Stan: Great telecon! If you'll send me your email address, I'd like to send you a few pix of my layout, which will include an invitation to visit me....
After better understanding Phil's setup, I attempted to duplicate his situation - using both a Z-4000 and a regular unadulterated transformer to drive the TIU Variable Input(s). Since I have an oscilloscope, I could see what was going on at the waveform level. The experiments were quite interesting (to me anyway). For example, under some situations I got spurious DC offset voltages (sufficient to trigger a whistle circuit) even with "pure" sinewave transformer voltage going into the Variable channel. And I can see material differences in the output wave-shape between VAR1 and VAR2, with varying load, with input voltage, and so on. But since very few OGR readers have a scope, providing a prescriptive approach to solving spurious whistles is not forthcoming.
Instead, I'll just repeat what has been said earlier: if you are getting spurious whistles when using a TIU Variable channel for conventional mode, lower the Variable Input voltage and/or add a 10uF non-polarized capacitor at the Variable Input.
So, you're telling us that both Z-4000 and "unadulterated" trannys....." can give spurious DC offset voltages (sufficient to trigger a whistle circuit". So if there's any blame to be cast, it's on the TIU.
It gives me great relief to know that my situation is not unique.
I'm a bit surprised that this problem has taken so long to surface!
I've had issues running various conventional locomotives with the TIU, I've just resorted to pulling out a real transformer and bypassing the TIU to test those. I never bothered to try to chase it down.
This goes beyond just conventional issues. Phil reported effects on Command PS-3 engines.
SO just to be clear, this only occurs with a Z-4000 feeding one VAR channel and a different but pure sine wave feeding the other VAR channel? When this happens does just the Z-4000 channel have the spurious DC offsets or do both TIU channels do it? G
GGG posted:...SO just to be clear, this only occurs with a Z-4000 feeding one VAR channel and a different but pure sine wave feeding the other VAR channel? When this happens does just the Z-4000 channel have the spurious DC offsets or do both TIU channels do it? G
I don't think anyone has been this specific.
SO what did you test? I think it is important to understand. If your saying any Z-4000 or pure sine wave transformer plugged into a variable channel with nothing else powered and you get DC offsets at values above 18VAC I am not sure why others have not reported this issue?
So things to understand is how is the TIU powered: Aux Pwr or FIX1 and what type of power DC or AC. Is this with different sources of power feeding both VAR channels at the same time or just one VAR channel. I don't see how the DC Offset is being generated, unless it has to do with 2 or more sources of different power being applied and some bleed over between channels.
We already have heard some issues when DC used as AUX power with AC on Fixed (maybe vice versa). G
I've used DC on the aux power and AC on all four channels, no problems at all that I can see.
John,
I've used DC on the aux power and AC on all four channels, no problems at all that I can see.
The issues reported were when using AC on Aux. Power and DC on Fixed #1.
Haven't tried that Barry, I was responding to George's comment. It could be what you describe, that's a configuration I've never tried.
John,
That was an issue that Marty stumbled upon some time ago and he called me for a consult. If I recall correctly,we determined that it's only an issue with AC on Aux. Power and DC on Fixed #1. All other combinations and channels worked fine.
gunrunnerjohn posted:Haven't tried that Barry, I was responding to George's comment. It could be what you describe, that's a configuration I've never tried.
I was not sure which way; which is why I said or maybe vice versa. It was with AC to AUX and DC to Fixed as Barry stated. G
GGG posted:SO what did you test? I think it is important to understand. If your saying any Z-4000 or pure sine wave transformer plugged into a variable channel with nothing else powered and you get DC offsets at values above 18VAC I am not sure why others have not reported this issue?
So things to understand is how is the TIU powered: Aux Pwr or FIX1 and what type of power DC or AC. Is this with different sources of power feeding both VAR channels at the same time or just one VAR channel. I don't see how the DC Offset is being generated, unless it has to do with 2 or more sources of different power being applied and some bleed over between channels.
What I am saying is it's a your-mileage-may-vary situation. I was able to get spurious DC offsets on the track even with a unadulterated transformer feeding the Var input. I am not claiming I performed a rigorous "test"...just messing around looking at waveforms and offsets under various conditions. I did not even consider trying DC vs. AC for Aux Pwr. My loads were just power resistors (not real trains). As mentioned, after I saw what was going on at the waveform level, and seeing actual DC offsets confirming it "can" happen, I stopped the experiment.
I think others have reported this. As I understand it, in an earlier post, GRJ recalled the 10uF non-polarized cap idea from previous report(s). If my lack of specificity is only contributing to an urban myth or legend, then I'll accept the criticism. I just don't think this situation is of much concern to the vast majority of users when some simple and effective remedies are available.
Got it, but I do not recall a post with the significant level of DC offset causing all types of trains to constantly blow their whistle. Given how much stuff we retread around here, there would be plenty of post about spurious whistles with a TIU yet I can't remember any that were not from dirty track, or engines or a defective engine board. So to me this is new and I read all these post. If there is an issue with different types of transformers being used together at high voltages causing issues I could understand that not being reported. Hence my question. We already know about noise and spikes, but an actual DC offset significant enough to constantly activate whistles or horns, is new to me. G
All: I'm glad to know that my post & this thread were not in vain!
