Jaycar Mk11 Build questions

Posted: 1/11/2017 11:58:08 AM
Mercom

From: Sydney, New South Wales

Joined: 1/11/2017

Hello Theremin World and thank you for your hard work love and support.

My young nephew exhibited and interest in electronics and I always wanted a theremin so I bought him a soldering iron and a Jaycar theremin DIY kit not really knowing what I was getting either of us into. 

Two months into the project he has done a pretty good job albeit dumping an assembled though not working theremin in my lap. I have read many of your posts and realize that with out the tools and know how that we are flying blind though look forward to any light that the collective community can shed on our project. 

I found the following,

- All polarised parts are fitted correctly.

- A short on one of the chips, (I cant remember which one or what terminals but could this blow the chip)

- He has been adjusting the transistors with a magnetic metal screw driver and they seem striped.

- There is only a couple of millivolts not 2.5 volts between TP GND and TP2.

- The power pack that we purchased from Jaycar is 1 amp and unregulated Part No. MP3026. please follow link for more info

https://www.jaycar.com.au/12vac-1a-plugpack/p/MP3026 

Thanks for your time.

Shane and Ben

 

 

 

 

Posted: 1/11/2017 7:42:34 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

Difficult to tell at distance if the solder short has blown the IC... Also difficult to tell at distance if the use of a magnetic screwdriver has damaged the variable inductors, basically, there are special ceramic or plastic tools for that.

You should perhaps follow my exhaustive and detailed diagnose/tuning instructions in the first post of this thread to locate potential problems. BTW, to prevent the typical beginner's fault, don't try to tune a theremin on your workbench, there is too much conductive material on and in it, thus the antennas and the circuit can't react in a normal way. Best is to set up the theremin on a microphone stand on the floor with a clear space of a radius of 1.5m (5ft) around, and at a height about the floor of at least 70cm (2 1/3ft). Then use portable versions of the digital multimeter, frequency counter, and oscilloscope. That's how I diagnose and fix successfully theremins.

Posted: 1/19/2017 9:18:09 PM
Mercom

From: Sydney, New South Wales

Joined: 1/11/2017

Hi Thierry,

 

Thank you for your timely turnaround. Yes I came across your thread.

I do not have access to a scope though I do have a good multi meter with Hz function. Initially I was hoping that someone could get back to me on the Power pack (1 amp and unregulated) and proprietary test issues (between TP GND and TP2) questions as perhaps a member has had a similar problem. 

I've called a few electronics repairers in my area (Sydney Aust) and they dont want to know me.

Thanks again.

Shane and Ben

  

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