Variable MU Pentode
This exhibit was almost the universal amplifier pentode
of the post war era, many manufacturers made versions of
this standard valve.
The CV138 Vacuum tube is a high gain, high impedance,
variable mu, screened pentode. It could be used from AF
to VHF up to about 200 MHz and was found in large
numbers in most types of electronic equipment. In radio
it was used for RF and IF amplification, for oscillators
and frequency multipliers.
Prefered Substitutes ..............6AM6, 6F12, 8D3
EF91, HP6, Z77, CV4014