Should be 12 volts.
Check the resistor values of R1, R3 and R5.
If OK remove the transistor or disconnect the collector and measure the gate voltage which should be appx 12volts.
If not then the mosfet is defective.

 

 

I've seen the schematic, you need to verify the actual values of those resistors in the circuit.

 

I've seen the schematic, you need to verify the actual values of those resistors in the circuit.

Resistor values are correct. With the mosfet removed, the gate voltage is 8.4V. did you mean the BJT removed?

 

Doesn't add up.
Remove the 2N3904 transistor and measure again.
Leave the mosfet out for now.

 

Doesn't add up.
Remove the 2N3904 transistor and measure again.
Leave the mosfet out for now.

With BJT removed, the gate voltage is 12 Volts.

 

Reinstall the mosfet and check again.

 

Reinstall the mosfet and check again.

With the MOSFET attached, the gate voltage is 3V. Then it is for sure a bad MOSFET?

 

Appears to be a defective mosfet and transistor.

 

Appears to be a defective mosfet and transistor.

I wonder how that could have happened? Both components were brand new and there is still a failure. Mabye there was a power surge somewhere or spike that blew out these components.

 

I do have a D44VH10 NPN transistor that I could try to work into the circuit to toggle the IN-3 tube if the voltage rating is high enough. It came from my attempt at making my own HV supply for the nixie tubes, turned out it was too inefficient under load.

 

Not sure why but one possible answer is the components are counterfeit.
Where were they purchased?

 

Not sure why but one possible answer is the components are counterfeit.
Where were they purchased?

MOSFET came from Mouser, and BJT came from an amazon BJT kit that has working transistors that I used in projects.

 

That DV44VH10 is rated at 100 volts max.
The schematic shows a 180 volt supply.

 

That DV44VH10 is rated at 100 volts max.
The schematic shows a 180 volt supply.

Got it, just found out. I’ll just order some new MOSFETs and see if that was the fix.

 

That DV44VH10 is rated at 100 volts max.
The schematic shows a 180 volt supply.

I really do appreciate all of the help that y'all have given. It has helped a ton and I am learning a lot about these transistors.

 

That DV44VH10 is rated at 100 volts max.
The schematic shows a 180 volt supply.

Driving a Nixie tube does not require a device rated as high as the supply, because there is a breakover voltage for the tube. You can drive Nixie tubes with TI's TPIC6B595.

 

Driving a Nixie tube does not require a device rated as high as the supply, because there is a breakover voltage for the tube. You can drive Nixie tubes with TI's TPIC6B595.

Driving a Nixie tube does not require a device rated as high as the supply, because there is a breakover voltage for the tube. You can drive Nixie tubes with TI's TPIC6B595.

That can work too, I ended up using 4 of KD155 Nixie tube BDC and 2 74HC595 to drive the 4 IN-14.

this switch was meant for an IN-3 colon as it’s only only thing thats left to be controlled.

 

That can work too, I ended up using 4 of KD155 Nixie tube BDC and 2 74HC595 to drive the 4 IN-14.

this switch was meant for an IN-3 colon as it’s only only thing thats left to be controlled.

Your processor output will have enough current to drive a nixie tube. Have you considered driving it common base? Use a high voltage small signal transistor. Base to 5V or 3.3V. Current limiting resistor between emitter and gate output.

 

Your processor output will have enough current to drive a nixie tube. Have you considered driving it common base? Use a high voltage small signal transistor. Base to 5V or 3.3V. Current limiting resistor between emitter and gate output.

I’ve never considered that. I just assumed that a MOSFET would be the best option for switching since there was high voltage present. I did put in an order for more MOSFETS so I’ll likely keep with that, especially since the PCB I made for the clock uses a circuit like the one listed.