# Aristocraft Train Engineer



## superdog404 (Sep 28, 2016)

Hi - Has anyone tried or done a convert from 75 mhz to 27 mhz in one of the newer transmitters? I have one of each and looking at the circuit boards they look identical for the most part except the 75 Mhz transmitter has a surface mount what looks like a potentiometer near to the crystal. Both have 4 mhz crystals. I did try to put a 27.045 mhz crystal in the newer transmitter. But messed up the traces. In farther looking I don't think that was the way to do it.

Thank you for any help
Harold


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## Dan Pierce (Jan 2, 2008)

I believe the 4 mhz crystal would be for the IF (Intermediate Frequency), not the RF. RF is usually done by a phase locked loop IC plus circuits and that is not easily changed for the difference in those 2 RF bands.


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## superdog404 (Sep 28, 2016)

Hi Dan - Thanks for the feedback. I thought I would post a couple pictures of the 2 boards. For anyone curious. The board with the yellow switches is the newer Transmitter. The single board with what looks like a pot is the newer version. I tried a continuity check on that pot but it had no conductance. At this point I don't know what it is. I need to check the 2 IC chips to see if they are the same number. I can't make out the number on the 1 board. Having not much education in electronics I though the newer board needed to have a 27.045 mhz crystal to replace the 4 mhz crystal to get it on 27.045 band. That turned out to be a real failure. 

Thank for the help
Harold


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## Dan Pierce (Jan 2, 2008)

That is not a potentiometer, it is a variable capacitor for tuning the frequency of the phase locked loop.

Misadjusting this will make the transmitter unusable and when turning it you can not use metal as metal will change the capacitance when trying to tune.


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## Greg Elmassian (Jan 3, 2008)

Other components in the system would also be changed to work with the different frequency.

I've never investigated to see if the communication protocol was the same between the 27MHz and the 75MHz.

Clearly you need to buy a unit for the frequency you wish to use. This is sort of like pulling the engine computer from a toyota and putting it into a John Deer tractor

Greg


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## barnmichael (Jan 2, 2008)

First, RF circuits are dependent on frequency. There is a huge difference between 27 MHz and 75 MHz circuit components and design. A fair amount of the board circuitry would need to be re-engineered for such a change. Also, 27 MHz controllers use AM (Amplitude Modulation) while 75 MHz controllers typically use FM (Frequency Modulation). The two formats are completely incompatible with each other. 

These controllers, like any other transmitter, are Type Accepted by the FCC. It is illegal to tamper with, change or adjust any of the transmitter design or frequency. Besides the controller, you would also have to change your receivers. I suggest you leave them as they are. If you really want to change bands, you will have to get new equipment.

Michael


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## superdog404 (Sep 28, 2016)

Thank you for the help guys/gals. Well I was hoping to convert the the 75 to 27 as the boards look almost identical. I got the new 75 for $39.00. I have 3 10 amp receivers and 1 10 channel 10 frequency transmitter 27 mhz. It has a problem with "C" key so would like to get another transmitter. Thinking (Killed the Cat) since the boards are alike I thought I could convert the new one. I was way off base there.
The 2 large IC chips are the same on both boards number wise. The circuits are so close to each other I thought they almost came from the same era. Some of the small resistors, caps etc. have different numbers but for the most part they are also the same.
Anyway I guess I'll abandon that idea and watch for a transmitter on EBay. If any one has a later transmitter that they want to part with please let me know.

Thank you
Harold


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## Greg Elmassian (Jan 3, 2008)

You can buy a replacement button for your C key, but honestly, you might have someone else replace it.

Greg


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## superdog404 (Sep 28, 2016)

Hi Greg - I should have said I replaced the "C" key with the "F" key but it didn't fix it.


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## Dan Pierce (Jan 2, 2008)

I have fixed many keys with new ones. Heat will destroy the ones when removing.
If desparate, take one form a computer mouse!!


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## Greg Elmassian (Jan 3, 2008)

yep, cut the 4 legs first, then remove them from the board one at a time... preserves the board... replacement switch about $1.50 each or less


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## superdog404 (Sep 28, 2016)

*Update*

I managed to pick up a complete set CRE-55470 new old stock from Ebay in the box. This set has the transmitter with the On/Off lower left key. The interesting part about this set is that the transmitter circuitry is completely different than any other's that I have seen. The motherboard is labeled as CRE-55003-L. I have uploaded a couple pictures front and back. This motherboard is also different than the 55003 at 75 mhz. Any comments are welcome. I'd like to know how all these different versions came about.


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## Dan Pierce (Jan 2, 2008)

Aristo had to tedesign the transmitter as a chip used in the older versions went out of production.
Newer version would drain the batteries hence the on-off switch.
Important to know that when turning on, hit the button 3 times on-off-on to make sure the unit remembers programming.


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