IDX-PRO: is my RX phase correct?

[golfnut]

Good luck with it. S

[golfnut]

Just to muddy the water a bit, my IDX has a single 4148 as per the original build and works ok.



The biggest niggle with mine is the Filter amps which oscillate some times, often chirping away at 8Hz. When it is wanting to go, it looses sens with the partial osciillation - in the momentary losses of sens I miss targets during the sweep. Sometimes it sounds like a click like static, with a few following.

Ive been looking how to increase stability of these filter amps with techniques like isolating the feedback node from the load etc. Anyone else got any better filter amp designs which are more stable. ?

S

[joop]

Just to muddy the water a bit, my IDX has a single 4148 as per the original build and works ok.

S

Is the anode or kathode of the 4148 connected to R23? On the silkscreen of the PCB I have from silverdog, the drawing is wrong in case you are using the 4148 as a 0.7V zener.

[golfnut]

This isnt really an error - this was covered in earlier posts. If it was a zener as per the earliest drawings it was A K one way

If the diode was a standard one the A K was the other way. So in original there was 2.7 volt zener action.

The other way it was just a 0.7V forward diode drop. Like a 0.7v zener if u like.


Its a feedbck idea which makes the dual comparator work with a logic AND function. So in use CH X AND Y have to be over the preset level on the ref input (via the user pot)

The actual volts across on this diode seems to be largley irrellevant.


Im suprised that your Iron reject began working after looking at this diode?

Steve

[mohandes]

Zener in this case can't be replaced with diodes in series because there is almost no current running there and voltage drop is below what you expect. In IDX you can't replace it with resistors because the PP channel interferes. So zener there is

hi
i have some question here please answer :
1-D3 is zener 2.7 volt or 4148???

2-my friend i finish the DD coil but i dont know where i put the probes of oscope on idx circuit to measure them ?
3-how can i shielding them?like TGSL coil?or turn 0.2mm around two DD coli , correct?can you tell me more
the data for my coil:
0.7mm wire 33turn 620mkh and 1.5ohm
0.2mm 258turn 37.5mh and 97.5 ohm
correct?

[joop]

This isnt really an error - this was covered in earlier posts. If it was a zener as per the earliest drawings it was A K one way

If the diode was a standard one the A K was the other way. So in original there was 2.7 volt zener action.

The other way it was just a 0.7V forward diode drop. Like a 0.7v zener if u like.


Its a feedbck idea which makes the dual comparator work with a logic AND function. So in use CH X AND Y have to be over the preset level on the ref input (via the user pot)

The actual volts across on this diode seems to be largley irrellevant.


Im suprised that your Iron reject began working after looking at this diode?

Steve

I must admit, don't fully understand how the feedback + zener works. Will look into it. Anyway, it is a source of confusion: whether people have to use a diode or a zener, different layouts and schematics say different things. So it is easy to get it wrong, that's what happened in my case.

[joop]

hi
i have some question here please answer :

Hi Mohandes, please ask your question in a different thread. It is outside the scope of this subject.

[Davor]

Zener is merely a level shifting device in this case. Comparators either pull down to the negative rail, or pose a high impedance. In transition from negative rail voltage to a signal voltage, a capacitor is charged, and it takes time. It takes less time to charge from a voltage closer to signal ground than from a negative rail, hence a zener diode. A "normal" diode does the same, but with less success, and hence slower recovery speed. In my IGSL I replaced a diode with a simple resistor (properly dimensioned) and it works very well.

[golfnut]

The thing I dont get - even after modelling it successfully one time, is the AND function.
X AND Y need to be over the common ref and both toggle.
I know its there, it works and its to do with the comarator outputs and the dioide is in the mix. But I dont have a clear picture of how you need both comp outputs to be ON or off to give a tone trip - (I do understand why! and I know this works well)

The feedback to the GEB input particularly leaves me cold.

If I was drawing this out from scratch Id be tempted to go to 74 logic at this point for the AND function.

S

[Davor]

It should work that way, provided you can convince the logic to consider a positive signal of a few mV to be a logical 1 (OK, you can amplify that and use Schmitt triggers), and if you put some gating to play audio enable/disable function. Comparators are convenient devices that do most of these functions in wired logic fashion, see http://en.wikipedia.org/wiki/Wired_logic_connection

Why people do not use wired logic more often is because it is slower than the active logic, but in situations you do not require fast switching it is very fine. It reminds me of the time I and a colleague of mine set the all time college record on minimum components solution in a Boolean algebra lab using a pair diodes. Boy was it funny!

[Koala]

just noticed that Pepe in post 1350 used a resistor in place of the diode. Is there any advantage ?

[joop]

See post #23 in this thread.

[mohandes]

hi all guru
I CAN adjust the coils I take foto and need to say me is ok?
first pics show us that coil not adjust and Phase difference near 50 deg.look


DS0014.BMP
DS0015.BMP
DS0016.BMP
DS0017.BMP

second pics when i adjust them , Phase difference 180deg, look
DS0018.BMP
DS0019.BMP

thanks
please tell me about the speaker it is always have sound
thanks

[golfnut]

bmo 18 looks ok.

My IDX is about 160deg
Joops is about 200deg

yours is about 180deg

this should be a good start - make sure you have the PP switch set to run in Disc mode.
Adjust the Threshold to quiten the tone.

you should be able to reject ferrite and iron

S