Post your Silicon Chip/Jaycar kit questions here!

Thanks Mark.. using the voltmeter the right way round certainly helps.

With a slightly old 9V battery I read +8.8V and get +5.6V on IC2 pin 8.

Back with my plug-in transformer I get +5.5V on IC2 pin 8.

I would not have thought +0.5V would be enough to stop it working.. but will continue tuning with the battery for now.

Thanks again.

Hi guys.. me again.. and getting close (maybe).

Using the 9V battery I get a range of +3.79V to +3.81V on IC2 pin 1.

Way short of the specified +4.3V (well Im assuming its way short - I find it hard to know at this stage).

One thing I did was put in 3 LINKs as they were marked on the circuit board, yet there is no link printed on the instructions between IC2 and IC3 - do you think maybe this is causing my drop in voltage?

Thanks yet again.

Hello again, sounds like you have good voltage going on. Please check your soldering around VR2 and the 2.2K resistor right by it. Is the circuit complete?

Regards

MarkT

I could really use some help here! Are there any other places to take readings to help track down problems? I've tried two different power supplies and my voltage readings are consistent:
T2 case to IC2 pin 8: 2.82V. T2 case to IC3 pin 6: 2.86V I'd really like to get this thing working but I'm at a loss. Anyone have advice?

Thanks in advance,
Mel

Hello Mel

What have you got coming out of the regulator?

As you look at it, there are three legs, one on the left is input, middle one is GND and the one on the right is output, take measurements on both outside legs.

Regards

Mark

MarkT,

Input to Output is 3.73 V.
Input to Ground is 8.87 V.
Ground to Output is -5.06 V.

Does that sound right?

Mel

Mel

They seem OK, but:
Ground to Output is -5.06 V.

Are the leads to your meter the right way round? You shouldn't be getting a negative voltage here.

Have you adjusted VR2 as per the instructions?

Regards

Mark

MarkT,

I measured -5.06V with the positive voltmeter terminal on the ground and the negative on the output, so that might be the cause of the negative reading.

I checked the VR2 adjustment again, and I'm nowhere near correct. From one end of the sweep of VR2 to the other, I read only 0.05 to 0.01 V. My readings on all legs of IC2 are:

1: 0.01
2: 0.01
3: 0.01
4: 0.01
5: 5.69
6: 2.84
7: 2.84
8: 2.83

In a properly working theremin, what should these values be?

Thanks again,
Mel

Hi Mel

OK, yes having the leads the wrong way round will be why you are getting a negative voltage reading, but thats OK in this instance.

You readings around IC2 are way off, so I suspect something else is going on here, where in world are you?

Regards

Mark

MarkT,

I'm in California. If you have suggestions for other points to test voltage on the board that will help me track down the problem I would really appreciate it. Or am I simply dead in the water here? Is this beyond repair?

Thanks,
Mel