All LED's Lit

All the LED’s are lit on my Shruthi and the display is blank, does this point to any particular problem?

I think it’s time for photo’s of your boards both sides…

To recap on my synth>>>>>

It was working, but I had a problem tunning the filter, this was proabably due to the fact I had the 5k and 20k trimmers in the wrong places i,e. the 5k display trimmer in place where the 20k filter should have been! doh! I bought two new parts and soldered them to the board, ever since I have all LED’s lit up and no display.

I am on my iPad now and need to switch to my Mac to make the photos of the board smaller, so I can upload them, BRB!

Here we go>>>>>

On the control board I see several joints with far to little solder on them. Best is you redo all of them. I hope the joints in the MCU are OK.

Thanks shiftr, I am concerned I may have to resolder the MCU, how on earth would I desolder the display? :confused:

Echoing @shiftr, quite a few of your solder joints look cold, although it’s hard to tell for sure from the photos. It might be worth heating all of the solder joints up a bit and applying a bit more solder to all of them, on both boards. I haven’t built a Shruthi in awhile but, for those leads that stick out of the 2-pole/4-pole area, shouldn’t two of those be jumpered or are you using a switch?

Usually desoldering the display destroys it. You could try using a desoldering pump or desoldering braid to remove as much solder as possible and that might let you get the thing off gradually. Otherwise, I’ve used a Dremel and cutoff disk, and then removed each lead one at a time. Not fun. The display is relatively inexpensive, but getting another one means waiting.

If you manage to get it off, and you resolder some of the connections, it is possible to test and even use the Shruthi without the display, using only the LEDs.

Thanks Piscione, I am going to try and desolder the LCD tomorrow then check every solder point.

Don’t desolder de LCD(yet)
First just resolder all the the other joint’s you can reach. Especially the joints on the 165 look bad and can cause problems because the MCU might think a button is pressed on startup
Maybe you can already solve the problem this way and you won’t have to desolder the LCD (which is some pretty advanced desoldering).

All joints resoldered, all LED’s still lit!

I think I may have to remove the LCD to get to the other solder points shiftr :confused:

To add, power is also intermitent, sometimes the LED’s light up, other times they don’t.

I just don’t get it, one minute it was all working fine, I replace two adjustable resistor things and now the unit has a ton of faults!

Ooh not good Adam I feel for you :frowning:

Ok, two questions.

Are you sure that all of the headers that connect the boards are connected properly? Basically, are they all making contact.

Is the Shruthi back in its case?
If it isn’t, make sure it isn’t resting on a conductive surface that may cause shorts between the bare solder joints. Place it on the bottom part of the case to insure that does not happen.

Thanks analoguekid, audiohoarder, I am fairly sure they are okay, it was working a little while ago, it just stopped working after I replaced the potentiometers. The synth is out of its case and on the operating table now :confused:

Do you have insulation tape under your LCD? I had some issues as parts of my LCD were conductive. You could try to lift the LCD a little bit.

A typical fault is that the 595 and 165 have been swapped by accident … the labels are hard to see on the pictures, so perhaps check ?

And another fault may me to accidently fry the 165 by shorting it to the regulators on the filterboard. If you have a spare 165 you can change it.

Thanks for all your comments and suggestions :slight_smile:

I am at a loss as to what is wrong with this synth, so I am paying a professional electronics engineer to fix it for me.

Yikes! Adam, where are you located?

I live in Plymouth, United Kingdom. Actually I just spoke to the electrical engineer and he said he ‘might’ be able to help, but can’t guarantee he will get it working. ‘sigh’

I tested the filter board and it is getting all the right voltages in the right places, so it seems to be an issue with the control board, but I am not really sure as I have know idea what I am doing when it comes to ellectronics!

The Shruthi synth is beautifully designed and I am confident there is nothing wrong per se with the unit, its faults are purely of my own making :confused: