Forum: µC & Digital Electronics AVR Mega328 does not exit the test mode

Author: Dimitris K. (Company: Advanced user) (karatzdi)
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I have a Transistor Tester based on the originals circuit diagrams and 
code under the mikrokontroller.net site.

It worked well for so many hours. I had measured many unsorted 
capacitors transistor and coils last weekend.

While was working it started moving slowly between menu's, as an example 
I wanted to move from Capacitor menu to coil menu and then to 
transistor. Moving out and into the menus was a bit slower than before.

So I decided to reboot the Tester. On Reboot it delayed popping up the 
first screen around 1.5 minutes.

Finally I got the message on the LCD

29mv   2mv
VCC=4.98 Volts. Then immediately after the two minutes the messsage:
on the LCD:

Short Probes ! <Blinking for more than 2 minutes contnuously>

After the two minutes have elapsed, the LCD showed:

1 --||-- 3 > 100nF

So I Inserted a 100nF. It took the tester 3 minutes refreshing the 
screen coming back to the same

1 --||-- 3 > 100nF. Finaly after 2 or 3 minutes it counted the Capacitor 
right, and exited displaying on the LCD

FW Version 1.2k
Tests Ok

Pressing the button will reboot or shutdown.

Pressing the button will enter the same diagnostics again.

Is it the code gone bad ? The Schematic features all the new revised 
parts by Karl-Heinz.

Troubleshooted all Transistors and replaced them anyway with 2 2N3904 
(NPN) and 1 2N3906 (PNP)

Has anyone else faced this problem  or similar ?

On the board there is an smd device P6KE6V8A and TL431 for Reference 
2.49v and another transient device protection smd SRV05−4

I am suspecting that one of these has gone bad ! Any ideas welcome.

Thank you

Enjoyed reading the manual.

Author: Sikri (Guest)
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yes I managed to cause the same problem on 3 of my testers, and after 
receiving the 4th one i figured it out and fixed all of them XO go 
figure. It's the 6 pin ESD protection In my case I tried to float the 
ground on the pwm output +6V(beginner obviously) and the supply for that 
chip, MC5 i believe are the SMD marks I have datasheet if you need it, 
has narrow max voltage between its supply rails (+/-5 iirc)
Good luck!


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