开云体育

12/07/2012 23:23

My new old stock 7633 has on screen graphics that look like they are
hand drawn, and have never been incredibly sharp. I have seen an ad on
a well known internet auction site for a 7704A showing some screen
shots. the on scren graphics are far sharper and in a totally
different font. Why are the two models of scope displaying such
different on screen graphics please? I have put the shot taken from
the 7704A ad and from my own 7633 on my web site as:

7704A



and my scope



Thanks.

--
Best Regards,
Chris Wilson.
mailto: chris@...

Chris Wilson <chris@...> wrote:

e.com???

You messed up the second link, but anyway, it's because the 7633 has a
storage tube.

--- In TekScopes@..., Chris Wilson <chris@...> wrote:

12/07/2012 23:23

My new old stock 7633 has on screen graphics that look like they are
hand drawn, and have never been incredibly sharp. I have seen an ad on
a well known internet auction site for a 7704A showing some screen
shots. the on scren graphics are far sharper and in a totally
different font. Why are the two models of scope displaying such
different on screen graphics please? I have put the shot taken from
the 7704A ad and from my own 7633 on my web site as:

7704A



and my scope



Thanks.

--
Best Regards,
Chris Wilson.
mailto: chris@...

and



Sorry for broken link, and thanks for the reply

The 7633 is normal 7K R/O, looks like the astig may be a bit off.
The 7704A doesn't look like the one I have, nor the one I had as
a bench scope in my Tek days. More like a 7854 than 7K R/O.
-ls-


David DiGiacomo <daviddigiacomo@...> wrote:

The 7633 shown does look like a storage mode is on. The one I have is a bit
sharper, etc. in non-storage mode about the same in storage mode/s.

That said, the storage capable scopes in general (7633 and 7844) are not as
sharp on the readout functions as the non-storage counter parts.

(they are however for sure better than yours...except again in storage
mode/s..... not sure what to make of that)
Hopefully somewhat helpful.
Rob

Looks like the astigmatism needs adjusting on the 7633

Dave

The readout font on my 7623B and 7934 oscilloscopes looks nearly identical to that of the 7704A. The 7623B and the 7934 use a newer design of the readout board that generates the characters using a single custom ROM IC instead of the several different custom ICs used on the earlier board. With the exception of my 7854, all of my other 7000 series oscilloscopes have a readout font that looks similiar, but much sharper to that of the 7633. I believe that all of the very late production scopes had the newer readout board installed, but I can't confirm that.

Brian Henry

13/07/2012 11:27

Is the astigmatism adjustment internal on these David? If I look
closely it almost appears to be trying to show two numerals / letters
at the same time, possibly the figure 1 (one)? As it's otherwise 100%
and new old stock I'd quite like to get this facet of its operation
fixed. Thanks.

--
Best Regards,
Chris Wilson.
mailto: chris@...

--- In TekScopes@..., "Brian J. Henry" <bhenry@...> wrote:

The readout font on my 7623B and 7934 oscilloscopes looks nearly identical to that of the 7704A. The 7623B and the 7934 use a newer design of the readout board that generates the characters using a single custom ROM IC instead of the several different custom ICs used on the earlier board. With the exception of my 7854, all of my other 7000 series oscilloscopes have a readout font that looks similiar, but much sharper to that of the 7633. I believe that all of the very late production scopes had the newer readout board installed, but I can't confirm that.

Brian Henry

Brian, thanks for the reply, would you know if the later board is retro fittable to my earlier scope? Thanks.

Chris Wilson wrote:

Would you know if the later board is retro fittable to my earlier scope?

I believe that it would be if you can get your hands on one.

The astigmatism adjustment is internal on the Z-Axis board (pages 5-35
and 5-36 in the service manual) and there are two adjustments: One is
for full scan operation and the other is for reduced scan operation.

There is also a character scan adjustment (page 5-53 in the service
manual) on the readout board which control character overscan. I
would fiddle with that first. The "m" and any character with a closed
loop make good calibration targets.

If there are issues with the characters wiggling as the trace position
changes, then vertical thermal balance and horizontal transient
response calibration may help.

The diagrams showing the locations of the internal adjustments are at
the end of section 8 in the service manual.

After calibration, my 7834 readout was sharper than my 7603 with the
worn CRT and not significantly worse than my 7905.

On Fri, 13 Jul 2012 11:30:34 +0100, Chris Wilson
<chris@...> wrote:

13/07/2012 11:27

Is the astigmatism adjustment internal on these David? If I look
closely it almost appears to be trying to show two numerals / letters
at the same time, possibly the figure 1 (one)? As it's otherwise 100%
and new old stock I'd quite like to get this facet of its operation
fixed. Thanks.

HI CHRIS,
I would do the astig and refocus….astig…and refocus for sharpest beam definition. use the calibrator and adjust for best looking sq wave…then kill the vert deflection and the horz deflection…turn the intensity down and adjust both again for the sharpest spot….increase the intensity and readjust both again…then go back to normal sweep…….

NOW DO THE CAL procedure on the display bd.

there are a couple of adjustments on the bd that will straighten out the "jumpy double" characters.
won't take much time but will make a big difference.
if i remember right these characters were created by different currents at different times… so a little too much or too little current misshaped the characters.
i often find the right controls, then adjust them by eye for best display, by finding the sweet spot of the adjustment. i.e. find the ends of the range where the adjustment makes a total mess with the adjustment one way then going back thru the best look…until you get a mess again……...then splitting the difference.
jim

Astigmatism adjustments are on the Z-Axis board (inside, on top of the HT box). You see four pots in a square together. All locations based on looking at the PCB from the right hand side of the scope. The right hand two as you face the board from the side of the 'scope are the astigmatism adjustments - the rear one for full scan, the front one for reduced scan.


Regards,
David Partridge

When Barrie Gilbert came up with his brilliant idea for the on-screen
readout system for the 7000 series the idea came to him from earlier
experiments he had done using conductive paper called Teledidos paper (I'm
not sure of the spelling). By changing the shape of the paper cutouts he was
able to create a series of X and Y currents that traced out letters,
numbers, symbols (and just about any shape) on the screen. They had a
definite hand drawn quality to them which I came to personally love because
it was such a brilliant concept and elegantly executed with the ICs he
designed to make it possible. Obviously it was a huge success. So Tek
invested in simpler digital follow-on readout circuits to generate
characters from ROMs as digital circuit capabilities improved but each time
I see the earlier symbols they remind me of how far we have come. Their
awkward appearance has a humble charm not shared by the computer generated
characters. Barrie was not interested in digital circuits. He went on to
invent many more analog circuits while at Tek that change our lives
including the Current Gain Cell and the Gilbert Four Quadrant Multiplier.

Dennis Tillman

16/07/2012 21:06

Thanks for the replies re this issue. Whilst I agree the "hand drawn"
quality is somewhat charming my old eyesight isn't what it was and I
have to peer at the screen to work them out sometimes. I am convinced
there's now something not quite right about this. The numerals /
letters also waver very slightly, but only horizontally. I have been
offered the display board from a breaker 7704A, is it safe to plug it
in and see what happens, or is it not that simple? Thanks gentlemen!

--
Best Regards,
Chris Wilson.
mailto: chris@...

--- In TekScopes@..., Jim Popwell Jr <jpopwell@...> wrote:

HI CHRIS,
I would do the astig and refocus….astig…and refocus for sharpest beam definition. use the calibrator and adjust for best looking sq wave…then kill the vert deflection and the horz deflection…turn the intensity down and adjust both again for the sharpest spot….increase the intensity and readjust both again…then go back to normal sweep…….

NOW DO THE CAL procedure on the display bd.

there are a couple of adjustments on the bd that will straighten out the "jumpy double" characters.
won't take much time but will make a big difference.
if i remember right these characters were created by different currents at different times… so a little too much or too little current misshaped the characters.
i often find the right controls, then adjust them by eye for best display, by finding the sweet spot of the adjustment. i.e. find the ends of the range where the adjustment makes a total mess with the adjustment one way then going back thru the best look…until you get a mess again……...then splitting the difference.
jim

I don't feel 100% confident fiddling with it that deeply, to be honest Jim. if it was an old nail, no worries, but with it being brand new old stock I would rather pay someone that knows what they are doing to have a look, or to just try another display board. I'd kick myself if I @#~%$*@ it up ;) I know it's not worth a lot, but it's kind of nice being "new", I doubt I'd find another very easily. Thanks for the detailed reply Jim.

Chris - where do you live - I'm happy for you to visit me in Kenilworth, Warwickshire with the scope if you are unhappy to fiddle with it yourself.

Regards,
David Partridge

I haven't followed the thread but several years ago I was working on a 7704A
that had characters that weren't stable vertically. There?were adjustments on
the backplane / vertical interface board (I don't remember?what they were
called) that ended up fixing the problem. They were a pain to get to and someone
on the list suggested it several times before I finally?tweaked?them. I had
spent several hours?trying board?swaps and other things with no success and the
adjustment?removed all the jitter and gave me a solid display.
?Jim W4JBM



"With a soldering iron in one hand, a schematic in the other, and a puzzled look
on his face..."