What do the numbers on vacuum tubes mean?

1. What do the numbers and letters in a tubes name mean? There are several different tube numbering systems that you may see on tubes, which generally are a result of where they were built. Most commonly the numbers contain digits only (e.g. 5751), or are some combination of numbers and letters (12AX7, ECC83, CV4004).

How do you count vacuum tube pins?

Re: Tube pins on schematic As shown in the previous picture, the first pin to the right of the key, counting clockwise is pin one. You count clockwise, 1, 2, 3, 4, ect. That is looking at the bottom of the chassis. This is the side you are working on.

How are vacuum tubes matched?

Some companies offer matched sets of replacement tubes. This means that the tubes have been tested — the plate current draw is measured under normal operating conditions — and each tube in the set has been determined to have the same current draw.

Do vacuum tubes need to break in?

Yes, they do break in. Do they NEED a break in? Not really. Small signal tubes especially will sound good within a few minutes of warming up but they will tend to sound better after a while because everything gets baked and molded into shape so to speak.

How close should tubes be matched?

We match tubes to be within 5% of measured plate current (that is, the tubes wont differ from each other by more than 5%, or 1 milliamp in 20).

How do you know if your tubes are matched?

Think of a power amp with four tubes as a car engine with four carburetors. If there is an idle adjustment for each carb that would be the same as an individual bias adjustment screw for each tube. If there is only one bias screw for each two tubes, you need a matched pair of tubes.

How long do vacuum tubes take to break in?

While power tubes take 100-200 hours to break in , input/driver Tubes also require some time. Usually less . If your tube pins ( legs ) are oxidized , clean them with De-oxit and a Q-tip .

How do you know if a vacuum tube is good?

Any color from grey/silver, to black is healthy. When a vacuum tube develops an air leak (a small crack or bad seal by a pin for example) this getter color will change to pure white. If you see this you know with 100% certainty that the tube is bad.

Do vacuum tubes go bad?

When a vacuum tube develops an air leak (a small crack or bad seal by a pin for example) this getter color will change to pure white. If you see this you know with 100% certainty that the tube is bad. Third, look for a purple glow that is very focused around specific elements inside the tube.