On Sun, Feb 11, 2024 at 02:40 PM, Don - AC2EV wrote:
Device Under Test:
Tektronix 465B #107437 with option 5 (TV Sync Separator). Boards have date of 1978d
Nice scope, that option is what I'd hoped for, but didn't get, when I found my 465B. Not useful anymore, with digital TV. The rest of the scope is a great classic Tek portable.
First thing I'd suggest would be to turn down the beam Intensity. You don't want to burn the phosphor.
Next, take a close look at the +5 V rail. Yes, it's too low, and it can be difficult to figure out whether it's a power supply problem or too much load from a failed component somewhere down the line. I'd start by looking on that rail for the AC voltage. If things are good there, the AC component will be mV. With your DVM leads connected to the +5 and ground, switch the DVM from DC to AC. If there's lots of AC (ripple) then the PS is the more likely culprit. Look for an electrolytic cap that is no longer a capacitor. One way to test for this is to simply solder a similar capacitor across the Tek one (with the power OFF!) and see if the problem disappears.
