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7104 readout issue


Sean Turner
 

I feel like this has been discussed before, but I cannot find the thread now. Does anyone know of a solution for the 7104 readout not displaying except in "pulsed" mode when slaved to the gate (also works in manual)? Mine started doing this, and I have found very little information about it on the internet.

Thanks!

Sean


Chuck Harris <cfharris@...>
 

Most 7000 series scopes that have readout seem to have a little
switch on the readout board that selects whether the readout
is sharing the display with the traces, or has its own time
slot after the sweep is finished.

Perhaps your switch has become intermittent?

-Chuck Harris

sdturne@q.com wrote:

I feel like this has been discussed before, but I cannot find the thread now. Does anyone know of a solution for the 7104 readout not displaying except in "pulsed" mode when slaved to the gate (also works in manual)? Mine started doing this, and I have found very little information about it on the internet.

Thanks!

Sean






Sean Turner
 

Chuck,

Good call; I should open it up and take a look. I'm not sure where the readout board even is on a 7104...the internal layout is *vastly* different compared to the 7904(a)!

Sean

On Sun, Jan 31, 2021 at 01:30 PM, Chuck Harris wrote:


Most 7000 series scopes that have readout seem to have a little
switch on the readout board that selects whether the readout
is sharing the display with the traces, or has its own time
slot after the sweep is finished.

Perhaps your switch has become intermittent?

-Chuck Harris


Sean Turner
 

Chuck,

Looks like mine has a more modern readout board, that contains no switch. It has a large socketed ROM where the switch would be in an older style readout system...the plot thickens...

Sean

On Sun, Jan 31, 2021 at 01:30 PM, Chuck Harris wrote:


Most 7000 series scopes that have readout seem to have a little
switch on the readout board that selects whether the readout
is sharing the display with the traces, or has its own time
slot after the sweep is finished.

Perhaps your switch has become intermittent?

-Chuck Harris


Chuck Harris <cfharris@...>
 

Hi Sean,

I remember now. My 7104 spends most of its time, all dressed
up, with no place to go... So, it is not one of the scopes that
I am most familiar with.

If you look on the front panel, you will see an outlined area that
has two intensity pots (A and B), a READOUT intensity pot, and two
push buttons for the readout.

The one button is marked +GATE or OFF, and sets the readout to be on
at the end of the GATE signal, or off. The other push button is
marked "MAN", which causes the readout to be on always.

Something there is probably in the wrong position, or misbehaving.

Also, I keep my plugins off of AUTO on my 7104. Because of the
MCP's limited life, you do not want to be wasting it with continuous
readout display, or baseline display. I keep my readout in "GATE"
mode, so it is off if the sweep isn't being triggered.

Typically, I also keep the A and B intensity turned off when the
scope is off, to avoid intensity flair during turn on.

-Chuck Harris

sdturne@q.com wrote:

Chuck,

Looks like mine has a more modern readout board, that contains no switch. It has a large socketed ROM where the switch would be in an older style readout system...the plot thickens...

Sean

On Sun, Jan 31, 2021 at 01:30 PM, Chuck Harris wrote:


Most 7000 series scopes that have readout seem to have a little
switch on the readout board that selects whether the readout
is sharing the display with the traces, or has its own time
slot after the sweep is finished.

Perhaps your switch has become intermittent?

-Chuck Harris





 

Said switch is on the front panel of the 7104 - turn the readout pot fully clockwise into the detent at the end (PULSED position). To quote page 2-10 of the manual:

The READOUT control determines the operating mode of
the Readout System. With the READOUT control set to
free run (out of OFF or PULSED detent positions) the
Readout System operates continuously, interrupting the
crt display at random (for about 20 microseconds) in
order to write each character on the crt. With the
READOUT control set to the PULSED position, the
Readout System operates in a triggered mode; one
complete frame (up to eight words) of readout is
displayed. The + GATE or EXT switch determines
whether readout is displayed at the end of the + GATE
or when an external signal is applied to the rear-panel
GRATICULE/READOUT SINGLE SHOT input. The+ GATE
switch selects whether A gate or B gate triggers the
readout.

HtH
David


Sean Turner
 

Chuck,

All good advice. Personally, I guess the readouts really aren't that critical. I get used to not having any when using older scopes like my 585A!

Maybe I'll just not worry about beyond checking for obvious problems (dirty or stuck switch contacts, for instance).

Sean

On Sun, Jan 31, 2021 at 04:07 PM, Chuck Harris wrote:


Hi Sean,

I remember now. My 7104 spends most of its time, all dressed
up, with no place to go... So, it is not one of the scopes that
I am most familiar with.

If you look on the front panel, you will see an outlined area that
has two intensity pots (A and B), a READOUT intensity pot, and two
push buttons for the readout.

The one button is marked +GATE or OFF, and sets the readout to be on
at the end of the GATE signal, or off. The other push button is
marked "MAN", which causes the readout to be on always.

Something there is probably in the wrong position, or misbehaving.

Also, I keep my plugins off of AUTO on my 7104. Because of the
MCP's limited life, you do not want to be wasting it with continuous
readout display, or baseline display. I keep my readout in "GATE"
mode, so it is off if the sweep isn't being triggered.

Typically, I also keep the A and B intensity turned off when the
scope is off, to avoid intensity flair during turn on.

-Chuck Harris


Steven Bender
 

Sean,

A friend of mine found a burned resistor and bad TO-5 metal can transistor on the Readout Board in a military version of the 7603. The R was 3.9k, the TO-5 can something like a 2n2905 or 2n3440 with an OEM number. Maybe examine / check for those parts, if that transistor loses beta over time, it may overheat the R, then self destruct causing a loss of display.

Steven