Re: Tek 2467B Erratic Intensity controls


peter bunge
 

My reasoning that the NOVRAM is causing the delayed response to the pots is
that maybe it is marginal at writing but OK at reading with low battery.
Anyway it should be replaced.
What is a good replacement?
Are the ones listed from China and Hong Kong OK to use?
How do I know if the battery is good in a "new" one?
What programmer is good to use?

On Sun, Dec 1, 2019 at 7:48 PM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

The Trig Level goes through a different Mux to the Intensity and position
controls. The three Mux O/Ps are joined and feed comparator LM311 U2510
(all on Tab 2 schematic) The Mux O/Ps (TP9) are clean and jump when a pot
is suddenly turned, the same for the comparator O/P. I am trying to find
something common to the Position, Trig Level, and Intensity Pots. The
comparator O/P goes through U2220 and it seems to respond immediately to
pot changes. Then there is the dv and dt switches that seldom work and when
they do the dotted lines are jumpy when moved with the pots below the
switches.
I assume the various positions are saved in RAM (the NOVRAM). Could it be
getting slow because of a low battery?
Is there a quick check I can make?

On Sun, Dec 1, 2019 at 5:39 PM peter bunge via Groups.Io <bunge.pjp=
gmail.com@groups.io> wrote:

Yes they are 'sticky' especially if I move ch2 then ch1. Also the digital
display of the DC trigger point is sluggish and often does not change
with
the +/- level knob. It acts like a delay to the ADC which is not a
component but a complex group.
It could be a sluggish DAC U2101 sending to the sequencer via U2530 and U
2630 but I can't understand how (Analog Control tab 2). I am about to
'scope them. It is interesting that there is signs of work done around
the
DAC, perhaps a broken trace but it is difficult to tell hence 'scoping to
look for a suspicious signal to follow. It could be an address line
floating but I would expect more problems. They look clean. pins 19 & 18
look messy but they are current O/P so look at U2630 pins 3 and 12. The
voltage here does not follow the intensity pots but is delayed. It jumps
suddenly but is clean. Moving on......
Peter.

On Sun, Dec 1, 2019 at 3:35 PM Bob Koller via Groups.Io <testtech=
yahoo.com@groups.io> wrote:

On Sun, Dec 1, 2019 at 12:01 PM, peter bunge wrote:


"The symptoms are that changes in either of the intensity pots takes
several, and up to many (30 or more), seconds to respond either in
intensity on the screen, or voltages at the sequencer pins. Without
touching anything on the 'scope the 'trace turn off' counts down from
minutes, to 59 seconds, down to 2 seconds, then starts again at (8)
minutes
without shutting off the display. So that feature is not working. At
very
bright it did drop the intensity after 30 seconds but did not turn it
off
so it may be partly working. I remember it turned the displays off
until
a
knob was moved.
Delta v and delta t are erratic placing the dotted lines on the
screen,
and
dt sometime shows dv lines or nothing. And they have the same
sluggish
delay to doing anything."
This is interesting, do the Position controls exhibit similar laggy
behavior?

I have a 2465B control board that does something similar; all the
analog
controls are much slower to respond than a normally operating
instrument.
It passes self test, and works normally other that the very laggy and
jumpy response to control changes.







Join TekScopes@groups.io to automatically receive all group messages.