I moved my off line MLA2500A off of the project shelf and on to the bench
to resume a project that I started back in 2001. I had previously built a
new HV filter capacitor board and added a glitch resistor to the B+ line
going to the plate caps. I would like to modify the grid current circuit
to
allow for full scale on the meter at 100 ma Ig. After spending several
nights reviewing the schematic for the MLA2500 and looking at some web
resources, it appears that I need to add a second shunt resistor to the
metering circuit. I found a web sight with schematics for the MLA 2500A
and
MLA 2500 B. It appears that one of the changes on the B model modified the
grounded grid configuration of the A model by adding several bypass caps
and
a second shunt resistor to float the grids a little bit above ground and
running a line to the meter switching board. I have not been able to find
a
good picture of the bottom side of the tube sockets in a MLA 2500B on the
net to see how these caps and new shunt are configured. If one of you QRO
hams that have a MLA 2500B and a digital camera could flip that puppy over,
shot a couple of pics of the tube sockets and email them to me, I could get
this thing on line.
TNX ES HAPPY NEW YEAR
73,
Jim Zellmer, KA0VSL
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