Hi Ampers,
I bought a used Ameritron AL-572 in June and have just been able to
check it out the last couple of weeks. (It's a long story involving
moving into an OLD house...)
Output seemed fine, but plate current reading was high with zero drive
(over 150 mA), BUT the grid current seemed fine. A call to Ameritron
confirmed what I suspected, Q3 and possibly Q2 and Q1 had blown. I was
shipped new transistors and I decided today would be a wonderful day to
work on the amp.
I replaced Q3, since it's the easiest to replace, and on a pwer up, I
now have erratic plate current readings and NEGATIVE grip current. (Or I
guess I should say, the grip current meter is being pulled down) Most of
the time, plate current reads zero with no drive, but often on power up,
the reading wobbles a bit, between zero and 75 mA and then eventually
settles on zero.
I suspect the tubes are OK, because I'd been getting 700 watts output
with 25-30 watts drive before I replaced the transistor. I saw nothing
to indicate a flashover or anything else when I powered the amp up after
I replaced Q3.
I have not attempted to TX on the thing in this condition.
Any Ameritron experts out there with with any ideas? I'm not an
engineer, so keep that in mind when you respond.;)
73,
Scott, N9AA
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|