[Johnson] Are there " good" modifications ? -yes!

[Jim Brannigan]

How about the 3-500Z's in the SB-220?

Jim
> Also, as Gary pointed out, with many high power transmitting tubes, i.e.
> plate voltages greater than 1KV, the "instant on" should not be used.
> Either control it with a separate switch or use some type of  time-delay
> circuitry to bring the filament(s) up to operating temperature before
> applying the high voltage. Of course, tubes like the 572B, used in the
> SB-200/201, have no cathode, and so Heath decided to not provide any
> standby switch or time-delay. 2K plus volts hit the plates as soon as you
> turn the rig on.
> 
> Pete, wa2cwa