Mesa Bass amps: Causes for Blowing fuses?

[ksmith63]

Hey guys....thinking about picking this one up:

http://cgi.ebay.com/Mesa-Boogie-400...ms=66:2|65:3|39:1|240:1318|301:1|293:1|294:50

It's labeled as a 'repair' and it blows fuses. What could be the general cause with this on an old tube amp? Bad tubes? Old fuse? Not the right fuse? Bad wiring in building? Any thoughts on something MAJOR WRONG WITH THIS AMP?

My D-180 blew fuses when I first got it but the tubes in it were mismatched, from different decades and garbage. Also I had to replace the fuse holder. Zero problems of this sort ever since.

 

[glassman]

Re: Mesa Bass amps: Causes for Blowing fuses?

Blown fuses can result from any number of things but he most frequent reasons are as follows and in order of occurance:

Shorted power tube(s)
Shorted power supply capacitor
Shorted output transformer primary

It is impossible to determine the true cause without going inside it. One interesting note is the numbers written on the top of each power tube; they appear to be the plate current at idle for each tube. This would have had to been measured at a point that the amp wasn't blowing fuses and they seem to have a lot of variance tube to tube. The transconductance of a tube changes over time and when they have this much power to throttle, one could easily short if it is already drawing more current than the others. This would be the most likely cause but I would certainly not bet the bank on it.

This would be a gamble...I can't recommend what to do in this case.

Jerry

 

[Zerberus]

Re: Mesa Bass amps: Causes for Blowing fuses?

^^ I agree in all points....I would probably get it if I had the spare change, because even with the cost of a larger repair than just a retube and refusing it may still be cheaper or at least similiarly priced to a functioning specimen....

 

[glassman]

Re: Mesa Bass amps: Causes for Blowing fuses?

^^^I agree with Zerb...If you have the xtra coin it might be well worth taking the chance. Be prepared, worst case scenario, the repair will cost more than what you are paying for the amp.

Jerry

 

[ksmith63]

Re: Mesa Bass amps: Causes for Blowing fuses?

Well it appears that the guy took someone's 'best offer' of $250. If he went that low on a Bass 400 then either 1. He really needed the $$ or 2. Something was seriously wrong with it.

Thanks for the input guys.

 

[dystrust]

Re: Mesa Bass amps: Causes for Blowing fuses?

:spam:

This isn't exactly on topic, but my bass player has a Bass 400 that they're looking to unload. Nearly new EH 6L6s with a spare sextet of tubes included. Let me know if you're interested.