#1
So I'm having a hard time getting this straight. I've watched the eurotubes video over and over again and I can't figure it out.

1) I need to get the plate voltage first, right?. I do this with the old tubes? Does the chassis need to be plugged in and hooked up to the cab when I do this, or can I do it without all that.

2) What can potentially fry me? The videos over at eurotubes show the guy working on it with both hands, which I hear is a bad idea what with potential currents running through your heart. They don't really say anything about potential electrocutions or draining the caps to be safe. I don't like the idea of messing with stuff inside when it's turned on. Then there's getting the chassis back into the case after it's been plugged in. Right now I've been letting it sit for over a month and I'm sure the caps are good and drained. But once its plugged in they'll have charge again and I'm goign to need both hands to stick it back in the case.

3) This si kind of dumb, but how do you keep the chassis propped up like he does in the video? Mine just wants to fall over.
#2
1. Yes, you need to measure the plate voltage first. Yes, the amp needs to be powered up and the tubes need to be in the amp to measure it. You may get away without having to measure it though if your amp is in the list he's compiled on that page. He has a lot of amps he's tested for average plate voltage they run, just scroll down the page with the vid. The safest way is to actually measure it is to use a bias probe, which is basically just the pins from the bottom of a tube, with a regular tube plugged into the top of it. The probe is then connected to a multi meter, so you can take measurements from the different pins. Some bias probes have a switch to read between plate voltage and current, so you can test both. I don't really like poking around inside the amp like he does in that vid when it's on, so I bought a probe that can measure both. Easily worth the small investment if you plan on owning tube amps for a while.

2. there are many ways to be potentially electrocuted working on an amp. Any part of the circuit that is connected to the capacitors, or powersupply when the amp is on, can give you a jolt. Just measuring with a probe, and adjusting the bias pot with an insulated screwdriver however, you should be fine as long as you aren't slipping around. Everything has to be measured with the amp on, and the tubes should be warmed up. You NEED a cab plugged in also, it still needs to see an impedance load. He's a pro, you probably shouldn't use both hands. You really don't need to unless you are holding it up like he does. As long as you're holding just the chassis though, you should be fine anyway.

easiest way to get it in and out of the cabinet IME, is to grab hold of the transformers like he does in that vid. Lift it up a little, and slide it out on it's side like he does.

3. He's almost balancind it in that vid. I used something to prop mine up by the tranny to position it like the vid, but sometimes the tranny isn't in the right position. I've also found using the actually headshell, putting it face down so the back is open, and resting the amp on it at an angle with the tubes down can also work.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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#3
Well, I've got a bias probe. I thought I had to use just the multimeter probes and connect one to the 3rd pin of the socket and the other to the chassis for ground for plat voltage? So I CAN do it with just the bias probe? According to the sheet that came with the probe, one volt = one amp, and that means DCA and DCV measurements are the same. Does this mean I just have the probe stuck in the socket, and then connected to my multimeter, and setting the meter to read DCA will give me the bias and setting it to DCV will give me the plate voltage?

This seems like its supposed to be really easy but all the tutorials skip so may steps they just assume are obvious.
#4
Quote by cutslikedrugsx
Well, I've got a bias probe. I thought I had to use just the multimeter probes and connect one to the 3rd pin of the socket and the other to the chassis for ground for plat voltage? So I CAN do it with just the bias probe? According to the sheet that came with the probe, one volt = one amp, and that means DCA and DCV measurements are the same. Does this mean I just have the probe stuck in the socket, and then connected to my multimeter, and setting the meter to read DCA will give me the bias and setting it to DCV will give me the plate voltage?

This seems like its supposed to be really easy but all the tutorials skip so may steps they just assume are obvious.

depends what kind of probe it is. The Weber Bias rite has a switch on the actual meter that comes with it. The cheaper one Eurotubes sells only measures bias current, which I assume is what you have. I'm not sure what it measures, but I think it measures voltage, since it's using a 1ohm resistor across the circuit. So you would set your meter to read mV, and that should be the same as the mA measurement of bias current. The sheet that came with it should say what to use on your multimeter.

That kind of probe will not read plate voltage however. My meter has a switch on it, that changes what pins are getting read, so it can read plate voltage. You either need one that reads both like mine, or you need to measure it like he shows in the vid. Have you already checked down his list of amps though? Yours might be listed.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
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#5
He says that its just a average plate voltage though, I'd rather get mine to make sure. The map is modded so I don't know if that would affect it or not, but I'd rather just leanr to do it right.
#6
so i got a reading of 463 with the meter set to DCV and the old tubes in. That sounds about right given the numbers eurotubes guy gives.

Do i need to measure it with the new tubes or will it stay the same? And I've got to find a chart to find what to bias it at. Does anyone have one that has info for e34l's? None of the ones I can find do.
#7
Ok, I read somewhere that e34l's were different than el34's, but they bias the same then?

And running hot will make it distort more, but lower the tube life, right? Would I get a noticeably heavier sound at, say, 73%. I know 80% is supposed to be too high. Or would it not matter enough to bother with?

And once I'm done, what specifically should I avoid touching when I put it back in the cabinet? I can touch the chassis and the tranformer without getting shocked, right? Anything else to look out for? I'm doing this with rubber gloves just to be safe.
#8
Well the new tubes had a bias of about 45 and I got it them to about 37.8-38mA. That should be good, right?

Now I've just to get the thing back into the cabinet.