[R-390] On the topic of HP410B repair

[Barry]

I needed a replacement 500-ohm wirewound pot for the DC calibration pot in my HP410B and I found these:

ttp://www.westfloridacomponents.com/mm5/merchant.mvc?Screen=PROD&Store_Code=wfc&Product_Code=P067&Category_Code=>

They have a shorter shaft than the originals but, other than that, they make a fairly nice original-looking replacement.  They are large enough so that the lock finger fits in the appropriate hole too.

Of course, if you're not concerned with "looks original", the calibration pots could all be replaced with ten-turn pots which would make a very smooth adjustment possible.

Ashley at KISS Electronics (they refurbish 410B's 410C's and other test equipment) suggested using trimpots as well.  A single board with several trimpots on it would make a nice retrofit.

Regards,
Barry - N4BUQ