Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jennings on January 07, 2018, 07:48:59 am
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Anyone have any experience of Bugera's go at a cheap and updated Ampeg SVT, the Bugera BVV3000 bass head? It's the 300w valve beast, with the so called infinium circuit.
I have one, and over all for the cash it's a decent amp...my one niggle is that randomly whilst playing all sound cuts and it seems to go into standby mode, then a few seconds later just comes back to life as if nothing happened. It seems to occur randomly...with no correlation to volume, settings, or how hard you hit it whilst playing.
Before I go rooting about I wondered whether anyone had any starters for ten and tips on working this one out!
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I had this happen once. I think it was a bad powertube. One EL34 was redplating during the interruption... If you observe that, the problem is either in the power section of the circuit or a powertube.
With the Infinium circuit it's hard to say what could be going on, this could be an error or it could be attempting to protect your amp from a tube/bias problem. Are any lights on that indicate tube health and/or problems? If not, do you know the indicator lamps for the Infinium system are at least working, so you'd know if it was trying to show an error?
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Well a couple of months on and I can say I've bottomed out the problem yet...I've re-tubed with known good valves (pre amp and power amp) and it's just the same. As far as I can tell with quick peeks round the back at the Infinium lights, there's no power tube highlighted when the problem occurs. At this stage I suspect the Infinium circuit as in other respects the amp is behaving. I'm wondering about simply removing this aspect of the amp and building a normal bias section to replace it. I'll have to get it open some time and maybe take some measurements.
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I had a fender ss bass head do that when it got hot. After cooling it was fine. Blew a fan into it and the problem subsided. Like I said, it was solid state though.
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Even before reading davidwpack's reply I was thinking:
Sounds like a possible weak thermistor or thermostat.
It will be easier to find if it's on the primary side but without a schematic we're all guessing.
With PC boards there's always a chance that you have an intermittent connection in a board plug pin.
I would unplug all board connections and visually inspect the plug/pins.
I would also have to try davidwpacks method of running it with a fan on it to see if temperature is a factor.
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bad s/b switch ?
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any luck?
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+1 any luck?
I've got a trirec infinium from them. I love it. Tons of features for less than a ton of money.
Mine had a faulty "varipower" circuit. A single front panel pot connected to God-knows-what kind of circuit to adjust output power from 5 watts to full 100 watts. I finally decided to send it to an authorized tech, before the warranty runs out. I don't have it back yet.......
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Sorry for the delay in an update, and thanks for the replies! I’ve had an enexpecyedly manic year thus far, and the only thing I’ve tried this far is the temperature idea and a complete set of known good valves. No joy...I still get occasional outages! So it’s looking likely to be along the lines of the other suggestions. I’ll go hunting for a schematic and aim for a weekend I can open her up to check connections etc. When she’s not having a momentary nap she’s a great sounding amp!