Electronics > Repair

Help with ThaiKit Curve Tracer NOW W/ Calibrated Instrument OpAmp

(1/11) > >>

I changed the to account for the improvements.  See  end of the thread.

I assembled this kit and made a nice enclosure, etc.  I have twice blown up signal transistors.  I feel like a watchmaking student who keeps testing his watch hoping for an improved result with no changes.  Neophyte.  But I like the puzzle to solve.

I have the schematic and I also looked up the Elektor article for the waveform information.

I verified the 2 ICs are ok and the same with the two transistors via substitution.  Both chips give out clean crisp signals.

I am leaving both jumpers open; small signal, NPN.  Both relays click when jumpers are added.  Checked all diodes out of ckt.

So I am doing something incredibly stupid.

Below are my waveforms at the collector and base inputs.  Emitter is zero.  I looked for the step signal from pin 9 of the 4024 chip but it is a simple square wave.  No transistor being tested.  I get the sawtooth at the scope horizontal output but nothing at the horizontal where the elektor article sez I should get a step (again, I have no transistor being tested/smoked).

I get that the emitter feeds the last opamp before the power transistors.

Can someone who has built this confirm my signals?

Conditions are :

No transistor
Small Signal


Looks close to what I get with same settings. Sorry for the scope photo. Hantek USB doesn't work (piece of junk).  Pretty sure it's the same kit as yours. Added the signal from pin 9  of the 4024.

Which small signal transistor are you testing. If I have one I'll see if I can blow it up.

Now you have me wondering what's going on. Large transistors test fine but as you, small signal transistors quickly get hot and fail. I don't use many small signal transistor in special applications. Mostly power applications. So I didn't notice the problem until now.
So given the evidence, your probably not doing anything wrong and there is an issue with the kit.

Little update. The tracer works on most of my transistors. It won't test Darlingtons. BC517 Darlinton burns up and TIP142 (also a Darlinton) just shows a dot in the middle of oscilloscope and gets hot. Bost tested fine on a BSIDE ESR02 Pro.

Thank you and I'll be damned.  I spent 3 DAYS on this following all the signals and marking the board with w/ the paths. |O

I just found this youtube.  He does an excellent job of explaining the design and its limitations.  He made me think I need to look at my 1 ohm resistor.


[0] Message Index

[#] Next page

There was an error while thanking
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod