Transistor Tester crash

[manstoblame]

Howdy all at BdCaps purchased one of these transistor capacitor testers from you know where. Had it a few months and now the thing wont power on, the power on led just blinks and display don't light up. I've checked the voltage on the 9012/9014 NPN BJT Transistors and they measure within specs from pin 1 emitter and pin 2 the base and all the way to the pins of the digital display. Has anyone had

[redwire]

Re: Transistor Tester crash

Check if the HT7550 LDO is making 5V for the MCU and display. The 9012 PNP transistor switches on power to start the 5V regulator, and then the MCU is supposed to run and keep the 9014 /9012 on.

[stj]

Re: Transistor Tester crash

that's an ancient design, you only had it a few months??
they got outdated several years ago!

[manstoblame]

Re: Transistor Tester crash

that's an ancient design, you only had it a few months??
they got outdated several years ago!

well that's probably why i got it so cheap and its a piece of it!

[manstoblame]

Re: Transistor Tester crash

Check if the HT7550 LDO is making 5V for the MCU and display. The 9012 PNP transistor switches on power to start the 5V regulator, and then the MCU is supposed to run and keep the 9014 /9012 on.

nope the 7550 only has 2.50 volts from Gnd to Vin and 2.98 from Gnd to V out
now to find a replacement or equivalent thanks bro, hope this fixes it!

[stj]

Re: Transistor Tester crash

that's not logical - how do you get more output than input?

[R_J]

Re: Transistor Tester crash

There is some info on this device here https://goughlui.com/2016/10/27/proj...or-tester-kit/
along with a hand drawn schematic if it helps.

[manstoblame]

Re: Transistor Tester crash

that's not logical - how do you get more output than input?

True I got numbers crossed just know its not the 5 v needed. Would you know of a substitute I could use in place of the 7550

[manstoblame]

Re: Transistor Tester crash

There is some info on this device here https://goughlui.com/2016/10/27/proj...or-tester-kit/
along with a hand drawn schematic if it helps.

Hey Thanks RJ, couldn't find this info on my own I love BadCaps

[redwire]

Re: Transistor Tester crash

Would you know of a substitute I could use in place of the 7550

I use LP2950CZ-5.0 or ACZ. But different pinout, have to bend output pin around.

[R_J]

Re: Transistor Tester crash

What are the voltages on Q9012, Is it getting hot? It could be bad and not supplying the 9 volts to the regulator. Is the 7550 regulator getting hot?

[stj]

Re: Transistor Tester crash

i would remove the regulator and see if you get 9v to the input pad.