[Amps] Al-80a problem.

[kb4tcu]

my al-80A hicuped tonight. I do not have the schematic for this amp. It =
does not show HV now. After inspecting the meter, the reading was open =
from the outside terminals. i have removed the meter from the chassis =
and disasembled. Inside the meter
is a small 1/8 or 1/16 watt resistor in seris with the meter coil. This =
resistor reads open. The meter coil reads around 400ohms and also the =
volt ohm meter deflects the meter upward about 20%. What is the value of =
this resistor inside the=20
plate, HV, Power, alc meter. ? Also the plate current shunt resistor is =
blown. I also need the value for that.

What happened.

With the amp tuned and working properly a electrical pop or bang was =
heard. A flash of light emmited very breifly from the exaust vent on the =
side of the amp. The output droped to zero. The Multi meter was in the =
Power out position. It also droped to zero. Switching to HV the meter =
still at zero. Switch to IP no current with drive.  Removed Amp from =
station location, removed power and removed the cover.  Straped the HV =
from the plate choke to chassis with gator clip jumper for safety. =
Removed tube checked for short p to grid , p to fil none found.A visual =
inspection reveled quite a bit of dust at the bottom of plate choke, no =
sign that it flash over. The shunt resistor is blown open on meter =
board. The series fuse resistor open inside the hv, ip , alc =
multi-meter.=20

Any other thoughts what went on. And how to make preventative measures =
for the future.

thanks Victor Vickers kb4tcu








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