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