Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: macula56 on August 08, 2013, 05:42:47 am
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My Bassman started blowing fuses for some reason yesterday. I played it with no problems Monday and Tuesday and yesterday it started blowing fuses. I was banging out some power chords and it just dies. I replaced the fuse and went back to the power cords and it died again. I replaced the fuse again and tried just playing some nice quiet stuff and it was fine until I stated bashing out some power chords. I've never had an amp do this so I was wondering where to start looking for problems. I checked my bias voltages and everything looks normal. Tubes are not wobbling around. Nothing has changed physically that I can see. I did a search about fuses blowing but didn't see anything that sounded like my particular issue. Anyone ever had this happen? As always, any help greatly appreciated. Thanks, Jmac.
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Bias too hot . When playing "strong" or loud, curent rise in power tubes . If bias too hot power tube need more current , if too much, fuse blow.
Are you realy sure you know how to bias ?
Also power tubes too old .
Many other things may do fuse blow ; Amps have some mods ? bad solder ( intermittent current flow ).
Too old filter caps ?
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yes i am really sure that i know how to bias. the bias is not too hot. it's the same bias voltage that it was 2 days ago when the amp was working properly. and the tubes work just fine in my other amps. filter caps are a possibility.
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Wich Bassman, there's so many ???
Bias voltage do not mean bias is OK . Bias voltage is the negative voltage apply to tubes's grids. This do not mean bias current flow inthe tube is right. You must read plate's current on each tube .
Tubes change with time . Each time we have some trouble , the day before everything work fine :laugh:
Check power tube ; Do not use tubes tester , but new tubes.
Check tube rectifier if your amp had one