xr-71 sniffer powerscan coil

[dbanner]

Ahhhh...! This is beautiful, wonderful board, nice and compact. I like it.

[dbanner]

Sorry for being so blunt. You need some basic tools, namely, soldering iron, solder, DMM, de-soldering tool etc. Then you can proceed to diagnose board problems. Begin by checking diodes, transistors, mosfet et al. Make sure they are all good, then check power supply voltages. From there you can have a general roadmap of where to start looking for problem. But you must have basic knowledge of electronics.

[Sulyman27]

Thank you all,
I think i have to de-soldering Any piece when testing right?
I know how to check diodes and mosfet, but what about the ICs how i test them ? Can i test them while they connected to board?.

[dbanner]

You don't have to desolder anything at this point, just do some basic measurements to see diodes and transies are ok, If everything checks out, then connect battery and check for power supply voltages(refer to schematic diagram) with DMM, while also noting if any of the chips or any other component is getting hot, if so then switch off immediately, Do this with coil disconnected. Your chips are they soldered directly to board? Or are they plugged into sockets?
Now my next question is important, did your rig come with setup/calibration instructions?
Now I will send to you testpoints and voltages you should expect to see at various parts of the circuit. This will give you more information to see whats going on with your pcb. I have to look for my files, so give me sometime.

[Sulyman27]

My chips (Ics) are soldered directly to board not sockes.
Yes it comes whith some instructions ( see pic)
You have to know that the fuses blows immediately when I connect the battery!!.

[dbanner]

Your mosfet could be bad, does your board have zd1 on it,( the diode associated with mosfet), I see it on schematic. Can you check mosfet and zd1 to see if they are good?

[dbanner]

check mosfet

[dbanner]

The fuse blowing immediately means you have a dead short somewhere, a component(s) has definitely failed.

[Sulyman27]

Zd1 (zener diode) is not installed on the board while it 's on schematic, i checked the mosfet and it seems bad, because there is short whith drain-sourse pins, but i will desolder it to make sure...and also i found other six bad zener diodes ( current flows in both directions).

[dbanner]

Those are not bad(zeners), they are in-circuit. If mosfet is shorted, then you must figure out why it tossed in the first place.

[dbanner]

If you can, remove mosfet and connect the battery.

[dbanner]

Also, mosfet should be on heatsink.

[Sulyman27]

I desoldred the mosfet and D8&D7 zener diodes, they are all good ,
But i know now my big mistake, i painted my inside plastic box with Graphite then i atteched the pcb directly on the box base without insolation,, and connected the battery!!!
So what did you think happended!!??

[eclipse]

So what did you think happended!!??

Board shishkebab!? Sounds to me like there's a curse on this board.
You might save yourself nerves and build a new board (plenty of pcb layouts available here on the forum) and just toss the damn board in the bin where it belongs

[dbanner]

OH MY LORD!!! That's not good, not good at all! If you are brave man, then you might remove all chips and install sockets. Then you can put in chips stage by stage and check circuit as you go along.