38 N5X Construction guide
Checking dissipation - EL84
If your readings are all close to the 'typical' values in the voltage chart, then we just need to do a few
calculations to conrm that the amplier's biased right and we're not burning up the valves prematurely.
This section covers an EL84-based amplier. Skip to the next section if you are using a 6V6/6L6/EL34.
1 - EL84 cathode current: Divide the cathode voltage (H-N) by the value of R16 (150 Ohms). A typical
result is around 43mA. Contact Amp Maker if it's more than 50mA.
_________mA
2 - EL84 screen current: Divide the K-L gure by the value of R18 (2.2k Ohms). A typical result is 4mA.
Get in touch if it's more than 6mA.
_________mA
3 - EL84 plate current: Subtract the screen current (2, above) from the cathode current (1, above) to
get the valve's plate current. A typical result is 36-40mA. Contact Amp Maker if your result is more than
45mA.
_________mA
4 - EL84 plate dissipation: Multiply the N-M gure by the EL84 plate current you've just calculated (3,
above).
_________W
For example, 225V * 0.039A = 8.78 Watts dissipated by the EL84's plate. This is a typical result. A value
under 8W or over 10W needs some consideration; contact Amp Maker.
To Next Page
Loading...