[Amps] sb-220 tuning question - closing in

[R.Measures]

>The plate tune capacitor should be the LAST thing that you tune.
>It should also be the first thing that you tune.
>
>When you start out apply a small amount of drive and dip the plate with 
>the plate tune cap. Or peak it for maximum output of the amp. 

**  For grounded-grid operation, peaking for max-out is somewhat better 
because a fully-driven, fully loaded-tube has a very slight dip with a 
Pi-tank.  
- Starting with a lesser amount of drive is not useful since the settings 
will be different at full throttle due to a different RL.  

>Then 
>increase the drive slightly and increase the loading for maximum output. 
>Retune the plate tune again. You can do this in 3 stages as you mention, 
>each time doing it with more drive until you get to full drive.
>
>  You want to end up with full drive applied, tune plate tune for 
>maximum output, tune load control for maximum output and then tune plate 
>tune for maximum output again. If you get much of a change on the last 
>retune of the plate tune then readjust the load control again and the 
>plate tune again.
>
>By the way, keep one hand on the carrier level on the exciter as you are 
>tuning up. Only insert carrier for the short time that you are actually 
>turning the knobs. Then reduce the carrier until you get your other hand 
>on the next knob to adjust. This way you will not have excess current in 
>the amp for very long while it is not in tune.

**  Very few Ham amplifiers have a HV supply that will not sag under a AØ 
/ dead-carrier - thereby producing a mistune.  The Henry 3K-A is one of 
the few that has such a supply, however, it's 3-500Z cooling system is 
not adequate for doing so (solder in pins 1 and 5 melts).  //  note - One 
way to reduce average current during tuneup is to use a tuning pulser.  
>
>
>It sounds like you are not loading the amp heavy enough and the plate 
>circuit is arcing when you apply drive again.
>
>Are you turning the exciter on the second time with full carrier applied 
>at turn on? If so the relays on the amp may not have enough time to 
>connect the antenna before power is being generated causing arcing.
>
**  Good point, which is why the relay in the SB-220 needs to be upgraded.