Members anothertxn Posted November 7, 2005 Members Posted November 7, 2005 Hello there, I was just wondering if any of you could give me some advice as to what might be going on with my recently obtained 300T. Initially I had a fuse blow, and after replacing it everything was normal. Then, at a gig, 2 more fuses bite the dust. I was worried, but needed to make it through the gig, so I put in 2 replacements and finished the set. I'm now worried this may have been quite the mistake. The next time I tried to use the amp, if I turned the volume up beyond 3 or so instead of reproducing the note I would get shrill feedback that only goes away when I turn down the volume. Also, if I leave the volume down the notes ring but have distortion. I've tried isolating the various power tube pairs as well as trading out the preamp tubes. Any idea as to what else I should be looking at? I love this thing when it is working, but now I'm completely rigless.
Members Detox Posted November 7, 2005 Members Posted November 7, 2005 Sounds like you've done just about all the testing a non-techie can do. I may just have to go to the shop. BTW, what kind of shape are your guitar/speaker cables in?
Members catphish Posted November 7, 2005 Members Posted November 7, 2005 Maybe a dumb questions but, do you have the ohm setting correctly set for your cabinets? The feedback thing makes no sense. In the year I owned it I never had a single problem. If no one else here knows off the bat, I'd say take it to a shop. ps, you have a PM
Members the_big_geez Posted November 7, 2005 Members Posted November 7, 2005 As always, it is nigh unto impossible to troubeshoot electronic over a distance and without the faulty equpment in from of one. As a general rule however, I should note that when a fuse blows, it does so for a REASON. That reason needs be determined and corrected before the item is put into further use. On rare occasions a fuse will itself be faulty (sometimes while still appearing to be normal!). These instances ARE rare, however, and once the same fuse blows after being replaced, it can be certain there is another cause. Most often what blows them (in tube amps) is a failure in the filter section of the power supply, but many times I've seen this occur from bridged terminals on one or more of the tubes. (Which can be corrected with a simple tweak of a chopstick). THere are other reasons as well, that I won't getr into. Suffice it to say that one should heed the warnings: 'No User Servicable Parts Inside' and 'Risk of Shock'. It is clear that if the question needs be posed here, it is beyond your scope to diagnose and/or correct. But there is hope that it is actually a simple and inexpensive problem. The Reader's Digest version of the above is: 'Take it to the Shop!'
Members Ole Man Blues Posted November 7, 2005 Members Posted November 7, 2005 Contact the Manufacture customer service and find out if this is a common problem and if there is a quick fix without taking it to a tech...........go from there on their advice......... OMB
Members anothertxn Posted November 7, 2005 Author Members Posted November 7, 2005 Thanks guys. Yeah, I know I need to take it in. I was just hoping someone might say, "hey, I had the exact thing happen and it was just a _____." Of course, I didn't expect to get that kinda lucky. I can't believe I'm saying this, but at this point I'm just hoping it's the tubes. Anything else and I probably can't afford it...even the tubes are a stretch. Of course this would happen right after I sell my backup. At least my BDDI got me through recording this weekend, but I certainly would have prefered the Sunn. Catphish, PM back your way.
CMS Author Craig Vecchione Posted November 7, 2005 CMS Author Posted November 7, 2005 Does the 300T have a user-adjustable tube bias? If so, make sure it's set correctly. Are you stubbing a tuner into one of the input jacks? Some amps don't like this and will distort and feed back. However, blowing fuses is not a symptom of this. If you have run the amp with all new tubes and bias correctly set, there's nothing else you can do. Get it to a tech before something worse happens.
Members anothertxn Posted November 7, 2005 Author Members Posted November 7, 2005 Originally posted by Craigv Does the 300T have a user-adjustable tube bias? Yes, good idea. Although, I'm not sure why the bias would change on me like that... Are you stubbing a tuner into one of the input jacks? Some amps don't like this and will distort and feed back. However, blowing fuses is not a symptom of this.I have the tuner in my signal chain that runs into my main input. However, I've bypassed all my pedals and I have the same problem going straight in.If you have run the amp with all new tubes and bias correctly set, there's nothing else you can do. Get it to a tech before something worse happens. Thanks for the suggestions.
CMS Author Craig Vecchione Posted November 7, 2005 CMS Author Posted November 7, 2005 Originally posted by steers b-c Bias can sometimes change as tubes age. When it happens quickly that can indicate a failing tube. If you change power tubes you should always check and adjust as needed. Bias has no bearing on preamp tubes.
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