dentron gla-1000b help needed

[ddbddg1]

I have a gla-1000b that works fine on all bands but 80.
when I tune into my dummy it seems fine but when I switch over to antenna the swr pegs out.
if I tune into the antenna for max out its fine while tuning but when I release and rekey the swr max out again.
I switched all the jumpers and checked all the connections 3 times
has anyone run into anything like this before?
80 is ok without the amp

 

[n0zna]

coax breaking down.

 

[ddbddg1]

I am running open line and checked it all the way to the antenna..even re soldered all connections....it only does it on 80m

 

[Shockwave]

It's almost certain something in the antenna system is breaking down under load at full power. Many insulators or matching networks may not arc or break down if the power level is gradually increased to the same point where it will arc if the power comes up instantly.

Lower frequencies are more prone to RF arcs than higher frequencies where RF heating is the bigger issue. You may find keying the amp at night with someone looking at the antenna and feedline insulators could reveal flashes of light that were missed during the day.

The only other option would be the amplifier is oscillating. The reason this is not first in line is because that typically happens on 10 meters long before it shows up on 80. This amp also has all the other elements of the tubes tied directly to chassis ground, minimizing the chances of oscillations.

One other thing you may want to check to insure decent tube life is that you have a GLA-1000 that matches the published schematic with a 3 pole relay. At some point Dentron got cheap and started using 2 pole relays that left the sweep tubes biased in the linear mode continuously!

 

[n0zna]

yep,something breaking down.I was leaning coax with the added pwr.

 

[Shockwave]

yep,something breaking down.I was leaning coax with the added pwr.

Agreed. Since he says in a recent post it's open line feeder, the problem could just as easily be a defective insulator or crack in a molded plastic feeder.

 

[ddbddg1]

guess i will go up on the roof again in the morning and recheck connections...I have homemade 12ga. open wire from the tuner all the way to a alpha delta dx-cc so theres only 1 connection point up there....and might as well change all the jumpers again too and try that