RELIC HAWK

[robopatt]

Just had to be shore.
So now we stuck to that Q1.

[ivconic]

I do.
Right now i have original RH coil and 6 (!!!) various Excelerator coils for RH and Musketeer, here at my place. Those are right in front of me now.
I can only check any eventual connections via coil connector, with multimeter...right?
So... no connections at all between RX and TX.
I measured only resistances and inductances of RX's and TX's on all coils.
Those are:
from 2.1 to 3.0 ohms for TX and 1mH for all,
from 32.9 to 34 ohms for RX and 15mH for all...

[robopatt]

This will clear any doubts.I will be glad if we make it work.
It will be great progress.
Do you now what are conections inside the coil.I mean is there conection between TX and RX ends?
I connct coil directly to PCB TX to TX and RX to RX.
Hope you understand my question.

[ivconic]

Look this shot. It is so clear those two are BC547 and BC557...
Third one ( and probably most important one) is smt...and i can not see any label...hmmm...

[ivconic]

Dont be sorry, i havent understand your post as insult.
I am just very interested and curious about this long term RH issue. Same as you, i also want to disclose all the "secrets" about this project.
You are very right at some points. This not supposed to be very specific or very critical design. Must be simillar as any other; to have more tolerance and to start working even if we make it with some tolerances.
Mostly i draw my schematic respecting previous one...i think Max posted a while ago. That schematic (Max's) i guess is proven already. I only omitted mode switching parts and choosed S mode only. That is all i done.
So.. i understand your points and also want to solve it.
My pcb is not ready yet. Shame. I had so much other things to do latelly and couldnt manage to finish it. Hopefully these days i will finish it and try... than i can take more serious part in this discussion.
Regards!

[robopatt]

Sorry.
I didn't mean to insult you.
Just try with changes I spotted but no change.Now will have to wait for another chance to test with musketeer coil.And in same time will try other coils.I also spend many hours trying to spot a mistake.And with no luck.
Maybe porkluvr is right.But I have used BC557C there.
I am not 100% shore

[ivconic]

RRRRRrrrrrrr
I get mad.When I say there is mistake.After finished this whit only new parts and enthusiasm!There must be.I now you cant spot it maybe because of your skills but there is!I have to correct the PCB now then test again and later the results.........

I spent hours trying to locate any possiblle mistake on my pcb...without success. So...if you know something we dont, it would be fair you to inform us here..right?
If you say "..there must be..", than this means you are 100% sure and you know where and what is, right?
So..tell us here about mistake you know about.
Regards!

[porkluvr]

I could probably take a PN2907 and put it in the coil driver and it works OK. But I must still have a high gain transistor for the other PNP.

I could probably use PN2222 for the NPN.

I don't want to sound like an elitist, but PN2907 and PN2222 are "junk box" quality. A dime a dozen, so to speak. Now, but the 2N2907A and 2N2907A (in the metal can), are Quality (just kidding, they're also junk).

Enough kidding. I've gotta go. Maybe I'll get some more ideas but I don't know what else to tell you. Maybe I'm wrong but I believe the PNP transistor with emitter connected to V+ is what needs most attention.

The horse is dead, I'll quit beating it.

[robopatt]

This dont make a lot of sense.
Problem until now were that this TR(Q1) is special in some kind of way.
And this TR(Q2) that must have exceptional gain is BC557C PNP on both relic hawk and musketeer.So you get the wrong path!
The solder and desolder is much more hard way.But I also don't belive those simulations.Don't get me wrong they are useful but you can only be shore if you make it in real world@
You are wellcome.
Try to simulate previous PCB oscillator in that LT.And look for diferances if you want.

[porkluvr]

[quote=robopatt;87027]RRRRRrrrrrrr
quote]

Oops, I didn't mean to insult your parts.
What I mean is that just because your parts are new doesn't mean they'll work.

I tried my favorite transistors, and they don't work!

The PNP transistor "Q2" must have high gain at "high" current. So, low noise high gain transistors won't work if that gain was measured at 2mA.

Famous last words: "It's good enough".

The average collector current through the two PNP transistors is 25mA, peaking at 50mA. The transistor connected to the coil doesn't absolutely need to be extra special, but the circuit works best if the other one has some exceptional gain. Why, I don't know.

[robopatt]

RRRRRrrrrrrr
I get mad.When I say there is mistake.After finished this whit only new parts and enthusiasm!There must be.I now you cant spot it maybe because of your skills but there is!I have to correct the PCB now then test again and later the results.
Yes I have used 25 but your sugestion will only optimize working oscillator!!!
And what the hell means:?
This is a clue as to why your average junk-box PNP device fails

Only brand new quality parts!I wouldn't make such climes if I used junk parts.
Thanks for your attention.

[porkluvr]

As I increased coil R above about 3 ohms, when simulating with "parts" like I have in stock - it wouldn't work until I installed some high beta transistor like BC557C.
BC557B is ok for a 3Ω coil but not working for me at 3.5Ω. BC557C works at 3.5Ω.
BC857B is ok for a 3Ω coil but BC857C is needed with 3.5Ω.
BC327-25 is OK at 3.5Ω but BC327-40 is best of these four mentioned.

Of course these are only virtual tests and not the real thing. And there is no guarantee that BC327-40 will work in anyone's circuit. Still. I would rather rely on spice RATHER THAN to solder and unsolder transistors and god knows whatever else at random ad infinitum.

I am not a spice guru; can't look at a model file and determine transistor hfe from model parameters. But, from looking at datasheet I may be able to understand why BC327-40 would "test" so much better than the others in this batch.

The collector current is kind of high in this circuit, peaking at about 50mA. This is a clue as to why your average junk-box PNP device fails. (I "sucessfully" revved the RH oscillator up to 20kHz, but after seeing how much current is drawn - I won't be using it with my transistor radio battery project, no noooo!)

from transistor datasheets:
BC327-40 hfe 250~600 @100mA
BC557C hfe 420~800 @2mA
BC857C hfe 420~800 @2mA

I believe BC327-40 is best of the bunch for the RH oscllator. It's a SOT23 device. If you can get your hands on it, do so!

[robopatt]

Hi,
yes, all right. Many dubts on that also here... I'm not totally sure of that transistor there.

I just know that when I used the bc337 it worked , with good results... but I know... the osc section is so tricky part that changing a few a resistor it will not work anymore with all the rest unchanged.

What to say... I think the unknown transistor it's something with selected gain to have oscillations and components are really strict on tolerance in original ML mds.

People here must know making osc work it's not trivial task cause it's primary source of troubles most of the times in homemade RH clones.

No easy, good, always right solution for that... just trial and error.

Kind regards,
Max

I agree with you.But they can't produce 10000 units with trail and error?Just we need to find what is still missing.And oscillator will work from the first switch on.
I have some ideas on this unknown TR now.But problem is elsewhere.Because every TR can be changed with similar.
I will draw my conclusions and will post them so I can hear your opinion.

[robopatt]

For me testing with musketeer coil is equal to factory relic hawk coil.So oscillator don't work.I think they were 3,3 ohms for TX on original coil.
My coil is good enough for tests.1mH 3,5ohms
There is something small that is still missing.
If you have free time you can try simulate TX section.And look for mistake too.

[porkluvr]

Relic Hawk uses a low Q oscillator. Inductive reactance is only about 32 ohms, so keeping your coil resistance low and using a high gain amplifier makes a whole lot of sense - it does to me anyway. Compare to a Tesoro Bandito with coil reactance of about 350 ohms (and tank Q in the hundreds) - erk - it's a wonder the RH transmitter oscillates at all.

There are two PNP transistors in the TX oscillator. My test show that the one NOT connected to the coil is most critical and needing high gain. The higher your coil resistance - the greater the need for high gain. That transistor was labled Q2 in one of the drawings, and BC558 in another drawing. I'll call it Q2.

If your TX oscillator won't function maybe you should concentrate on getting a high gain transistor for Q2. If you've already tried a bunch of good quality transistors and it still won't work, and if your coil resistance is more than 3 ohms - you may want to try a coil with lower resistance.