Loud Hum.. Loose Tube?

[stingray96191]

I recently sold an Aguilar DB-359 All tube amp on the forums here, and After confirmation it arrived and no further contact from the buyer, i assumed it was good. This morning i got an email saying that it has a hum that makes the amp unuseable. I never had a problem with this one, im just wondering if this could have been a complication of shipping, a tube coming loose>Dirty Speaker cables? I'm not really in a position to offer refunds as the money has already been spent to help cover medical costs. (chemotherapy is expensive)But i want to make this right. Any Suggestions?

[JHorstmann]

could be a loose tube i guess... or a bad preamp tube?

Sucks man.

[BassmanPaul]

Get the new owner to check if one of the output tubes has a glowing red plate. Could well be that a tube hasn't survived the trip.

Paul

[MAMMOTHvolume]

Originally Posted by BassmanPaul

Get the new owner to check if one of the output tubes has a glowing red plate. Could well be that a tube hasn't survived the trip.

Paul

+1 think if it's been redplating though and it was humming you'd have seen smoke by now.

i'd get him to try swapping the preamp valves around to see if it makes the hum better or worse.

[johnk_10]

if its himming and unuseable, its probably more likely to be a power amp tube-not a preamp tube.

[BassmanPaul]

Originally Posted by MAMMOTHvolume

+1 think if it's been redplating though and it was humming you'd have seen smoke by now.

Not necessarily, it depends on the topology. If only one tube is causing the problem and there are no cathode resistors or fuses there will be no smoke. A lot of amps have low value resistors in the output tube cathodes that burn out and disconnect the faulty tube. That's where the smoke comes from generally. In the later case you would have to replace the blown resistor before you can replace the tube.

Paul