Members diocide Posted January 3, 2012 Members Share Posted January 3, 2012 Hey guys. Long time member here, but I've never really madeir over to the bass forum, but I had a question I think you all would be best suited to answer. I have a very old Sunn Coliseum 300 head, that I've had for about 10 years. The thing was a total tank up until abut a year ago. I've used this thing first as a guitar and bass amp, and then later as a power amp for my PA system. Anyway, about a year ago, The main board fuse (not the power one next to the power cord) blew. So I changed it once, and it blew again immediately. The fan powers up and spins, but no sound is produced. My guitar tech said he'd take a look at it, for a bench charge of 50 bucks, which would be taken off the final cost if I decide to have it fixed. So here's my question. Although this thing has some sentimental value, I do not want to dump hundreds of dollars into it. In your guys experience, am I better off fixing this beast, or just keeping an eye out for another bass amp? Will I get anything near the Sunn amp for anywhere in the 200-300 range? What do you guys think? What would you do in my position? Link to comment Share on other sites More sharing options...
Members guitargod0dmw Posted January 4, 2012 Members Share Posted January 4, 2012 I would fix it, but it very well may cost a few hundred to fix. You're not going to find a vintage tube amp for that kind of money. A Traynor YBA, Ampeg V4, or beat to death/non functioning SVT could be found for roughly $600...give or take a few hundred depending on what you find. On the used market, in the $200-$300 range you could find a GK 800RB, and probably a few other nice amps. Whether you like the sound is totally up to you. Link to comment Share on other sites More sharing options...
Members perrydabassman Posted January 4, 2012 Members Share Posted January 4, 2012 Most likely the MOSFETS shorted out. It could be a cheap fix if the parts are available. The FETs usually run about 30 bucks apiece, and looking at the schematic for the coliseum it looks like it has four of them. Link to comment Share on other sites More sharing options...
Members pickinatit Posted January 4, 2012 Members Share Posted January 4, 2012 The Sunn Coliseum 300 is a solid state amp, not tube. From what I've observed, If you can fix it for under $300 you are ahead of the game as far as the amps re-sale value is concerned. As far as replacing it is concerned, you probably can't do better then that for the cost of a repair and you said yourself that the amp has been a "tank". Link to comment Share on other sites More sharing options...
Members pickinatit Posted January 5, 2012 Members Share Posted January 5, 2012 The Sunn Coliseum 300 is a solid state amp, not tube. From what I've observed, If you can fix it for under $300 you are ahead of the game as far as the amps re-sale value is concerned. As far as replacing it is concerned, you probably can't do better then that for the cost of a repair and you said yourself that the amp has been a "tank". Search of price history on e-bay doesn't turn up much. The Coliseum 300 doesn't come up very often. Only one listing shows a sale price of $675 for a Coliseum, not a Coliseum 300 (used, of course). Search for what you are looking for like you are looking to buy/bid. When you get there, look directly to the left of the first item listing for the vertical strip menu titled "Categories" (not the "Categories" pull down menu at the top of the page) and follow that side strip down to "Show Only". The third checkbox under the "Show Only" heading is "Completed listings". Check that box and the ended auctions will load, both sold and unsold. You can follow this auction though.http://www.ebay.com/itm/Sunn-Coliseum-300-Bass-Amplifier-Head-Rebuilt-Amp-/320809329251?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%252BC%26itu%3DUA%26otn%3D5%26pmod%3D300639748792%26ps%3D63%26clkid%3D5399467435648144430 Link to comment Share on other sites More sharing options...
Members guitargod0dmw Posted January 5, 2012 Members Share Posted January 5, 2012 The Sunn Coliseum 300 is a solid state amp, not tube. Hmmm. Shows what I know about Sunn amps! Well that changes my outlook on things. I'd probably get rid of it, and up my budget to $500 or so... Link to comment Share on other sites More sharing options...
Members Reverse Entropy Posted January 6, 2012 Members Share Posted January 6, 2012 FYI, I just got a nice QSC Powerlight amp off eBay for under $300, so despite my fondness for old Sunn gear, I'd probably punt it. However, the most likely points of failure in those old amps are the output transistors or the driver transistor feeding one of the output pairs. Generally a pair of transistors fail together. So figure $60 or so in parts. Link to comment Share on other sites More sharing options...
Members diocide Posted January 6, 2012 Author Members Share Posted January 6, 2012 Some good info here guys. Thanks. I'm going to double chek with my tech once more and just have him look at it. More than 200, I'll probably scrap it. Less, I'll keep it. Link to comment Share on other sites More sharing options...
Members pickinatit Posted January 6, 2012 Members Share Posted January 6, 2012 .QUOTE] I didn't make my post very clear before What follows is instruction for how to look up "Auction/Price history" of particular items on E-Bay. Search for what you are looking for like you are looking to buy/bid. When you get there, look directly to the left of the first item listing for the vertical strip menu titled "Categories" (not the "Categories" pull down menu at the top of the page) and follow that side strip down to "Show Only". The third checkbox under the "Show Only" heading is "Completed listings". Check that box and the ended auctions will load, both sold and unsold. Link to comment Share on other sites More sharing options...
Members Bill Chambers Posted December 30, 2019 Members Share Posted December 30, 2019 On 1/5/2012 at 2:56 PM, guitargod0dmw said: The Sunn Coliseum 300 is a solid state amp, not tube. Hmmm. Shows what I know about Sunn amps! Well that changes my outlook on things. I'd probably get rid of it, and up my budget to $500 or so... I have one that needs parts to fix. I will buy yours for $100.00 for parts. Where do you live. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted January 9, 2020 Members Share Posted January 9, 2020 You need to check the posting dates. That thread is 8 years old and I haven't seen them posting here in a long time. I am familiar with that head however. I did repairs on my buddies head for awhile so I've seen them on the inside. I was going to buy his so I had the matching head for the 6X12" cab I bought from him a couple of years earlier. I didn't have the cash on hand so someone else bought it. Not sure what parts you need, but some of the components are common and easy to find and others are totally unique and no longer manufactured. Sunn did some novel things with transformers to add tube like compression with its coils woven into the power amp circuits. Getting a replacement transformer might be really tough if not impossible to find. Allot of the problems are caused by the caps too. I had a buddy give me a 76 Concert lead head and I immediately replaced all the power caps I could find. If you keep good caps in them they can last dam near forever. If they get leaky and short you can kiss that sucker goodbye. Once one power cap shorts it can take out allot of other devices if the fuses don't save it. FETs, were used for the power stages. They hadn't perfected Mosfets for high powered audio amps the years those amps were built. At least Sunn hadn't used them yet, they used FET's. Transistors, Pots and stuff like that should still be available. It really comes down to how much you want to spend on it. I bought a 350W Class D Ampeg Portaflex head for $200 in mint condition. You can find plenty of others in the 300 to 800W ranges for less then it costs to get a competent technician to look at that head no less repair it. If you're like me though you hate giving up a useful garment while its still got some wear left. There does come a point in the life of ever amp where you have to decide whether its smarter to repair it or upgrade and the weight alone is 40 Lbs. My Portaflex is 350W and weighs 8 Lbs in comparison. I'd need to strap it to a 32Lb concrete block to match the weight of the Sunn. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.