Ventura
Well-known member
Alright "Enlightened Ones", perhaps you can shed some light on the matter...
Recently I acquired a used VH4S in primo condition. I replaced the tubes with the SED 6550's, re-biased to mid 90'smA per pair, and run the head into a stereo Diezel 4x12 at 16 ohm per side. This evening I turned it on, let 'er warm up, hit the RUN switch and started noodling around - low volume. So about 5 minutes in, playing around on Channel 2 doing some funky lil' SRV ditty, the amp pops a semi-loud pop, followed by a bigger 'crack' and to what I could see, a power tube lit up and then dimmed back to normal. I instantly switched the RUN to standby and was freakin' out. Well, since then, hit RUN again and it seems to be running okay. There's a hum/buzz happening, but that was happening before I even changed the tubes. All the tubes are glowing as they normally do - 9 preamps included (brand new Tung Sol 12AX7's). Nothing smells burnt, nothing is cracking since...
Is this normal? Is it the tubes adjusting themselves (rather abruptly and aggressively)? I tested both sides of the stereo outputs - they're both responsive and operational. I haven't cranked this rig up, as I'm awaiting some feedback from you all "out there" in Diezel-land. I do have new tubes, extra EL34's, 6L6's the whole nine yards, but rather than avoid this by thinking swapping out is the way to go, I'd rather get to the root of the issue and see what's really problematic, if at all.
THANK YOU in advance for ANY feedback on this. I think I covered all the related necessities in this post - biasing levels, the cabinet's impedance, the tubes, etc.
V.
Recently I acquired a used VH4S in primo condition. I replaced the tubes with the SED 6550's, re-biased to mid 90'smA per pair, and run the head into a stereo Diezel 4x12 at 16 ohm per side. This evening I turned it on, let 'er warm up, hit the RUN switch and started noodling around - low volume. So about 5 minutes in, playing around on Channel 2 doing some funky lil' SRV ditty, the amp pops a semi-loud pop, followed by a bigger 'crack' and to what I could see, a power tube lit up and then dimmed back to normal. I instantly switched the RUN to standby and was freakin' out. Well, since then, hit RUN again and it seems to be running okay. There's a hum/buzz happening, but that was happening before I even changed the tubes. All the tubes are glowing as they normally do - 9 preamps included (brand new Tung Sol 12AX7's). Nothing smells burnt, nothing is cracking since...
Is this normal? Is it the tubes adjusting themselves (rather abruptly and aggressively)? I tested both sides of the stereo outputs - they're both responsive and operational. I haven't cranked this rig up, as I'm awaiting some feedback from you all "out there" in Diezel-land. I do have new tubes, extra EL34's, 6L6's the whole nine yards, but rather than avoid this by thinking swapping out is the way to go, I'd rather get to the root of the issue and see what's really problematic, if at all.
THANK YOU in advance for ANY feedback on this. I think I covered all the related necessities in this post - biasing levels, the cabinet's impedance, the tubes, etc.
V.
NOTE: Fuse indicator light on for 4th power tube (when viewing the rear panel head on, it's the last power tube on your right).
Enlightened Ones...