Ken is right. It sounds to me like the third fret is the bad guy. As instruments age, frets can become uneven because of wear or the finger board drying out.
There are techniques for leveling and re-rounding frets. If you don't feel comfortable working on instruments, a guitar repair person should be able to fix the problem for you.
It's probably not the 2nd fret that's the problem. Check the action height on the 3rd and 4th frets as well. I suspect the 3rd or 4th fret has risen for some reason -- humidity usually. Has the instrument had this buzz even when it was 5 strings?
Contacting Mike is probably your best bet for speedy resolution, unless you have another pet luthier in your back yard!
Your terminology is a bit confusing -- dulcimers have a melody string and two drones - the middle drone and the bass drone. So you've reduced the original 5 strings to equally spaced melody, middle drone and bass drone, correct?
Mike Clemmer Mtn Dulcimer - built in 2002; vsl 28 1/2"; tuned DAdd; strings - .012/.012/.014/.022w; original owner
Basically I'm a neophyte & started taking lessons & studying the dulcimer the last 4 months so an expert I'm not. I changed out the old strings with those listed above & I've tried both larger & smaller middle & base strings but I still have a disturbing buzz on both of those strings when playing on the 2nd fret. Open or any other fret is no problem. The height of both strings at the 1st fret is slightly more than the thickness of a dime & slightly more than a nickel at the 7th. This was a 5 string dulcimer but I've taken off the drone string, moved the base to the drone location & the middle string to the center on the nut & bridge. Space between the melody to middle string and base to middle string is the same. I've not altered the nut, bridge or any of the frets.
Any suggestions are appreciated.
Sharon that's a great question. I guess it's hard to know for sure unless you have little kids or grandkids around to ask!
It's reassuring to read Dusty's reply, that many of the same songs are still taught today in school. 
If that's so, then you might find some good ideas in this old forum thread:
music-discussions/what-songs-were-you-taught-in-kindergarten-grade-school
It's mostly the same tunes, but with updated lyrics. Instead of "If you're happy and you know it clap your hands" you have to sing "If you're happy and you know retweet this meme." 
Seriously, my kid was in kindergarten about a decade ago, and the songs were basically the same as when I was a kid. In fact, you're giving me a good idea for a "Call the Tune" for any songs for kids. We could all share our ideas for good songs for kids.
I don't measure! I "feel of" the wood panel as I'm thickness sanding to the right thickness. Flexing the panel and from experience knowing the right mass I'm looking for for a particular tone. Harder denser woods can be sanded much thinner than a softer less dense piece.
As for sustain? Panel thickness is just one variable factor in a multitude of factors involved. String selection, nut and bridge hardness or softness, nut and bridge placement, over all mass of the piece, wood selection, possibly the finish, intonation, and so on.
If sustain is what you look for, I'd try harder more dense woods sanded to around .090 if you can, harder nut and bridge, and possibly a zero fret?
Some place to start....
@Sharon-Day Great question! I know what songs I've sung to/with a little niece or nephew yet have no clue what songs kindergarteners today know.
I’m going to be teaching mountain dulcimer at our library’s Kids Fair? Do today’s kids still know Aunt Rhody? Twinkle, twinkle? Mary had a Little Lamb? My question is what songs do doday’s Kindergarteners (and beyond) sing? I’d like to teach them to play songs that they know.
Don Grundy...my mind's eye saw 'DAD (as in Daddy, Father) Tuning and I thought to myself (obviously short on morning coffee) "Awww....that's so sweet! His Daddy tunes his dulcimers for him! I wish my Daddy would do that!"
Debbie, thank you. I do not have a website. Building dulcimers is a primarily a hobby for me. What you see is the second of my builds. About half of my builds are donated to local charities such as Habitat for Humanity and Pink Gala. The rest of my builds are commissioned pieces simply generated by word of mouth. Being this is a hobby, and I prefer not to work to deadlines, I don't promise a finish date but usually have them completed within a month or two. It is nice to be able to enjoy retirement at my own pace. Other posts of mine contain photos of some of my other builds; each one is a unique/custom build.
I was wondering if the Brazos Valley Dulcimer Club is still active. I saw a website that advertised Brazos Valley Dulcimer Club in the Granbury, Glen Rose, Stephenville area (Texas). It was dated 2009...and to contact Peggy Freeman. I did send an email but it was kicked back. Let me know if you know anything!
Thanks!
That's really nice John. I bet it sings sweetly.
Ken
"The dulcimer sings a sweet song."
well looky there :-) Very, very sweet!
It looks cool, John, and I bet I could get plenty of tunes out of the little critter.
I love it John! Let us know when they are available for sale. 
Yes I know all too well about "ideas" gettin' in my head, I got a fire barrel chop full of great ones.... Wonderful work John, I'll play you a door chime folk tune at the Gathering!
What a cutie! I can't wait to see it when it grows up!
Cute! I like the scalloped fretboard, John!
Dang John, that's just cuter than a bug's ear! And I love the built-in tuning key storage.
Here is the outworking of some brainstorming I've had recently. You know how an idea gets in your head and won't go away peacefully? Well, this lil' guy is less than 12" long, but can be played-- SORT OF. It's my version of a true "pocket dulcimer". Just thought you might like to see it!
So, full steam ahead! Congratulations on building your first dulcimer. You'll get lots of ideas for future ones now.
Since the fretboard is level I do not see a problem with playing it on your lap. As long as the glue joints are solid I do not see a problem with it coming apart. Some dulcimer builders put a curve on the bottom intentionally.
Ken
"The dulcimer sings a sweet song."
Some builders actually build-in a bowed back -- the idea that the curve acts as a kind of projector for the sound.
Joolsy,
You could try sanding the back flat if the bow is minor, or you could glue 3 feet on the back like they did in the old days.
Hi all.
I recently finished my walnut fokcraft teardrop dulcimer kit & have noticed a slight side to side rocking motion when placed on a flat surface. I think this may have happened because when I glued the sides to the back, they may not have been perfectly at 90 degrees, so when the fretboard/top was clamped on, it caused a slight width ways bow in the back. I'm wondering if it may eventually cause any problems later on, i.e. delaminnation or cause the neck to bow.
Other than the slight side to side rocking, I've checked the fretboard & with straight edge & winding sticks & it's all good.
Thanks for reading, any thoughts?
I've always seen CBG's and CBU's tuned in fourths. You can tune ukes and guitars in fifths but it is rare. Tenor guitars are probably tuned in fifths most of the time.
I’ve been looking at three string cigar box guitars and most seem to be tuned as GDG, or similar tuning. Often played with a slide. Check out https://www.cigarboxguitar.com/knowledge-base/5565/
Sorry to hear this news. Condolences to Ruth's friends and family.
I am so sorry Patty....
Prayers for her family and friends........
May each one hold tight to the precious memories 🙏💕
I knew Ruth from several dulcimer events I attended. I enjoyed sharing music with her. We talked about her on another dulcimer site (probably one of the Facebook dulcimer pages). She is missed by many.
Ken
"The dulcimer sings a sweet song."
I met Ruth in '09 at Ken Bloom's Pilot Mountain Bowed Dulcimer fest. She was generous, gracious, a prolific knitter, and all-around good gal! Ken called her Saint Ruth for her work transcribing his chicken scratching on paper to music. Ruth was a treasure.
Thanks Patty.
I met Ruth over 20 yrs ago, she let me come and look at her Keith Young dulcimers before I ordered one from Keith. She was very gracious.
Sad to know she's passed on.
Many may not know Ruth but I wanted to share that she went home to the Lord March 4th. She was very much a part of the Northern Virginia Dulcimer Group. I believe she was one of the founding members of that group. She knew Keith Young. She went to many workshops and some of you may have met her. She often gave dulcimer lessons at her home. She wrote a lot tab. We went to quite a few jam sessions together. I know she left a wonderful musical legacy to her sons. They sang at her memorial service. Ruth touched so many lives. She is already missed.
There are photos of two different instruments there... one with a walnut back, one showing a maple back with a thin walnut 'racing stripe'. One with a maple fretboard, the other with a walnut fretboard.
Hi Ken,
A couple posts back I stated that I had purchased a second dulcimer. The maple backed pictures were posted at the beginning of this thread. I did notice that if your looking at pictures and start scrolling them, the forum will show all attached pictures from the entire thread. I thought that might be confusing!
Wmacky, you have purchased a beautiful instrument. Congrats. I saw it on ebay but did not pursue it.
I have purchased 5 dulcimers over the years which appeared that someone purchased, looked at, and put in a closet waiting for the "some day" when they would learn to play. But never did. One even had the pick and noter stick still sealed in a little envelope. So long as they have been stored where there is not extreme temps or humidity, one can find some good buys in this scenario. Usually the dulcimer will need new strings, and sometimes some care of the fretboard as frets will sometimes oxidize a bit over time.
I know you are looking forward to many years enjoying your dulcimers. It sounds like your DAD (dulcimer acquisition disorder) may be at bay for a while. Thankfully, that disorder is not harmful, unless it makes the spouse unhappy.
