[Harp-L] Continuing trouble with '59 Bassman LTD:blows fuses, substitute rectifier tube?

[Veli-Pekka Haanmäki <vphaanmaki@xxxxxxxxxxx>]

Hi all!

I have a new Fender '59 Bassman LTD amp and I'm having continuing trouble with it.This is actually third Bassman LTD I have here now,the other two I sent back because of the same fault in them: all of them blow fuse around every 5th time I turn them on.

I replace the fuse with correct one (F1.6A250V,this is EU export model) and it works another 5 times turning ON and OFF and then it blows the fuse again.
Fuse doesn't blow during the amp is ON (while playing) or when the Standby is switched ON,just when the amp is TURNED ON,usually after 15min-1 hour break.May have something to do with tubes since the rectifier and power tubes are warmed up when the fuse blows,in most cases anyway.

I don't switch the power ON and OFF all the time,I use Standby for shorter breaks.Standby is OFF when I turn the power ON,I use correct,correct quality fuses.Power source is not the problem since this has happened in several different locations.I've swapped all pre-amp tubes,no effect.

Any idea what could be wrong? Where to look for the fault? I will take it to repairtech,yes but we need to find the REAL cause of this trouble before he can fix it.Like I said,this is third '59 Bassman LTD with same fault in it,does anyone else have similar experiences and what was done?  

I also changed the 5AR4 rectifier tube to 5U4G rectifier tube.Most of the information I've searched say that this is OK to do,in most cases anyway since 5U4G is weaker that 5AR4.I'm not sure about this though,is it safe to use 5U4G as a substitute for 5AR4 on Bassman LTD?
This doesn't have anything to do with blowing fuses since it happens with both rectifiers.But I've changed back to original 5AR4,I'm not taking any chances now.By the way,5U4G does have better sound,gives the amp a bit more sag than 5AR4 and allows me to turn the volume to 5-6 (pre-amp tubes are ay7-ax7-au7,right to left from the back of the amp,good combination for this amp,sound is great but that is the only good point of this amp for now)

Any information on these problems will be appreciated,thanks.

(all this makes me wish I had money for Victoria 45410-T though : - (