545/Repairs

Fan mounts

See also the general article on Fan mounts .

Ken Chorney says:

Just wanted to add an alternative supplier for replacement fan mounts for the Tektronix 545 oscilloscope fan. Digi-Key currently stocks two part numbers which fit and work perfectly: RPC1597-ND and EAR1345-ND. Both are 1/2" length (same as original) and both have 8-32 male threaded ends (same as original). Both are slightly smaller in diameter (0.4" vs. the 0.5" originals) but this does not affect their fit at all and likely does not affect their function appreciably. I have installed three of the RPC1597-ND standoffs in my 545 and they fit and work perfectly.

Vertical Amp Fuse

Late-production 545A adds F1054 to protect the delay line when a vertical amp output is shorted to ground. If the fuse opens, all twelve 6DK6's will try to draw the usual current, but all in the screen grid. A long time ago someone (Stan Griffiths?) worried this would fry them, but I did the math. The 130mA combined screen current drags it down to 220V which is 35V above the cathode which inputs 0.35W of heat which is under the maximum rating. However, R1218 will fry at 17W. I think we can head this off by rewiring R1218 so it too is downstream from F1054. Then V1033 saturates sending about 100mA to the control grids, I guess that's okay. The mod can be retrofitted to any 541/543/545/541A/543A/545A.