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Hi All

Have two issues with my Tek 2246 scope display. Looking for common faults before digging in.

1) Display brightness fades after approx half hour after power on. Display geometry is fine, it just dims

2) Display seems to have a slight flicker . . . it's also noticeable on the green LED's illuminating buttons

Bought it in not working condition. Replaced rectifier in -15VDC supply. All now working well except these two issues.
All other supply voltages look steady, although have not taken time to look at any ripple/abnormalities.

Thanks in advance,
Mike

Mike,
The display flicker might be due to the on-screen readouts stealing the beam at times.
Does the flicker go away if you turn the readouts off?
--John Gord

Thanks for the reply.

The "flicker" seems to go away with readouts turned off (clear display button).

Oddly, the flicker I'm seeing on the green button indicators goes away with signal input (using built-in 1khz calibrator tab).

The volts/div and sec/div readouts (which I don't think can be turned off) appear to have noise on them at all times, same with the other readouts
when those are turned on.

I realize there's a jitter adjustment for the readouts as per service manual, but would like to get opinions/advice first.

Hi

With reference to the display fading only.

You are probably seeing a little understood / acknowledged problem with the high value resistors around the CRT. They normally go high in value with applied voltage, this effect can take a considerable time to fully occur. 15 to 20 minuets is quite common.

To fix replace the resistors with high working voltage ones from the likes of the Vishay VR26 range.

George G6HIG UK On Friday 28 February 2025 at 04:18:38 GMT, saturn.v2000 via groups.io <saturn.v2000@...> wrote:

Hi All

Have two issues with my Tek 2246 scope display. Looking for common faults before digging in.

1) Display brightness fades after approx half hour after power on. Display geometry is fine, it just dims

2) Display seems to have a slight flicker . . . it's also noticeable on the green LED's illuminating buttons

Bought it in not working condition. Replaced rectifier in -15VDC supply. All now working well except these two issues.
All other supply voltages look steady, although have not taken time to look at any ripple/abnormalities.

Thanks in advance,
Mike

On Thu, Feb 27, 2025 at 09:52 PM, <saturn.v2000@...> wrote:

Oddly, the flicker I'm seeing on the green button indicators goes away with
signal input (using built-in 1khz calibrator tab).

If trigger mode is in "Auto Level" does moving the tigger mode to "Auto" and changing trigger level away from zero stop flickering?
Ozan

Thanks George, I'll make a note of that.

- Mike, de W9MAS (USA)

Ozan:

The green indicator flicker I mention is very subtle.

This flicker seems to go away when trigger mode is set to "auto", regardless of position of trigger level control
and with no signal input.

On Fri, Feb 28, 2025 at 01:06 PM, <saturn.v2000@...> wrote:

Ozan:

The green indicator flicker I mention is very subtle.

This flicker seems to go away when trigger mode is set to "auto", regardless
of position of trigger level control
and with no signal input.

===
Mike,
In that case it is normal and expected. When trigger mode is "Auto Level" with no input signal trigger range is set to peak to peak amplitude of input noise and triggers randomly.
Ozan