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  2. Tek 314

Re: Tek 314

John Clark
 

OK, using my now pristine 475 (thanks to everyone here,) I did a little more probing around on my dead 314. I checked the L/R horizontal deflector pins and have nice opposite sawtooth waveforms there. I then checked CRT pins 9 & 5. I have a 100vpp square wave on pin 9. Just as you say, the pulse is on longer than it's off. The on/off time does change when I change the tim/div knob, which makes sense to me. I'm pretty sure that's all as it should be.

On the other side, on pin 5, I have a steady +100VDC. Seems to me that's what I should be seeing there, too. If there's 100v on each side then the display should be unblanked. When one side goes to zero then it blanks...am I understanding that correctly? If so, I'm thinking I either have a bad CRT or a problem in the HV section. I did order a Fluke 80k-40 to go with my 87V that should be here in a day or two as I figure I'll need it sooner or later.

Anything else I can check before my HV DVM probe arrives?

John

Key section is at the bottom of FO 10.
I must admit that I have not done much of anything inside my 314 but I
guess you really need to know what is happening at CRT socket pins 9 & 5
before you can call the CRT bad.
The circuit is a bang-bang it just switches from a low near 0V( blank )
to a high near 100V ( unblank ).
In a normal ( auto trigger ) sweep mode the low pulses should be short.

Please other list members check me up on this since I've been mostly a
software guy since this was built even though I started in electronics
in the late 50s.

Bert


If you are aware of this, just let it go by...
On the 314 blanking is accomplished by a extra deflection plate which

moves the beam off screen.

When blanked the deflection voltages are not relevant.
Bert
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