On Jul 3, 2004, at 9:01 AM, N7uvh@aol.com wrote:
Hi guys..great reading.
I have a sb220 with the original tube Eimac 3-500z. I think i have a
short
in one tube. Keeps cooking the rf chock on pin 4 of tube to ground.
So what
I am wondering if it is ok to buy a 3-500ZG to replace it.
Yes, Patrick, but the grid to gnd chokes should be replaced with
fusable resistors to protect the tubes. Also, the grid bypass C should
be increased by c. 1000pF per socket. The suspect tube should not be
discarded unless a grid/filament check with a high-potential tester
confirms that the breakdown is <5kV. Better parasitic suppressors might
help. An article on my Web site describes problems & fixes with the
SB-220.
thank you
n7uvh (first time in a amp)
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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