help needed with old detector

[dbanner]

to92 is just the package type, this number is not on transistor. Look for these types, if you find one, post the number on it. I will then tell you if you have a winner.

[keith777]

i know there is loads of the first image one's. (index) with different numbers on. i have two old CB Radio boards that have a lot of then on the boards. i think they mainly start with CN on them.

[dbanner]

Perfect! One of those should work. just record the numbers on a few of them and post. I''ll check to see which one will work.

[keith777]

here is some.


C711
6ZF

A733
A0103

C2296
7X3C

A999
9XF

CI675
M2X0

C1342
B
0K 2

N13T1
01

C945
02X8A

C2076
D 89

TA78L
009P .OB

[dbanner]

C2076. Remove this one. Post a pic of the one you chose, then i will show you how to orient legs to put on new board. In fact i will show you now. refer to pic

[keith777]

Hi again dabanner.

i changed that part but still no joy. the machine is just the same.

[dbanner]

Give it a rest for time being?

[keith777]

let me know when your ready to have another bash at it.
thanks a lot mate for all the help that you have already given me. it was so much appreciated.

keith

[keith777]

Hi again dabanner. sorry to bother you so soon.

i decided to buy a new replacement part for the circuit board. i put it in tonight and was surprised when i checked it against some metal. this is what is happening.
i am picking up my fridge door at about 2" 1/2 inch. when you turn the volume potentiometer whilst the search head is picking up the metal. the volume/sound doesn't kick in until you are just about at full turn. basically it's not a gradual volume, it pops on at full turn.

least i am picking up metal now but,,,,,why the lack of depth as well.

[dbanner]

Hello there, sorry for taking a while to reply. That is good news. At least it,s working, sort of. Sounds like your null of search coil is a bit off. There is an adjusting capacitor i think on the main board. Mark the original position with a marker pen so you'll know where to set it back to its original position, then try adjusting it for better sensitivity(null) of search coil. Other than that, it may be your threshold potentiometer(control) is bad. Could be other things as well, but you can try these things first.

[dbanner]

Something I just remembered. The resistor you replaced on small board now becomes critical since you assumed you replaced it with the correct value resistor. A wrong value would affect the sensitivity of detector.

[dbanner]

What value resistor do you currently have in the small board(the one you replaced)?

[keith777]

Hi again dabanner.
thanks very much for replying back again.

i haven't tried the adjusting capacitor yet as i have just seen your post. the resistor replacement that i put in was a 30k

thanks in advance.......

[dbanner]

Something tells me a 10K resistor is more likely appropriate. But i not sure. If you are 100 percent sure about 30K then thats fine.

[nickel_n]

Looking at pic two on post #110 I think your PCB tracks, may be broken /corroded and measure Hi resistance.
I would get some methylated spirit and a small paint brass and give them a good clean. I would do that to all PCB’s.

Then I will just measure the resistance of the tracks make sure that is NOT hi or broken

I think will make a difference.

Give it a try.