Strange issue with MTH Premier SP GS4 Proto 2

Edit- added explanation in (red)

@Texchap posted:

I powered up the transformers (More than one transformer, the order they power up can be important) running to the TIU and the track.  I had not turned on the remote yet.  As soon as the power hit the tracks all the passenger car lights went on and for some reason the GS4 Daylight started up.  I turned on the remote and tried to shut it down but it was non responsive. (Because it started in conventional mode missing the watchdog signal) All of the other trains responded appropriately.  I killed the power and moved the Daylight to another track.  It worked fine. I shut the power down again and shifted it back to the original track and it worked fine.  It started itself up one other time, I shut down the power to that track, made sure the remote was on and powered up the track again it worked fine.  I am suspicious that Fixed Power 2 on the TIU is the culprit and not the engine.  Any ideas?  Thanks.

Easy answer- If you power fixed 2 BEFORE fixed 1 is powered- the TIU logic is not powered and thus no watchdog is sent. Also a watchdog is ONLY sent when a track channel goes from not powered to powered state as sensed by the TIU.

Again, the facts:

#1 TIU needs power for it's own logic and DCS signalling. It gets this power one of 2 ways- either via aux input jack on the end of the TIU or borrowing power from fixed 1 input. No other channel can be powered first BEFORE the TIU has logic power.

#2 Watchdog- the DCS signal is present signal to keep a loco from powering up in conventional is ONLY sent out a TIU channel when the TIU has logic power- either via fixed 1 input being powered first or aux power in. Then the second part- when a channel goes from not powered to powered- then the watchdog is sent. If fixed 2 had power BEFORE fixed1 and there is no power also going into aux power jack- the TIU fails to send a watchdog.

#3 PS2 and PS3 engines look for this watchdog DCS signal on the track when first powered, then switch to conventional mode and may not respond to DCS commands if started in conventional by missing that critical watchdog signal.

Highly recommend powering the TIU itself via aux power in. This allows any channel to be powered independently (first, instead of fixed1) and send the watchdog and DCS signal in general.

@Vernon Barry posted:

A 12 to 22V AC or DC supply ideally about 1.5 to 2A rating.

MTH made a part number but it does not have to be this supply MTH 50-240 Z-DC24 24-Watt Power Supply

If just using the TIU- 12V is fine and the lowest source I would use, however when using the TIU with an AIU- the AIU is getting and using a 12V source from the TIU- so input to the TIU needs to be greater than 12V for proper headroom to provided that output voltage to the AIU. Again, better here is that 14-22V input range.

Not trying to make this confusing, just trying to be complete. My own layout, I do not use AIU normally, so 12V DC 2A aux power input works great. I discovered however when testing AIU functionality (just to learn more about the AIU and it's technical details), a higher voltage input was required or else the AIU did not work for me.

@Vernon Barry posted:

Reach into the surplus pile of wall power adapters many folks have left over from old wireless routers- many are 12V with at least 1A or greater and have the correct coaxial power jack.

@Vernon Barry posted:

Easy answer- If you power fixed 2 BEFORE fixed 1 is powered- the TIU logic is not powered and thus no watchdog is sent. Also a watchdog is ONLY sent when a track channel goes from not powered to powered state as sensed by the TIU.

Actually, that's not true.  If you power FIXED 2 only, indeed no WD is output as the TIU logic is inactive.  When you power the TIU however, FIXED 2 will indeed get a full WD output.

The TIU logic is not powered, thus is can't react to the fact that FIXED 2 was already powered.

A warning about using cast off walwart power supplies.  Double check the coaxial jack for polarity.  At one time, things that ran primarily on batteries, but could take a walwart, had the center pin negative, while other devices that ran solely on a walwart, had the center pin positive.

@CALNNC posted:

A warning about using cast off walwart power supplies.  Double check the coaxial jack for polarity.  At one time, things that ran primarily on batteries, but could take a walwart, had the center pin negative, while other devices that ran solely on a walwart, had the center pin positive.

The TIU aux power input is AC or DC- any polarity. So in this case, that doesn't matter but yes- always good to read and understand the label.

Hi since you saying it starts up sometime and sometimes not It would check your dcs signal strength with remote should be all tens ! Alam

Well, in order to check the signal strength with the remote, it has to actually be checking a locomotive.  If you want to strictly check the output DCS signal from the TIU, the DCS signal tester is the best way to do that.

This device was an outgrowth of the extensive thread on testing the DCS signal from the TIU.

Design of a $10-20 DCS-TIU Port Tester Tool?