[Heathkit] SB-610

[Eddy Swynar]

Hi Guys,

I recently had a most interesting experience with my SB-610 monitorscope here...

Periodically the horizontal trace line would "spike" upwards, randomly: in its absolute worst case, the line would become all jagged on a continual basis, and the envelope traces of my signal would be near obliterated. The trace looked almost like that of a spectrum analyzer when tuned to a noisy band...

Rotating the two switches---either one---would "cure" the problem, for varying lengths of time.

Anyway, I concluded that maybe it was time for a new 6U10 compactron, as I have had to do absolutely nothing to the scope since its acquisition (used) over 20 years ago. I replaced the original tube with a new 6U10---but then I could not get a full sweep of the horizontal trace line with the thing set for its slowest rate. The line would become a simple dot at anything less than having the sweep pot set at some 75%!

I then replaced the original 6U10 back into the SB-610, and voila! All is well again---no "spikes", & I can get a full trace even at the slowest sweep.

I guess that by my removing & replacing the tube, I must have somehow "restored" continuity between its pins & the tube socket...I can't come up with any other explanation. As for the bizarre behaviour of the new tube in the circuit, well, I wanted to compare test results between both 8U10's on my "Stark"-brand model 9-66 dynamic tube tester, but this compactron was made after the tester was, & I had no test criteria for the Stark to evaluate them...

Anyway, most interesting in that "...things aren't always what they first appear to be."

~73~ de Eddy VE3CUI - VE3XZ