Digitrax DB150 Booster Question

[shark_jj]

I have been trying to track down an intermittent short on the layout for several weeks now.  In the course of that search, I noticed an anomaly with my DB150 Booster.  Here is the setup I am using.  I have a DCS100 Command Station, with a DB150 Booster, and 4 PM42's.  The issue I am having is with Track Power.  When I first turn on the layout I throw an AC Switch to power up the transformers attached to the DCS100 and the DB150.  When the DCS100 turns on the Track Power for the Command Station is OFF.  However the Track Power for the DB150 is on.  To turn on the Track Power for the DCS100 I use a throttle with the standard Power + activation that Digitrax uses. 

My question clearly is why is the Track Power already on in the Booster.  I would have thought as a Booster it would take Commands from the DCS100.  My first thought was maybe it was no longer in Booster mode.  I got out the manual and had a read.  The Power On light on the bottom left of the DB150 was flashing at a steady beat every 1/2 second which shows it was in Booster mode.  To be sure, I disconnected the DB150, powered it off, disconnected all of the wires in front with the exception of the jumper from Config A to Ground and then went through the Booster setup protocol again.  Same results, the Power On light is flashing at a steady beat every 1/2 second which shows it is in Booster mode.  I looked up in the manual to see if there was a way to manually connect Track Power to the DCS100 but had no success other than the possibility that OP Switches 33 and 34 might have something to do with it, but the way their description is written it is hard to tell.  Digitrax manuals are certainly a challenging read. 

In any event, this setup has been operating for over a dozen years so its not an earthshattering problem but I would like to solve it if I can.  If anyone has encountered this or can give any guidance I'd appreciate it.  I've attached a picture of the front of the units and the setup.

[Hiroe]

Do you normally set the track power to off before shutting down the layout, or do you leave it on and just shut off the power supplies? I'm no digitrax expert (and honestly I loathe how deeply flawed and unnecessarily technical the system is), but I seem to recall that the boosters retain the last track power setting before they lost power.

[GaryHinshaw]

I have a similar hardware setup (but with a DCS240 command station instead of a 100).  I rarely power down the input power supplies, I just put the two systems into sleep mode, which draws minimal power.  When I want to operate, I flip the stations to run mode and toggle track power with the throttle.  This toggles both the command station and booster sections simultaneously. 

When you turn track power off with your throttle, does that toggle all of your track power or just the command station's sections?

I can test what happens when I power cycle the booster when I get home tonight.  I vaguely recall that it behaves as you describe (which is weird).

[John]

Change the batteries lately in the DCS100?

Make sure your settings in the DCS are still set properly ..

Also, the recommendturn on the DB150 first, flip switch to run, then the DCS100 and flip switch to run

[GaryHinshaw]

I can test what happens when I power cycle the booster when I get home tonight.  I vaguely recall that it behaves as you describe (which is weird).

Ok, I misremembered; no combination of mode switch or power cycling caused my track power to spontaneously turn on in my booster segments (or in my command station segments). 

I do now recall one quirk of my setup: when my DB150 is in booster mode (i.e. with the GRND/Config A jumper as you have) I had to reverse the polarity of Rail A and Rail B relative to the command station's polarity.  If I read the colour coding in your photo correctly, you have the same polarity on both sides.  Do your locos cross a power district without shorting?

[shark_jj]

Hi Gary, I was doing some reading about the DB150 and read what you described, that the polarity of the command station (DCS100) and the polarity of the booster (DB150) were reversed.  Some time ago when doing the wiring  I did have to reverse the track buses at the PM42 to sort out the polarity between the track sections powered by the DB150 and those powered by the DCS100.  I have now reversed the Rail A Rail B connections on the DB150 and put the track busses at the PM42 back to normal.  Polarity is good through all power districts.  I am wondering if my intermittent short due to change of polarity was occurring due to the Rail A, Rail B not being wired in the correct order, even though it has operated fine for over 15 years.  I have been running a train around the layout for hours now and the short has yet to appear again.  Fingers crossed.

As for the DB150 staying powered on even though the DCS100 is shut down, I am wondering if that might be tied to the fact that the DB150, which was a Command Station when I first got into DCC is in effect a "smart" booster as opposed to the DB100 or DB200 which are in effect "dumb" boosters and need to be hooked to a command station to receive commands.  Bottom line, since it is causing me any issues I am going to let sleeping dogs lie.  If the short reappears I think I will contact Digitrax and see if they can offer any advice.  if that happens I'll let everyone know what they say.

[Maletrain]

Should the "ground" terminals on the DCS100 and the DB150 be connected together?  That is the way it is set up on our club layout.  My understanding is that connecting these "grounds" (which are NOT the same as the ground in your house wiring outlets) is needed to pass current when there is a loco bridging the rail gap between the booster and the command station.

[shark_jj]

That is a really good question.  The Digitrax manual makes no mention of that.  It simply says that you connect the Config A to Ground on the DB150.  It is that connection which converts it from a Command Station to a Booster. 

[shark_jj]

Maletrain, your suggestion made so much sense, I have been doing a little bit of research and found numerous references on the web to connecting the grounds between the command Station and the Booster and watched a couple of videos by Larry Puckett, "The DCC Guy" who also makes the same reference.  I went back to the Digitrax Manual for setting up the DB150 as a Booster and there is a wiring diagram which does not show that connection.  There is also no mention in the write up in the Manual.  I have had previous experience with poor manual writing by Digitrax so I'm going to follow your guidance and hook the grounds together between the Command Station and the Booster.

[John]

Also boards line se8 and bdl’s need a ground tied to the boosters.  Best to run a ground wire around the layout for those items.  Not sure about the newer Digitrax detectors and signal boards

[shark_jj]

Thanks for that point John.  I don't have those devices but my buddy who is putting in detection and signalling does, I will share your thoughts with him.  I think part of the issue is Digitrax's use of the word Ground which has a certain connotation, when it appears that the ground wire from the command station is more of a common hooking everything together.

[shark_jj]

I want to say a big THANK YOU to everyone who responded to this thread.  I haven't solved the original problem I posted, but with your insights and help I have resolved a much bigger problem.  That "Ground" wire definitely needed to be connected between the DCS100 and the DB150.  One of the reasons I purchased the UR93 and the DT602 and UT6 throttles was an apparent inability to maintain radio control around the layout.  This showed up as a lack of control of locomotives at certain points in the room.  You would lose the ability to reverse or to alter speed without plugging in.  My buddy was over Friday and we were reviewing everything you had shared and trying to recreate my intermittent short and we were running a set of locomotives around the layout using a DT402R and sure enough he encountered the loss of control in certain sections. 

After he left I was thinking about it and the sections he lost control in were the sections controlled by the DB150.  I connected the Ground wires in the manner described by Maletrain, which was an interesting little challenge since two 12 gauge wires will not fit in that little slot Digitrax gives you, thank God for suitcase connectors, anyway I digress.  I started up the same two locomotives and ran them around the layout.  In each power district I stopped, started, reversed, and changed speeds without any loss of control whatsoever.  The lack of that Ground wire connection was at the root of my loss of control problem not the radio signals from the UR91.  As another aside, when I was at the same buddies on Thursday, I looked at his DB100 Booster and that connection is not called Ground but rather Sync.  Which in retrospect makes more sense since it appears to synchronize the signals between the Command Station and the Booster. 

My Command Station/Booster have been setup this way through 2 layouts now and I never realized it was wrong.  I will be the first to admit that my knowledge level of electronics is somewhere north of zero, but what I can do is follow instructions.  To that end when it comes to DCC stuff I am very reliant on the manufacturers manuals and instructions.  Digitrax clearly did me no favours with there DB150 manual as both the written directions and the diagrams never show this hookup. 

This may also clear up my intermittent short problem, but only time will tell, that is the nature of intermittent.  In closing THANKS AGAIN guys, your assistance was truly appreciated.

John

[GaryHinshaw]

Well, I hate to muddy the waters, but I had exactly the opposite experience with connecting the grounds between my command station (which is a DCS240) and my DB150: I could not get the pair to start up properly without beeping incessantly, so I removed it and everything works fine.  I'm not suggesting that you remove the connection, but I think your experience points to a problem with the Loconet connection between your command station and booster.

Think of your system this way: each power district is like its own standalone layout with its own command station.  The role of a command station is to provide power to the track (really it's just passing through power from the 5A power supply) and to provide commands to the decoders to tell your locos what to do with the power.  When you have two districts, the second command station (the DB150) is just getting its commands from the command station and passing them on to the second track district.  These commands are routed via the Loconet cable between the command station and booster, then sent out to the layout.

The fact that you couldn't command a loco in the DB150 district strongly suggests a problem with the Loconet connection between your two units, i.e., that the DB150 was not passing commands (reliably).  I think it's possible that connecting the grounds fixed that connection in a back-door way.  If you're willing, I would suggest replacing the Loconet cable between your units and removing the ground connection, then see if you still have loss of control or not.

[Extra credit] I thought the only reason to connect the ground terminals was the following: when a loco is bridging two power districts, it is getting power from two different power supplies and the current is split between them.  If there is a momentary imbalance in the current leaving and returning to a given power supply (for example, if the resistance in your Rail A bus was slightly different than your Rail B bus in one or both districts) then current might prefer to flow between the two power supplies during the moment of bridging.  If you don't connect the grounds between the two stations, I believe its possible for this imbalance current to pass through the ground of the (skinny) Loconet cable.  (I may be wrong about that though.)  In any event, it should only happen when locos are bridging two districts and there is an imbalance in your power wiring, and it should only be a few mA for a few seconds, so not typically a big risk.

TLDR: test and/or replace the Loconet cable between your DCS100 and your DB150. 

[John]

This is worth watching .. starting about minute 7

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and this

starting minute 6

[shark_jj]

Gary and John, thanks for the info.  Once again I want to re-iterate I have no expertise or experience in anything electronic.  For me this is about research and making the best informed decisions I can.  With regards to the Ground question and following in John's footsteps I have been watching Larry Pucketts videos.  One in particular he put out 3 years ago which was called Wiring Your Model Railroad for DCC - Boosters and can be found at:

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he calls for a ground connection between a Digitrax command station and a Digitrax Booster.  Those comments can be found around 12.28 in the video.  He agrees with both of you that this is about bridging the gaps between power districts.