V 600mamps regulated. Someone mentioned that using a different size end bit helped it get better contact (?) and that made it work, but not in my case.
I hope it’s something stupid that I’ve missed/bad solder joint or something. If the 1054 is bust I may have to wait till Moday to get a new one… I was hoping to be making noises on the Shruthi tomorrow! Such is life.

So I’ve also attached pictures of the top & bottom of the board. Please excuse the occasional blobbiness/butchering! I’ve built working things before, but often they aint all that pretty.

Any help is very appreciated, thanks!

I would recommend reflowing some of those wonky joints. My eyes aren’t the best but on the bottom of the board the joint second from the far right looks like a cold joint. A general rule of thumb for me is that if I would describe any of my joints as blobby or butchered, I would reflow them. And of course double and triple checking components can never hurt :stuck_out_tongue:

Ha! It appears you were right, weNiverse. I went over the dodgy looking joints (i’ve already done it once but obviously not well enough and she’s alive) Absolutely overjoyed.
Well, hopefully no more idiotic mistakes followed by mild panic attacks from me.
Thanks again, and sorry for littering the forum :slight_smile:

i have the exact same problem, i went over the joints and still nothing. if the 1054 is still producing some voltage does that mean its alive and just not soldered right?

also pherkad, what joints did you re-solder?

im not too good at analyzing solder joints, but are the wonky joints in question the 104 caps on the right side of the board?

Hi musicalsoles,
I started off with the power socket and slowly re-did them all, taking off old solder and applying new. I’m pretty sure it was one of the socket legs that wasn’t quite done properly, but I can’t 100% confirm that.

In other news, it seems my joy was premature. I have virtually finished putting the shruthi together (I’m @ step 11 controller board now) and it just isn’t working. The LED’s (all of them but LED5) flash in a sort-of-regular-but-not-really sort of way. The buttons don’t respond, neither do the pots. I tried playing it through midi with audio into the interface but I only get really transient sounds in time with the LED’s flashing, nothing else. I’ve checked the power supply rail on the side, and while the connector thing between the boards is 5v, the solder point on top of it only gives between 0.1 and 0.9v, oscillating constantly. I have also checked and re-did the joints on the IC sockets, resistors etc. to no avail.
Have I broken something?

You have inserted both small IC’s the wrong way around…

Also both of them are swapped (6N137 in place of the eeprom). If MIDI doesn’t work or other weird things happen when you put them back in the right orientation, it might be that you have damaged them.

Thanks shiftr and pichenettes for pointing that out, I’m an idiot. Inhaling solder fumes till a late hour is not the one.
Right so I’ve put it together now, and it’s all good! Fatty noises on the go.

Again thanks very much for your help guys, I’ll be sure to pay more attention next time. Off to make the walls shake :smiley: