Delta Pulse

[Andi68]

I should not write anything anymore, I do not know the DP

[Jose]

Andi68 With some damping resistor + LF356 the detector is absolutely obedient no noise no chatter and i can turn all pots to maximum without much noise but it detects no target whatsoever. Whats else can cause this non detection other than LF356? $he same board works with TL071 but depth not as expected.
Thank you

In the distance, it is difficult to know what causes the malfunction of your DP.
The logical thing is to think that if it works with TL071, with LF356 or it should work better.
I am traveling now, in the next few days I will try my DP with TL071 to see what the difference is, and I will publish it.

[chuubaba]

Thank you Jose. Anxiously waiting for your test results.
Don't know why the maker used such obsolete and widely counterfeit chips when other better and authentic options were there.
Safe journey.

[kt315]

why vd4 cathode on anode pad?

[Andi68]

And I see some nasty solder joints

[chuubaba]

And I see some nasty solder joints

Yes very ugly but working good.

[Andi68]

No, a good solder joint must also look good.
And look at post #3634 of kt

[Vadim18]

Why are you not happy with 60cm ?, those 357 are hard to get.

Hi 6666!
I'm was happy with that first test results. Now my limit is 90cm to aluminium cola can with clear signal.
My setup: L475 uH, D27cm, R 2 Ohm, Rdamp 414Ohm. Delay1 and Delay2 at minimum, TX 100uS, PPS 300. Gain near x1500.


I have no problem with LF but... i stil use old BC548 transistors, ceramic caps in offset correctors and maybe fake Wima 100nf MKP capacitor - magnet can easy stick to it. Also my problem is laziness...

some fake ic on photo

[kt315]

you can do Delay2 to maximum and get more depth on test.

[kt315]

No, a good solder joint must also look good.
And look at post #3634 of kt

unattentionable

[chuubaba]

No, a good solder joint must also look good.
And look at post #3634 of kt

Yes i see the mistake there with VD4. I don't want to solder again and again so i ignore beautification. The solder joints are good because i checked with DMM.

[chuubaba]

I have corrected VD4. Nothing has improved after correcting this mistake. The 356 chip is still not working

[Jose]

Buy two LF357 and two TL081 to perform the tests.
Install a socket to test the chips.
With the LF357, set the Delay to 22 us.
The TL081 turned out to be false.
Recover a TL081 from another board and it worked, the delay was set to 70 us so that the DP was quiet.
I also tested an LF356 and the delay was set to 35 us.
All other controls and damping resistance were not altered during the tests.
Other Chips, 5534; LM318; 709; they didn't work.
LF357 is preferred, followed by LF356, but with TL081 sensitivity to small and medium objects is lost.
Attached do images taken with the oscilloscope, at the exit (leg 6) of the LF357 and TL081.

[Jose]

I have corrected VD4. Nothing has improved after correcting this mistake. The 356 chip is still not working

It is likely to be false or damaged due to improper installation of VD4.

[Vadim18]

you can do Delay2 to maximum and get more depth on test.

Thank for advise kt315!
I will try that option in field tests.
For me i discovered that Delay2 can also make some emi supression (i think for 50Hz+harmonics), but only if proper adjusted and stay at proper point/point's of scale.