Hi, I'm trying to build this TENS circuit here:
http://chemelec.com/Projects/Tens/Tens-3.png

It calls for a 2SD401A PNP transistor.

Can I just replace it with a generic, high voltage NPN transistor? I believe the TENS circuit simply switches high voltage (80-100v) at around 300hz. I think the speed is fine for modern transistors, so all I need to do is find one that can handle the voltage?

 

And current. I agree that if you find something with similar voltage and current ratings it should be fine. Note you need a PNP, not NPN.

FWIW, I made my TENS unit by switching low voltage and then stepping it up with a transformer taken from an old wall wart.

 

Your number jives with an EGC 375, an npn Si. vertical deflection, freq. of 8 Mhz BVcbo 200v in a TO220 package...

 

Hi, I'm trying to build this TENS circuit here:
http://chemelec.com/Projects/Tens/Tens-3.png

It calls for a 2SD401A PNP transistor.

Can I just replace it with a generic, high voltage NPN transistor? I believe the TENS circuit simply switches high voltage (80-100v) at around 300hz. I think the speed is fine for modern transistors, so all I need to do is find one that can handle the voltage?

My databook has that listed as NPN; 2A 200V 20W 10MHz. It lists comparable types; BD239F, 2SC2660, 2SD610, 2SD1138.

 

Hi, I'm trying to build this TENS circuit here:
http://chemelec.com/Projects/Tens/Tens-3.png

It calls for a 2SD401A PNP transistor.

Can I just replace it with a generic, high voltage NPN transistor? I believe the TENS circuit simply switches high voltage (80-100v) at around 300hz. I think the speed is fine for modern transistors, so all I need to do is find one that can handle the voltage?

I was just thinking you might do better with the MOSFET from the primary side of a small appliance SMPSU, when I looked at the schematic you posted, and noticed the intensity pot & resistor looks a bit unlikely - you might be better off varying the pulse width. I did a quick search for "CMOS PWM">

 

The thread is little old though-- thread starter is showing a circuit from chemelec.com and the site author is Gary Lecomte. The transistor is 2SD401A (2A, 150V and 25W) EXACTLY because today I got some parts from him and I got 7 pieces of 2SD401A NPN. They are NPN, I tested, however all the information I wrote here, has been already notified in the schematic of the TENS there. Any high voltage transistor like 13003 (available inside CFL bulbs or cell phone wallwart supply) could do the job.

 

Build the modern version using 555 timers and a mosfet...


http://chemelec.com/Projects/Tens/Tens-2a.png