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Oct 22, 2019 - 11:42:58 AM
99 posts since 7/12/2010

I just bought myself a '78 RB-250. Now before you get on my case for buying a notoriously bad banjo, hear me out... I heard a lot of potential in it with a good setup.

Everything seemed to be in order, the multi-ply rim isn't delaminating at all and the tone ring seems solid. But I noticed the skirt of the ring was sitting RIGHT up against the raised collar that the 2 piece flange sits up against, there wasn't a noticeable gap as there usually is.

I guessed the ring might not be making good contact with the top of the rim, and it might be sitting on the skirt instead. So I put a thin layer of vaseline on the lip of the ring and pressed it onto the rim (it's a very loose fit)... There were only 1 or 2 shiny spots left on the rim. I took a razor blade and gently evened out those high spots. I checked again, and there were no shiny spots.

Then I put 2 layers of masking tape on top of the rim as a shim, and put it all back together. The banjo now sounds a LOT fuller, but just a little muted (I'm guessing that's the tape)


Heres the question:

How should I make the ring fit better? Take some off the rim at the collar that the tone ring skirt sits on, or should I sand down the skirt of the tone ring a hair? As is, I don't believe the lip of the ring is actually touching the rim enough to transfer vibration.

Thanks,
Jon

Oct 22, 2019 - 12:34:58 PM
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Players Union Member

rbfour5

USA

1002 posts since 11/9/2010

I have removed a sliver amount from the rim so that there was no contact at the bead on the outside of the rim. It made a BIG difference for that particular RB-250. I would remove some wood as opposed to "sanding" on the tone ring...

Oct 22, 2019 - 2:14:19 PM
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Alex Z

USA

3654 posts since 12/7/2006

Congratulations on your ingenuity in checking and diagnosing what's going on.

Tape off -- as you know.

Take a single edge razor blade or the blade of a sharp utility knife and scrape the lip/ledge of the wooden rim.  Not a chisel pushing motion, but a scrape pulling motion with the blade vertical or leaning a bit toward you.  Kind of like a cabinet scraper.  Go around a few times, taking off just a tiny bit each time.  All you need is a couple of thousandths of an inch more room, barely measurable to the eye.

With a vertical blade and a pulling/scraping motion, you can control the blade, and it won't dig in.  Utility knife with new blade works great, because the blade is pointed, so you  won't be bumping into the side of the rim.

Hope this helps.

Edited by - Alex Z on 10/22/2019 14:16:39

Oct 22, 2019 - 3:40:22 PM
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beegee

USA

21368 posts since 7/6/2005

I'd send it off and have somebody fit a new rim to it.

Oct 22, 2019 - 4:00:47 PM

Alex Z

USA

3654 posts since 12/7/2006

Just to be clear, want to use your terminology.  I'm talking about scraping what you've called the "raised collar that the 2 piece flange sits up against,"  not the top of the rim.

This the spot where you've noticed that the bottom edge of the "skirt of the tone ring" hits.

That's the little ledge that needs scraping down a bit.

 

Another contact point that Steve Huber shows how to check is the contact between the tone ring and the top of the rim, looking at the inside of the rim.  He says to put a small piece of aluminum foil between the ring and the rim, sticking out toward the inside of the rim.  Then seat the tone ring on the rim firmly.  Then pull on the aluminum foil.  If it is grabbed between the ring and the rim, then the fit in that spot is good.  If is slips right out, then there is a gap, and the top of the rim has to be leveled better -- or -- the skirt is hitting the ledge.  He says to do this at several places around the rim.  If they all grab, then you have a good fit.

Oct 22, 2019 - 6:01:29 PM

99 posts since 7/12/2010

Thanks for the advice everybody! I took an exacto knife to that bead and gave the ring a much better fit.

Then I put it all back together and the action was STUPID high. Turns out it's got a stripped lag bolt too, so now I'll have to get on that before I can report on how it sounds.

 

...and to think I traded a good banjo for this one ??

Jon

Edited by - thejd123 on 10/22/2019 18:02:12

Oct 22, 2019 - 6:06:19 PM

10173 posts since 6/2/2008

quote:
Originally posted by thejd123

Now before you get on my case for buying a notoriously bad banjo, hear me out... I heard a lot of potential in it with a good setup.


Congrats on your acquisition. Probably the most affordable way to get a real Gibson.

Fit of parts was one of the knocks on the 70s RB-250s. But as you're learning, that's repairable.

Beegee's suggestion to replace the rim is a good one.  This time last year I bought a 70s RB-250 that a previous owner had converted from multi-ply rim and 2-piece flange to 3-ply rim and 1-piece flange. They did a clumsy job of modifying the heel (and that's now off being fixed) but the banjo sounds and plays great.

Oct 22, 2019 - 6:56:52 PM

99 posts since 7/12/2010

Thanks, Ken.

I already have a 1928 TB-3 conversion that I absolutely LOVE, so that's why im a lot more willing to do major work on the 1978... I can mess it up and not feel too bad!

I traded it for a parts banjo with a Huber Vintage ring, Sullivan FF rim, and Neat neck... On paper it was a killer banjo but somehow it just didn't have it, and I was convinced I had it as good as it was going to get.

This one seems to have more potential though! It sounded kind of electric when I bought it, but it rang all the way up and down the neck. Since all the parts are in good shape, I hope to make this one of those banjos that makes people's eyes bug out when they hear what it is. Everyone knows a 70s mastertone isn't supposed to sound good, right? ;)

Oct 22, 2019 - 7:34:42 PM
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1335 posts since 11/29/2004

Some of these instruments sounded great as they were. In the late 60's and most of the 70's the multi ply rims were standard on Baldwin, Vega, Gibson and Fender. Think of many of the recordings that were done and then think.... Do I really need to buy something else?...... They were good enough for many pickers then and if you just give them a try, you'd be surprised as to what they will do for you.

Oct 22, 2019 - 8:02:57 PM

10173 posts since 6/2/2008

quote:
Originally posted by thejd123

... it rang all the way up and down the neck. 


That's what I experienced with mine. It rings in a way none of my other banjos do.

Anyway: With the tone ring off and the top of the rim visible, do you confirm that it's a multi-ply rim? I thought Doug has said on the Hangout that by the late 70s Gibson had gone back to a 3-ply rim. 

Oct 22, 2019 - 8:24:46 PM

99 posts since 7/12/2010

It's got that darn black paint all over it, even on the top of the rim, so you can't see from there. The finish has settled a little bit between the plies on the underside, though. If you hold it up to the light, you can barely make out the indentations between plies. It looks like 5 or 6 ply to me.

Also, Alex, thanks for the aluminum foil tip. I just checked all around with that and found a couple of high spots that the ring was sitting on. Shaved them off, now it's snug 90% of the way around the rim (all but one low spot). I figure that's good enough. I ended up taking off just enough to get through that God-awful black varnish and down to the wood in a couple places, it felt good to see that stuff come off! ??

Oct 23, 2019 - 7:39:17 AM

2714 posts since 5/29/2011

On another note you mentioned; when a lag bolt strips out of a mahogany neck I have always preferred to drill out the hole in the neck and glue in a 1/4" maple dowel. When you drill a pilot hole in maple it is less likely to strip when the lag bolt is put in.

Oct 23, 2019 - 8:14:28 AM
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99 posts since 7/12/2010

That's what I would've done, but I'm a college student in a small apartment so I don't have a drill/drill press to use. I went with the toothpick and Titebond method, and if that pulls back out, I can always borrow tools and fix it right.

Oct 24, 2019 - 7:40:07 PM
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99 posts since 7/12/2010

For those interested:

I fixed the lag bolt (toothpicks are holding tight) and shaved even more off the bead on the rim since I noticed the skirt still touching in a couple places. The banjo is starting to sound amazing. HUGE difference from before.

It's starting to feel like I'm playing a real banjo, not just an electric or something. I can feel the resonator vibrate a little as I play, and I can feel the neck doing the same. The skirt of the tone ring still appears to be VERY close to the bead on the rim in a couple places, so I'll shave those down more when I tear it apart to stain the bare wood back to match the rest of the rim.

But initial impression, WOW. What a difference. It's still missing a little bit of growl on the low end, but I'm to the point where I think messing with strings and bridges will do more than tweaking the setup.

Thanks again for all the advice!

Jon

Oct 25, 2019 - 11:30:45 AM

10173 posts since 6/2/2008

quote:
Originally posted by thejd123

... shaved even more off the bead on the rim since I noticed the skirt still touching in a couple places. The banjo is starting to sound amazing. HUGE difference from before.


Great to hear.

I guess the ideal fit -- according to Steve Huber and others -- is for the ring to sit solidly on the top of the rim and the outside ledge or bead at the same time.  If it can only be one, I'd choose solid seating on top, as you did.

Bill Palmer's Tone Bell rim modification chooses solid seating of the tone ring skirt outside the rim with the top inside edge of the rim cut back to eliminate contact. I've never heard a banjo with that setup. I have no desire to try it.

Oct 31, 2019 - 3:01:31 PM

150 posts since 1/26/2003

Back in about 2004 Bill Sullivan changed out the plywood rim and original ring in my 1970's RB 250. The plywood rim was not symmetrical and the ring did not sit on it properly because of the shape of the rim. He installed and Tenn 20 ring and one of his 3 ply maple rims. He also reset the heal of the neck. It was a great banjo after that conversion. The tone, to me, sounded like a well setup RB-75. I eventually sold it and have kicked myself most days since then for selling it.

Oct 31, 2019 - 6:45:47 PM

99 posts since 7/12/2010

I know that sort of stuff works often, but at that point, you don't have an RB250 anymore. I wanted to keep mine original, and It seems to have worked this time.

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