[SOLVED] Shruthi XT screen flips between "let's jam!" and "lfo 1 shape"


I’ve just finished a build of a Shruthi XT kit.

When I turn it on the screen will flicker really fast between “Lets jam” and “LFO 1 shape” like those buttons are constantly being pressed.

All the rotaries override and I can see them change value on the screen as for all the buttons for oscillator/mixer section. But I can’t tell if the menu buttons are working and the lfo shape buttons seem not to be working.

Any ideas what I should be taking a look at.


Jón Hallur

Try booting the synth with the encoder pressed until the screen shows:

shruthi xt
(full control)

1 Like

Tried that.

Shruthi mode flickers through all the filter settings
XT classic flicks through a lot of settings (can pause the flickering by pressing the encoder)

shruthi xt full control flickers the least.

Keep it in “XT full control” mode.

Check the soldering of all 4051s.

Does it still flicker if all pots are set to minimum value?

If it stops, can you make it flicker back by turning 2 pots in middle position? If so, do you see a pattern in the pairs of pots that make it happen?

Went over all the solderings of the 4051s, the resistor networks and the 74HC165s and now I have funtionality on the menu buttons in the middle section. I can also now change the shape of “lfo 1” with the encoder, but if I change it to “tri” it reverts back to “sqr”. Previously I couldn’t change the shape.

All rotaries and buttons work except those connected to IC3, (S3, S4, S9, S10 & S11) but the behaviour still persists even if I remove IC3.

I did not notice any changes with the pots sets to minimum, or when I change them. The synth emits a sequence when I turn it on, like it is getting a signal from the jam button and the lfo 1 shape button, as it it flips between those two pages constantly.

Have you tried swapping IC3 and another 165 (for example IC9). Is the polarity of the resistor network RN2 ok?

Swapping does not change anything. And as far as I can see, the dot on RN2 as where the 1 is on the board.

Without pressing any button, what are the voltages on each pin of RN2?

On second thought, one of the 165 is behaving badly. If I put it in IC2 the screen is blank. If I put it in IC8 the leds will go crazy blinky. I’ll try to get a replacement and report back. Thanks for all the help.

Stupid user error, IC8 isn’t a 165.

I had put the 595 in a 165 socket, and that was causing all the problems. All good now.

I just felt its time to resurrect this one :wink:

He at least socketed the chips.

Well, at least we now the symptoms of swapping a 595 for 165 :stuck_out_tongue: