Red plating, need advice?

charvel pointy head · Post by **charvel pointy head** » Mon Mar 26, 2007 11:22 pm

Playing on my 100 watt tonight, had a noticeable volume drop and the tone started sucking in a big way. Took a look inside and v6 &7 are cherry red. I'm not taking apart tonight, too tired. Have not had any problems w/ it since finishing it last Nov or so. Play it dimed a lot, into a hotplate. Amp has sat for about 3 weeks though, been out of town and stuff. Tubes are those "Mullard" reissue el34's. I'm thinking the tubes just shot craps, need a new set and a rebias, but could something have detached and fried these? Amp is NOT gigged, but I have played it quite loud at band practice. Fuse is not blown, shut it down pretty quick. Tomorrow I'll pull it and check voltages. Any advice? clark

charvel pointy head · Post by **charvel pointy head** » Wed Mar 28, 2007 10:31 am

Like I figured, it was thte tubes, the "mullard" reissues. These are total crap. No way these should have gone this fast, at least that one pair. I put hte original e34l's from the kit, though they don't sound as good, at least they work and aren't fried from when I was having arcing in the original tube sockets. eh, screw it, i'm calling tube tramp and getting NOS. Ya get what yoou pay for I guess.

justonwo · Post by **justonwo** » Wed Apr 04, 2007 8:06 pm

These high plate voltages can be a pain sometimes. After battling with red plating for a while, I ended up just getting a variac to drop B+ to 450 VDC.

Wicksy · Post by **Wicksy** » Thu Apr 05, 2007 6:49 am

The Shuguang EL34 is a nice low cost alternative but NOS is always the way to go IMHO. Tube tramp will sought you out.

wdelaney72 · Post by **wdelaney72** » Thu Apr 05, 2007 8:46 am

So far my Shuguangs are taking the 500v... and liking it.

justonwo · Post by **justonwo** » Thu Apr 05, 2007 1:11 pm

wdelaney72 wrote:So far my Shuguangs are taking the 500v... and liking it.

Did you try other production tubes at 500 VDC and get red plating? If so, which ones?

Nevermind, I re-read what you posted in the other thread. Sorry.

You ended up biasing your Shugs at 65%? I've had to keep my JJs at about 50% to keep them out of the danger zone (though they only red plate with the volume on 5. Any other setting is fine).

charvel pointy head · Post by **charvel pointy head** » Fri Apr 06, 2007 10:02 am

I went w/ NOS Siemens rft. No red nothing and sounds better. clark