Tuesday, May 13, 2008

Sunn Concert Bass

Recently, through of inquiries over the internets and train rides to and from the south suburbs, I acquired a Sunn Concert Bass free of charge from a gentleman named Tariq who plays in the excellent south of Chicago metal band Couldron, who are looking for a new drummer at the minute should you happen to be one. The only caveat was that it was in non-working order. Some asshole had apparently decided it would be a good idea to let the magic smoke that typically resides in capacitors, transistors, diodes and other such enigmatic electronical elements into the outside world where we all know it should not be. My task was to put it back in there.

I live my life car-free so it is often a trial to get out to the 'burbs. I knew it was worth it though as soon as I set this magnificent bastard on my speaker cab at home:


Looks pretty sweet, don't you think? How'd it sound? Well, at this point, it was still broken so it sounded like crap. I was hopping that the magic smoke may have found it's way back in there on its own but, sadly, that was not the case. Guitar sound would come out of the amp but not much and a ton of buzz came w/ it. Obviously not the best situation.

I opened it up to see what was up. Bear in mind, I followed the proper safety procedure of not being a retard before I started probing around. If you are a retard, I recommend you not open any amps up.

These are the amp guts:


At this point, I realized that somebody had actually tried to put some kind of magic smoke back in there. I can't say what kind but, seriously, this thing utterly reeked of nag champa incense, leading me to suspect that it'd been tampered w/ by a hippy at some point.

Closer inspection lead me to my first clue, two burned out resistors:


Even though I knew it wouldn't work, I tried swapping out those two resistors. The only good thing to report here is that only one of the resistors burned up this time. Apparently, the other one had just been taken out by the first one. I was one resistor down now but at least I had something to show for it. I replaced the one that burned up again and set off about the internets to find the real source of my problem. After some research, guided by several fine gentleman on the Unofficial Sunn Musical Equipment Web Site, I managed to narrow down the source of my problems to a few transistors in the power section. I am not sure if this is normal but they are stuck to the back of this amp and covered w/ little plastic pieces:

You just have to unscrew the screws and they pop right in and out, no soldering required. I tested them using a multimeter and the method described on this page. Three of them were bad out of five. Good thing I ordered four. Once replaced, it fired up just fine. It's loud as balls and your mom keeps calling me to ask about it. I've had it down at my band Sun Splitter's practice space for a couple weeks now and it's still going strong. Sounds pretty good for guitar or bass but I use it w/ my drum machine, Sober Bill. Here's the full rig:


As I said it's been going strong for a while now and I'm happy w/ it but I posted some pics of the board on the Sunn forum and someone noticed that a couple electrolytic capacitors had leaked out some of the crazy capacitor juice that's inside of them. I am OK w/ this since it works anyway but they're telling me that those caps could short at anytime--leading possibly to total protonic reversal--so I'm gonna replace them pretty soon. There's also some old resistors in there that I want to replace as some have drifted pretty significantly over the years. I will, of course, keep you posted.

2 comments:

Anonymous said...

Frank , I cannot find another way to reach you , anyway I just picked up a jazz bass body that needs neck pocket , jazz pick ups , and volume and tone routing .
can you please help me . I really enjoy reading your step by step articals they are very insightful .
James Gilardi

Luigi said...

It looks pretty sweet! I'm sure it will sound well!

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