A tube inside an SB-220 I rebuilt 3 months ago suffered a grid to cathode
short. I heard a loud
bang and found the meter shunt resistor blew apart and the grid fuse
resistors way out
of spec. The amp has all the upgrades in place...
I replaced the bad tube, meter shunt and grid resistors and things are
now back to normal
full output. Even a nonfatal parasitic has the potential to stress the
.82 metering shunt
resistor.
cheers
skipp
>Subject: Re: [AMPS] AL-80 Excessive Grid Current METER Shunt SCHEMATIC
Solved
> The hard way, I finally figured out that this AL-80 came with the wrong
> meter and face in it
:What was that I said about making sure the reading was real? I have
never
:come across that one before but it is always a good idea to check a
meter as
:what is on the scale and what the current is can be very different if
:external shunts and multipliers are assumed. Typically, a 750mA meter is
a
:100uA meter with a shunt inside to make it really read like a 750mA one,
but
:not always.
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