Only 15 Volts via TPC 400

15 volts is just a little low but not enough to get to excited about.  On our modular layout, we 2, 180 bricks per TPC 400 and our max output is 17 volts from all 3 TPC's.

You can put your TPC in command mode. No need to dial up voltage.

I have two trains running with passenger cars so there is a load on the layout.I currently have  the TPC 400 programmed in command but the max I can get is 15 volts.I mentioned using the red button only as one of teh things I did to try to dial up voltage. I replaced wire from TPC to track with new 14 gauge wire, no change.Voltage coming from two power paks is 18 V, going into back of TPC is 17.6 V and coming out of back of TPC to track is 15 and at track 15.Everything runs well so I guess I will not get concerned.

What kind of meter are you using to measure

the voltage. What comes out of a brick is a sine wave

which any volt meter will give a correct reading.

What comes out of a TPC and most power supplies

with a controler is a shark fin which will read lower

with a common volt meter than with an RMS

meter. At full voltage, the ZW L output is very

close to a sine wave and so a common voltmeter

gives the same reading as an RMS meter. Even a

full voltage, the TPC may not be a sine wave so a

common voltmeter will give a low reading.

Normally, the TPC drops about a volt.  My PH180's put out almost exactly 18 volts, so I get 17 out of a TPC-300 at full throttle.  If the TPC is dropping 3 volts, my take would be there's a problem.  OTOH, if you are loading the input supply, it may not be putting out full voltage, I'd check that first.

gunrunnerjohn,Thanks. I dont understand what you mean," if I am not loading the input supply'.Appreciate claification in the event I am doing soemthing wrong.

Al

When you put a load on a transformer, the voltage will, understandably, go down.  The amount of droop will be in relation to the amount of power draw as well as the quality of the transformer.

 

For instance.

 

I took a PowerHouse 135 out, and measured it's no-load voltage, it's right at 20 volts.  I then put a 6.5A load on it, and the voltage drops to 18.25 volts.

 

I then tried the PowerHouse 180, no-load voltage is 18.99V, with a 6A load, it drops to 17.30V.

 

Bottom line, you have to know what voltage is going into the TPC to be sure it's the TPC that is dropping the voltage.

Ok, I get it now. I tested rear of power blocks and it is 17.8 , rear of TPC going IN is 17.8, coming out of TPC is 15.2, same meter used in all cases.Reset TPC and programmed and it is still 15.I have no idea why it is dropping that much as it goes through TPC.

Guys, any suggestions on a good economical true RMS Voltmeter. It has been recommended here and now by Lionel that I should only use a True RMS meter to measure voltage from a TPC.All the ones I have looked at are $ 125 plus. Al B

Unless you are a purest and worry about the voltage

readings of odd wave shapes like the shark fin from a

tpc, the rms meter is not worth the extra

money.

 

The volt meters on the new ZW L appear to read

RMS voltage

My $20 Gardener Bender digital multimeter  from the local hardware store  gives an accurate reading. With the TPC set to Max I have 17.8 on the input side and 17.8 on the out. If I turn the knob counter clockwise I can watch the voltage drop.

 

 

 

 

 

 

 

 

I'm a bit surprised you get the same voltage on the input and output of the TPC, there has to be some voltage loss going through the switches.  Is this with no load or a load on the TPC?

That's more like it.   I would expect about 1V, and that's what I have seen with the TPC.  I don't currently have one installed, but I dig it out of the closet for tests.  With Legacy and the MTH TIU, I have all the variable voltage and command stuff covered.

Not so sure I am a purist, rather trying to understand why only 15 Volts from TPC with two 180 W power pals hooked up.

Lionel suggests a 1-2 V drop but not 3. In any event things seem to work OK.

I have to believe there is some issue there.  Does the voltage drop remain constant for light and heavy loads on the TPC?

Yes, three trains running , 8 switches all lights on accessory CW 80

i have the same setup you do---a tpc400 and 2 180 watt power packs. i get a consistant 17.65 volts when track power is applied to the track. i don't think your setup is correct, you may have spun the red knob before you set the voltage---take the setup booklet and go through the setup again.

Will do, will disconnect all , reset and do it again. Will advise as to result.

Unless a meter is designed to indicate a true RMS voltage,

it will most likely respone to the average voltage (rectified)

that is applied to the meter. There are three voltage

measurements, peak, rms, average. For a sine wave, the RMS is

.707 times the peak and the average is .637 times the peak. Non RMS

respone to the average voltage but the scale is calibrated to read RMS.

The output of a TPC is not a sine wave but a chopped or shark fin

vave. What goes into the TPC is a sine wave which any AC volt

meter can read correctly but what comes out is not a sine wave

so unless the meter is a true RMS meter the reading will be lower

than the RMS meter will give.

 

15volts is marginal for coupler operation. Well, at least on my layout using a kw fed tpc300.

Yep, I tried 16 volts a while back, just to see what the "lower voltage" discussion was all about, and that's the only problem I had with a number of engines.  I'm back to 18 volts.