Re: troubleshooting Tek453 Mod 210H

Fabio Trevisan
 

Hello Chuck,

When it comes to intensity control inoperative, and highly intense trace, I`m afraid that you're going to set your fears aside about the CRT circuit and playing around it (with all its indeed intimidating High Voltages)...
Still, a lot of those circuits can be troubleshoot on the "Low" side, and what can't, can be troubleshoot by rising one lead of the components and measuring them (with scope turned off).
The regular caution is advised though... To keep one hand in the pocket, to remember to discharge the H.V. points before poking around and, preferably, don't be isolated in the bunker with nobody around.

About the focus, I think you probably don't have a problem in that dept. The trace is fat and the focus can't tame it because it's too intense and the beam is "bloomed".

An inoperative intensity control can have many causes, from a short between grid (G1) and Cathode (K) of the CRT tube, to problems (mostly leakage currents) in the DC restorer circuitry, to defects around the CRT bias circuitry, which encompasses the Intensity control pot and the CRT bias control (usually a trimpot).

All that I`m saying above is general to CRTs and not exactly specific to the 453.

In order to get more specific, anyone in the group will ask you 2 things:
1. If you have a manual, whether in Paper or PDF form (which for the 453 vintage is simultaneously a user and service manual). Some options to download here:
http://w140.com/tekwiki/wiki/453
2. What is the serial number? And if it's really a plain 453, or if it's a 453A.

Please let us know... and we take from there.

Kindest Rgrds,

Fabio

On Wednesday, October 10, 2018, 2:38:26 AM PDT, chuck
<@chuckyorbalinda> wrote:

Folks,
just bought a 453 and of course there are problems. The trace is fat!
Using the 1Khz internal signal when I put it on either channel the trace is
out of focus and really hi intensity. The focus knob works to an extent but
the intensity knob does nothing. I traced the signal thru the z amp and it
behaves as it should as I adjust the knob the signal at the output stage
(prior to going into the CRT control circuit) changes. I'm intimidated by the
CRT circuitry and would love to get some feedback so that I'm not going in
blind. The Tek troubleshooting guide talks about Typical High Voltage problems
but does not really point me in a direction.
Any help would be appreciated. I have a couple of DVM's and a pocket
scope (Chinese knock off) to work with.
Chuck


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