I recently bought an Art Tube mic preamp. We were doing a recording session and didn't have a properly rated power supply for it, so I used it anyway (foolish I know!) and after 12 hours of use I burned something out. The preamp wont power up at all. The MP is 9v AC and is rated at 700 mA, and i used a 9V AC rated at 780 mA. If anyone has any suggestions on which compoments I might take my voltmeter to first it'd be appreciated. p.s. is the tube still okay?
Art Tube Mic preamp not working!
- Thread starter michaelq
- Start date
taperocket
New member
I dont think the power supply is your problem there, those two are very similar values. You may have a faulty tube, try replacing that first.
taperocket said:
I can't say for sure but I've heard several times that those starved plate designs don't need the tube to function, it's really just a solidstate pre that takes a small detour thru the tube to get some grit on a recording. Just wanted to throw that possibility out there.
I don't think that's a tube blend circuit. I haven't seen the schematic, but I believe the tube is a real gain stage, at least as real as a starved plate design can be. As far as the power supply, the 700 mA is the requirement, and the 780 mA is the maximum output of the poewr supply. It isn't that the power supply forces 780mA into the circuit, the circuit draws 700mA, and in this case the surplus capacity of 80mA isn't used. So, you did nothing wrong.
If the unit doesn't power up at all, look for an internal fuse, looking more like a resistor than the kind of fuse most people are used to seeing. If it's blown (measure resistance across it, should be approx 0 ohms) then the question is why did it blow? Look and smell for signs of overheated components, and consider swapping the tube. A bad cable could have caused it also. Sometimes it's nothing but infant mortality of a component, with no real cause.
good luck
If the unit doesn't power up at all, look for an internal fuse, looking more like a resistor than the kind of fuse most people are used to seeing. If it's blown (measure resistance across it, should be approx 0 ohms) then the question is why did it blow? Look and smell for signs of overheated components, and consider swapping the tube. A bad cable could have caused it also. Sometimes it's nothing but infant mortality of a component, with no real cause.
good luck
michaelq said:
The output should be rated at 9v @ 1000 mA.
You need to determine if the original power supply is still working properly, as they are usually one of the first things to go. From what I recall there is no inline fuse with the Tube MP, but I may be wrong. If the power supply is fine, then you will want to check the connection, to ensure that it is working properly. Beyond that, it would have to be bench tested.
