Re: Tek 314

John Clark

Thanks Bert. Yes. When I push the "Store" button I get two, sort of oblong, out of focus beams, maybe 0.5" in tall and 0.75" in width that start out near the center of the screen and quickly move in opposite directions and go off the left and right sides of the screen. If I turn off store and hit store again within a second or two I don't get them again. If I wait around 5 seconds before pressing store again I'll get them again but they don't start out in the center. If I wait 10-20 seconds before pressing store again they'll start out near the center and go off the sides of the screen again. The screen is supposed to light up fully when pressing store but instead I get these two quick beams. If I'm reading them right, the diagrams show that when the store button is pressed it closes S500A and completes the circuit to pins 7 and 4 putting -90V to the flood gun heaters. That appears to, at least, be doing something.

I've looked with the lights out and can see no other screen activity with exception of the above.

I unplugged P700 and ohm'd out the CRT heater (that's what's on pins 12 & 14, correct?) and got OL. If that's supposed to be a low ohm reading then that would be a bad sign. It won't be surprising if the CRT is bad since it does have that very small piece of something rattling around inside it that I mentioned a while back. It was suggested earlier in this thread, though, that the small piece rattling inside wasn't necessarily the end for the CRT, in and of itself. I was hoping it might still be OK.


Did you say earlier that the flood guns ( store ) did something? i.e.
some light on the screen.

If this is no and if the vertical pins are set to about the same voltage

with the position control,

I guess I'm out of ideas except to wonder about the CRT.

(2) Are you checking for CRT activity in a dark!!! room?

Some possible faults can result in a very dim trace.

Also check for any!! CRT activity during power up / power down.

(3) Did you "Ohm out" the heater?

This should show a low reading.

On 12/25/2015 9:55 PM, John Clark [TekScopes] wrote:

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 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?


Join to automatically receive all group messages.