Marshall 6100 LM blows fuses after tube swap! Help!

[rosssurf]

So the other guitar player in my band has a marshall 6100LM 30th anniversary head and we felt it was time to retube it. I recently got a set of JJ's 6l6's from Eurotubes to replace the old 6l6's that were in it. Just for testing purposes a set up the rig including connecting the speaker cab and I used my old SRS bias socket attatched to my DMM to see how the old tubes read and they were at about 25mv. I put in the new tubes and powered up the amp with the bias socket still in place to measure and bias the new tubes and "pop!" I blew the fuse next to the power plug. I went out and got a few new fuses and tried again and got no power at all this time. I checked the three fuses that are accesable from the back as well as openeing up the amp and checked the fuses inside. I the glass ones look fine and read continuity on my DMM. One of the interior glass fuses, the one closest to the power plug input, does show continuity however it looks to be filled with sand!? is this normal?

What else might be going on here. I hope this is enough information for you to help. Please let me know if there is more I can provide that may steer me in the direction of a fix. I am very frustrated here

[Albert Kreuzer]

The sand is in the fuse to extinct arcs. Replace the blown fuses and power up without the 6L6's. If the fuses don't blow now, it's probably a shorted tube. Sometimes they are bad out of the box. Now try with the old tubes first (they did work, didn't they?).

[rosssurf]

Albert, Thanks for your help. The old tubes did work fine. I will do as you said and report back. Thanks again!

[Ampzone]

In the last couple amps I retubed, the off the shelf JJ EL34 quads used had a redplating (runaway bias) tube, and another was shorted. Like Albert said it's most likely a faulty tube. Try another set.

[Rhodesplyr]

Yes, JJ has had quality-control issues with some batches of tubes. I'll only purchase their output power tubes from tube dealers who do thorough testing on them. The good ones are nice tubes, but they have to be checked at working voltage.

I bought a quartet of JJ KT77s when they first came out, and they were leaning every which way in the bases. My ST-70 looked like it had four leaning towers of Pisa in it.

I like the SED/Winged-C 6L6GCs myself.

[ttung51]

I bought a pair of 6550 tubes from Eurotubes and put them in my leslie and they kept blowing fuses. So i put my Tungsols back in and all is fine. I called Bob at eurotubes and he told me to send them back, so i did and he said the tubes were fried and blamed my amp. that was almost a year ago and my amp works fine. i even had my tech go over it and all is fine. This crook Bob who owns Eurotubes didnt even send me back the defective tubes. Ill never do business with them crooks again.