On 03/22/13 13:21, K4MT wrote:
I am still refurbishing my SB-230 and I have noticed the grid ring on the tube
looks badly tarnished. I have checked it with an ohm meter and I see a low
resistant connection but that tells me nothing about the RF connection. I have
replaced the stud mount bypass caps and re-tightened grid ring. I assume a bad
contact on the grid ring would hurt stability. I had both bypass cpas open and
the amp worked fine and I saw no difference after replacing them.
What would be the symptoms of a dirty grid ring? I do notice that when
producing full power of over 600 watts I never see more than 10 MA grid current
no matter how the amp is tuned. I have rebuilt the entire grid circuit
replacing all out of tolerance resistors and caps. The power supply has been
rebuilt, TR relay cleaned, Tank circuit rebuilt and bandswitch cleaned (I am
retired an have too much time on my hands). The input circuit is fine and I
have low SWR between amp and radio on all bands.
Should I try to clean the grid ring or leave well enough alone? Looks like I
would have to remove the tube and I have read some posts that the socket might
fall apart trying to remove it. Can the grid ring and collet be cleaned
without removing the tube?
leave well enough alone!
Tarnished silver is harmless and it will just re-tarnish.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
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