Help EE's...I'm stumped!

[ejaf]

OK...here's the problem...

Want to do a 49 MHZ PCB swap. Bought 2 different bullet clones (Super Racer and Thor), both at 49 MHZ (actually, confirmed the crystal in the transmitter is 49.860).

Neither of the Cars PCB's will respond to my ZZ 49 MHZ contoller. One of the clones transmitters will control the ZZ PCB.

I want to keep my ZZ controller, instead of the clone controller.

Any suggestions or ideas as to what may be causing this behavior?

[bill]

Heh, i'll give my same answer I gave you before. Just click me .

I'm not sure there's any electrical engineers on this board. Maybe a lot of googling is in order.

[ejaf]

bill...thanks again for replying, and I had read that article.

I would have NO clue as to what search parms to try in google.

There was also a good thread somewhat related to this in the "tuning" one can do to the POT on the PCB (which, as NightWing had written, is not really a POT at all, but a form of POT used in "regenerative receivers", as compared to using superhetrodynne receivers...awesome thread if you search in the MS forum for "tuning wand"). I had also tried to tune this on the clone, to no avail.

If the signal being sent covers a wide variety of frequencies, then it IS nailing the correct frequency that the ZZ pcb is listening on, since it does control that PCB. Therefore, if the band that the clone transmitter is sending out is "wider" than the band the ZZ is sending out, then the clone receiver must be listening on a narrower band than the ZZ pcb.

Clear as mud? Pure speculation on my part, so therefore I am hoping someone like Nightwing can offer some insight, since I may be talking out of my a**.

I will gladly take any suggestions on what search parms I could use regarding google, though. I have tried several, and the hits are not near what I am looking for.

[ejaf]

I was hoping Nightwing would have answered me here, but I will quote from that other board:

FYI...Got some new ideas

Two thing to think on and could try

1) Could temporary flip xtals from the one that works over to the one that does not.
2) Use a nylon tunning wand to adjust the coil in the bit to reset its center receive frequency. Note slugh closser to coil lowers freq away raised freq.

There are some tool to help. One is a FSM or Field Strength Meter and another one is a sentitive Frequency meter. The first will tell you approx how much you are putting out and the 2nd shows you your transmit frequ. If too far apart could answer your problem.

Of all the thread and looking at the difference "sets" the only difference so far is the RF side. The actual controll is done by a TX2/RX2 chip set.

OOPS sorry about that.

The xtal is the metal can with a number like in your case 49.xxx on it. Of the two its the simplest and easy one to put back. If it controls the car when you switch then you should be set. Either leave the xtal that works or replace the other and adjust the car.

The SKU for the tool set is 64-230a. Note that they usualy use wax or something to lock the slugh that you turn so it wont change freq when it hits something. Also its so small and easy to break.

The Field Strength meter can be made from parts from RS. It handy to see if a transmiter is really outputting and a measure how far it signal goes. Its simply a crude receiver that drive a analog meter.

The Freq is usualy purchase but sound like a one time item may just want to try the Xtal switch swap.

Need to make this note. Different mfg can wire the switched that feed that long chip inside the controller different ways. For example the 13 dollar RC from TRU control correctly Forward & Back on a ZZ car but steering is reversed. On other F & B are reversed. Others all are fliped. I think it comes out to 16 different ways to do it. With a simple DPDT switch can flip either F/B or L/R. Or with two switch both controles for anything.

There is one last thing that could help. There is a resistor that sets part of the internall osc on the IC marked TX2. On a ZZ its set with two resistors in line { 68k + 100k } on a Bit its around 220k with one. Oh one end is connected to pin 11 and the other to pin 12. Pin one has a mark next to it. Counting down and aroung so the pin on the other side of one is 14. You could pop one lead and temp jump lets say a 220 in place or a valur added to the others to get 220 or what ever is uses in the OEM controller.

Like this: ( top view )

01\ / 14
02| |13
03| | 12
04| | 11
05| | 10
06| | 09
07| | 08

Good luck!

I'll give some of these a try, and report back.

FYI...maybe I could convince my wife that we need a sensitivity frequence meter to scan the house for bugs!

[ejaf]

Nightwing mentioned a SKU for the tuning wands, but that part number doesn't match on the Radio Shack site.

Questions...
Is SKU = Part number on the site?
Is that kind of part even listed on the online catalog?
What should I try to search for (tried "tuning wand", but no hits resembling the tool). Perhaps there's a more exact name that someone would know here?

TIA...E

[Nightwing]

HI!

Hum... Strange they cant take the 'a' if you just type in the 64-2230 it pops up with this. Strange the letter means its a updated package. They list it at 4 dollars. Not bad.

http://www.radioshack.com/product.as...5Fid=64%2D2230

Any luck on the xtal switch? Also do they have different OSC resistors?

[ejaf]

Thanks...picked them up today at RS near me...

64-2330A (no offense, but your original post said 24-230, missing a "3"). Couldn't find them online, but there's a guy at my RS who actually knew what I was talking about (he used to fix color TV's for a living), so I picked them up.

Also picked up 64-2220 (5 piece TV tuner), but they were too large (probably could shave them down).

Now all I have to do is get a couple hours free to perform the tests/ideas you gave me. Seems as if there are too many damn holiday parties around taking away my fun time

I will first swap the XTAL (done that betwen a 27 and a 35, just for kicks....it actually worked!?!), and let you folks know how that goes.

Haven't had a chance to pop open the Xmitter to flip or change R on that pin out from the TX 2. I'll probably try that second, before playing with the regenerative reciever.

[Nightwing]

Did forget the three! Good catch!

Instead of a Freq counter could use a Oscope to measure freq.

Good luck on the hunt!