Delta Pulse... not working

[Majarit]

Hello all.



I have build the Delta pulse but is doesn´t work well.


Without a coil the circuit draws 120 mA from the battery. Sound and display seems to work ok.
When i connect the coil it draws 3.5 Amp. from the battery and the IRF740 gets very hot.
I have replaced all the I.C´s, transistors, diodes and the irf 740 but still have the same problem.
I have tried different coil´s like a 45 cm 340 uH 3.1 ohm coil and also the LAN cable coil.
The LF357 is replaced with an LF356



Any idea where to look for the error ?


thanks in advance

[Jose]

It may be that the 556 does not work, or the TX pulse very wide, it may damaged IRF740.
LF357 is better that the LF356.
Jose

[mikebg]

Majarit, the problem is that current without coil is too large. Don't try to connect coil before to fix this problem. First check the polarity of all electrolytic capacitors and diodes. Then measure resistance of potentiometers connected to NE556. The third step is to connect headphones in output of NE556 (if you have no oscilloscope). You should hear how potentiometers operate. You should adjust with these potentiometers minimal volume. Then measure current from battery and let we know the result.

[Majarit]

hello jose and Mikebg

thanks for your respond

I connected my headphones to pin 9 and -i could hear sound but adjusting the potentiometer didn´t change anything

i replaced the 2 diodes around the 556 and now i do hear some change in the sound (not much) when adjusting the potentiometer


Current is now 82mA without coil. adjusting the potmeter does not have any effect on the current

[Majarit]

i couldn´t resist and connected the coil again.....and the delta pulse works now

total current is 160 mA now with the coil connected

thank you very much mike