19 December 2014

A Speedy Refinish of a Mahogany Ibanez RG321

I just bought an Ibanez RG321 MH (mahogany) on eBay. I have wanted to try one for quite a while and the price was low enough for an impulse buy. When I got it, it had a couple more scratches than were visible in the listing photos (a pox upon thee, seller!). One of the scratches was kind of deep, so the exposed wood was in high contrast to the guitar's dark stain.

Fig. 1. One of the eBay listing photos for the Ibanez RG321 MH.
You can see that the finish is not perfect, but the worst gouge
does not show up in this photo.

 I started lightly sanding it to remove the scratch. One thing led to another, and in only a couple of minutes, it looked like Fig. 2 below. If you have ever tried to sand a poly-coated guitar, you know that this amount of sanding can easily take an afternoon. The stain came off quite easily, so I kept sanding. While I was at it, I rounded the lower horn a little. The original was too pointy for my liking. It's not that noticeable, but woodworking is not my thing, and I didn't want to risk altering the guitar too much.

Fig. 2. In contrast to poly-coated guitars, getting down to this much
bare wood only took a couple of minutes on this guitar. Also note
the slightly more rounded tip on the lower horn.

Over the course of a couple of short evening sessions, I removed the neck, hardware and electronics, and sanded the body down to bare wood. The only tricky part was sanding the back without scratching the chrome string ferrules. I used an old razor blade for that (Fig. 3) to scrape around the ferrules. Keeping it flat and working slowly, I was able to remove the finish without scratching the ferrules or gouging the wood.

Fig. 3. Using an old razor blade instead of sandpaper to avoid 
scratching the shiny chrome finish on the string ferrules.

On each of the next three evenings, I put on a thin coat of tung oil, lightly sanding with fine steel wool between coats. I ended up with this:

Fig. 4. The body, after three light coats of tung oil.
Unfortunately, the seams between the different pieces of mahogany show up more clearly with the lighter finish. But I like it better than the original dark stain, which made the guitar look too dated. I just reassembled and restrung the guitar—here are the before and after pics:

Fig. 5: The guitar as purchased (left) and after refinishing (right).
Not a huge difference, but the scratches are gone, and I greatly
prefer the lighter finish.

15 October 2014

Fixing a Sears Silvertone 1448 Guitar Case Tube Amplifier

Fig. 1a. Sears/Silvertone 1448 Guitar Case/Tube Amplifier
Fig. 1b. The innards—a 3-watt tube amplifier with a 6-inch speaker.

In the summer of 1984, I bought a Sears/Silvertone 1448 guitar and amp-in-a-case at a flea market for $3. Several years later, before I starting buying and selling on eBay, I sold it for $125. It currently goes for $500 and over on eBay these days, depending on the condition. Whenever I regret selling it for only $125, I remind myself that at least I didn’t sell it for $3. I only played through it a few times, and the amp had a sweet bit of overdrive when cranked.

The one you see in these photos did not. I was charged with repairing this one, which had very low output and an input jack that had been pushed through the control panel (Fig. 2). The first thing I did was to secure the input jack, so I could play through it. I had a washer on hand, drilled the center hole big enough for the jack and tried that. It’s not pretty (Fig. 6), but it’s cheap and solid.

Fig. 2. The input had been pushed through the control panel. Also note the missing bolt to the right of the Volume knob.
With the input jack in order, I tested it myself, and the output was very low, with a lot of crackle. The first thing I noticed was bad connections on the speaker wires (Fig. 3), which had been pretty poorly spliced and not even soldered. I found two other bad joints under the panel, which was a mess (Fig. 4). Five bolts were missing, so the transformer and capacitor were just hanging loosely, as was the bracket holding the tubes.
Fig. 3. The speaker wires were just pinched together, like the red one in this photo. (Another missing bolt in the upper right.)

Fig. 4. This is seriously what the guts looked like when I removed the control panel. The missing bolts attach the big capacitor, the transformer and the bracket holding the tubes.

I re-soldered the bad joints and bolted the cap to the back of the panel. The bolt head looked like hell, and I couldn’t justify using it on such an old amp, so I removed that and used rivets instead (Fig. 5). These rivets alone were too small for these holes, so I had to buy some rivet washers. The rivets I used for this were 1/8” (3mm) diameter with a 1/4” grip. The washers were 1/8” (hole diameter). This worked very well. When I was done, everything was securely attached—no wobble—and looked much better on the front of the panel (and on the back of the panel for that matter—see Fig. 6).

Fig. 5. The rivets and rivet washers used to secure the chassis, capacitor and transformer

Fig. 6. These rivets were the perfect size. Unobtrusive, but big enough to secure everything tightly.

Before looking too much further for any other problems, I plugged in and tried it again. It worked and sounded pretty good. There was a little crackle when adjusting the volume, so I sprayed the pot and called it good. Here's the finished panel:

Fig. 6. Good to go. The rivets fit in with the vintage vibe. The input jack less so, but it is sturdy and easily replaced.

04 October 2014

Installing a Pickup and Preamp in a Yamaha FG700S Acoustic

Fig. 1. Yamaha FG700S
If this post isn't all that informative, that's at least partly because I didn't take that many photos. I was so intent on not destroying the guitar that it didn't even occur to me to take photos until after I successfully cut the first hole. But first things first.

I have an inexpensive Yamaha FG700S, which is a $200 guitar new, but I got mine used for $140. For a solid top guitar, it's hard to beat for the price, and I like this one a lot. However, shortly after buying it, I wished I had bought an acoustic electric. I put it on craigslist so I could upgrade to an acoustic electric, but got no bites. So I bought a $13 piezo pickup, and a $22 preamp and input on ebay. I didn't want to spend too much, because I felt there was a decent chance that I would destroy the guitar while trying to install the pickup, since I had never done this before. And I figured if I liked it, I could always upgrade to a better preamp and pickup.

The part I feared most, obviously, was cutting two holes in the guitar. Measuring and cutting a hole in a flat plane is easy, but the preamp goes on a curved section of the guitar. I measured the preamp housing several times, placed it along the edge of the curve in the guitar body to see where it would fit best. After finding a sweet spot, I used a razor blade to make little nicks in the finish marking the border of the section to be cut out. I then marked the border with masking tape (Fig. 2).

I drilled the corners with a 1/2" bit. I started to use a jigsaw to cut the hole, but the wood was too fragile. It made a sloppy cut. I tried a utility knife to score the border of the hole, and I kept scoring until it poked through. This didn't take as long as expected, and the cuts were pretty clean. I sanded the hole and inserted the preamp. It was a little tight here and there so I sanded it again and it fit. I didn't get photos of the preamp installation, so here is the during and after shots of the input and the after shot of the preamp:

Fig. 2. Cutting the hole for the input. Installed input and preamp.
I did the same exact thing with the input. Then I plugged the piezo pickup into the preamp and stuck it under the bridge.
Fig. 3. About to place the pickup under the bridge.

I should note that the preamp came with as under-the-saddle pickup (Fig. 4). I preferred the kind that mounts inside the guitar under the bridge (Fig. 3, above), so I snipped the input off the former and and soldered it to the latter and used that.

Fig. 4. Cheap under-the-saddle pickup

Everything's in, and although I made the input hole a hair too big (so there's not enough wood in one corner for the screw to grab), it went better than I expected.

30 September 2014

It Pays to Have a Little Fun—Fixing a Marshall Master Lead Combo 5010

Have you ever checked to see if an amp or pedal was working by sticking a cable in and tapping the other end? Or noodled on the guitar for a moment to make sure that whatever you just fixed works? My latest repair highlighted the importance of taking the time to ensure that the problem is indeed fixed. And as a mere dabbler in repair, this is something I need to remind myself from time to time.

I recently was given an Marshall Master Lead Combo 5010 to fix (Fig. 1 below). When I tested it, it had output, but it was intermittent and there were occasional dropouts and static pops. Turning the Preamp control caused a lot of crackle and garbling of the signal. There was crackle with all the other controls as well, but not as bad.

Fig. 1. Marshall Master Lead Combo 5010 Solid State

I removed the chassis and thoroughly cleaned all the pots. I plugged in a guitar and it sounded fine, even when I turned all of the controls. No static. So I played for a few moments more and thought I heard a pop. I stopped and waited, but didn't hear it again. I played again, and after five or ten seconds, heard another pop.

I did the chopstick test, poking all of the components (of which there are not many—see Fig. 2). The corner of the board near the two big caps was pretty loose, and when I poked it, I heard loud crackling. I poked at the caps and one of them was markedly looser than the other. I looked at the solder joints with an inspection mirror while I wobbled it, and sure enough, I could see the wire and solder moving freely back and forth as I did so (Fig. 3)

Fig. 2. The simple layout of the board was refreshing when troubleshooting.

Figure 3. A very loose and sloppy solder joint

Apparently, when I played, the vibration was causing that bad joint to wiggle enough to cause the pops.

When I removed the board, it was immediately apparent that previous repairs and other sundry misfortunes had been visited upon this poor amp (Fig. 4). It all seemed to work except for the joint in question, so I ignored the other stuff, resoldered the bad joint, plugged in the guitar and played for a bit. None of the problems were evident, so that did the trick.

Fig 4. Some of the copper traces had previously been scraped and exposed for reasons unknown.

After cleaning the pots, if I had just done the cable-only test or noodled on the guitar for a moment, I would have assumed that the problem was fixed. The bad solder joint might not have had the opportunity to cause a problem, and I would have called it good and returned it as supposedly working. Playing it normally for a little while saved me that embarrassment.

When I fix an amp, I always play it just for fun for five to ten minutes. Often, it's likely the only opportunity I will have to try a particular amp. It's usually an amp I haven't played before and it's almost certainly one I will never own, so it's a nice chance to try a new amp in the comfort of my own home. But more importantly, this indulgence also serves the purpose of making sure I'm not too hasty in calling it fixed.

29 September 2014

Classing up a Washburn WI-64 Headstock

Several years ago, I bought a Washburn WI-64 in transparent red. Although it is the most comfortable guitar I have ever held, and I love the design, I didn't like much else about it.
Almost new—all stock except the new knobs for the SG look

The first thing I did was replace the knobs with SG style knobs. Then I stripped the paint, which took a very long time. This was before I had kids—I can't imagine spending that amount of time on a single guitar ever again. After coating it with some tung oil, I was glad I did it. It's a nice looking guitar. Except the headstock, which I will come to.

I replaced the stock pickups with GFS pickups (bleh on the pickups and GFS's customer service). After trying Dimarzio Super Distortions, I settled on Seymour Duncan Distortion pickups and loved those. I stayed with the original wiring for a while, but eventually replaced the pots and rewired the VCC setup as a traditional set up (two volume, two tone). I wanted a single coil option, so I put in a coil tap switch, which is wired to both pickups. I could have gone with push-pull pots, but I had the DPST switch on hand, and I am not a big fan of push-pull pots unless there is a reason that the guitar shouldn't be drilled.

After refinishing, still with the Dimarzio Super Distortions

After adding the coil tap switch

I did not do all of this at once. I poked away at it here and there over several months. When it was done, I loved it. It felt, played and sounded great. But the headstock always bugged me. Not so much the shape, which I could take or leave, but the cheap logo:

The original headstock

These are $500 guitars new (I paid $350 for this one), but the logo design and quality always seemed more at home in the $200 and under category. I often wondered if I could peel off the template, but never had the guts to try until recently.

It ended up being a very quick job. I removed all of the hardware on the headstock and placed a scrap cloth on the face of the template. I accidentally used a rag with an iron-on on it, leaving gunk on the template, visible below. No harm done this time, fortunately.

 I set the iron to cotton (hot) and ironed cloth, moving it slowly back and forth. I removed the iron and tried the edge with a scraper and was just able to get it under the template. I applied some more heat and was able to slide the scraper the rest of the way to the nut. Another NOTE: the template is wedged under the nut just a little bit, so don't pry the template up. Rather, when you get the scraper most of the way to the nut, gently pull the template away from the nut, as parallel to the headstock as possible.
Applying heat to the cloth on the headstock face
After enough heat was applied, I was able to get the scraper under the template

The template is pretty sturdy. I wasn't sure if it would melt, but it did not at all. The only thing the iron did was warm up the glue underneath, enough to get the scraper under it.

I was relieved to see that there was no glue residue or any other gunk on the wood. It actually looked quite good even before sanding it. Here are the first few steps:

Before, hardware removed, template removed.
I sanded it a bit, then coated it with the same tung oil I used on the rest of the guitar, and I think it looks great. In fact, having no cheap logo on it somehow makes the headstock shape a bit more pleasing to the eye. Here is the headstock with the hardware back in. The whole process took about 45 minutes, and considering the cheap look of the original logo, it was worth it.

Refinished headstock

02 July 2014

Laney VC30 212 Tube Amplifier: No Output and Falling Apart

Note: This amp was a pain to get back together. I don't mention it in the narrative below, but before I put everything back together (with any amp), I drain the filter caps. When you're trying to position the chassis just right with one hand while fumbling with the bolts and screwdriver in the other, it's best to be safe.

Anyway, this Laney VC30 212 (PCB 9072-3)— was beat. It was missing most of the bolts holding the chassis in the cabinet, and there was no output.
Fig. 1. Yes, that is duct tape on the handle.
The high temp fuse on the back was fine, but the fuse on the board was blown (at the far right on the board in Fig. 6). I replaced that and it worked fine. I spent quite a while in a car parts store, then the hardware store trying to find matching bolts and speed nuts (see Fig. 2). Both places had one part but not the other matching part. Frustrating. And if you're looking for replacement bolts, these were metric: M5 .80.

Fig. 2. What are speed nuts? These thingies. 

After messing around all morning hunting down parts, I finally was able to put it all back together (no easy task) and there was no output again. Because it worked when it was apart, I thought maybe one of the bolts was touching (and therefore grounding) one of the parts inside the chassis. I removed the bolts and stuck a plastic rod into each hole to see if it bumped anything. As I expected, I bumped something in one of the holes. The right hole holding the board on back of the chassis had very little clearance. The original bolt must have been shorter than the one that was being used when I got the amp. The bolt was grinding away at the backside of the PCB every time it was screwed in. I got a M5 .80 20mm bolt (roughly 3/4"), and it was just right. Long enough to get some purchase in the threads, but not so long that it touched anything inside the chassis.

I took the amp apart again and removed the board to check the back for damage. To remove the board, by the way, you will need to desolder the wires connected to the Bright and Drive switches. Other than that, it was pretty easy—remove the nuts and washers from the knobs and inputs and two screws holding the board to the chassis. On the back, the damage from the bolt was apparent. It gouged two separate copper areas (Fig. 3). I scraped between them to ensure that there was no continuity and put a piece of tape on it in case the wrong bolt was ever used again.

Fig. 3. Damage from the bolt that was too long.

Fig. 4. I ensured that there was no untoward continuity among the damaged traces and covered the area with electrical tape in case someone ever uses a long bolt in that spot again.

As I mentioned, getting the amp back together was no mean feat. The speed nuts tend to move around when you slide the chassis back into the cabinet, so some of the holes lined up the the holes in the cabinet, but some did not. The top bolts were easy, but the four side bolts were not. There is room to reach into the cabinet and up over the front lip of the chassis with your hand and move the nuts that are closer to the front of the cabinet (see note at the top of the page), but not the ones toward the back. To do that, I slid a little ruler up into the gap and wiggled the nut into place (Fig. 5).

Fig. 5. Blindly moving the speed nut into position with a small ruler.
It's hard to do this with any precision, but you only need to get it close enough to be able to stick something in the hole and finish lining it up. I used my plastic rod again for this.

I got it all zipped up the second time and it sounds fine. Here are some board pics, in case they might be of any interest:
Fig. 6. As you can see, this amp has been modded previously. Some of the components have been soldered to the clipped legs of components that have been removed. I found a resistor that looked okay, but when I poked it, it moved. One of the legs was broken and you couldn't tell by looking at it. I replaced it.

Fig. 7. There are a lot more surface mounted components on the back of the board than I would have expected. The covered bolt damage is on the right.

27 June 2014

Fixing a Defective Drive Circuit in a Fender Hot Rod Deluxe

I just finished repairing another Fender Hot Rod Deluxe. A lot of problems that people have with this amp often somehow involve the Drive circuit and a couple of resistors that are prone to overheating (R78 and R79). The issue here was that the Clean and Drive channels both worked fine, but when the More Drive switch was engaged, there was no output and the LED turned off instead of turning red.

The first thing I noticed was that the amp had been worked on before, clearly because of the two aforementioned resistors. (If you're interested, this Premier Guitar article about the overheating resistor problem will bring you up to speed better than I can.) The first sign of previous work was that all of the bolts holding the circuit board to the chassis were missing. Oopsy. The only thing holding it in place is the board-mounted pots jacks, which are bound to fail eventually because of this. The second sign was the clearly non-original solder joints on R78 and R79. There was also hot glue or silicone under the resistors (Fig. 1a), which I don't think was stock in the 90s USA Hot Rod Deluxes (but I'm not positive about that). The back of the board all around those resistors was blackened as well (Fig. 1b), which I'm sure is the reason it was serviced.

Fig. 1a. Hot glue or silicone under R78 and R79

Fig. 1b. Blackened board and non-original solder beads on R78 and R79

After trying to figure out what had been done already, the first thing I checked was the solder joints on the Drive/More Drive LED (Fig. 2).

Fig. 2. The Drive/More Drive LED.

I looked at the joints and poked the leads (labeled R, C, and G in Fig. 2 above). G(reen) and C(ommon) were fine, which I expected, since the Drive channel worked fine, and when that's engaged, the LED is green. When I poked the red lead, I could see the tip wiggling loosely in the bad solder joint (circled in Fig. 3). Even without wiggling it, you can see that it's a bad joint. I touched that up and the amp worked fine.

Fig. 3. The culprit: a bad solder joint on the Drive/More Drive LED.
Most indicator lights have no effect on output, but in this amp, the LED is part of the Drive circuit. So if the LED isn't not functioning correctly, the Drive circuit isn't either. The LED's location in the circuit is outlined in red in Fig. 4.

Fig. 4. Unlike a lot of LEDs, the Drive/More Drive LED is part of the circuit, rather than just an indicator.
It doesn't take to much research to realize that this is not an isolated case of this particular LED causing issues with the Hot Rod Deluxe, so if you're having issues with the Drive channel, it's definitely worth a quick peek.

Line 6 Duoverb Head: Is Everything Glued?

I will start by admitting I was not successful at fixing this amp. I was pretty sure I wouldn't be, and I told my customer that I am not set up to diagnose or repair modeling amps or anything else that is mostly surface mounted components (which are tiny). But I said I'd take a look anyway. I always learn something, and this time was no exception, so I am sharing in case anyone else runs into the same problems I did.

To remove the chassis from the cab, I removed the four usual bolts—one near each corner of the top of the cabinet. The chassis didn't budge, so I removed the four bolts from the handle. That usually isn't necessary, but these handle bolts were indeed attached to the top of the chassis. The chassis still did not budge. There were no other bolts to remove, so after tugging a bit by hand and triple-checking that there were no other bolts, I got a putty knife and gently pried the chassis from the cabinet. That worked, and the reason it was so difficult to remove became apparent when I removed the chassis from the cabinet. In addition to the six bolts, it had been secured with a couple spots of glue.

I ran into a similar problem with the knobs. I didn't want to destroy any pots by pulling too hard on the knob, so I did a quick search to see if Line 6 also puts little dabs of glue on their knobs. I found a lot of forums saying that Line 6 knobs are difficult to get off, but none saying that they were glued, so I tried some pliers and a piece of plastic tubing to protect the finish (see Fig. 1 below). I put the tubing around the narrow part of the knob, gently rocked the knob back and forth a few times then pulled and they all came off with no problem.

Normally, when pot knobs are hard to remove, you would put something on the faceplate to protect it, then use a couple of small screwdrivers—one each side—to pry them off. However, most of these knobs were flush with the surface of the faceplate. I could have just fit a razor blade under them, but that would have damaged the surface.

So if you have the misfortune to work on one of these amps, the chassis does come out and the knobs do come off. Just be careful in both pursuits.

17 June 2014

Fixing the Reverb in a Mesa/Boogie Lonestar

This amp is one of the heaviest and by far the purplest that I have had the pleasure of fixing. It's so heavy (69 pounds, according to my bathroom scale) that I didn't even take it down to my workshop. I brought a bunch of tools up to the living room just to see if it was an easy fix. No sense lugging it for nothing, says I.

Fig. 1. Sixty-nine pounds of purple suede

I played through it for a a few minutes, of course, and the reverb was definitely on and turned up, but not audible. I tapped the tank and could hear the springs rattling around through the speaker, so the output side (black cable in Fig. 2) was good. I swapped the cable for some good ones and it still didn't work.

Fig. 2. The white cable is connected to the input jack on the reverb
tank, and the black cable is connected to the output. 

I took the cover off the reverb tank (it was mounted to a small piece of plywood), and immediately noticed a loose green wire (see Fig. 3). It was attached to the plastic connector that connects the input wire to the input transducer. I picked out the little bit of wire that broke off in the connector and reattached the wire.

Fig. 3. The culprit: a loose wire that somehow got disconnected from the plastic connector on the left.
(The cream-colored block under it is the input transducer)

I tested again, and it worked fine. I put everything back together and took my tools down to the workshop, which sure beat having to lug this beast.

11 June 2014

1964 Fender Blackface Super Reverb Repair

The latest bum amp in my workshop was a Fender Blackface Super Reverb, ca. 1964, which is quite possibly the heaviest amp I have ever carried. The Normal channel was fine, but the Vibrato channel had an intermittent volume drop, just enough to be noticeable.
Fig. 1. The Beast.

Fig. 2. This is why The Beast weighs 70 to 80 pounds.

A visual inspection revealed a missing solder joint on the bias capacitor (see Fig. 3 below), which was not the cause of the problem, but certainly worth soldering.

Fig. 3. A conspicuous absence of solder.
I didn't see anything else untoward, so I did the chopstick test (with the amp on, poking each component with a chopstick). Still nothing. New tubes did not solve the problem either, so I did another chopstick test to no avail. I recorded all the voltages, but nothing jumped out as weird.

I started testing continuity among all the components and I found a cold solder joint on the board going to pin 1 on V5. I resoldered it, and the problem was gone. I took voltage readings again, and THEN the first measurement looked weird, even though it didn't jump out at me at the time. I guess I was too busy not electrocuting myself to notice the first time.

Both problems appear to have been the result of a recent recap job (I didn't do it) that was mostly good, but with a couple of iffy solder joints.

27 May 2014

Marshall JCM 900 Dual Reverb Repair (No Presence Control)

My latest repair was a Marshall JCM 900 100 watt combo, which sounded great except that the Presence control did not have any apparent effect. A bad pot didn't make any sense. Usually, if a pot goes bad, there is some sort of funkiness, like scratchiness, odd dropouts, etc.

A visual inspection revealed nothing particularly noteworthy. I did notice that the two reverb pots had the back removed, pictured here:
Fig. 1. The backs had been removed on both reverb pots. Note the board version
on the left. You might need that when tracking down the correct schematic. 
Both were double gang pots, so removing the back only disabled the half that wasn't connected to the board anyway. That is worth noting only because the presence control (immediately next to the left reverb pot) was also a double gang, and one row of pins were snipped off so that they looked like they were connected to the board but were not.

I removed the board from the chassis by removing the knobs, the plastic nuts on the input and footswitch jacks, and finally the nuts on the Preamp (Ch. B) control and the Ch. B Reverb controls using a 10mm socket (pictured below).

Fig. 2. You'll need a 10mm socket for the nuts on the Preamp (Ch. B) control and the Ch. B Reverb pots
With the board out, the problem was quickly apparent. Someone had already worked on the Presence control and installed a jumper incorrectly, so that all pins went to ground regardless of the position of the control. I think the jumper was installed because it looks like the solder pad had lifted.

Fig. 3. I did not do this.
I would like to add that I did not put all of those scratch marks there. This work looks like it was done in the back of an offroad vehicle. Anyway, I removed that jumper and installed a longer jumper to the correct spot (C28), after which the Presence control worked fine.
Fig. 4. The new jumper. 
And here it is. Lovely.