Sammish Sid changes values by itself

MIDIbox SID
1

Hi everyone!

I’m a newbie to this forum and in need of some assistance.

Just finished my first build. A SammishSid!

Everything is up and running and it plays beautiful!

When I use midi all is ok but when I try to change patch or parameters by hand it goes crazy.

Actually when my hand comes near the lower right side of the box it goes crazy and starts changing parameters by itself and random led’s flashing.

Has anyone stumbled across anything similar to this?

I suspect that there’s something going on with the grounding of the box but any clues where to look?

(When I build it I had to replace the two 74HC165 ic’s on the controller board).

Kindest Regards,

Anders

2

Sounds like a similar problem that I had. You should check that the inline resistor networks are soldered in the correct orientation, and that the 74HC165’s are in the right way around.

Get yourself over to the sammichSID wiki page and download the test app, that will give you some clues as to what’s going on.

3

Thank you Alex.

I’ll have a second look at the soldering and download the program you mention.

Cheers,

Anders

4

If it’s doing things just when your hand is near, sounds like some pins on the 74HC165 are floating (not connected) so your hand is acting like an antenna, channeling interference into that pin. It’s a bit like the buzz you hear when touching an audio plug that’s plugged into an amp.

Check there’s no shorts between encoder/switch pins and the heatsink… check all the solder joints there, resistor network orientation, parts in the right place, etc.

5

Thank you again Alex and thank you Wilba.

I could not find anything wrong with orientation or solder joints.

But after replacing the 4 pieces of 6-pin resistor networks all works as is should. :frantics:

Again thank you for pointing me in the right direction.

All the best,

Anders

6

Hi 

Sorry im a newbie her. Kinda has the same problem. Where is the 4 pieces of 6-pin resistor networks ?

thank you

arne

7

Hi

Thank you!! Its alive and kicking!

It was all about the 10k pull-up resistors.

arne