IDX-PRO+VDI

[medj]

Possible change my mpsa13 not I find
Changed the transistor in place mpsa13 ___tip140
The device works poorly
But tip140 very heated
What should I do

[golfnut]

Ok so I have 0.04v ac with coil.
I am going to go to my local electronic repair shop and see what it would take to do a couple of tests with a oscilloscope.
This is my board.

Replace the 39k on the Tx oscillator with a 39 ohm

S

[Koala]

Did you use BC327 BC547 or equivalents some of the equivalents have different pinouts. Check they are in the right placement. Is the missing resistor top right on the other side of the board. Have you measured the + and - volts of the PSU.

[gtdavid]

Ok so I have 0.04v ac with coil.
I am going to go to my local electronic repair shop and see what it would take to do a couple of tests with a oscilloscope.
This is my board.

[Koala]

Yes, but overdoing it renders PP useless.

Thanks thought it was going to be normal.
Its good to do some testing to familiarize yourself with the detector. Just found out I have not dug a genuine target DOH . If a coin is on it's edge and at 90 degrees to the coil you get a double beep one one each edge of the coil then if you sweep at 90 degrees you get a single beep at the center. Had that exact situation on the beach and did not dig as I thought the target was too big and was going to be another piece of aluminum. You live and learn.

[Davor]

Yes, but overdoing it renders PP useless.

[Koala]

Just a quick qestion

Is this normal.

Set threshold in PP mode then switch to Disc mode I get a slight increase in depth if I then turn the threshold up slightly. I am talking slight also the higher the threshold the louder the sound in Disc mode?

[Koala]

I read the datasheet for your chosen darlington and it has only 1/2 of the gain of the designed part.

S

Just an update to say it worked
MPSA13 arrived yesterday been testing and much better THANKS again

It's near enough twice the detection range on both PP and Disc modes than an original "Classic I" using the same coil. More than happy

Might be getting greedy here but I think there might be less missed marginal targets in the real world a bit more punchy audio.

[Koala]

I get with a working detector 16v peak to peak with a scope but when measured with a digital fluke meter on AC I get just under 4 volts and 0 volts DC that's with the coil connected.

[golfnut]

Put the meter on ac with the coil on. should see about 15v AC.

post a good pic - get access to a scope.

Without any useful info we cant put right your error.

S

[seadoggy]

now its correct i think....you have to do this little modification

[ATTACH]25732[/ATTACH]

ok mate thx

[gtdavid]

With the coil I get almost 0v

[golfnut]

I guess without a coil - a mode you would not normally use for fault finding - Q2 in on, as a result, Q1's b-e junction is also on. You are then measuring the 8v supply minus Vce of Q1.

S

[gtdavid]

My transmit voltage is 6.37 dc with no coil what would cause this??

[Schatztaucher]

now its correct i think....you have to do this little modification