12 November 2017

Ibanez MS10 Metal Charger: Low Output by Design

I got a non-working Ibanez MS10 Metal Charger for $40 recently. I was glad that it was an easy fix (See Fig. 1), and pleasantly surprised that the switch works (these are often spotty in the old Ibanez pedals), but I was disappointed in the pedal itself. The main issue was the level. The pedal was not as loud as the bypass signal (unity) unless I had the distortion and level cranked. Below that, the distortion sound wasn't that interesting or particularly usable. At first I thought the pedal was defective, but after a bit of poking around online, I found this post on killall -9 humans effects blog, describing the same issue. (I am a fan of mirosol through his significant contributions to Guitar FX Layouts, and was grateful that he posted this particular tidbit).

My first thought was that this pedal is a collectible, but after not being able to sell it for $50, I'm skeptical. It very well could be a collectible, but not necessarily one in high demand, at least as of this writing. At any rate, since I couldn't sell it, I figured I'd mess around with it and see if I could make it not sound bad.

Several years ago, I bought (and have thoroughly enjoyed) Brian Wampler's book, How To Modify Effect Pedals, which includes a mod for the MS10. This mod corresponded with what I had already seen in forums here and there, but included a couple of other tweaks that I hadn't seen. Brian's awesome, so I went with his suggestions.

I started by removing D5, D6, and C12 and changing R11 from a 4.7K to a 1K resistor. I zipped it up and noticed a bit of an improvement. The pedal seemed a bit louder and the distortion sounded a bit more pleasant. I then removed D3 and D4 and think I noticed more of the same. I judged only by ear, not with an oscilloscope or anything, so it's hard to tell. I can say that I plugged in and actually enjoyed playing with the pedal for a while, which was not at all like my initial experience with this pedal.

Fig. 2. D3, D4, D5, D6, and C12. D1, D2, and R11 are up near the ribbon cable.

I might try replacing D1 and D2 with a different configuration (Brian suggests 4148-4148 in D1 and 4148-1n5001-4148 in D2 for "better clipping, fuller and thicker." I will probably put sockets in so I can try several different diodes without ruining the trace. But for now, at least the pedal is usable:

18 December 2016

Electro-Harmonix Holy Grail Reverb Repair

I recently bought a non-functioning Electro-Harmonix Holy Grail Reverb. It's chock full of surface mounted components, so I wasn't sure if I could fix it, but having successfully repaired one of these before, I thought I'd give it a go.

Fig. 1. EHX Holy Grail Reverb, original enclosure.

Visual inspection revealed nothing, except a few solder joints that looked sloppier than stock. I plugged it in to verify that it didn't work, and indeed it didn't. Oddly, though, when I turned the knob, I briefly heard a reverb-soaked pop/clank sound, almost like when you jar an amp with the spring unit in it. Thinking something must be loose, I left it on and poked every wire and component that was big enough to poke with no luck.

Fig. 2. Everything looked good on both sides of the board, except for the three solder joints on the upper left of the board, which looked like they had been redone. That turned out to be irrelevant.
I ran out of time, so I left it for a week or so. I plugged it in again and it worked (?!). I moved all the controls, unplugged it and plugged it in again, and it did NOT work. After poking everything again and even wiggling the board while it was on, it occurred to me that the pot might be the culprit. I sprayed the crap out of it with DeOxit, gave it a little squirt of compressed air and turned it back and forth several times.

I plugged it in and it worked. I fiddled with all the knobs and plugs like before and it still works. It must have had some gunk in the pot. It turned out to be less complicated than I expected.