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Beware ! You're in Kamikazie here. Not many pro luthiers around, more often brave souls experimenting in their kitchen.

H420 broken bass - by François

Cracked during transport

Harmony H420 bass lutherie

François : I bought on ebay this '72 H420 bass in september 2006, from a German seller. This guy had (and still has) a good feedback, and he always has dozen of guitars to sell. And it came from the near Germany, I was confidfent about the packaging. See above the received package : a large cardboard, somme air cushions, a bass deposed on the cushion in the diagonal of the parcel, some more air cushion and voila... Nothing to stop the guitar from moving freely inside, sliping on air cushions !

Easy result : the mint bass arrived badly cracked, a bump somewhere on the ground opened it on all the lower bout, more than half the top circonference...
I still can't understand how someone who's selling so many guitars could pack so bad and stupid...

It took me some months to get a partial refund (30 %), I have more than sixty mails in the directory... Then it took me some more months to decide how to repair it. Every other week I was holding the disassembled body, scrutinizing it in every angle, to discuss with myself the best way to... Last week I decided to *do* it for real ! I have some other guitars to fix, a H73 Roy Smeck damaged exactly the same way, but the bass will be the first on the bench...

Harmony H420 bass lutherie Harmony H420 bass lutherie

fanfab4 : That's crazy. Good luck on the repair. Could have been worse. It might have been a snapped neck. Still a shame.

Michael : This was actually packed better than my H-22 (also from Germany). It was in the same type and size of box but no air cushions or anything to keep it from moving around ! I'm amazed that it arrived in one piece.

François : Let's have a closer look...

First I disassembled it... I took some time to compare this bass body (right) with a Rocket-style guitar body (a Barclay H74-3, left). Note the different pickup places, and the deeper neck pocket, going below the inner woodblock on the bass body.

Harmony H420 bass lutherie

View inside to the end wood block. (I already had drilled through it in this photo, to use a special homemade tool). I understand at this point that the end block, in slim line bodies, is not really glued on the top an back. It's glued only on the sides... The block is rectangular, and it would need a special trapeze-shaped one to be flush with the top and back...

Harmony H420 bass lutherie

Did you ever dreamed to see how was reinforced the jack area ? This photo was possible only through the open crack...

Harmony H420 bass lutherie

And that's a rare "view from inisde", from the bottom to the upper bout (photo from the opened crack again). We see the wide block occupying most of the upper bout. Note the center post between top and back came unglued in the "accident"...

Harmony H420 bass lutherie

One of the bridge's screw goes in the square post

Harmony H420 bass lutherie

Below is to detail the damage at the end block

Harmony H420 bass lutherie

I home made this special tool (photo below) called a "silly-packaging-result-reversing-extractor", unique model # 00, to be able to pull out the wood block and all the endpin area from the inside, in a attempt to reverse the destructive process. The important thing is to replace all small wood particles at their original place, in the original order..
I took time to made a specific tool because I have 4 (or is it 5 ?) guitars damaged more or les the same way, some are larger acoustic archtop, so I chose all dimensions and angles to be able to use it on every guitars.

Harmony H420 bass lutherie

It worked great, and after filling the cracks with glue (white titebond) I used these 4 mini-clamps to hold everything flat and flush. At this step I am only glueing back the left and right sides to the inner woodblock, next I will glue back the top.

Harmony H420 bass lutherie

robdefries : Pardon for being a pain again, but that looks like old hide glue on the block. So it had been glued to the top in an earlier life.
Update mode on :
I had a look in a stripped H75 body I have laying around. It looks like it's partially glued on the top, 3cm or so but totally on the bottom. It's late and dark now, I'll make some pics tomorrow. But it's fur sure glued to the top, even if it's only at the very last end of the block.

François : Rob, you're perfectly right, it's been glued on the block, but only about 1/2" at the edge, because the block is rectangular, its sides are parallel, but the top and back are not.

Now I glued back the top, in two steps. The photo below is the first half, comprising the central woodblock. I did not take pictures for the second half, but it's the same of course...

Harmony H420 bass lutherie

After closing the body, I wanted to add some reinforcement to the bridge area. Below, you see the bridge, the original wooden spacer (placed just under bridge, *above* top), and the screws used. I found this was not very solid, I mean, the top is not very thick, these screws could easily pop out under pressure. This guitar did not see a lot of use, but some of the holes alreday were a bit opened, with the top layer of the laminate going out...

Harmony H420 bass lutherie

So I made a wood plate to glue under the top, to have more thickness for the screws. Sorry I didn't have a photo of this plate before glueing it, but you can see an example of the laminate wood I used on the photo below. It's a "heavy duty" laminate, an expensive product that I used when I was building model airplanes (gliders to be precise). I think it has 7 layers laminated together, and it's only about 1/8 thick.

Harmony H420 bass lutherie

Harmony H420 bass lutherie

Below, my trick to spread apart the back and the top, just a bit to be able to place back the post. This could be used to place a new post in deeper bodies too... But this works best in an electric guitar with a bridge pickup hole.
I use two thick laminated wood plates, to protect the guitar and evenly distributethe pressure. The hole in the upper plate is not threaded, it's a bit wider than the screw. There is a hex nut, and a washer, that you can't see, they're hidden under the upper plate. Using the wrench on this hidden nut I'm able to spread the body, just enough to comfortably place and glue the post inside. Tip : you don't have to use millimeters nuts and a French wrench, it should work with imperial dimensions too ;-)

Harmony H420 bass lutherie

Below, the bridge screwed back in place. You can see the added plate inside, in the mirror. Of course I had to shorten the sound post by the thickness of the plate.

Harmony H420 bass lutherie

Harmony H420 bass lutherie

An historic detail : we can see below that they re-used in 1972 a "new old stock" headstock plate (from a H27 ?) wich had the older Harmony logo... Did they rubbed off the old logo before applying the new one ?

Harmony H420 bass lutherie

Wiring and pickup details if you're interested...

Harmony H420 bass lutherie

Harmony H420 bass lutherie

Harmony H420 bass lutherie Harmony H420 bass lutherie

Harmony H420 bass lutherie

This should have been a happy end... Unfortunately it was not, because after tuning it to pitch, I had to lower the action. Easy task, the neck was a bit bowed, so I just had to adjust the trussrod. I made a big mistake : I applied to much force on the trussrod nut, strings were still in tension, and I heard that awful and definitive CRACKK : I broke the trussrod. Shit !
I'm so upset after me, that I will wait another year or two before fixing this... You will read the report here...
In the meantime, when you feel any resistance when adjusting a trussrod, remember to release string tension, and to clamp the neck in position before turning the nut.


Billieg2 : Also, always spray WD-40 or some other lub. on first and ALWAYS back off the nut a quarter turn before trying to tighten it. If it is tight, spray it again and let it sit over night and try again.

François : Good advice Bill. I forgot to mention it, but I had lubricated it before tightening. This is the first thing that I do, each time I buy a 'trussroded' guitar (even before tuning and playing it !). I remove the trussrod cover, check if the nut is still there, I remove the rod nut if I can, but in all cases, I apply some drip of this special "unseizing" oil (a specific product, not WD40). From my experience in mechanics, I know how long it takes to unseize rotten 50 years old nuts... So the oil has the time to do its job (slowly penetrating inside the threads), even if I need to turn the nut one year later...

But this bad experience made me think about it... And now, I will always release strings tension and bow the neck "manually" by clamping it, before trying to bow it with the nut. That way no force at all is needed to turn the nut, the rod will not be twisted at all during the adjustment, you have a lot less chance to break it that way. Then, the rod only works in its length, after you release the clamps. And since this fatal day, from time to time I read the same advice from some real luthiers on the web...


François, september 2008

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