RELIC HAWK

[Max]

Hello Max, Fred , Everyone , I was just wondering is the transistor BC-557 next to tx-coil correct which would be NPN. On the copied Cheap-Version of Relic-Hawk they are using BC-558 a PNP !!! Bad oscillation occuring at tx-coil because of this ? OR ,If Rev. 1.6 values are correct , then dc resistance , Coil wire gauge and number of windings are not o.k.??.............Thanks....Eugene

Hi Eugene,
the BC557 and BC558 are both PNP and about same stuff so not a problem changing one for another in most of the cases.

I suppose the real original RH has different ones inside... that's the real trouble... I think I will simulate a few well know types and see if can sustain oscillations at 2.5ohm or higher resistance.

With 850uH , 1mm wire coil I get it oscillate pretty easy, with strong magnetic field around.

Kind regards,
Max

[VUJO]

Hello, I measure resistance with multimeter PC5000 of the company SANWA. Resistance of the cable-probes when they are in short-circuit was 0.08ohm.
Best regards

[KingJL]

Hi Eugene,
the BC557 and BC558 are both PNP and about same stuff so not a problem changing one for another in most of the cases.

I suppose the real original RH has different ones inside... that's the real trouble... I think I will simulate a few well know types and see if can sustain oscillations at 2.5ohm or higher resistance.

Max, I think the transistor that will have the greatest impact will be the NPN that is driving the PNP cascade and provides the oscillator feedback.

Regards,
J. L. King

With 850uH , 1mm wire coil I get it oscillate pretty easy, with strong magnetic field around.

Kind regards,
Max

[Max]

Max, I think the transistor that will have the greatest impact will be the NPN that is driving the PNP cascade and provides the oscillator feedback.

Regards,
J. L. King

Hi,
I agree and will make some tests about. I also spotted an interesting stuff when testing with a power supply with current limiter... sometimes also with the 1mm wire coil it fails to start.

When you use a 12v battery this never happens and the low resistance coil works on that dang oscillator... but using limit on current at supply give so drop the voltage that it doesn't start. If I rise the current to 500mA limit I can start oscillator each time but at e.g. 200mA it doesn't start at all.

I retested the 0.5mm coil but without success so far... even using a 12v gel type accumulator.

I will try different NPN there to see what happens. Tested also tl074 model on simulator but all the same story so op. amp. impact is few unless of using very special slew rate parts.

Kind regards,
Max

[Max]

Hello, I measure resistance with multimeter PC5000 of the company SANWA. Resistance of the cable-probes when they are in short-circuit was 0.08ohm.
Best regards

Hi,
this is an accurate one: 0.2%rdg+ 6dgt on 500ohm endscale.

So I think your measure is probably one of the most accurate we have on that coil.

We have to understand why works on its circuit and not on the cloned one...

Kind regards,
Max

[Max]

Hi,
I think I found the source of all troubles... at least in my previous simulation... the dang 22K resistor I have in the circuit I had like 27k in previous simulation.

Now, I changed it to 22K and got 13.6Vpp for a 2.5ohm resistance coil, 1mH and about 18Vpp if the coil resistance drops to 2.2ohm.

So, for the simulator... the 2.5ohm coil MUST work though not optimal one... and with ideally maximum voltage of 13.6Vpp on it.

Now the problem is that I have the dang 22K in the real pcb but it doesn't work... cause probably the NPN I've used is low gain BUT I used an BC547B so still don't understand that, must check again.

Simulations are cool... but often reality is truly different stuff..

Kind regards,
Max

[Max]

Tested an NPN with hfe=600 there and change nothing... just lower resistance coil works!

Neverending story with this oscillator...

[amtech2005]

RELIC HAWK

Max,Fred,KingJL. I am looking for the the best possible Spice simulation software to download. So I will then try maybe a MPS3638A- "PNP" and 1n779A-diode as alternatives to test. I think both schematics have small errors in the part numbers from the "Relic Hawk" tx oscillator circuit..........Thanks Again for your "Great Posts" here in the last few weeks..............Eugene

[VUJO]

Hello Max
You are right! In the proto board
I changed 27K with 22K and oscillator work. Voltage on the coil is 19.2Vpp
Best regards
Vujo

[Max]

Hi,
I've found another mistake on PCB : the 4K7 pull-up resistors at U2 are not connected to the + rail.... I solved making a solder joint between the up "+" near them and one terminal.

Kind regards,
Max

[Fred]

Hi,
Here is last version of PCB:
Corrections made:
-1M2 resistor was missing
- Removed 360K resistor
- + to 4k7 resistor

Even if there are no more mistakes,let me know for possible improvements

Regards,
Fred.

[Max]

Hi,
Here is last version of PCB:
Corrections made:
-1M2 resistor was missing
- Removed 360K resistor
- + to 4k7 resistor

Even if there are no more mistakes,let me know for possible improvements

Regards,
Fred.

Hi Fred,
my testing stalled cause I cannot find suitable wire to make the tx coil... I need 0.7-0.8 wire... I had in past but now I'm out of it (well I have some... but just 15-20meters now) and I have to order or find somewhere... so could take a bit.

At now I can get oscillations just with some 1mm wire coils, and low resistance on them. I get around 6.5KHz so still far from 5Khz then I decided I need first the right wire to make the tx coil otherwise other testing will be influenced bad way by the incorrect frequency there.

The ridiculos thing is that I have plenty of 1mm, 1.5mm and 2mm wire but I cannot use in this kind of stuff!

Shame... today is so difficault find that wire cause many dealers refuse to sell you small quantity but they wanna just sold something 30-40Kg rolls... good for many coils... but a bit expensive and heavy!

I've ordered something 500gr but will take a while till I get it.

Stupid dealers... idiotic monkeybusiness...but this is the world today: MONEY and no time to waste! JUST TON ROLLS TO SELL!

Kind regards,
Max

[Fred]

Hi Fred,
my testing stalled cause I cannot find suitable wire to make the tx coil... I need 0.7-0.8 wire... I had in past but now I'm out of it (well I have some... but just 15-20meters now) and I have to order or find somewhere... so could take a bit.
Max

Hi Max,

Yes this kind of wire is really only for people wich build their own stuff, and this specie disapearing...
Again degauss coils in TV´s have nice wire, depending of size of TX between 0,5 and 0.8 i guess.
There is a sellers on ebay that have 500grs reels of almost any size,internet is a great thing sometimes.Before i searched a lot for wire to make Kv transformers for tubes RF PA´s...and never found suitable except as you say 40kgs reels...
I am still waiting for the PCB ...so stalled too.
Should arrive early next week...
Regards,
Fred.

[Max]

Hi Max,

Yes this kind of wire is really only for people wich build their own stuff, and this specie disapearing...
Again degauss coils in TV´s have nice wire, depending of size of TX between 0,5 and 0.8 i guess.
There is a sellers on ebay that have 500grs reels of almost any size,internet is a great thing sometimes.Before i searched a lot for wire to make Kv transformers for tubes RF PA´s...and never found suitable except as you say 40kgs reels...
I am still waiting for the PCB ...so stalled too.
Should arrive early next week...
Regards,
Fred.

Hi,
yes, the wire is not hard to find but in big rolls nobody of us will never buy!

I usually found good buying 500gr or 1Kg depending on gauge, so meters available, and is good solution in most of the cases. The problems start arising when you need a particular diameter and just finished it or think you have some... and you have... but not enough! Like my case...

Now I'm dealing with the big coil...1mm diameter wire... ugly thing, but at least it works for now...I'm awaiting shipping of the new wire... but I see it hard to get in few days.

Kind regards,
Max

[Max]

Hi,
I've tryed an RF transistor there , the 2N2368 (vhf kind) and found it's a little more easy getting oscillator start but it's not big result cause the 0.50mm coil failed also with this on PCB.

I think the stuff is hard now... cause I've tested 6 different op amps there and no results... so probably at least a true 0.7-0.8mm coil is needed there.

The stupid thing is that the simulator still say the 0.50mm coil MUST work there!

No way...

Kind regards,
Max