I'm helping an older ham get rid of some of his gear. He has nice Alpha 76A with three 8874's in it. I bought it home and put the transformer in it, brought up power on variac and let the tubes cook before introducing any RF. Just really being cautious.
It works well on 10 - 15 meters with just 35 watts or a little more from my FT-710 and it will peg my 1k meter on my Imax antenna or with the Vectronics 1.5KW dummy load.
Problem is when I used a dummy load and tried to tune 40 meter and lower, I couldn't get off the manual's recommended starting point for that band without the hearing buzzing or worse arching sound in the amp. Factory starting point were very close on other bands. I couldn't tune it for any real output. Same when I tried tuning amp on my wire antenna.
Is there something possibility wrong with amp where it works great on 15 meter and higher not on the lower bands? Something to visually look for insidet the amp?
Or should I go a read the sticky, How to Tune a Tube Amp more thoroughly? I am a newby at manually tuning and working lower bands. My Acom 1000 has spoiled me and I never really learned on the older amps.
Any help is always appreciated!
73
Uneasy
It works well on 10 - 15 meters with just 35 watts or a little more from my FT-710 and it will peg my 1k meter on my Imax antenna or with the Vectronics 1.5KW dummy load.
Problem is when I used a dummy load and tried to tune 40 meter and lower, I couldn't get off the manual's recommended starting point for that band without the hearing buzzing or worse arching sound in the amp. Factory starting point were very close on other bands. I couldn't tune it for any real output. Same when I tried tuning amp on my wire antenna.
Is there something possibility wrong with amp where it works great on 15 meter and higher not on the lower bands? Something to visually look for insidet the amp?
Or should I go a read the sticky, How to Tune a Tube Amp more thoroughly? I am a newby at manually tuning and working lower bands. My Acom 1000 has spoiled me and I never really learned on the older amps.
Any help is always appreciated!
73
Uneasy