having trouble with marshall 2555 50/100 watt.NEED HELP?

[GREGART44]

I bought this amp and it sounded killer,then I started to blow fuses win the amp was turned up.So I did a inspection and found arching on one tube socket,so replaced all sockets minus pre-amp with ceramic sockets,problem still exsits,so recaped everything ,the LCR cap electrlitics,all diodes ,all resistors that were below par.Still having problems.Output tube sockets got new wire wound resistors and also new resistors on on pin4.I also replaced the bias trim pot. Power tranformer checks out,with all the tubes removed ,I can power up and hit the standby switch and no fuses blow ,then I can put in the preamp tupes and power on and they light up,and hit standby and the fuses do not blow. However though if I install the output tupes and power up the preamp tubes light up but the output tubes will not,and if I hit the stand by with the output tubes in it the ht fuse blows,but take out the output tubes and hit the standby the ht fuse will not blow. Thats the problem I am having with this head,also the output tubes are brand new?. Please does anyone have any info on what this issue might cause this.Thanks Gregart44 YOU CAN ALSO LEAVE ANSWERS AT greglavender@excite.com

[Flames1950]

It doesn't matter if the tubes are new or not, if the fuse only blows with those tubes in they're probably bad. It's really not uncommon for new tubes to be bad -- check out George's experiences with the GT KT66's that he's not going to carry anymore.
New tubes my friend, new tubes.

[Billy Batz]

A while back I had a Fender V Champ that had what I thought was an arcing socket. It sure sounded like it. Sounded like machine gun fire. I did the usual check by swapping tubes and after I swapped the poping was gone but now the volume kept cutting out. I swapped again and the distortion would get ugly after a certain volume. I mustve taken that thing apart 80 times trying to figure it out. Turned out both new tubes I bought for it were messed up. Ive never bought a bad tube before that. Go figure.

[GREGART44]

Thanks for the feed back but I have a new set of EH EL34s and a set of Ruby EL-34s plus the set that came out of the amp.Now not all of these tubes could be bad satistically. Like I said the pre amp tubes lite ,but not the out put tubes and with the tubes out , I get normal voltages on all pins ,though the bias runs a little high ,but It can still be turned down to a normal operating voltage.Before I told you guys that the fuse would blow with the gain up and volume all the way up, or just the gain all the way and volume around 5 , 6 .The amp fuse would blow,I could replace the the fuse and as the volume didnt get to high the fuse would last a little longer but it still would blow.So I, replaced the tubesockets because ,I found carbon arching marks on one that was bad also it looked like it had file marks on it as well . But the out put tubes still will not lite.,and if you hit the standby the HT fuse blows,I even replaced that.I talked to a tech and he said its probly so simplle that I am over looking it.Any other suggestions on what to check out would be greatfull.
Also not to be a pain but, I also have a 2203RI and I wanted to retube it and the pcb has no bias pot.I did notice two varible resistors that can be turned with a screw driver,they are labled VR1 and VR2,also the output tube sockets look like they are wired for6550s but the head has EL-34s in it can this head operate on both?I hate to be a pain,I have learned a lot about tube amps and how they work,and I have alot more to learn.Its just saving the money for them is one thing but I would rather work on them my self than pay a guy 50.00 for 15 minutes work ,no offense ,but I am sure thats how a lot of people learn ,because they cannot afford to have it fixed else were or they are like most of us,we just want to know how it works ,or we know we can trust in ourselves.THanks again. Your a bunch of good guys and KEEP UP THE IRONS lol.

[Flames1950]

I missed the part where the ouput tubes don't light up anymore. Did they still light up at least before the socket replacement, before you hit the standby? All the tubes run off a common, parallel filament supply, so a wiring mistake is the most likely reason for those tubes not lighting if the preamp tubes still light normally.
The variable pots on the 2203RI are a bias adjust (VR1) and a hum balance adjust (VR2). Usually you'd have to make bias resistor adjustments to get from EL34's to 6550's, a real pain on a PCB unless you start out set up for the 6550's, in which case you can usually parallel a second resistor over the original. Typically there are some other minor changes for 6550's, like the bias splitter resistors.