Big Theremax Problem

Posted: 8/22/2012 11:15:55 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

From now on, my first question I ask anyone wanting help, will be: "Did you buy a kit, or did you rip it off from some on-line site and/or make the board yourself" ?

And, once again, I must remind myself - dont expect people to tell the truth, the whole truth, and nothing but the truth - All the advice about checking for solder splashes and debris under the IC socket etc..... These pale into insignificance compared to the problems one can get when one etches your own board.. even if you dont put the bloody components on the wrong side.

But, Boerker was right about one thing on which I was completely wrong..

it was a BIG Theremax problem!

Fred.

Posted: 8/23/2012 1:28:13 PM
boerker

Joined: 8/15/2012

sometimes it´s better to get a bit distance to something you working at. i realized that all other components are in the right way. no need to switch. the mirror action only had influence on the IC....thats why all other voltages are what they should be.

...the opamp doesn´t work. i probably destroyed it during the seeking-time. i´ll buy a new one. so i couldn´t test the thermax yet...

far be it for me not telling the truth!!! in my first post i wrote, that i build my own theremax. yes that wasn´t worded clearly...sorry for that. 

never ever thought about the mirror-problem when i wrote my first post ...so i didn´t saw a difference between the paia board and my "homemade"board....stupid me :-D

boerker

Posted: 8/23/2012 2:44:19 PM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

its ok, Boerker! Some of us make bigger, inexcusable mistakes at times (like marrying a Ferengi!) - At least your mistake is repairable without too much pain - even if you had to make a new board and start again!

Fred. 

Posted: 8/24/2012 12:36:25 AM
FredM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................

Joined: 12/7/2007

" i realized that all other components are in the right way. no need to switch. the mirror action only had influence on the IC" - Boerker

One other set of components you need to check are the IF transformers - particularly the tapped winding (the 3 pins in a row) as mirroring these is likely to disrupt the operation of the oscillators.

Without looking at the layout I cannot easily visualise mirror image and connect this to the schematic, but I would think that any component with more than 2 pins needs to needs to be looked at carefully. The IFT's for example have a tapping which is not in the centre of the coil - one side is lower inductance (fewer turns) than the other - get these muddled up and if it works, it certainly wont work as it should!

Fred.

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