Guild F-30 end block crack repair

This is an old repair that I never wrote about, but I learned a lot of important stuff from it, so I think it’s worth being documented.

My Guild F-30 was shipped with a cracked end block. I don’t know if it was cracked prior to shipping (bought it from Guitar Center’s used section, so not a lot of pictures), or if it cracked during shipping (the end pin wasn’t removed from the block). Anyway, it was cracked and I took my time figuring out how to fix it.

Frank Ford has a pretty good guide to fixing those cracks. I kept reading this one and going back to it. I think Frank Ford is the authority when it comes to guitar repair and I always try and follow what he does. I know his website looks rinky dink because it’s HTML, but the guy is a wealth of knowledge.

Now to the crack itself:

First a picture of the crack on the outside, taken right after getting the guitar.


Not the best picture, but it shows what was up.

And the crack from the inside:



Notice that there are these streaks along the crack? These baffled me. They looked like that could be glue, but the crack was still open. Also, They seemed to be “on the surface”, so I figured that if it’s glue it’s not epoxy, which coat the surface, and is probably CA glue. It didn’t make sense for it to be anything but glue, because why would anyone smear something on the end block?

Removing the previous glue is important, because it would prevent the glue I’d be using to adhere to the wood. So I took some acetone, and very carefully got it in and swabbed the crack. The streaks are gone:


Notice the wax paper inside the guitar. I don’t need any acetone accidentally dripping on the sticker inside and ruining it. Same thing on the outside, I wrapped the top with parchment paper in case any dripped.

Ok, cool, so it’s superglue. Now I needed to remove it from the inside of the crack. The obvious candidates to getting inside the crack were q-tip (not that great) and brushes. I tried different brushes that I had around, but none were long enough and thin enough to reach the entire crack. So I went and got a really thin fan brush. I need to take a picture of it, but it fit in the crack easily. Just dip it in acetone and get in the crack. Like Frank Ford, I used a long clamp to push the end block inward so the crack would open.


Checkout John Fahey’s How Bluegrass Music Ruined my Life, also parchment all over the top, and cork to prevent damage to the finish.


The crack is clean at this point, so it was time to figure out how I’d glue it. Like Frank Ford, I decided to use Titebond Original and reinforce the block from the inside.

I made a reinforcement patch with its dimensions matching the end block. The patch (as you can see in the picture) is beveled: on the top  the beveling starts 2.3cm from the edge, and on the sides it starts 1.6cm from the edge. Honestly, I don’t think the amount of beveling matters that much. The piece is 1/8″ thick in the middle.


I forgot what piece of mahogany it is, but I got it from a lumber yard, and it’s real mahogany as opposed to whatever tree that looks like mahogany but isn’t.

For what it’s worth, this was my first time making a patch like that. I wasted a lot of mahogany trying to thin it. Shaping it was easy with sandpaper.

I experimented with clamping a bit. One spool clamp through the end pin hole, and thick acrylic cauls on the inside and outside. That was given, and also what Frank Ford does. Clamping it top to back wasn’t so obvious to me. I tried spool clamps, but they didn’t provide enough clamping pressure. Someone suggested trying quick clamps, and those did it – the crack was closed shut.

One way one could get the glue in the crack is using  a filler gauge or palette knife, but what made most sense was get the whole bottle inside the guitar. I just aligned the glue bottle’s nozzle with the crack and squeezed. I got a lot of glue and got it all over the place. That was fine. It’s an easy cleanup.

Check out how much the crack was open when I pried it open with a clamp between the end block and neck block:


Whole lot of glue:


Spool clamp coming through:


Nice and clean before the mahogany patch goes on:


Patch is on  and clamped:



A word on getting the patch on: With a long threaded rod, the patch bumps against the braces and it’s impossible to get it on the block. What should be done is pull the rod back so it only sticks a little bit on the inside, then reach in with the patch, hold it against the block, and push the rest of the rod in. Then get the other end of the spool clamp on, and tighten the wingnut. Yeah, I bet if you read this now you wonder why is the wingnut end is on the inside. It’s not easy tightening it from the outside with the quick clamps on.

Here’s what it looked like from the outside:



And one more after it dried for about a day.



I think I did a good job!


Guild F-30 work, Studer B67 recap: Part VI

Yesterday I started with the F-30. It needs a new nut, which is why I started the work on it that led to it falling and cracking.

The previous nut had a shim glued to it, and that’s a real pet peeve of mine. If the slot is too deep, then that happened because someone put glue at the bottom of the nut, so when it was taken off last, it pulled some wood with it. Then someone leveled the slot and as a result the slot became deeper. The quick solution is to shim the nut, which is usually done with whatever piece of wood is at hand. The appropriate solution (in my opinion) is to restore the original depth of the nut slot. So this whole preamble is to say that the slot is too deep on the F-30 and I was going to put a shim there to bring it to its original depth. The original depth is so that the bottom of the slot (which is the neck’s mahogany), is at the same height as the bottom of the fretboard.

I’ve cut some mahogany shim blanks before because I needed one for my S-300. Thinning these are always a problem. It’s not easy to rub them on sandpaper and get them flat – the fingers put an even pressure so they get all lumpy. But I figured out a way! I’ve already fitted a nut blank to the slot – just the thickness and flatness of its bottom. I stuck 320 grit sandpaper to its flat bottom, laid the mahogany strip on top of sandpaper that is on top of a granite blank, and sanded away. This way the mahogany was held in place by the sandpaper on the bottom, and it helps that the bottom sandpaper is coarser grit. I also used the bone blank + sandpaper combo to flatten the slot before gluing the shim.

I glued the shim with hot hide glue and clamped it down with a piece of acrylic that’s cut to the slot’s length. To keep the shim flush with the fingerboard, I used my rule to push it against it. However, I used it this way:


So only the center was flush. I realized that after I started clamping and quickly took the clamp and caul off, put more glue on there, and pushed the bass side of the shim against the fretboard. To avoid this problem I should have used the ruler this way:


Or better yet, use something like an old debit card so my fingers don’t get in the way of clamping. Should be done with this guitar very soon. I’m very excited.

While that was drying I started recapping the Capstan Speed Control board. First cap out was C17, a 220uf 3V tantalum. I tested it for continuity and it wasn’t shorted! I didn’t have the right tantalum on hand (I thought I ordered one), so I replaced it with an electrolytic. I wrote before about how electrolytics seem to be a better alternative to tantalums now, but since my electronics knowledge isn’t 100% (far from it), I’m not sure it’s fine for all applications. I definitely don’t want to throw in the wrong capacitor in a circuit that is “time-sensitive” like the Capstan Speed Control. Anyway, it’s a Panasonic FM series cap that has a 56 mOhm impedance, so it should be fine. I hope.

Next I pulled C20, a 100uF electrolytic. That’s the cap that sits between the -12V rail and the 0V rail, and it was short! Problem (most likely) solved!

Then my wife came home and we had to go to dinner, so I had to stop.

Time to humidify!

Over the last couple of weeks I noticed the RH inside drop by about 20%. When I glued the F-30 it was 58%-60%, today it was %42. I’m in Chicago and I assume everywhere in the Midwest and maybe Northeast saw a similar drop.

I try and keep my acoustic guitar at 50% (in its case), and I keep a big bowl of water on the radiator that’s the closest to where my electrics are. I use a Dampit, and also moist sponges in plastic soap boxes that I drilled holes in. I also keep a hygrometer in my acoustic’s case to monitor it.

This stuff is important!

Guild F-30 neck and headstock crack repair – finally done!

Finally glued up the F-30, but I also realized that I never posted pictures of the crack, and I’m no sure I wrote what happened. Basically, I put it on a stand, and it fell face down. It didn’t have any strings on so the crack was manageable. Here’s what that nightmare looked like:




The “nice” thing about this break is that it wants to close under string tension, so it should have very little incentive to reopen. Gluing it was a matter of opening the crack, getting glue inside (not so easy), and clamping it. I was worried about gluing the truss rod in place, but I talked to a friend who works with this guy who was the foreman at Guild in the 80s, and he said that even if the rod is glued in place it won’t matter since it’s on the first 3 frets and the rod doesn’t do much work there anyway.

Now there are three areas to clamp, as can be seen from the pictures: the neck, the nut slot, and the headstock’s face. For the nut and headstock I used 1/4″ thick acrylic, and for the neck I made some cauls which I’ve mentioned in previous posts. Here’s what they looked like after I glued leather strips (to protect the neck and fingerboard):


Unfortunately, I didn’t take any pictures of them before I glued the leather, but here’s one from when I was chiseling little grooves to fit over the frets:


As far as the gluing, the idea is to clamp the neck in a vise, use one hand to open the crack and the other to get glue in. I don’t have a proper bench, or a vise, so I improvised and used my neck rest and a clamp to hold the neck in place.

Sorry for the terrible back-lit photos.

Sorry for the terrible back-lit photos.

This wasn’t a bad idea, but the clamp was flexing as I was twisting the headstock, so you know, use a vise if you have one.

People recommended to get the glue in with a syringe, or a syringe with a surgical tube attached, but those are too thick. So I went with a little syringe (a mistake). What I did first was get some hot water in the crack to help the glue spread inside. Then I would open it, get glue in there directly from the bottle, then with a syringe, then blow some compressed air in there. Those syringes have very thin needles with really small openings, so there’s not a lot of glue coming out of them. Also, the needles would bend and I had to keep changing syringes. So I wouldn’t recommend those, or at least fill them all up with glue first. I didn’t think the compressed air was getting anything further in the slot either. I would have been better off using a palette knife, thin feeler gauge, or this wide and thin brush that I have. It’s glued alright, though, I think.

I didn’t practice clamping the thing enough. In fact, I never practice clamping all three areas together, which was a huge mistake. The problematic area was the nut slot. I tried a capo and I tried a pony clamp, but both were hard to fit there. I should have clamped the nut slot first, then the neck, then the headstock. Luckily, the nut slot is a straight and level as it were before.

Here it is clamped up:


That unopened compressed air bottle was my backup one.

Humidity in the room was at 58% when I glued it up. It’s a little higher than what I would have wanted, but I had no choice. The glue I used was Titebond Extend.

I waited a day and a half to take off the clamps, and immediately took pictures (because I always forget):

The headstock is glued perfectly. It's flat just as it were before the break.

The headstock is glued perfectly. It’s flat just as it were before the break.


The pictures aren’t pretty because there’s still glue there, but cleaned up it looks alright. The only problem is that there’s a ridge where the crack is. I don’t know if the wood swelled because of water/glue, or maybe it distorted when I clamped it? However, the neck doesn’t have a twist, so I’m happy with it and hope that the lacquer touch-up would diminish the ridge.

I cleaned up the glue and let the guitar rest for another couple of days before trying to flush in some CA glue. Wood glue has very different drying times when it’s not exposed to air. Think about it, the glue doesn’t dry when kept in the bottle. It needs to come in contact with air for it to dry. When you glue something and clamp it up, it can take the glue several days to fully dry. I know it sounds crazy, but I’ve put together a joint before, and then a couple of days later I took it apart and there was still “fresh” glue in there. I don’t know how the CA will interact with fresh wood glue, so I prefer to let the guitar sit for a little bit.

Here are a couple of pictures after I tried to get some CA glue in:

IMG_20151011_163540 IMG_20151011_163559

The glue was just sitting there and didn’t seep in, so I’m going to say the crack is glued tightly. I’m not too worried about the marks around the cracks because these will buff out once I touch up the finish.

Now to finish cutting the new nut. Hopefully the guitar won’t fall off a stand this time. After a couple of months under string tension I’ll fix the finish. Maybe around the holidays when I don’t get to play it as often.

Studer B67 recap: Part II, other studer work, some guitar work

I edited this post on September 22nd, 2015. If you’ve referenced it before that day, you might want to re-read it.

The next step after replacing the caps on the motor control boards was to check the voltages in the power supply. There are test points on the stabilizer’s PCB, so that’s easy enough to do. I did that and the -12V rail was reading 0. So I decided to take out the power supply and recap it. Removing it is a bit of a pain. There are two screws on the top, one horizontal screw that you need a 6″ T-Handle wrench to undo, a bunch of connectors that need to be removed, and the 50/60hz switch on the power supply.

The PCB is different than what the manual shows: The -12V regulator is a Motorola MC7912CK while the manual shows National LM320K-12. The manual shows some SAL caps next to the regulators while my PCB has all tantalums there. Turns out, my PCB is the same as what they used on the Mk I of the B67 (figured that one out after downloading the Mk I manual). The Motorola regulator is a variant of the LM320K-12, so no problems there, and the tantalums can be replaced with high grade electrolytics (which I’m going to do). They layout of my PCB seems to otherwise be identical to the Mk II manual, and the Mk I manual also shows a very similar layout. The only differences I could see are that D4 and D5 are interchanged (shouldn’t matter since they’re oriented the same way), and that the Mk I uses a 4.7mF cap for C3 where Mk II uses 10mF.

While waiting for high grade electrolytics to use instead of the tantalums, I replaced the axial lytics and a couple tantalum caps. I ordered a 1000uF filtering cap instead of 10000uF, so I’m waiting on the big caps until it’s all here.


See those blue tantalums? Those are the ones that should have been SALs.

I also recapped the little monitor board under the front panel. The one that drives the built in speaker. No pictures of that because it was late and I forgot.

I also cleaned the front panel of the machine real nice. Someone said that toothpaste is good for that, and holy cow – it is! It’s much better at removing years old grime than isopropyl alcohol. I also poked around the card cage and noticed that the stabilizer card has a blown capacitor. I’ve never seen anything like it! The is torched and got black sooth all around it. According to my french friend who’s a Studer expert, this is the result of it being really close to the heat sink. I’m going to replace those tantalums with electrolytics also.

As far as guitar work, I think I mentioned making cauls to fix my F30. Trying to shape a single piece of wood to have 12″ radius did not work. I did something similar when I built my neck rocker, and it came out somewhat ok, but required a lot of rasping, chiseling, and filing. I thought I’d have better luck here, but no dice. It was too hard to maintain the radius along that block of wood.

I was at the hacker space trying to figure out how to do this, and a guy suggested cutting the radius on a bunch of small pieces of wood and gluing them together. Then another dude suggested doing that with the laser printer/cutter. I complied, and the thing does cut a very accurate radius, but it can only cut slightly thicker than 1/8″ pieces of wood, and since I need a 5″ long caul, that meant having to cut (and glue) lots of pieces. I tried gluing all the pieces at once and it was a disaster. They kept slipping, then the glue was drying real fast on me (what the hell, it’s Titebond Extend which is supposed to have longer open time).

So I googled and found this page. I followed his advice and cut 7 pieces from pine on the bandsaw. Here’s what one piece looks like:


I’m gluing them up in pairs (to avoid what happened last time), and it’s working out well. Only one piece left to glue.

I hope this guitar will be fixed by the end of this week. I still get filled with sadness every time I think about it.