Skip to main content

Yep, both of you are already on the list.

Just spend some time prepping more enclosures for the TMCC Buffer, trying to stage things so it doesn't all happen at once.  Also worked on an assembly fixture to install the thru-hole parts after the SMT boards come back.  Stuff like the indicators need the exact spacing to be properly exposed on the top of the enclosure.

I have to say, making a complete unit is a bit more complicated than building boards, lots of little hardware issues to work out.


On the TMCC Signal Booster (SMC) schematic in the PDF there is a AD774SQ op-amp part. The AD suggests its an Analog Devices part, but I did not see any 774SQ parts. Is this the correct part number? Do you have a link to the datasheet for this part? You might want to include a complete parts list with the instructions. Is the 24VDC wall wart power supply regulated? What is the amperage rating on the wall wart?

Actually, the part is an AD744JN, don't know how I got that number in there, but I'm using the correct part.

Yes, the 24V power is regulated, it's a 1A supply.  The original prototypes had a 700ma supply, but the 1A seemed like a good idea.  I compared it to a 2A supply, and there was no difference in operation between the two driving a 50 ohm load.


It appears as if there is a connection missing from the TMCC Signal Booster schematic. See MissingLine.jpg

The missing line appears in red.

The AD744 according to the datasheet recommends bypass capacitors which do not appear on the schematic.

See NoPowerSupplyBypass.jpg and the recommended bypass schematic from the datasheet AD744PowerSupplyBypass.jpg

Were these left off the schematic?



Images (3)
  • MissingLine
  • NoPowerSupplyBypass
  • AD744PowerSupplyBypass

Actually, the bypass caps weren't on the prototype or my original thru-hole version.   For a large part, we tried to take Dale's basic amplifier circuit and just embellish it with some added features.  Since it worked well, I wasn't going to tinker with what he had working so well.  One issue here with the caps is we have what amounts to a virtual common, not sure what introducing the caps from the power to that floating ground might cause. 

I may skywire them in to one of my prototypes and see what effect they have.

Almost there!  Here's the SMT version on the bench, everything works as expected, just like the thru-hole version.  That's obviously what I was planning, but sometimes things don't go as planned.  I sky-wired the bypass caps onto this one, the "final" artwork has them added.  I discovered that I just overlooked the bypass caps, they actually were on Dale's original prototype.  One of the little problems of not having the full documentation and having to reverse engineer it from prototypes, occasionally things fall through the cracks.   One task is to make one more pass through the prototype to make SURE nothing else was missed, though the buffer seems to function as well, or actually a bit better than the prototype. The astute among you will notice I socketed the AD744 chip, even though I probably didn't need to.  This was to have the assembly house do that it of soldering of the socket to save me from having to do that as well.

I'll be sending the PCB and build info off to the assembly house for a quote on the boards, components, and assembly.  Once that is in hand, we'll kick off the actual order process. I already have prepped a bunch of cases, but I will have to order more, as well as more power bricks.

It's been a long road, but I see the destination in the distance.

After the PCB house gets done and I get the boards back, I have some discrete stuff to still solder on.  The LED's are somewhat tricky as they have to be extended up to protrude from the top of the case, so spacing is critical.  That being the case, I decided to solder a few parts myself after the automated build.  Trying to space the LED's by hand was tedious and difficult, so I created this little fixture to aid in the process, it's used to place the four components indicated.  The pins are alignment pins, they engage the mounting holes to precisely position the board in the fixture.  The extra holes are just to clear the capacitors already on the board.

This is the board in place for the soldering of the four components.  You can also see the two bypass caps I added.  It didn't seem to miss them, but since they're probably a good design practice, why not include them while I can.


Images (3)
  • mceclip0
  • mceclip1
  • mceclip2
leapinlarry posted:

Being that the Question came up about the ground plane that many of us TMCC/Legacy operators have installed, would it be possible to use Both, the ground plane and your new system? Also, any idea when they will Be Available? Happy Railroading.

We at the NJ HiRailers have an extensive network of earth ground wires installed.    Which helped a lot.  We then added Jim LeFevre's analog (tube) "booster", which helped even more.  After Gunrunner built a prototype of his version of Dale's Booster we swapped that in for the tube booster and it improved even some more.

Long story short,  the earth ground enhancements and the booster are a great combination.    If you have earth ground wires installed don't remove them.  Every little bit helps.  

I'll go one step further to say that ground plane wires and the booster are not mutually exclusive. Each addresses the signal issues in a different way.

To really know if your layout requires the booster, you should build a signal strength test car, and measure signal levels around the layout. Technically, you should only employ the booster after you've exhausted the possibilities with ground plane wiring. If you haven't done that, the booster alone may not solve your problems. Further, not all signal problems are the fault of the layout. Some may be caused by factors unique to the locomotives themselves

Having said all that, I don't want to discourage anyone from purchasing one. At worst, it's a $20 donation to the American Cancer Society in Dale's name. At best it might be a magic bullet for you.

I have one of Dale's prototypes on my layout right now, and while signal strength has greatly improved layout wide, I still have problems with some engines, leading me to believe that the trouble can be internal to specific engines, things like antenna placement and length or shielding of a coil on the rail sounds board on earlier TMCC engines.

gunrunnerjohn posted:

I don't see why you couldn't leave the ground plane.

All the folks on the list will be getting email when I get my quotes back for the board build.  I'd estimate a few days before the "official" announcement of actual orders.

Thanks for following thru with this John, looking forward to it.


The emails to all the interested parties have gone out, please check your SPAM filter if you haven't received it.  I have already received a couple of bounces, if either of these seem familiar, please contact me with a good email address if you're still interested in the TMCC Buffer.  If I get no response, I'll assume you are no longer interested.


Images (2)
  • mceclip0
  • mceclip1

Add Reply


OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)

Link copied to your clipboard.