For sale bare boards for Delta Pulse/Sniffer XR-71

[dbanner]

Andi . God sent me an angel. I am going to find and check it immediately.

Where is this transistor?????

[Andi68]

Ouch, I do not have a schematic in front of me, sorry

[dbanner]

Ouch, I do not have a schematic in front of me, sorry

[chuubaba]

No problem Andi. At least you decided to help. Thank you man.

[Andi68]

Now I am very sad.

I wanted to relieve my best friend KT315

[chuubaba]

longest rip away you send him seeking this transistor. DP mosfet is driving directly from/by NE556.

I changed all the IC but not working.

[kt315]

Sorry Chuuby, I couldn't resist.

[Qiaozhi]

BTW which transistor drives MOSFET? I want to replace it.

Beyond hope, I'm afraid.
Did you not see KT's answer below? There is no transistor.

longest rip away you send him seeking this transistor. DP mosfet is driving directly from/by NE556.

[chuubaba]

Beyond hope, I'm afraid.
Did you not see KT's answer below? There is no transistor.

Yes i saw his answer and i am waiting for his diagnosis.
As i said before your knowledge about electronics is equal to mine because you also can't figure out what is problem with this board.

[Qiaozhi]

BTW which transistor drives MOSFET? I want to replace it.

Yes i saw his answer and i am waiting for his diagnosis.
As i said before your knowledge about electronics is equal to mine because you also can't figure out what is problem with this board.

To try and diagnose a fault remotely is extremely difficult, especially when the person at the other end doesn't know what they're doing. Even with the best will in the world, you're chances of getting this working are very slim. Do you not have a friend nearby who can assist you?

[Andi68]

This is an infinite story

[chuubaba]

Surprised to learn remoteness an issue for expert.
All was working fine when i changed C3 from 15nf to 18nf and the tone changed and red LED blinked when DEPTH pot to near full.
Then I installed new block connectors.
I also touched up solder of R52.
Next i power the board but no green or red LED, no detection, no tone.
Next i replaced MOSFET, all IC, DA7, VD7,VD8,VD9 but no success.

[kt315]

desolder mosfet.
set tester probe in control point -E, another probe in GND and after in +E. write what you see.
tester range 20V, DC.

[chuubaba]

desolder mosfet.
set tester probe in control point -E, another probe in GND and after in +E. write what you see.
tester range 20V, DC.

-E 0.08v and +E 0.18v

[kt315]

nice seek the problem. has to be
+E - +10V
GND - +5V