Re: Puzzle of the day: 465b will not trigger on channel 2 SUCCESS!


jeffbathwater1
 

I did a bit of digging around the normal trigger pickoff. I noticed that (what the block diagram calls the delay line driver next to the pickoff) transistor Q1426 is a NE472 not 151-0472-00 or NE41632 equiv. Q1428 is the correct Tek one, 151-0472-00.
Is this causing the bad trigger problem?
The voltage on the collector of Q1426 is -1.5v not -1.2 as on the schematic but I guess that is down to the wrong transistor.

Thanks,
Dave

--- In TekScopes@yahoogroups.com, "jeffbathwater1" <jeffbathwater@...> wrote:

I tracked down the correct transistor for Q1746 and replaced the
temporary 2N3906 and I still get my stable CH1 and CH 2 when the trigger
source is set to CH1 or CH2 (with the calibration signal going into both
channels).
I do have one more problem though and I thought it was the 2N3906 that
was causing it so I didn't pursue it. When the trigger source is set to
Normal, The trigger light flashes and I don't have a stable trigger. If
I set the trigger mode coupling to LF REJ, I get 2 stable traces again.
(AC, HF REJ or DC do not get a stable trace).
If I set the trigger mode coupling to AC and the Vert Mode to Chop I
also get stable traces.....
Do you think I have more fault finding to do on the vertical Preamp
board?

Thanks...
Dave

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