indyj_son Posted September 5, 2021 Share Posted September 5, 2021 OK so weird thing happened at my gig with my HD100 head last night. I use a ver. 1 of the FBV board controller. I am using all patches that I have created. No presets. Essentially things would seem fine, I have one channel setup for lead that is a little louder. When I would switch to my lead patch the entire amp would get quiet..even if i went back to my original rhythm patch it was quiet. I would tweak the master volume on the amp and it would get a little louder...then after few minutes it would start blasting at high volume out of the blue. Very frustrating..could not get it to hold a consistent volume level. It almost seemed fbv related because when I changed channels using the amp front buttons it seemed to work OK. I ended up just unplugging the FBV and using one patch the entire night just to get through. At least volume stayed consistent. The tubes are relatively new and were installed and biased by an official service center. I tried messing with it this morning and could reproduce the issue sometimes, but other times it seemed to work fine. I ended readjusting the individual patch volume levels just to see if it would do anything. I have them at about 50% with the lead a little higher. Very frustrating when you can find something to "fix". Any ideas? Note I was trying to play at fairly quiet volume with the master not up very high. I have noticed some cracking in the master volume control at low levels with this amp and at very low volume levels always seemed a little flaky...This amp worked fine last weekend and I made no changes since then and the amp has been comfortable stored. Quote Link to comment Share on other sites More sharing options...
psarkissian Posted September 7, 2021 Share Posted September 7, 2021 When was the last time the tubes were changed out? Quote Link to comment Share on other sites More sharing options...
indyj_son Posted November 8, 2021 Author Share Posted November 8, 2021 On 9/7/2021 at 12:33 PM, psarkissian said: When was the last time the tubes were changed out? I went back and looked and it appears I put in a new set early in 2020 (February) so a 3 or so months short of 2 years old.. I don't crank the amp but it is my main go to for my cover band gigs and we play about 4 times a month/ 3 hours per show.. Think they may already need replacement? Quote Link to comment Share on other sites More sharing options...
psarkissian Posted November 8, 2021 Share Posted November 8, 2021 What is the tube number and brand??? Are they a matched set??? Quote Link to comment Share on other sites More sharing options...
indyj_son Posted November 14, 2021 Author Share Posted November 14, 2021 Sovtek 5881WXT / 6L6WGC Vacuum Tube, Matched Quad Something else odd happened at my gig last night. I was using the line out of the head direct to the board..all the sudden it started blasting..over driving the board. Almost like the XLR line out level shot through the roof. The amp output through speaker cab did not change. I turned the amp off and on and it did not fix. Sounded awful...unsure if it is all a part of the same issue? Quote Link to comment Share on other sites More sharing options...
indyj_son Posted November 14, 2021 Author Share Posted November 14, 2021 On 11/8/2021 at 11:53 AM, psarkissian said: What is the tube number and brand??? Are they a matched set??? Sovtek 5881WXT / 6L6WGC Vacuum Tube, Matched Quad Something else odd happened at my gig last night. I was using the line out of the head direct to the board..all the sudden it started blasting..over driving the board. Almost like the XLR line out level shot through the roof. I turn the amp off and on and it did not fix. Sounded awful...unsure if it is all a part of the same issue? Quote Link to comment Share on other sites More sharing options...
psarkissian Posted November 15, 2021 Share Posted November 15, 2021 Were the power tubes biased by a L6 authorized service tech? Quote Link to comment Share on other sites More sharing options...
indyj_son Posted November 15, 2021 Author Share Posted November 15, 2021 1 hour ago, psarkissian said: Were the power tubes biased by a L6 authorized service tech? Yes in Feb of 2020. Quote Link to comment Share on other sites More sharing options...
psarkissian Posted November 15, 2021 Share Posted November 15, 2021 Very good. Quote Link to comment Share on other sites More sharing options...
indyj_son Posted November 20, 2021 Author Share Posted November 20, 2021 On 11/15/2021 at 1:57 PM, psarkissian said: Very good. I checked the biases and they were 31, 33, 32,34 I know that target is 35. That to me seems like it would be close enough? Quote Link to comment Share on other sites More sharing options...
psarkissian Posted November 22, 2021 Share Posted November 22, 2021 +/- 2mV, so 31mV and 32mV need to be adjusted to be within the +/- 2mV range. Quote Link to comment Share on other sites More sharing options...
indyj_son Posted December 16, 2021 Author Share Posted December 16, 2021 On 11/22/2021 at 11:25 AM, psarkissian said: +/- 2mV, so 31mV and 32mV need to be adjusted to be within the +/- 2mV range. I tweaked the low ones up...got them steady around 36. It actually seems to have helped....I need to do a bit more testing but so far so good. I noticed if I use a volume control (simple POT) inline with the line out line in, bump up the master volume,. then use that inline line out/line in POT to tweak the volume to the power section, that seems to add some stability...the real issue seems to be when the master volume is at really low levels. I guess the amp just likes to be cranked up a bit in the power section. Quote Link to comment Share on other sites More sharing options...
psarkissian Posted December 16, 2021 Share Posted December 16, 2021 36mV is fine, spec is 35mV. Quote Link to comment Share on other sites More sharing options...
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