[R-390] OT: HP-410B Tubes

[Barry]

This is one of the early models that does not have printed circuit boards.  I had one of the PC-board models a few years ago and I know what you mean about them.

This one has some very sturdy, old-fashioned solder "posts" (for lack of a better word) to which the parts are soldered.  Very nice, solid joints.

I found the DC calibration pot is quite bad.  Once I get that replaced, perhaps things will settle down a bit with the new tubes.

I didn't check the 12AU7A's for gas.  That also might be a problem.

Thanks again,
Barry - N4BUQ

> Barry,
> 
> I observed somewhat the same behavior on my 410B although not as 
> pronounced.  I had enough 12AU7's to swap around until I got the 
> meter to zero with the zero pot pretty much in the center.  Not much 
> else I can offer here.
> 
> Another thought.  The 410B I have had numerous bad solder joints 
> especially on the printed circuit card(s), believe it or not.  It 
> took many hours of elbow grease to ferret out all of these 
> problems.  They certainly didn't make working inside the unit very
> easy.
> 
> Regards,
> Jon - WA3MVM