Distortion problem with Express build

[rawnster]

Over the last several days I’ve noticed that the tone is getting more and more overdriven. As it currently sounds with a pair of good SED EL34s, I cannot set the amp higher that 1.5 (about 8:30 oclock) without it breaking up. I checked all the voltages again, and nothing has really changed. I pulled the SED, and replaced them with a pair of JJ EL34s. With the JJ’s, I get quite a bit of the headroom back. That’s good, but it’s got me puzzled. I had plenty of headroom with the SED when I first used them. The bias is set to 42ma. Another thing I noticed is that V4 glows quite a bit brighter that V5. If I turn the amp up to around 9 – 9:30 and turn my guitar all the way up and pound a chord, V4 brightens up and then dims down again to its normal glow. V5 doesn’t do that at all when I pound a chord.

Please forgive my novice/ignorant knowledge here. Just trying to figure out what’s up.

FWIW: On a positive note I put a JJ ECC81 Gold Pin in the V1 slot. Great sound…AND a much lower hiss level. I like it!

Thanks for your help!