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From: "Mike Merigliano" <mmerig@...>
To: "tekscopes" <[email protected]>
Sent: Friday, April 1, 2022 7:58:51 AM
Subject: Re: [TekScopes] Tek 453 resistor specs -- Horiz amp

Hello Mark,

Thanks for the advice -- I will try it soon. I will probably put in 1/4W
1% carbon film to replace the broken ones. That might be over-kill, but
the cost difference should be small. I usually order from Mouser.

The broken lead was on R631. Also R638 -- I should have said two
resistors in my earlier message.

In the midst of my repair, a wire came out of the intensity pot (the
wire did not look broken, looked like a cold solder), and I started
chasing down problems in the Z-axis circuit until I went back and looked
at that pot. There was a slow-blow fuse for the Z-axis (should be
fast-blow), so while checking the HV oscillator, I switched that out.
This scope did not work at all when I bought it used years ago -- just a
dot on one channel, and then only with the beam finder pressed. There's
a strange diode addition in the B-delay sweep circuit, and some other
obvious repairs, so whoever had it before me changed some things in that
circuit for some reason. Some of the transistors were plugged in the
wrong way. Broken horizontal deflection transistors were a key problem.

I will re-visit that diode addition. It looked superfluous, or maybe
helpful, but that diode could be part of the issue.

On 3/31/2022 7:34 PM, Mark Vincent wrote:

Mike,

Which resistor did the lead come out of?

As for replacing or new build, I use 1% Xicon 1/2w. I have found that the
Chinese sellers on "that auction" site have excellent 1-5W 1% types and are of
the proper physical size. The temperature drift of these is 100 ppm/deg.C while
the Xicons are 50 ppm. Using 1/4W 1%, I will use in places where the power is
low enough. I like the low drift, very low noise and accuracy of the 1% types.
This is my personal choice from using them long enough in enough things to
decide to use these. Carbons are alright in some places. Replacing a carbon
with a film type is usually better.

By the dot being off that much, it sounds like your "mag register" pot need
adjusting. That is done by putting in a signal, setting the horiz. pots to
centre, setting the sweep to 10x then getting the centre of the signal in the
centre of the screen. Using the 1kc test signal to the input will give ten
waveforms on 1ms/sec. in the normal position. You would want the centre of
waveform five in the centre at 10x setting. This should get the dot in or near
the centre when in XY mode. Moving the position knob some is likely.

Mark