help needed with old detector

[keith777]

Hi again dabanner.

there is no small circuit board on this one. also no speaker. just a head phone socket that allows you to use headphones with or with out the meter attached. how would i compare measurements with the coil?

cheers mate.

[dbanner]

Cheers. First of all, the wires from the first coil were black, red, white, and green, brade. What do the wires from the second coil look like-are they the same? Post a pic so i can see.

[keith777]

Hi again dabanner.

here is some pics bellow. also i tried changing that 30K resistor that i used for a 10k resistor. the color bands on it were (brown, black, orange, gold) it still made no difference.

[dbanner]

perform one last test. Set up multimeter to check transistors as before only this time remove base leg and place red probe to base leg and black probe to each of the other legs. Test this transistor on small board.

[6666]

perform one last test. Set up multimeter to check transistors as before only this time remove base leg and place red probe to base leg and black probe to each of the other legs. Test this transistor on small board.

removing the leg from the pcb is one way to do it, but it can cause damage to track and transistor , Its a simple pcb, so another way and much less messy and less work is to just cut the track with a razor blade and resolder,

[dbanner]

Good idea. Either way, get that transistor checked, if it tests good then all your transistors and diodes check out o.k. You will then have to look for bad capacitors or possible a damaged coil.

[keith777]

Hi again dabanner.

here is the result that i got for that transistor test. i think i had the meter setup right. the 254 number was slow to build up. the other number went strait up. pics bellow.

[dbanner]

You have meter setup correctly. Did you remove base leg from circuit? If so, then this transistor checks BAD!! Since this is transistor which drives the speaker, I think we have possibly found the problem. Look at transistor and tell me the number on it.

[keith777]

yes i cut the track with a blade like you suggested. the speaker kept crackling when i was doing the test. don't know if that is normal or not.
i will go and see if i can find the numbers for you now.

[dbanner]

Actually, if its a darlington transistor, it may not be bad at all. you'll have to cross reference the number to see for sure.

[keith777]

the number on it is. 2n 3053
what is the small brass bar on the transistor. it looks adjustable. pic bellow.

[chevesne]

Emitter indicator.

[dbanner]

This is called a tab and indicates position of emitter leg of transistor. Well you have found the bad guy! Now you must find a replacement. 2N3053 NPN AF(audio Frequency) Driver. You said earlier in thread you have junk boards lying around? You might be able to salvage an appropriate substitute transistor.

[dbanner]

Any old NPN driver transistor will work for your purpose. Salvage one from junk board. IT DOES NOT HAVE TO LOOK THE SAME ROUND SHAPE, IT COULD BE RECTANGULAR SHAPE(TO92M PACKAGE). Take note of the number and check online datasheet to see if its NPN.

[keith777]

Hi again dabanner.

i can not see any round shaped one's on any of the boards that i have.
what do the rectangular ones look like and do they have to have TO92M on them.