Re: Tektronix 465 No Trace, No Dot


Elliott Li
 

Well well well.

You folks had some good ideas.

Here is what I found so far:

Unregulated +15 fuse is good.

Vertical deflection voltage (measured differentially) is -31.5 to +32.0 (seems about right). Left it around zero.

Horizontal deflection voltage (measured differentially) is -10 to +83 (seems wrong). I have always felt like the "center" of my horizontal knob was way off, now I know why. I don't think this is the root cause of the no-trace-at-all problem though. I left the knob at approximately "zero" volts, about where I always had the dial it seems. Something to troubleshoot later. Measured separately, the L wire varied (reference to ground) from 58.1 to 48.3. The R wire varied from 11.8 to 94.8, also referenced to ground. Presumably the circuit driving the L side is the one most out of line, I would think.

Then I got brave and hooked up my Simpson 260 from chassis to the "-2450" test point (TP1423 I believe). On the 5kv range it hardly moved. On the 500 volt scale it went about half way up. On the DMM this measured -490V. Now, it's 11 pm and I know better than to keep at it this evening (as much as I want to). Any pointers? I will review the cathode voltage circuits tomorrow and take another peek tomorrow evening.

Thanks very much again,

--E

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