hypothetical 10 meter amp question

[Tallman]

If looking at tube amps spend more upfront and get all the power you think you might need in the future if you can afford too. You can buy a legal limit amp and not use all of it's power output. Buy it once and have it for life!

By Jove I think he's got it!

 

[Onelasttime]

When looking at tube amps they should be considered a 20+ year investment in the hobby and budgeted for accordingly. The bane on American society is living for today and forgetting about tomorrow in the business world people look 1/4 quarterly not 2, 4, 10, 20 years ahead. Amps do not have high wear mechanicals in them so really no reason they should not live a long long life. The better the parts and the better the design the greater it's life expectancy!

 

[Tallman]

booty, the amps you posted work on hf, they are basically a rm italy cb amp with filters and a few things added, the basic amp is still the same circuit as the cb amps, the negative feedback circuit works the opposite way to what it should in a decent hf amp,
output climbs as you go down in frequency if you dont reduce drive,
a few locals use them, seem work ok but they can break out into self oscillation on certain frequencies and drive levels, some sound better than others right out of the box, overdrive protection does not always work if you accidentally input 100w.

You hit the nail on the head! I was working on a HLA-300 that had band switching problems. RF output was good and symmetrical on AM modulated.
The unit was not keyed up. I was taking voltage measurements around the Programmable logic array and the unit popped the fuses. It must have been oscillating.
I called the factory and told them what happened and they ask me to return the dead unit. That same day they sent a replacement unit for the customer. Later that month they did confirm oscillation was the cause of failure. I have a two meter amp that is unusable for the same reason. Hook it up to test load and connect to the power and turn on and it goes to maximum output without being keyed.