Hey guys, been gone from here for a long time ( had kids, changed jobs, got busy with life's hurdles lol) but I gotta weird problem with my amp. I had asked this question a few years ago, but never got to fixing it. What's happening is I have a 1998 JCM2000 DSL 50 head that I got when it first came out. Loved the amp and used it relentlessly during my younger years when I actually had a band, had the time to play etc. Fast foreword many years and barely getting to play like I used to, I decided to start toying around with this amp again but it went on the fritz. I changed my tubes all out ( using 2 JJ El34B and 4 Shuguang Silver Dragon 12AX7Bs) they seem to be glowing fine but the amp is pathetic sounding now. When using the classic channel without crunch, i have to dial it up to around 4-5 just to get a sound out of it. Hitting crunch, it's about 3-4. Neither has any gain hardly at all, yet the preamp controls all seem to work, as does reverb. Meanwhile, over on the Ultra Channel 1 it's got some mild gain at around 3, click it over to 2, it's about the same volume with just a touch more gain. I noticed if using a processor/preamp plugged directly into the FX loop return ( bypassing it to a Poweramp) it's volume is fine. But trying to use the FX loop thru send and return, plugging into the front kf the amp, nothing really. This has got me fairly stumped to be honest. I checked the bias output and metering between the center pin and left side, it's at 42mV ( that's the pot all the way down) and on the right it's 43mv ( pot all the way down as well). I even tried replacing each preamp tube with an existing Svetlana 12Ax7 I had, one socket at a time, nothing. I figured I'd come here and see if I could find some great advice and try to fix it myself. But worse for worse, I guess I would have to send it off to the nearest certified repair center : Sundown Productions in Ashland, Ky ( anyone ever had any experience with them btw? Marshall recommended them) Thanks in advance!