Topics

067-0912-00 needed


Eric
 

I am thinking about trying to tackle a calibration on my 7854. I have confirmed that the digital and analog sections are out of adjustment. The digital section is about .8 division left of center. In looking through the calibration document It seems I have everything I need to do the calibration except the 067-0912-00 the analog test board. How likely is this something that I am going to be able to acquire it does not look too complex from the schematic just a few IC’s and a data bus.


 

Hi Eric,
I can't help with a schematic, but there is some information on this card on TekWiki at
http://w140.com/tekwiki/wiki/067-0912-00
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Wednesday, October 21, 2020 8:55 AM
To: TekScopes@groups.io
Subject: [TekScopes] 067-0912-00 needed

I am thinking about trying to tackle a calibration on my 7854. I have confirmed that the digital and analog sections are out of adjustment. The digital section is about .8 division left of center. In looking through the calibration document It seems I have everything I need to do the calibration except the 067-0912-00 the analog test board. How likely is this something that I am going to be able to acquire it does not look too complex from the schematic just a few IC’s and a data bus.







--
Dennis Tillman W7pF
TekScopes Moderator


Dave Daniel
 

A schematic for the -00 version of the board is in the datasheet link on the TekWiki page to which Dennis pointed.

DaveD

On Oct 21, 2020, at 13:45, Dennis Tillman W7pF <@Dennis_Tillman_W7pF> wrote:

Hi Eric,
I can't help with a schematic, but there is some information on this card on TekWiki at
http://w140.com/tekwiki/wiki/067-0912-00
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Wednesday, October 21, 2020 8:55 AM
To: TekScopes@groups.io
Subject: [TekScopes] 067-0912-00 needed

I am thinking about trying to tackle a calibration on my 7854. I have confirmed that the digital and analog sections are out of adjustment. The digital section is about .8 division left of center. In looking through the calibration document It seems I have everything I need to do the calibration except the 067-0912-00 the analog test board. How likely is this something that I am going to be able to acquire it does not look too complex from the schematic just a few IC’s and a data bus.







--
Dennis Tillman W7pF
TekScopes Moderator





Clark Foley
 

Dennis,

Did you ever make duplicates of that early 7804N conversion board (K7-1286-XA)?

Clark


Dave Casey
 

That schematic has some curious idiosyncrasies. The logic is powered by
+5VD, but all the pull ups being used are to +5V. (The ones that are shown,
anyway; there are unused inputs on U420 and U520 that must also be pulled
high for the board to work, but these aren't indicated in the schematic.)
Also, the inputs from the mode switches on A2 are referenced to +5V (not
+5VD). +5V and +5VD are basically two copies of the same supply, powered
from the same output of the switcher, and their domains cross in a few
places within the scope without any real decoupling. That spirit continues
in the 067-0912-00 board.

The parts list and schematic do not appear to line up 1:1 (C621 on the
schematic is very probably C620 on the parts list, but R520 is in the parts
list and so far escapes detection on the schematic.

Another interesting observation is that the _FPR ("Front Panel Read",
active low) signal is left floating when using the 067-0912-00, meaning
that A2U61 and A2U62 are not guaranteed to be tri-stated and could be
fighting U430 and U530 of the 067-0912-00 for D0:D8. I'm sort of surprised
there's no pull-up on the A2 board, but the schematic shows that signal
being driven directly by the MPU board (which would be absent when using
the 067-0912-00).

Enough mysteries for tonight...


Dave Casey

On Wed, Oct 21, 2020 at 1:12 PM Dave Daniel <kc0wjn@...> wrote:

A schematic for the -00 version of the board is in the datasheet link on
the TekWiki page to which Dennis pointed.

DaveD


On Oct 21, 2020, at 13:45, Dennis Tillman W7pF <@Dennis_Tillman_W7pF>
wrote:

Hi Eric,
I can't help with a schematic, but there is some information on this
card on TekWiki at
http://w140.com/tekwiki/wiki/067-0912-00
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Eric
Sent: Wednesday, October 21, 2020 8:55 AM
To: TekScopes@groups.io
Subject: [TekScopes] 067-0912-00 needed

I am thinking about trying to tackle a calibration on my 7854. I have
confirmed that the digital and analog sections are out of adjustment. The
digital section is about .8 division left of center. In looking through the
calibration document It seems I have everything I need to do the
calibration except the 067-0912-00 the analog test board. How likely is
this something that I am going to be able to acquire it does not look too
complex from the schematic just a few IC’s and a data bus.







--
Dennis Tillman W7pF
TekScopes Moderator









Eric
 

Dave,

The board is weird. My understanding of this is all this board does is allow you to check the lights “I know mine are ok” and it passes analog signals to the tube amplifiers so you can calibrate the analog portions of the scope with out any of the digital circuits being installed.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dave Casey
Sent: Thursday, October 22, 2020 4:48 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 067-0912-00 needed

That schematic has some curious idiosyncrasies. The logic is powered by
+5VD, but all the pull ups being used are to +5V. (The ones that are
+shown,
anyway; there are unused inputs on U420 and U520 that must also be pulled high for the board to work, but these aren't indicated in the schematic.) Also, the inputs from the mode switches on A2 are referenced to +5V (not
+5VD). +5V and +5VD are basically two copies of the same supply, powered
from the same output of the switcher, and their domains cross in a few places within the scope without any real decoupling. That spirit continues in the 067-0912-00 board.

The parts list and schematic do not appear to line up 1:1 (C621 on the schematic is very probably C620 on the parts list, but R520 is in the parts list and so far escapes detection on the schematic.

Another interesting observation is that the _FPR ("Front Panel Read", active low) signal is left floating when using the 067-0912-00, meaning that A2U61 and A2U62 are not guaranteed to be tri-stated and could be fighting U430 and U530 of the 067-0912-00 for D0:D8. I'm sort of surprised there's no pull-up on the A2 board, but the schematic shows that signal being driven directly by the MPU board (which would be absent when using the 067-0912-00).

Enough mysteries for tonight...


Dave Casey


On Wed, Oct 21, 2020 at 1:12 PM Dave Daniel <kc0wjn@...> wrote:

A schematic for the -00 version of the board is in the datasheet link
on the TekWiki page to which Dennis pointed.

DaveD


On Oct 21, 2020, at 13:45, Dennis Tillman W7pF <@Dennis_Tillman_W7pF>
wrote:

Hi Eric,
I can't help with a schematic, but there is some information on this
card on TekWiki at
http://w140.com/tekwiki/wiki/067-0912-00
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Eric
Sent: Wednesday, October 21, 2020 8:55 AM
To: TekScopes@groups.io
Subject: [TekScopes] 067-0912-00 needed

I am thinking about trying to tackle a calibration on my 7854. I
have
confirmed that the digital and analog sections are out of adjustment.
The digital section is about .8 division left of center. In looking
through the calibration document It seems I have everything I need to
do the calibration except the 067-0912-00 the analog test board. How
likely is this something that I am going to be able to acquire it does
not look too complex from the schematic just a few IC’s and a data bus.







--
Dennis Tillman W7pF
TekScopes Moderator









Dave Casey
 

For sure it's a weird board, but there's one more thing it does besides
letting you test the lamps and control the analog portion of the scope
without the processor. Item 4 in the list of "other analog test functions"
indicates it can be used in calibrating the vertical channel switch in
conjunction with a 067-0587 mainframe calibrator. For that, it just
provides a simple buffer amplifier for the pretrigger signal from the
067-0587 to convert it to TTL. It also has a few terminations for analog
signals that normally connect to the digital section so they don't
negatively impact the calibration process.
It looks like it will be a pretty simple board to build; my planned
approach is to build the functional parts of the board in two small pieces
which will then mount in a larger FR-4 or plastic frame for installation
into the scope. This will keep the board fab cost down.
The +5V vs +5VD discrepancy is probably moot. The engineer in me wants to
use the same rail for everything, but there's probably no real harm in
splitting them the way Tek seems to have.
The missing pull up on _FPR is the only hanging chad I find truly irksome.
Only the MPU and RAM boards even have a chance to touch that signal, and
only the MPU board actually does. For whatever reason, it wasn't important
enough to include on the A2J9 test connector. Perhaps there's a tendency of
the PNP inputs of the 81LS series to float high? I couldn't find a circuit
diagram for a device in the series to investigate further.

Dave Casey

On Thu, Oct 22, 2020 at 9:09 AM Eric <ericsp@...> wrote:

Dave,

The board is weird. My understanding of this is all this board does is
allow you to check the lights “I know mine are ok” and it passes analog
signals to the tube amplifiers so you can calibrate the analog portions of
the scope with out any of the digital circuits being installed.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dave Casey
Sent: Thursday, October 22, 2020 4:48 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 067-0912-00 needed

That schematic has some curious idiosyncrasies. The logic is powered by
+5VD, but all the pull ups being used are to +5V. (The ones that are
+shown,
anyway; there are unused inputs on U420 and U520 that must also be pulled
high for the board to work, but these aren't indicated in the schematic.)
Also, the inputs from the mode switches on A2 are referenced to +5V (not
+5VD). +5V and +5VD are basically two copies of the same supply, powered
from the same output of the switcher, and their domains cross in a few
places within the scope without any real decoupling. That spirit continues
in the 067-0912-00 board.

The parts list and schematic do not appear to line up 1:1 (C621 on the
schematic is very probably C620 on the parts list, but R520 is in the parts
list and so far escapes detection on the schematic.

Another interesting observation is that the _FPR ("Front Panel Read",
active low) signal is left floating when using the 067-0912-00, meaning
that A2U61 and A2U62 are not guaranteed to be tri-stated and could be
fighting U430 and U530 of the 067-0912-00 for D0:D8. I'm sort of surprised
there's no pull-up on the A2 board, but the schematic shows that signal
being driven directly by the MPU board (which would be absent when using
the 067-0912-00).

Enough mysteries for tonight...


Dave Casey


On Wed, Oct 21, 2020 at 1:12 PM Dave Daniel <kc0wjn@...> wrote:

A schematic for the -00 version of the board is in the datasheet link
on the TekWiki page to which Dennis pointed.

DaveD


On Oct 21, 2020, at 13:45, Dennis Tillman W7pF <@Dennis_Tillman_W7pF>
wrote:

Hi Eric,
I can't help with a schematic, but there is some information on this
card on TekWiki at
http://w140.com/tekwiki/wiki/067-0912-00
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Eric
Sent: Wednesday, October 21, 2020 8:55 AM
To: TekScopes@groups.io
Subject: [TekScopes] 067-0912-00 needed

I am thinking about trying to tackle a calibration on my 7854. I
have
confirmed that the digital and analog sections are out of adjustment.
The digital section is about .8 division left of center. In looking
through the calibration document It seems I have everything I need to
do the calibration except the 067-0912-00 the analog test board. How
likely is this something that I am going to be able to acquire it does
not look too complex from the schematic just a few IC’s and a data bus.







--
Dennis Tillman W7pF
TekScopes Moderator