Dennis, thanks! If there is enough interest, I might do another small run of 8-10 of these, hopefully before more components go obsolete. 
GRJ, you should design it using vacuum tubes and discrete components, those never become obsolete *lol*. (Actually, am surprised someone didn't serious suggest that).
Don't laugh out loud. I was the one who built the original signal booster. It used 2 vacuum tubes and a hand wound final output coil. Several large TMCC railroads with signal problems built it and it worked and solved their problem with TMCC signal loss. I am still using my vacuum tube one. Several people wanted a more modern one that was solid state. Dale took up the challenge and that is where it is today.
I miss the smell of hot Bakelite in the morning...
@cjack posted:I miss the smell of hot Bakelite in the morning...
Actually I was reminiscing about Bakelite reading of GRJ challenges with the case. I recently used a heat gun to shrink some tubing inside a plastic case....and the case started deforming!!! Bakelite would never do that!
Hi Jim Lefevre, just curious what Vaccuum tubes did you use when you built the tracks signal booster would like to see schematic. and parts values!
sincerely thanks
Alan
6J6?
I used a 6X4 for the full wave rectifier. A small power transformer with 6.3 volts and 250-0-250 volt secondary. A hammond part. The tube used for the amplifier was a 6AQ5 beam power tube. The output coils was custom wound on a piece of PVC water pipe and tuned 455 Khz. The schematic was on this forum at one time. Might still be there somewhere. If it is not and you are really interested I still have the plans and diagrams.
A simple search of this forum's database discusses the tube solution. The solution is illegal to use because of an excessive power level. The OGR Forum moderator had to shut down the discussion.
I observed the signal from my vacuum tube model and calculated the output. The waveform was no higher in Peak to Peak value than a standard TMCC base. As a matter of fact I did experiment with boosting the signal higher than the normal TMCC output and found that had little if any effect. The real advantage to my circuit was the custom wound output coil that was tuned to 455 Khz.
If you take an oscilloscope and look at the electrical signal on a large layout you will find a massive amount of electrical noise. So bad as to the point of obliterating the TMCC base signal. It just makes if to hard for the receivers to filter out the signal they need. The output coil in effect shorts the outside rails to ground and gets rid of the noise. The primary of the coil is in the plate circuit of the 6AQ5 and actually steps down the output since the primary has more windings than the secondary. In short it does more to clean up the signal by shunting the electrical noise ( all those rails are a huge antenna for any RF in the area ) and then only apply a clean TMCC signal.
A simple observation of the TMCC output signal from the standard base with nothing connected and the output of signal of my device are virtually the same. The advantage of my unit is that it couples to the track much better than a TMCC base output and shunts all other signals and noise to ground, reducing their intensity so the actual TMCC signal can now be clearly seen on the oscilloscope.
I did promote it as a linear amplifier at one point but I found that a signal with more amplitude was not any real benefit. The real trick is to get the TMCC signal injected onto the rails with a device that has really low impedance. The standard TMCC base does not do that.
I got sideways with someone on the forum over it and the subject was blocked. Dale did a good job of converting it to solid state and I have never seen his diagram or what was done to help with impedance matching of the output.
There was nothing illegal about the power output level of my device.
Jim, watch your mailbox. 
@Jim LeFevre posted:Don't laugh out loud. I was the one who built the original signal booster. It used 2 vacuum tubes and a hand wound final output coil. Several large TMCC railroads with signal problems built it and it worked and solved their problem with TMCC signal loss. I am still using my vacuum tube one. Several people wanted a more modern one that was solid state. Dale took up the challenge and that is where it is today.
Bob at NJ-HR said they cooked their tube one tinkering with the final output coil turns ratio, they currently have at least two of the solid state model, obviously only one in active use. 
Some interesting background on the buffer, this is something Dale wrote in 2013 before he designed the solid state model. I also found the tube schematic
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Yes. I was thinking about the capacitance when Jim mentioned the step-down output.
I did some testing on the ability of the TMCC Buffer to drive a large capacitive load vs the Legacy command base. I found that the TMCC Buffer could drive a much greater capacitive load than the command base, almost 5:1 difference.
When I suggested using a vacuum tube based model it if course was in jest, but not surprised someone would actually doing that, I am impressed
As far as the output power of a tube model being too high that is a matter of how well it is designed, tubes are high energy devices (the voltage taken to excite them), but the power output is a function of the design and how many tubes are used and what type. If this was a commercial unit it is true that it would need to be certified under part 15 of FCC rules, but a home brew unit doesn't have to meet that. The person using this might screw up reception in their own house, but unless it was affecting people in other houses (unlikely) there is no law involved.
I will purchase one as well.
@nvocc5 posted:I will purchase one as well.
Send me an email so I can put you in the request queue. I am ordering parts for ten of them, most are already spoken for.
@gunrunnerjohn posted:Send me an email so I can put you in the request queue. I am ordering parts for ten of them, most are already spoken for.
Hey John,
Give me a call about this. I think OGR might be interested in this for our / my layout. Perhaps a couple...but I would rather talk via phone without others having to put up with my questions in this thread! Thanks!
Let me say that I bought the components from GRJ a while back and added the buffer to our layout. Totally improved the reliability of the Legacy locos. No issues since adding it. It's worth the small amount of money and little time of construction. Wish there was something like this for DCS....... Thanks again to all who worked on this project!
Interesting thought. What’s the nature of the DCS signal?
@cjack posted:Interesting thought. What’s the nature of the DCS signal?
The DCS signal is bi-directional, and the ability for the locomotive to talk back can't be amplified without internal control from the DCS controller, AKA the TIU. The DCS signal is also just present when there is a command coming and going, and it's mandatory to know what is happening in the command so you know when to turn the buffer off.
@Adrian! did quite a bit of research on this topic, and no practical solutions were forthcoming. If he can't get it working, I'm not going to even try!
TMCC/Legacy, OTOH, is a unidirectional signal that can be easily buffered because it's always there and it only goes out, there is no return traffic.
The TMCC buffer is simple in concept, any buffering of the DCS signal is anything but simple!
@cjack posted:Interesting thought. What’s the nature of the DCS signal?
Per John above .... Reposted for you:
Legacy is one way (base to train) signaling, so "buffering" is easy. The triangle (amplifier) points away from the base and towards the train.
The first issue is DCS is two way (train to TIU and TIU to train) signaling... so buffering is complicated since ... which way would the triangle point? If it just points one way it's not helpful since it will isolate in the other direction and you'll have no reverse signaling... and if you put two pointing both ways.... well then its just a loop of two triangles and now you have an oscillator. To do this successfully, you would need to "know" when a packet is about to go in one direction or another and switch in or out your triangle directions accordingly, which means the switching thing you build needs other logic signals from deep within the TIU (tapping the logic upstream of the output drivers)... to give your switch enough time to get the amplifier setup. Not easy with a big layout that has 20 or even more different TIU channels. You would need to tap all that logic on all the TIU channels in the layout to see when one of them somewhere is about to transmit a sequence.
The second part is the DCS packet timing: While we do know the sequence is always TIU-to-train before Train-to-TIU the TIU-to-train part is variable length (different commands --> different times) so it's not as simple as having an RC timer or something switch the triangle direction after a certain time constant so the amplifier points one way then the other. Unlike the TIU (who's firmware knows what command it is sending and what packet length it will be, and what response length to expect), you the outsider would need to extract this information from the outgoing packet to get these details for setting direction, and you would need to do it very very quickly since the packet you're decoding is also the packet you're steering the triangles for. That also means you're going to need some kind of fast look-up of the outgoing commands, too much for a microcontroller, it'd have to be an FPGA with a respectable clock... so now you're getting into the $1000 range.
The third issue is that we're talking about trains which move: Like mentioned above it's TIU-to-train, and train-to-TIU signaling. Understanding where to place the TIU-to-train amplifier is simple... you'd put it at the TIU before the connection to the layout... but how would you place the amplifier for the train-to-TIU signal? If you place it at the TIU, well the signals already gone through the layout at that point and all the ringing, distortion, and noise is already in there so an amplifier won't help much at that point. You'd need to place it inside the train (at the point where the transmission originates and is "clean")... That is you'd need to put modules in each locomotive one by one... with a $1000ish FPGA inside tapped into the PS2/3 board to get timing info.
The more you think about it ... the less sense it makes... and that's why we don't have such a booster.
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Interesting. So what’s like that? Cell phones?
Cell phones are full duplex, so they don't have the issues of determining where a data packet starts and ends. DCS is a single channel that can only handle traffic in one direction at a time, so there has to be a traffic cop to determine when it's OK to talk. As Adrain! says, the other major issue is a single DCS channel only services at most a couple hundred feet of track, so any logic has to be duplicated over and over. Finally, the engine return traffic being amplified is very costly.
@gunrunnerjohn posted:This is intended to be a continuation of the original thread for the TMCC signal booster to avoid confusion. I was working with Dale to create the "production" version of the buffer. That involved creating the PCB and building some units. Sadly, Dale passed away before we really got started, so without his input and documentation, the project languished for some time until recently. I enlisted the aid of another forum regular, PLCProf, to assist in recreating the schematic and getting to the point of confidence that we had a working design again.
Here's a recap of where I started after Dale's passing.
As some of you may know, I was working with Dale on this project, my end was to be creating the PCB and packaging once the design was proven. Due to Dale's untimely passing, the project was stalled. Since I never got to actually receive the final schematic, I did manage to round up the prototype. I enlisted some aid in reverse engineering and testing the prototype and the project is moving forward. We have reverse engineered the prototype and are making some tweaks. I'm hoping to maybe have a prototype PCB at York next month, however timing may be tight, so that's only about 50/50 right now. However, rest assured that it's coming soon.
I have what I believe is a completed schematic and I've done a board layout that should work with the enclosure I've selected. I haven't received the boxes yet, so there could be changes, one of the delays I mentioned. The "production" unit will have an off-the-shelf 24V power brick that is detachable. The terminal strip you see on the side will be the "Euro" style, but my 3D library didn't have those. Those terminals are where all the connections to the buffer are made. The board projection with the TO-220 package will have a heatsink mounted to the two large holes and also be outside the box, this is to allow air circulation for cooling the buffer chip. The white line on the board is where the enclosure wall will be, a slot allows the board projections. There is a power LED that projects through the top of the case, and also some signal level LED's that indicate a poor or missing base signal and also a "good" base signal. Connections are also provided that output a DC level corresponding to the signal strength of the input base signal and the output buffered signal.
Discussions should continue in this thread.
DM TMCC Buffer Connections To Command Base & Track
Are there any more of these available? and what is the cost if available.
Thanks,
Joe
John
I have one of your kits but our club is now interested in one. Are there any options now (ie. kits, or boards or gerbers and BOM)? I know this is late to the party . . .
Bob
Bob, send me an email and we'll see what we can do.
TMCC/Legacy Track Signal Booster as a diagnostic tool
First, let me say that I hate long forum posts. And I am now going to violate my own rule . . . So if you are short on time, skip down to the Cliff Notes at the bottom.
I finally got around to building my TMCC/Legacy Signal Booster kit. I have always had trouble with some TMCC Steam engines responding on my 15x25 home layout. This was somewhat unexpected although I have a lot of parallel tracks and tracks crossing over others. I just kind of muddled along with it.
Fast forward to York this Spring. Legacy just would not work on our modular layout in Purple Hall. I blamed it on the building wiring, and figured we were going to need to add a ground plane wire, or I could just build the Signal Booster kit.
The kit went together easily with GRJ’s excellent instructions and photos. So I was excited to hook it up to my home layout for a test. Power on. What?? The signal strength LED is red. With adjustment of the Signal Booster gain control it gets brighter, but it is still red. Have I had a bad Legacy base all along? At this point, as I am anticipating getting an RMA from Lionel, I decided to disconnect the Signal Booster from the track. Now I have a beautiful emerald green signal LED.
OK, now I have a layout problem. I pulled out the ohmeter and measured between the earth ground lead on the buffer and the outside rail. I got 7 Ohms. That’s not right! The layout is pretty much shorting out the Legacy signal. I am amazed that I had any control of my engines. (BTW, the Signal Booster worked so well, that by adding it, my engines responded flawlessly even with the signal mostly shorted out!)
Now started the hard work of finding the short. I do not have any ground plane wires. How is earth ground shorting to the outside rails?
I run Legacy and DCS. Track Power is from a Z4000, a Z1000 brick and a PH-180 brick feeding the TIU. My Legacy base is connected to an LCS WiFi module via the DB9 to PDI cable. The LCS wifi has a PDI cable connection to a Ser2 module which is daisy-chained to 6 ASC modules (TMCC) and 1 BPC module (not yet connected to track). The ASCs control Tortoise switch machines which are powered through diodes from the 14VAC Accessory terminals on the Z1000.
I re-connected the Signal Booster to the track (LED is red again) and one at a time starting with the Legacy base, I followed the problem down the daisy chain of connections:
Unplug DB9 cable from Legacy Base (green)
Unplug PDI from LCS to Ser2 (green)
Disconnect data wire to first ASC (still red)
Disconnect comm wire to first ASC (still red)
Disconnect A and U power connection to first ASC (green).
That’s it. The power leads from the 14VAC Accessory output on the Z1000 to the ASC relay contacts are shorting earth ground to the outside rail. To rectiify this, I moved the power leads to my Z4000 14VAC fixed accessory output and got a nice green light.
14VAC power leads circled in green:
I did verify that the ASC's U connection went to the Z1000 Common, and the ASC's A connection went to the Hot on the Z1000. I thought about reversing the connections, but the ASC manual specifically warns against doing this.
BTW, the Z1000 18VAC track output is phased with the other transformers (I did not check phasing with the 14VAC Accessory output). There must be some common connection in the Z1000 and/or the ASCs to cause this. I’ll leave that up to others to figure out, but at least I have a solution.
Here is a big Thank You to GRJ, not only for making the Signal Booster available to us, but also having the insight to add the signal strength LED feature. I would not have even thought of checking for a short from earth ground to my outside rail had it not been for the signal strength LED.
I’ll post Part II of this story in a few weeks when I use the Signal Booster on our modular layout at the York State Fair.
Bob
Cliff Notes:
1. The Signal Strength LED on the TMCC/Legacy Signal Booster is very useful.
2. If your TMCC/Legacy Signal is poor, check for continuity from earth ground to your outside rail. There shouldn't be any.
2. In my case, the power leads from the 14VAC Accessory output on the Z1000 to the ASC relay contacts are shorting earth ground to the outside rail.
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Tis interesting that you had a grounded situation and the signal generator wouldn’t respond correctly, so you had to clear the ground.
My problem was almost the opposite. I needed a ground and didn’t have it so I had a similar issue. My power adapter didn’t have a ground. A Lionel help call was no help at all and after I made the fix I told them about it and they said well, that’s good to know, goodbye.
Please read my posting of June 4th (Command Control Issue) and let me know if you believe it relates in any way to your problem.
I enjoy reading detailed explanations of electrical issues and yours was really good. Thanks
Well, we both had signal problems. Yours was due to the lack of ground plug in the Cab-1L power plug and therefore no connection to the house ground wiring. Mine was due to the ground wiring being connected to the outside rail. For a good signal, you need a good ground connection and a good rail connection and they must be isolated from each other.
Bob
Always like to hear success stories. When I started reading Bob's first post I was thinking there was an issue with the buffer, red with it should be green, green when it should be red.
John
As I was doing this troubleshooting, I started to wonder how feasible would it be to make a TMCC/Legacy signal strength indicator circuit using a subset of the TMCC/Legacy Signal Booster circuit? Obviously the comparator chip, LED, some passive components are needed. Maybe even a battery powered version?
Keeping your bi-line in mind, is this a project worth looking at?
Bob
Seems like there was a signal strength suggested by Dale thread years ago. Maybe a diode, etc?
@RRDOC posted:John
As I was doing this troubleshooting, I started to wonder how feasible would it be to make a TMCC/Legacy signal strength indicator circuit using a subset of the TMCC/Legacy Signal Booster circuit? Obviously the comparator chip, LED, some passive components are needed. Maybe even a battery powered version?
Keeping your bi-line in mind, is this a project worth looking at?
Bob
Actually, the NJ-HR club made a rolling TMCC signal strength detection engine. Turns out there is an output from the R2LC TMCC receiver that indicates the relative signal strength. They used a BlueTooth capable meter and carried the whole thing around the layout and could map the TMCC signal strength.
Graphing the TMCC/Legacy signal strength over an entire line
Thanks, I found it. Interesting., This link has the details about the meter/car.
Chuck, that's the thread I posted.
@gunrunnerjohn posted:Chuck, that's the thread I posted.
Oh sorry. I'm a bit flustered today. Sciatic nerve pain and that dumb k line engine.
@gunrunnerjohn posted:Most of the original thread disappeared, so anyone that expressed an interest should let me know.
I’m in John, well done.
