Understanding Vacuum Tube Diagrams?

Discussion in 'General Electronics' started by Chris Cooper, Nov 10, 2003.

1. Chris CooperGuest

I've got an old wire record I'm trying to revive (see my "Reviving 50+ year
old Wire Recorder" post), one of the problems is that I don't quite
understand how to interpret the schematics for the vacuum tubes. Is there a
simple explanation (online preferably) that talks about the "standard
symbols" used in vacuum tube internals?

Thanks!
Chris

2. Robert BaerGuest

The reference that Jack gave is good for theory, but does not appear
to relate diagram(s) with terminology.
It is getting too late for me to scan some info for you; here is a
"quickie" ASCII pseudo-art:
|
_______ <--- plate (crude)
----- - - - - <---- grid (sort-of crude)
__________
| ^ | <---- cathode (crude)
| / \ <-------- filament
| | |
| | |

Have data on a large number of tubes and can scan what i have for you.
Will see if i can find something better Monday evening (later today).

4. tiger xGuest

A real simple explaination of vacuum tubes:
1. The source of electrons is the cathode.
2. To release electrons, the cathode must be heated by the filament.
3. Released electrons must be attracted & gathered up by the plate.
4. The flow of electrons through the tube is regulated by the control
grid.
5. Any other grids in the tube are for effecient operation of the
tube.
6. The cathode has a negative potential.
7. The plate has a positive potential.
8. The control grid potential varies according to the input signal.
9. On a schematic, the control grid is the bottom grid and enters on
the left of the tube.
10. The signal out of the tube usually leaves via the plate (top), but
may leave via a resistor connected to the cathode (bottom).

Easy as that!

Tiger

5. DboweyGuest

1. The source of electrons is the cathode.
Unless the tube has no "cathode." Older tubes used the filament as the negatve
element, so AC could not be used for the filament voltage, for hum
considerations.

Don

6. JeffMGuest

Dbowey
Tube rectifiers still do.

The classic H-K short (heater-to-cathode) can also cause hum,
defeating this design consideration.

7. DboweyGuest

jeffm posted
*some* Tube rectifiers do, not all do.

When did we change over to discussing defective tubes?

8. Mike EnoGuest

Man you must be a young buck not to know about vacuum tubes or i'm
just
an old #art. Wet behind the ears but interested in 50 year old vintage
electronic devices, all right then.
I know this is a late response but ...
Vacuum tubes share a lot of similarity to Depletion mode MOSFETs in
terms of the design equations. Mind you tubes require much higher DC
operating voltages plus the aformentioned filament juice.
Source Gate Drain are analagous to Cathode Grid Plate.

MENO

9. Robert BaerGuest

....and....i, as well as others posted labelled drawings and links to
numerous references.