Baracuda problem, beeps once

[Koala]

For new builders it's best to get the kit. Every is then known to work.

quite often its a silly mistake like a 100K resistor in place of a 10K (it has been known for the supplier to put the wrong part in the bag as well) or one of the legs on an IC bent under.

Anyway not much we can do until the replacement FET is fitted





Very hard to check the resistors from a photo on the Baracuda as so many stand upright.

[Detectojer]

The voltage at pin 6 of the 5534 is 4.48 volts with out the coil. Id I plug the coil in than it drops to 0.

[barleg]

I'm currently waiting for the tip127 to arrive, which will probably take a couple of weeks, but I coudn't help flipping the 2222 transistor just to see what would happen. The circuit behaves the same, beeps once and then goes silent, but there is a significant change in the beep. The beep is a bit longer and also louder than before. I've no idea if that is a good or bad sign though. Just to be sure, the board is supposed to sound non stop if there is no coil attached, right?

I'll check the resistor placements once again, but I'm fairly sure that I've placed them all correctly since I double checked the color codes each time i soldered them on (http://www.digikey.se/en/resources/c...or-code-4-band <--- a tip for beginners, useful site for reading resistor color codes)

I'll return again with a report after I've changed the FET.

[Detectojer]

Well I replace the 2n2222 transistor with a plastic one and still have the same problem. I though I would do that because I have the same problem that Rizal had and that fixed it for him. I would really like to get this thing running so if anyone has anymore ideas I'm open to them. If I can't get it going I'll just through it in the trash ( unless someone wants it cheap) and move on.

[Koala]

Try a few measurements

voltage pin 5 of 7660
voltage Vout of 7905
voltage Vout of 7805

Total current of circuit.


Sorry if its been asked before there are 3 baracuda board not working and I am loosing track of who is who.

In this thread two beeb then nothing

Detectojer tried a new 2222
barleg waiting for FET original gets hot quickly.
I believe the other in another thread is now fixed


Funny eneough when I had a 2222 in the wrong way the FET got hot but the detector would work if the volts were reduced to below 8V

[Detectojer]

Here is what I found on the voltage measurements.
voltage pin 5 of 7660 -11.6 volts
voltage Vout of 7905 -5 volts
voltage Vout of 7805 +5 volts

Measurements were taken without the coil. if I put the coil on then 7660 drops to -1.9 volts and the other two trop to 0 volts. I do have a tone in the headphones until I plug the coil in and then it goes away. also, pin 6 of the 5534 is 4.45 volts but it can not be adjusted it satys the same.

[Koala]

Here is what I found on the voltage measurements.
voltage pin 5 of 7660 -11.6 volts
voltage Vout of 7905 -5 volts
voltage Vout of 7805 +5 volts

Measurements were taken without the coil. if I put the coil on then 7660 drops to -1.9 volts and the other two trop to 0 volts. I do have a tone in the headphones until I plug the coil in and then it goes away. also, pin 6 of the 5534 is 4.45 volts but it can not be adjusted it satys the same.

Thanks that narrows it down quite a bit to a short or something around the FET and 2222. Does your meter have a diode test function.

Can anyone confirm if its safe to run without a coil I thought the FET would self destruct ??? but I could be wrong I normally am.

[Detectojer]

Yes it has a diode test function.

[Koala]

on the diode test and with everything connected what reading do you get with the positive lead on the middle pin of the FET and the other two legs.

[Detectojer]

I get continuity on the middle pin and the collector pin but I don't get anything on the base pin.

[Koala]

I get continuity on the middle pin and the collector pin but I don't get anything on the base pin.

I get .6v one way and open circuit the other. So something is a miss here. Can you lift the FET out of the board and test it out of circuit. If its okay leave it out and find the short on the board.

[Detectojer]

I removed it from the board. No mater what pins I use I don't get any reading , every thing is open.

[Koala]

I removed it from the board. No mater what pins I use I don't get any reading , every thing is open.

So the short is still on the board.

[Koala]

So the short is still on the board.

Sounds like you have a path from the battery plus and earth and the path is broken when you remove the coil. Suprised you don't get any reading at all in diode mode with the FET removed

[barleg]

I just got my tip127 fets and 2N2222 transistors from ebay, way past the expected delivery time. I've switched the old components on the board with the new ones and tried to fire up the barracuda. The good news is that I now am able to get a continuous tone when I regulate the thresh to one side, even when I connect the coil. I suppose that's progress? The bad news is that the FET goes extremely hot again after the coil is connected, even quicker than before. I'll get a multimeter for the weekend and try to measure the voltage between the pins you've described earlier in this thread. Another annoying thing is that I'm unsure which pin is the emitter on the plastic 2N2222 transistors, I need to figure out that as well.