Date   
Re: SC503 storage mode

 

I've got a 434, a 577 D1 (bipolar storage) curve tracer, a 7623A and a 7633.
Forgot to mention a T912 I had and sold. Same story: Better and more even after adjustment.

Raymond

Re: SC503 storage mode

 

As regards bistables: I've got a 434, a 577 D1 (bipolar storage) curve tracer, a 7623A and a 7633. I remember playing with them a few years ago.

I just drew out my 434 (split screen bistable with enhanced mode), which has been dormant for about two years and I played with it a little. A few memories came back and I could verify the following:

After switch on, the collimation of the flood gun is wrong; the display background is uneven and blooms badly.
After a while, things become better; the screen becomes darker. After about 20 minutes, things stabllise and the system becomes usable.
I have seen the same with the other instruments in bistable mode after a long period of non-use.
The 7623A needed some adjustment but became pretty usable after that.

In my experience, storage systems benefited more from adjustments after years of not being used than other subsystems. Aging of the CRT seems to continue, even when not used. This also held for variable persistence systems, though to a lesser extent. Apart from the 'scopes already mentioned, I have checked and adjusted my 464's, 466 and 7834. Bistable is usable but gives the worst results in terms of image quality (and usefulness).

With all analog storage 'scopes, it is important to allow sufficient time for stabilisation and recovery. This is as important while calibrating/adjusting as it is after a longer period of non-use. Bistable is more finicky than the other modes.

Raymond

Re: 7000 Series Delayed Sweep Compatibility Question

 

I tested this some time ago and found that the 7B92A works fine as a
delayed timebase in conjunction with a 7B85 but just to be sure, I
tested it again in my 7904. Note that I only ran tests with the 7B85
set to runs after delay mode.

1. With the 7B92A operating as a single delayed timebase, everything
worked just like it should. The intensified zone was shown correctly
on the A sweep and the B sweep operated just like they should. Even
the 7B85 delta delayed mode worked correctly displayed two B sweeps.
The 7B92A operates just like a 7B80 in this configuration.

2. The 7B92A will not work correctly in dual timebase alternating mode
but there is a good reason for it. The mainframe does one A sweep and
then one B sweep but the 7B92A expects two B sweeps in a row so it can
alternate between its own delaying and delayed sweeps. This means it
will only display one of its sweeps depending on timing.

3. When the 7B92A is set to delayed sweep (time/div pulled out,
rotated, and then pushed in), then everything works but the 7B85 and
7B92A delay times add together.

On 26 Feb 2016 04:47:37 -0800, you wrote:

I'm testing a recently acquired 7B85 delaying sweep plug-in in a 7834 next to a 7B92A. A mismatched configuration, I know, since the 92A has self-contained delaying capability, but these are the only available sweep modules. With the 7B85 set for "start after delay" and horizontal mode set for "chop", I'm not seeing the intensified portion of the delaying module sweep - or the delayed and expanded sweep. Before I get into serious investigations, I just want to check that this configuration allows the 7B85 to control delay with the 7B92A. In searching both manuals, I see no reason to suspect incompatibility. Delayed sweep appears to work fine using the 92A alone.

It's also possible I'm missing something about the multiple switch settings between the two modules, so any suggestions would be appreciated.

Re: SC503 storage mode

 

On Fri, 26 Feb 2016 14:31:11 +0000, you wrote:

On 26 February 2016 at 13:29, @Raymond [TekScopes] <
TekScopes@...> wrote:

I'm not very familiar - nor do I particularly like - bistable storage
mode, which is the only mode that the SC503 knows, AFAIK.
I find it less intuitive than e.g. variable persistence mode.

From my limited experience with bistable mode, I'd say the CRT is OK,
except possibly the sharply defined dark center area, which isn't too
serious.
It's operator error and/or a matter of adjusting.

If you're unfamiliar with bistable mode: A stored image has a more or less
visible/bright background with a brighter trace. Contrast is less than in
variable persistence mode.
I understand that the background won't be dark, but this looks too bright.
Nothing I do makes any difference to the brightness.

Malcolm
It is definitely not working correctly:

1. The collimation from the storage flood gun is wrong. It should be
more even.

2. The non-storage intensity at slow sweep speeds is too low.

3. Storage appears to not be happening.

I suggest tracking down the 2nd problem first. At least one thing we
know that the problem is not is the PDA (post deflection acceleration)
because the SC503 does not have it; there is no high voltage
multiplier to worry about.

I assume you will need an extender to power the oscilloscope outside
of the power supply mainframe so as to have good access.

Re: SC503 storage mode

Malcolm Hunter
 

On 26 February 2016 at 13:29, @Raymond [TekScopes] <
TekScopes@...> wrote:

I'm not very familiar - nor do I particularly like - bistable storage
mode, which is the only mode that the SC503 knows, AFAIK.
I find it less intuitive than e.g. variable persistence mode.

From my limited experience with bistable mode, I'd say the CRT is OK,
except possibly the sharply defined dark center area, which isn't too
serious.
It's operator error and/or a matter of adjusting.

If you're unfamiliar with bistable mode: A stored image has a more or less
visible/bright background with a brighter trace. Contrast is less than in
variable persistence mode.
I understand that the background won't be dark, but this looks too bright.
Nothing I do makes any difference to the brightness.

Malcolm

Re: 468 sweep offset issue

 

David,
That 55 MHz bw is far too low; can you explain exactly how you are measuring it ?Is the Bw limit switch stuck on ?What vert sensitivity are you making the measurement on ?It should probably be done on the 5-10 mV position; no probe
The generator should be terminated in 50 ohms, at the scope end.
Are both ch the same ?What is the risetime measurement ? Should be 3.5 nS (10/90) on a 465.
 HankC, Boston WA1HOS

[Non-text portions of this message have been removed]

Re: SC503 storage mode

 

Wow, I thought the SC503 was variable persistence. In the words of
Adam Savage, "well, there's your problem!" Ignore what I said about
the view time control.

I am not familiar with how the SC503 should look in storage mode but
from your video, it appears that there are at least two problems; the
slow sweep speeds should be brighter and bistable storage mode is not
storing at all although that is difficult to tell from your video. In
bistable storage mode, the writing rate is low so you either have to
have a repeating trace to store or you need to use a slower sweep
speed when doing single sweeps which of course is not going to work
with the current brightness problem at slow sweeps. The CRT cathode
voltage is no doubt correct but I think the flood gun or storage
calibration is wrong indicating a circuit problem unless someone
misadjusted it.

Someone else with experience with the SC503 or even bistable storage
will have a better idea but I would start I would start by checking
the various power supply voltages and then working on the non-storage
intensity problem at slow sweep speeds.

I did not have any trouble with the link once I removed the question
mark at the end. Did Yahoo add that?

On Fri, 26 Feb 2016 09:02:19 +0000, you wrote:

?Here's a video of both issues, which I hope should explain them:

https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc?

Re: 468 sweep offset issue

 

On 25 Feb 2016 22:49:27 -0800, you wrote:

Well that didn't quite do it, but it definitely helped.

Now B sweep only "lags" A sweep by 0.5 minor divisions. It also ends the same amount before A sweep, where they were both ending at the same time. According to the measurements I took, the transistor-diode combinations were within 200uV of each other. The diode pair for A sweep is also within 200uV, as are Q760 and Q772.

At least I am learning something practical about this type of circuit and how it reacts to matched and unmatched PN junction drops and such. I forgot to check the resistors again, and will do that tomorrow after work.
I guess if what has to be done to get this aligned is to trim the A sweep start circuit, I'll do it and figure out how to make it look clean.. I'll have to buy the trimmer, though, so I might as well buy an entire set of them. For now, maybe there's one that will work from the 475 main board or trigger board that I have laying around.
Probably should check for any out of tolerance resistors and any other unmatched components from A to B sweep start/miller runup, etc.
It will be easiest to change one of the diodes and introduce a
deliberate mismatch to move the sweeps into alignment.

How close are the sweep output voltages when both are reset? The best
way to measure this is between the collectors of Q967 and Q998.

It now see another way to trim the sweep positions. R758 and R778+774
add a current into Q760 and Q772 which the sweep output voltages
subtract from. Trim the value of one of the resistors to move the
sweep slightly. A parallel resistance of about 300 kilohms will move
the trace one minor division.

Re: SC503 storage mode

 

I'm not very familiar - nor do I particularly like - bistable storage mode, which is the only mode that the SC503 knows, AFAIK.
I find it less intuitive than e.g. variable persistence mode.

From my limited experience with bistable mode, I'd say the CRT is OK, except possibly the sharply defined dark center area, which isn't too serious.
It's operator error and/or a matter of adjusting.

If you're unfamiliar with bistable mode: A stored image has a more or less visible/bright background with a brighter trace. Contrast is less than in variable persistence mode.

Raymond

Re: SC503 storage mode

 

Neither Raymond's or Malcom's worked for me.
The funny thing is that I saw Malcolm's correct link in my e-mail client. Neo adds the characters after Gdmc, which is why I recommended to "delete characters after Gdmc in the link".

Come to think of it: My first response describing this never arrived. It's my impression that things are *not* getting better with Neo.

Oh well...

Raymond

Re: SC503 storage mode

Mark Wendt
 

On 02/26/2016 08:11 AM, Malcolm Hunter malcolm.r.hunter@... [TekScopes] wrote:
On 26 February 2016 at 13:10, Mark wendt.mark@... [TekScopes] <
TekScopes@...> wrote:

On 02/26/2016 07:59 AM, linuxlout@... [TekScopes] wrote:
https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc
Now that one worked. Neither Raymond's or Malcom's worked for me.
​That's my other email account, which I use for the Yahoo group :)

Malcolm​
Cheeky. ;-)

Mark

Re: SC503 storage mode

Malcolm Hunter
 

On 26 February 2016 at 13:10, Mark wendt.mark@... [TekScopes] <
TekScopes@...> wrote:

On 02/26/2016 07:59 AM, linuxlout@... [TekScopes] wrote:
https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc
Now that one worked. Neither Raymond's or Malcom's worked for me.
​That's my other email account, which I use for the Yahoo group :)

Malcolm​


[Non-text portions of this message have been removed]

Re: SC503 storage mode

Mark Wendt
 

On 02/26/2016 07:59 AM, linuxlout@... [TekScopes] wrote:
https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc
Now that one worked. Neither Raymond's or Malcom's worked for me.

Mark

Re: SC503 storage mode

Malcolm Hunter
 

That seems to work (the first link).

On 26 February 2016 at 12:59, linuxlout@... [TekScopes] <
TekScopes@...> wrote:



https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc
https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc%e2%80%8b
Test

[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]

Re: SC503 storage mode

Malcolm Hunter
 

Re: SC503 storage mode

Malcolm Hunter
 

Another reason why people don't like Yahoo groups :(

On 26 February 2016 at 12:55, @Raymond [TekScopes] <
TekScopes@...> wrote:



Wow, Do I love Neo!

As I said in an earlier message, which is not coming through (yet), delete
all characters after Gdmc in the link.

Raymond




Re: SC503 storage mode

 

Wow, Do I love Neo!

As I said in an earlier message, which is not coming through (yet), delete all characters after Gdmc in the link.

Raymond

Re: SC503 storage mode

 

Re: SC503 storage mode

Malcolm Hunter
 

On 26 February 2016 at 12:33, Mark wendt.mark@... [TekScopes] <
TekScopes@...> wrote:

On 02/26/2016 04:02 AM, Malcolm Hunter malcolm.r.hunter@...
[TekScopes] wrote:
​Here's a video of both issues, which I hope should explain them:

https://drive.google.com/open?id=0B2-hICzIGrsSM0J1VUlOQ0pGdmc
Hi Malcolm,

Get a 404 Not Found clicking on that link.
​Strange. It works for me, even in an incognito Chrome window or using
Firefox.

Malcolm​

7000 Series Delayed Sweep Compatibility Question

gerickson@ameritech.net
 

I'm testing a recently acquired 7B85 delaying sweep plug-in in a 7834 next to a 7B92A. A mismatched configuration, I know, since the 92A has self-contained delaying capability, but these are the only available sweep modules. With the 7B85 set for "start after delay" and horizontal mode set for "chop", I'm not seeing the intensified portion of the delaying module sweep - or the delayed and expanded sweep. Before I get into serious investigations, I just want to check that this configuration allows the 7B85 to control delay with the 7B92A. In searching both manuals, I see no reason to suspect incompatibility. Delayed sweep appears to work fine using the 92A alone.

It's also possible I'm missing something about the multiple switch settings between the two modules, so any suggestions would be appreciated.