I have a 212-HD130 and am in rural France. I posted here for the first time several months ago. The amp was producing a hum. Someone local replaced a single capacitor on March 11, 2014, which fixed the hum, and the amp seemed to be working well, it was producing very little noise on startup. I was thrilled. Today, suddenly, it is producing a fairly loud, low, rumbling hum on startup that does not go away, and the whole amp is vibrating a bit. The hum does not increase if I increase the volume on the amp, in fact it recedes a bit. The sound from the amp seems OK, if one ignores the rumbling hum. The hum is not as loud at the 65W setting as at the Hi, 130W setting, but it is still there at 65W. At either setting, if I increase the master volume to "7" or "8," the hum decreases a little bit.
Another possibly important clue to what is wrong: If gain volume is "2" or higher but Master Volume is set to zero, I still get sound. This was not happening before.
So, do you experts here have an idea about what is wrong? I did have the master volume of the amp turned on to about "3" or "4" and turned an external loop pedal that was connected to the amp, when the amp should have been at zero. I hope that did not cause this problem.
Thanks in advance.
HUM
Sound like he should have replaced ALL the electrolytic caps in the amp/ Sounds like it's in the finals, or power amp stages. Get all the power supply caps replaced AND have the tubes checked. One of them could have gone wonky. Subbing the tubes with known good ones is the best way to try it. Mike.
Hum
Thanks, Mike. This is sort of what I figured. The guy did not want to replace all the caps. Just a few other questions, because I edited my initial post after you posted. What does it tell you if I get sound out of the amp with Master Volume set to zero and Gain Volume set to "2" or higher?
Also, do you think there is a danger to the amp in continuing to play until I can get someone to rehab it, because I have a gig in a few weeks and I've been doing all of my practicing through this amp?
Thanks again,
ledocs
HUM
If it's humming, yes it's dangerous to the amp. If a cap shorts completely, it COULD take out he Power Transformer(read this as EXPENSIVE!) The tubes could go Chernobyl and take out some things too. If it's humming like that, that means the PS is definitely suspect and could burn up a LOT of stuff. Fix now, if any way possible. The fact that it hums with the volumes down tells me it IN the finals. Mike.
Need more help with my HD-130
I took my amp to a tech in Toulouse, France who has a good reputation. He is also a musician. Basically, he got rid of my hum, but upon getting the amp home, I find that it is distorting a lot at higher volumes. Block chords sound horrible, highly distorted, and muddy. If I compare the sound I'm getting through the HD-130 with that of my Yamaha Stagepass PA system, there is no comparison, the PA sounds clean, the amp does not.
The tech replaced all my power tubes, he replaced two capacitors, and he rebiased the amp. He said that it had been biased in a very bad way, but that could have been twenty years ago. The amp sounded good before this latest hum that he fixed had developed.
A strange thing is that when he was demonstrating the repaired amp for me, he had the master power level set to "10." He was not playing an instrument through it, it was some kind of small audio device, I thought this setting might have had to do with the low impedance of his test device. There is very little room in his work space, so just to get a guitar and my effects pedal in there would be difficult. When my HD-130 amp was working well most recently, my typical setting for loud volume was "Master" at "5" and "Gain Volume" at "3," that was plenty, my bandmates would complain that it was too loud.
So what is wrong here?
The tech seems either to have done something wrong or to have failed to do something. There is no way the amp should be distorting so much. This is all very frustrating for me, and I know nothing about amplifiers, I'm just a guitar player. I paid a fair amount of money for this work, the parts and three hours labor at a high rate.
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Update (9/4/2014): I have exchanged emails with the tech and done more playing around. Apparently, the amp is now biased so that the gain volume is minimized when going for clean sound. To play loudly, he is recommending that the master volume be set to "10," and that the gain then be adjusted progressively. This is very different from what I am used to. Is this normal?
The amp does sound better, now that I know this. It still breaks up too early as volume increases, I would say, but maybe it is peforming to spec, I don't know. There seem to be a lot of variables. I use a Boss multieffects pedal, and I was using a patch last night that I had not used, playing very loudly, and it sounded good. I'll have to see what settings that patch uses. I also bypass the pedal to test the amp at times, of course. The tech pointed out that I can't compare this amp to a 500-watt transistorized PA system and expect them to sound the same. I prefer the PA system, and it's not really close, but I don't want to take the PA system to every gig, and I probably could not, even if I wanted to.
I am also running the amp through step-down transformers. I seemed to be getting some anomalous results, in that if I run it through a huge transformer in a room that is different from my music room, the amp sounds better and cleaner. I have also tried different 300-watt transformers.