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gunrunnerjohn posted:
Gregcz1 posted:

Hi John,

Thanks again for this project.  I just hooked the buffer up and got a RED light.  I did run some engines that were always susceptible to interference like my K-line 2-6-6T and it had NO flicker at all with good response of commands.

The readings I got were: base signal - 1.085, output signal - 10.37.  Any thoughts on what I should do/check?

Thanks,

Greg

First off, is this a Legacy or TMCC base?  The TMCC base will usually get a red light and a few of them get the "no light".  A good Legacy base should give you a green light.

I agree with Chuck, something is very wrong with the readings, with a known good Legacy base I got 1.88 volts DC for the Base DC reading and 5.4 volts for the Boost DC reading.  Given the circuitry there, that's about what you should see.  10 volts on the Boost DC reading is knocking on the door to impossible!  What kind of meter are you using?

My "control" system is a Legacy Base which is also hooked up to a TMCC base.  My testing meter is a Sperry DM-4400A.  Now, today, I just retook the measurements and got .918 for base signal and 3.63 for Boost signal (but that reading was where it finally stop dropping after a minute originally registering at 4.2 v.  

I disconnected the command base from the Legacy Base and got similar readings. 

Does this mean my Legacy Base is faulty?  If so, is there anything I should look for to fix or must it be returned to Lionel?

Thanks,

Greg

The lights and the DC output voltage are a very simple rectifier circuit that then feeds the DC output terminal and a voltage divider to drive the bi-color LED.  In my testing I verified the actual input  base voltages that the would trigger the red and green lights.  I spot checked some of the buffers DC outputs, though given the light performance, I didn't expect them to be off.  The red light starts coming on right as the base PP signal goes below 4 volts, and the green light starts to illuminate around 5.26 volts.  Those numbers typically varied by around 5%.  I will say, if you get a red light with a Legacy base, I'm 99% sure you have a low signal output that should probably be addressed.  The only way to be sure is to measure the actual command base output signal.

All the voltage measurements were done with a Fluke 8012A bench meter, the 'scope measurements were done using the ATTEN ADS 1102CAL digital 'scope.  The test "base" signal was 455khz from an HP 3311A Function Generator.  In the development, I verified the operation with a couple of the original TMCC bases, one BASE1L, and a couple of Legacy bases.  That was to insure that my test setup would reflect the real world.  Obviously, I couldn't use a real command base for the actual production testing as I had no reliable way to vary the voltage from the base to test the buffer response at various signal levels.

I remember that Dale had spent significant time talking about the measurement using a similar diode circuit and in fact was including a cheap HF multimeter to get consistent results with every kit he produced to measure the TMCC/Legacy base output voltage.

I'm thinking maybe we need an independent cheap TMCC/Legacy test board just to verify the actual output of the command bases.

Well, Lionel is the folks that can address low output of the Legacy base.  If you know someone with a 'scope, you can measure the output objectively. 

I thought to further this discussion, I'd post a few waveforms that illustrate how I tested and why I felt the signal generator was a suitable replacement for the command base to test the buffers.

As you can see, all of the bases and my test generator put out a similar clean waveform.

HP 3311A Function Generator Output

TMCC Buffer Testing, HP Function Generator 455khz Output

Good Legacy Command Base Output

TMCC Buffer Testing, Legacy Command Base Output

Bood TMCC BASE1 Command Base Output

TMCC Buffer Testing, TMCC BASE1 Command Base Output

Attachments

Images (3)
  • TMCC Buffer Testing, HP Function Generator 455khz Output
  • TMCC Buffer Testing, Legacy Command Base Output
  • TMCC Buffer Testing, TMCC BASE1 Command Base Output
Gregcz1 posted:

"I'm 99% sure you have a low signal output that should probably be addressed."

How do I do that?

I am sure it is the Legacy Base, because I hooked up the buffer to the TMCC Command base and the buffer flashed green for a quick second and then went out.  So that seems to be "behaving" the way you described. 

 

I've seen a couple "low output" Legacy bases. I don't know what is fragile on their output circuit, but Lionel can and does fix it free.

If were looking for a low cost handheld oscilloscope to measure the output signal of either a Legacy Base or TIU  would this $25 one work??

New Assembled DSO150 2.4 inch LCD Display Digital Oscilloscope with Probe

eBay item number:
222948398748 
 
OR
 
NEW ATTEN GRATTEN GA1102CAL 100MHz 2CH Digital Oscilloscope 7" LCD 1G Sa/s
 
This one is $300 but with what I spend on trains this $$ is not much of an issue.

Obviously, the ATTEN one would work fine, but the DSO150 doesn't have the bandwidth in reality.  You want a bare minimum of 10x the sampling rate of the signal you're measuring, and the sampling rate of the DSO150 is 1Mhz, a 2x sampling rate. 

The ATTEN is very similar to the one I use, AAMOF, I suspect it's the same one with slightly different panel markings.  All the controls look identical as well as the bandwidth and sample rate. 

ATTEN ADDS 1102CAL Oscilloscope

Attachments

Images (1)
  • ATTEN ADDS 1102CAL Oscilloscope

And the DSO150 has an analog bandwidth of only 200 KHz. I have a DSO 068 which is a great little handheld OScope and has a bandwidth of about 3MHz with equivalent time sampling rate of 20MHz which would work for this repetitive waveform. It’s a kit, so it’s even more fun...but there are similar non-kits if that kind of fun is not in your desires. JYE Tech is the company.

Billsrr posted:

Got everything wired up got the green.  I have two questions, 1 do I need to have the legacy base above the track level and 2 can I link the TMCC base and the Legacy base together?  Thanks Bill

The only thing having the Legacy base above track level or line of sight is base to remote communication is better. 

The TMCC base and Legacy base being connected via the supplie Y cable that came with Legacy should have zero to do with the booster. When connected like that, the TMCC base sends its information serially to the Legacy base.  The Legacy base then sends that info to the track. Do not connect both Legacy base and TMCC base to the track or booster from the U connection. Just the Legacy base. 

The only other precaution is not to put the buffer right next to the Command bases, give it a few inches of space.  Also, don't bundle the buffered track signal and the TMCC/Legacy base signal, I had a report that caused crosstalk and scrambled the signal.  Since they're in phase and one is three times the amplitude of the other, I can easily see how that could build yourself an oscillator if there's enough of a run right next to each other.

gunrunnerjohn posted:

Yep, but I have to say, if you're going so spend $70-80 and hours of construction for a kit 'scope, why not spend $200 or so and have a 50mhz dual-trace 'scope?  There are a lot of times I find the dual trace to be very useful, and wish I had even more traces.

 

Yes, good point. I buy kits for kit fun. I have a Rigol that looks like your scope for daily use. Also a Tek 2215 on a cart for easy use off the bench. 

MartyE posted:
Billsrr posted:

Got everything wired up got the green.  I have two questions, 1 do I need to have the legacy base above the track level and 2 can I link the TMCC base and the Legacy base together?  Thanks Bill

The only thing having the Legacy base above track level or line of sight is base to remote communication is better. 

The TMCC base and Legacy base being connected via the supplie Y cable that came with Legacy should have zero to do with the booster. When connected like that, the TMCC base sends its information serially to the Legacy base.  The Legacy base then sends that info to the track. Do not connect both Legacy base and TMCC base to the track or booster from the U connection. Just the Legacy base. 

Thanks, Does that mean that I wont be able to use the cab 1's.  

It means you can use the Cab 1. The Cab 1 talks to the TMCC base and the digital output (DB9 connector) from the TMCC base goes into the digital input (DB0 connector) of the Legacy base. Then the Legacy base sends the signal out to the track...or in this case to the booster and then to the track.

Not at all Bill.  When you connect the BASE1 to the Legacy base, that enables the CAB1 to send commands over to the Legacy base and out to the track.  The buffer doesn't change any of that wiring, just leave it as is.

  1. The only thing you do to install the buffer is remove the wire to the track from the Legacy base and connect track to the buffered output. 
  2. Connect the legacy base track output to the buffer input.
  3. Finally, install the tether and connect the loose wire to the Earth GND on the buffer.

The buffer is installed ready to do, plug it in and away you go.

Good, news, I installed the DM Buffer and all the weak signal issues in the freight yard are gone! But there is some interesting news. First a little about the layout for background. It is S gauge, about 800' of track on 4 levels, 4 reverse loops with electronic auto reverser boards. Power is 8 independent power districts, each fed by one handle of a pair of ZW-L's. One Legacy base, 37 LCS modules. There are about 40 blocks spread across the 8 power districts, each block has both rails isolated since it is 2 rail. There are 25 .1microfarad capacitors across the 2 rails to assure all blocks have the Legacy signal on both rails.  All the track has aluminum tape under it for good signal.

When powered up the indicator appears solid red with flashing green. It flashes green irregularly but about 5 flashes/second. Voltage measures about 1.5V in and 3V out. Works that way with any one or all of PD's one through 7 powered up with voltage on the rails. The Legacy signal is perfect all over the layout. When I power up PD 8, singly or with other power districts the indicator goes solid green, the output voltage jumps to 15V, then over about 10 seconds it slowly ramps down to 11V and stays there. The input voltage does not change. What is really interesting is all the occupied track blocks in PD8 are unpowered at this point when I measure this high output voltage because the BPC2's controlling them are off. The trains run perfectly all over the layout. PD 8 is a 6 track passenger yard, an 8 stall roundhouse, 3 turntable feeder tracks and the rails on the TT. My initial thought was this is related to the auto reverser board that feeds power to the TT rails but thinking more about it I do not feel that is possible. As long as the system keeps working I am not going to worry about it but it sure is puzzling.

I have a second higher quality meter I need to find to get a second reading of the absolute voltages, but the voltage out definitely increases based on the indicator light.

BILLSRR:   I had the same problem,  Legacy control worked but my Cab-1's weren't responding.   I wrote to GRJ, he recommended I move the CAB-1 Base unit...   I ended up having to move it several feet, and down near the floor, but then it started responding to commands from my CAB-1 and flashing the red light on the CAB-1 base indicating it was getting a command....   Everything is working great now, both my CAB-1's and my CAB-2 controllers....     I would assume when your CAB-1's "aren't working", you're not getting any flashing red light on the CAB-1 Base when you attempt any control with the CAB-1 Controller ???  that was my situation.  

In 2 rail an auto reverser system is needed because when the TT rotates 180deg the right rail becomes the left rail and vice versa. In 2 rail a TT becomes its own reverse loop. In 3 rail the center rail is always the center no matter which way the TT track is aligned. Same reason I have all these relays to change which wire powers the frog when the turnout is thrown.

I did some additional tests with a better quality digital meter. Without any of the tracks powered I read 1.3V input and 3.6V output. This time I turned on all the track blocks so there was plenty of load with engines and passenger cars. When PD 8 is turned on The output voltage jumps to 13.5, then drops to 11.5 as before. With the better digital meter I see the input voltage jumps from 1.3 up to 1.7V and stays there.

I need to investigate your idea there is a connection somewhere between earth ground and the track. With the input voltage change that is the most likely cause. In the interim, the system is working.

Gregcz1 posted:
gunrunnerjohn posted:
Gregcz1 posted:

Hi John,

Thanks again for this project.  I just hooked the buffer up and got a RED light.  I did run some engines that were always susceptible to interference like my K-line 2-6-6T and it had NO flicker at all with good response of commands.

The readings I got were: base signal - 1.085, output signal - 10.37.  Any thoughts on what I should do/check?

Thanks,

Greg

First off, is this a Legacy or TMCC base?  The TMCC base will usually get a red light and a few of them get the "no light".  A good Legacy base should give you a green light.

I agree with Chuck, something is very wrong with the readings, with a known good Legacy base I got 1.88 volts DC for the Base DC reading and 5.4 volts for the Boost DC reading.  Given the circuitry there, that's about what you should see.  10 volts on the Boost DC reading is knocking on the door to impossible!  What kind of meter are you using?

My "control" system is a Legacy Base which is also hooked up to a TMCC base.  My testing meter is a Sperry DM-4400A.  Now, today, I just retook the measurements and got .918 for base signal and 3.63 for Boost signal (but that reading was where it finally stop dropping after a minute originally registering at 4.2 v.  

I disconnected the command base from the Legacy Base and got similar readings. 

Does this mean my Legacy Base is faulty?  If so, is there anything I should look for to fix or must it be returned to Lionel?

Thanks,

Greg

I just realize that I get the 10 volt readings when the transformers supplying the track power are turned on.  Is that normal?

It shouldn't affect the readings at all, if you're seeing that, looking at the schematic of the buffer, I'd suspect that somehow you're getting a 60hz voltage differential between earth ground and the outside track from the transformers.  When I do this on my test layout, I see no variation of the DC monitoring voltages regardless of the transformer setting.  Even introducing a 100 ohm resistor between earth ground and the buffered output, I don't see a significant change, just about a .2 volt jump.  I'm using a TMCC base, and I'm getting 1.25V base and 4.14V boost.

In short, I don't know what's going on.   With 2-rail, a lot could be different, I have very little experience with TMCC/Legacy on 2-rail of any scale.

Last edited by gunrunnerjohn

John, one of the reasons I posted some of the details is I was thinking I might be the only purchaser of the buffer with a complex 2 rail layout. Dale himself was curious about differences with a 2 rail layout. We were in communication about 3 months before his passing, making plans for a visit with his prototype and test equipment. He lived about 1 1/2hours north of me. Unfortunately that never happened.

In 2 rail there is no outside rail electrically speaking. Either of the 2 rails can be connected to the common post or the 0-18V variable post depending on the last action of any or all of the reverser boards. These boards actuate by sensing the short circuit current when the lead truck crosses a reverse loop junction. I will post a picture of one. Unlike the DCC version, in high current AC applications there is quite a visible spark before the board reverses the connections. The only other difference I can think of in 2 rail is the use of .1microfarad capacitors connected across the 2 rails for the Legacy signal. 25 of these cannot be enough to affect anything.

I will figure this out, due to the size and large number of connections it may take some time. The good news is every wire runs through terminal strips and all have spade lugs on the wire ends so removing and replacing any connection is easy, there are just A LOT of them. I also have all the wiring diagrams with the color codes and all the track feeder locations with the rail gap locations.

legeacy base with low output boost (.800volts) I called lionel to return and they said to reset channel and try. And should not have any other controller base connect to track. The other strange thing I noticed was when I unhooked my ground plane from the water pipe My reading on my cab-L increased and I now have no light instead of red with a voltage of 4.29 boost out

chris a posted:

BILLSRR:   I had the same problem,  Legacy control worked but my Cab-1's weren't responding.   I wrote to GRJ, he recommended I move the CAB-1 Base unit...   I ended up having to move it several feet, and down near the floor, but then it started responding to commands from my CAB-1 and flashing the red light on the CAB-1 base indicating it was getting a command....   Everything is working great now, both my CAB-1's and my CAB-2 controllers....     I would assume when your CAB-1's "aren't working", you're not getting any flashing red light on the CAB-1 Base when you attempt any control with the CAB-1 Controller ???  that was my situation.  

Thanks I moved the TMCC base down to cable limits and moved the buffer up and all things working, I didn't know anything about the signal led on the Tmcc base. I will look at that. Sure is nice to have all of you out there to help.

You connect the Legacy system EXACTLY as before to power!  That was an oversight in the pictures, but clearly you need the Legacy command base to have power!  The tether that is supplied just goes between the Legacy brick and the command base to tap off the earth ground for the buffer, the earth ground for the Legacy base comes through the Legacy brick's ground pin.

Hey John, here down at AGHR in LA, the buffer was installed a week ago. While the red light is on the buffer, previous bad signal areas have been resolved. Swapped out the Legacy base with another and LED was still red. Before we take any further action, I will have Adrian evaluate the situation. BTW, Adrian is on assignment in New Mexico for NASA and hopefully will be back soon. We miss him!

I suspect for whatever reason you're not getting the more than 5V to light the green indicator.  The red indicates you're getting 4V P-P or less, that's not what a good Legacy base should be doing.

Just for yucks, disconnect the track signal from the buffer and see what the signal indicator does with the base connected to the buffer.  It shouldn't have an effect, but who knows. 

The red light is strictly checking the base output, it doesn't have any connection on the output side of the buffer.  Since the buffer could be driving any kind of load, it was pretty hard to pick a number for what voltage you should see out.  I figured it was more important to know if the base was having an issue as that's far more likely, the buffer is a pretty simple circuit and should be very robust.  There's also nothing to adjust, it just does it's job.

Last edited by gunrunnerjohn

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