Alpha Amp Issues?

[Uneasy Rider]

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

 

[nomadradio]

I'll guess that a close look at the band switch with a bright light will reveal burned spots on the contact points for 40/80 meters. Probably never cleaned the oxide from the silver plated contacts. Once the arc begins, metal gets destroyed. Sounds as if the previous owner liked 40 and 80 meters better than he liked 10 and 15. There are some genius types out there who have repaired this kind of swtich. I'm not one of them. Probably need to be replaced.

73

 

[Uneasy Rider]

I'll guess that a close look at the band switch with a bright light will reveal burned spots on the contact points for 40/80 meters. Probably never cleaned the oxide from the silver plated contacts. Once the arc begins, metal gets destroyed. Sounds as if the previous owner liked 40 and 80 meters better than he liked 10 and 15. There are some genius types out there who have repaired this kind of swtich. I'm not one of them. Probably need to be replaced.

73

Thanks Nomad!
I will take a look and see what I can find.