I am showing my age here...and I have star wiring with some long lengths of wire heading out, and have hooked up the light bulbs to the terminal blocks (one per DCS output to each block). Has anyone ever figured out if they actually help the DCS signal?
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Yes, they help if you are using older TIUs and use the right amp draw of a bulb. If it doesn't draw enough, it won't correct the problem.
Ray's Electric trains used to recommend #1818 at the TIU output and # 1873 (? I think) at the track.
Other bulbs will work if they draw enough.
I really recommend these filters
https://www.slsprr.net/technical/filter.htm
Most don't help with the newer TIU version "L".
I go with Joe, do the filters. Why suck up power with current draining light bulbs? Although the light bulbs correct one issue, they create another one with the DCS signal. Light bulbs are a band-aid, they don't necessarily match the characteristic impedance of the track, and their impedance also changes with track voltage. The two light bulbs draw about 1/2 an amp, power that's not available to run your trains. 
The filters provide the impedance matching, but only provide the load at the higher frequencies of the DCS signal, they consume no measurable power at 60hz. Their impedance also doesn't vary with track voltage. Here's Susan Deat's page on making the filters.
@Engineer-Joe posted:I really recommend these filters
https://www.slsprr.net/technical/filter.htm
Most don't help with the newer TIU version "L".
Does that mean they aren't needed with the version L because of hardware changes, or that they don't help with the issue?
@Quietman posted:Does that mean they aren't needed with the version L because of hardware changes, or that they don't help with the issue?
Hard to say, it's never been clear to me why the filters wouldn't potentially have a beneficial effect with the Rev-L TIU. It's not like DCS suddenly changed the track signal or anything.
@Quietman posted:Does that mean they aren't needed with the version L because of hardware changes, or that they don't help with the issue?
Both.
They shouldn't be necessary with the version L. If the signal is bad, there should be another reason. Usually it's poor power or power dips. If the power isn't there, the signal probably will suffer as well.
Adding the magic bulbs/filters with a Rev L will actually make things worse. I had the filters and when I upgraded to Rev L TIU my signal went into the toilet. Remove the filters, all tens with bus wiring.
I believe my active TIUs are Rev I's.
I'll try removing the bulbs...
@Paul Kallus posted:I believe my active TIUs are Rev I's.
I'll try removing the bulbs...
No, I don't believe anyone is recommending removing them with an old TIU. Your bulbs need to draw at least .2 amps each to work well.
Roger-that, Engineer Joe! I reckon the bulbs are at least 3 volt, possibly 5 volt variety, and I built the assemblies a good many years ago.
@superwarp1 posted:Adding the magic bulbs/filters with a Rev L will actually make things worse. I had the filters and when I upgraded to Rev L TIU my signal went into the toilet. Remove the filters, all tens with bus wiring.
I have a real difficulty with bulbs actually significantly degrading the signal, and I can tell you from a quick bench test, the amplitude of the DCS signal with just a locomotive on the track or a locomotive and a couple of bulbs (one on each end of the power district) made no difference in the DCS signal amplitude at the locomotive or at either end of the track. This was measured with a 'scope in each location for the two configurations.
In the early days of running DCS on modular layouts, we tried bulbs, filters, insulated blocks, etc. to improve the DCS signal. A "solution" that tested OK in a controlled situation would be non-effective in actual layout operation. Re: light bulbs ... load up the track with a couple of lighted passenger trains chasing each other around the loop and you have pretty much trashed whatever impedance balancing you hoped to accomplish with lighted terminal blocks.
The one solution that significantly increased DCS signal reliability is discrete power and ground power feeds to each loop and consistent wire gauges in a buss loop configuration. We run with no filters, no lighted terminals, and no insulated blocks. YMMV.
GRJ, I had to remove my filter/bulbs from my mainlines where the TIU version L was connected. I remember getting varied results until I did.
I believe what you see on the scope, should be also tested on various layouts to average results before stating that.
@Paul Kallus posted:Roger-that, Engineer Joe! I reckon the bulbs are at least 3 volt, possibly 5 volt variety, and I built the assemblies a good many years ago.
.2 amps draw
@Engineer-Joe posted:GRJ, I had to remove my filter/bulbs from my mainlines where the TIU version L was connected. I remember getting varied results until I did.
I believe what you see on the scope, should be also tested on various layouts to average results before stating that.
I did state that it was one test. 
You're correct, it's not a general conclusion. As we know, or at least we should, every layout is different as far as signal propagation is concerned.
@gunrunnerjohn posted:I have a real difficulty with bulbs actually significantly degrading the signal, ...
Yeah, ah.... OK Sir! 
We knew what you meant.
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