I just finished rebuilding an SB-401 Transmitter. Looking at the pattern on
the SB-610 I have everything looks good except that the patterns are
trapezoidal, pinched at the top and splayed out at the bottom. I'm fairly
sure its the scope not the transmitter.I replaced the 3RP1 CRT in the SB-610
with 3RP1A because the original would not focus correctly. The voltage going
to the CRT are correct within the 10% list in the manual. Any ideas.
Thanks
Jack

Reduce the size of the trapezoid. If the pattern cleans up, it is the
scope.

Jump'n Jack Flash wrote:
I just finished rebuilding an SB-401 Transmitter. Looking at the pattern on
the SB-610 I have everything looks good except that the patterns are
trapezoidal, pinched at the top and splayed out at the bottom. I'm fairly
sure its the scope not the transmitter.I replaced the 3RP1 CRT in the SB-610
with 3RP1A because the original would not focus correctly. The voltage going
to the CRT are correct within the 10% list in the manual. Any ideas.

Did you see the problem with the original CRT?

That sounds like a vertical linearity issue. Look at the vertical drive
tube and check all the voltages around it.

Oh yes... and the usual recommendation for changing paper caps goes here
too. If the drive amp is misbiased you'll see goofy things.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Jump'n Jack Flash wrote:
I just finished rebuilding an SB-401 Transmitter. Looking at the pattern on
the SB-610 I have everything looks good except that the patterns are
trapezoidal, pinched at the top and splayed out at the bottom. I'm fairly
sure its the scope not the transmitter.I replaced the 3RP1 CRT in the SB-610
with 3RP1A because the original would not focus correctly. The voltage going
to the CRT are correct within the 10% list in the manual. Any ideas.


Focus problems on CRT's that have normal voltages are generally caused
by poor cathode emission.

A nearby magnetized object can cause display linearity problems like
you mention.

-Chuck