lost my buck converter internet link....

TOS doesn’t allow direct links to other sites, so:
Use these descriptions in your search engine depending on if you want ac/dc input or just dc input.

I like the ones with a meter best.

cjack posted:

I like the ones with a meter best.

i see dc to dc with meter, but not ac to dc.

Yes. I had to attach about a square inch of perf board to the DC input with a small bridge and electrolytic capacitor on it. Then it's an AC input. From the 18 VAC track voltage, the input then becomes about 25.4 VDC. On the 2 Amp supplies I bought, I used a 2 Amp small round bridge and a 330uF/35 VDC capacitor.

WeHonest?

What are buck converters used for?

Mostly for me, using track voltage to dial up a 4.5VDC for accessory signs, etc. 

If using the AC-to-DC converter you could attach an inexpensive 2-wire voltmeter module on the DC output. 

Here's the idea in action from a photo hijacked from a previous OGR thread.  The AC-to-DC buck regulator module on the left does/did not have an integral voltmeter.

Or, in this photo from an OGR thread, cjack's idea of placing a bridge rectifier in front of a DC-to-DC converter.

Depending on how much power you need, you might not even need an external capacitor...in which case you can get away without needing to fire up the soldering iron!  That is, 2 of the 4 wire terminals of the bridge-rectifier go right into the screw-terminal connector of the DC-to-DC module.  The calculation of a suitable capacitor value (if needed) is somewhat tedious - so best to confirm your application if considering this option.  But in any case this alternative is also inexpensive.

Thanks for the product identifications/sources Stan.  I've ordered up some for current projects.