Date   

Re: 485 super weak brightness control

Ondrej Pavelka
 

On Thu, 18 Mar 2021, 17:02 Ozan, <ozan_g@erdogan.us> wrote:


Now I have nice sharp trace and working intensity control!
Good progress.

Horizontal A sweep
The 5 2 and 1nS settings are not working at all.
485 uses B sweep generator for 5/2/1ns settings even in A sweep setting.
Since you are seeing functional 5/2/1ns in B sweep it is a problem of scope
not selecting B sweep in 5/2/1ns settings as it should. In those settings
do you see B sweep ramp (while you are in A sweep setting on the knob) at
collector of Q1236 of sheet <9>? What is the voltage at pin N1 sheet <12>
when you are in 5/2/1ns settings (0.6V expected) vs above 5ns setting
(-0.5V expected)?
This is flipping correctly between -06 and +05

I noticed when I move the picture all the way to the left in 521 mode there
is something on the screen but it's all crooked


I don't get any B sweep from 5s to 20ms then I get good B sweep for 10mS
to
0.2uS
0.1uS to 10nS is showing only first 4 divisions from the left
Probably next step of debug.

5 2 and 1 ns is working correctly.
See above. A sweep uses B sweep generator for 5/2/1ns.

Power supply fan.

Is quite picky, it sometimes runs and sometimes it does not.
Siggi's link is great. The other thing to check is if you give it a gentle
push if it starts rotating. The fan speed is temperature controlled, C1482
looks like it is placed there to give an initial kick. You may want to
replace C1482 to see if it makes any difference.

Ozan







Re: 485 super weak brightness control

Ondrej Pavelka
 

On Thu, 18 Mar 2021, 20:47 Ozan, <ozan_g@erdogan.us> wrote:


I think we are in a different time zone, I always get the messages as
soon
as a leave the workshop and go home.
I am close to San Francisco, California (more precisely in Silicon Valley
area).

I'm not sure if it's important observation but all the horizontal
calibration is miles out. When I have say both A and B set to 10uS A is
roughly 50% out and B is totally out by 300 or 400%
Just to make sure: Is variable setting of time/div in "cal" position? You
may want to exercise it few times to make sure switch is good.

I think you measured +50V and it was good. Timing uses +50V for its
current sources so it should be accurate and low ripple.
50 is beautiful with 2mV of ripple



These settings use different timing caps:
How much is A/B off in 0.1us to 1ns (I know only B side works 5/2/1ns)
and are all the speeds about same percentage off?
How much is A/B off in 0.2us to 10us and are all the speeds about same
percentage off?
How much is A/B off 20us to 1ms, and are all the speeds about same
percentage off?
How much is A/B off in 2ms and slower speeds, and are all the speeds about
same percentage off?

Are the sweeps linear, if you apply a sine wave does it cross horizontal
axis uniformly?
Nice and linear


Ozan










Re: 485 super weak brightness control

Ondrej Pavelka
 

Ok better observations

A sweep is actually spot on time wise

B sweep in the positions 10uS to 0.2uS is showing it 10x wrong

So 100nS is shown as 1uS

In positions 0.1uS to 10nS it displays correct timing but it doesn't
display it across whole screen. What is displayed is displayed correctly in
the right half of the screen but left half has super faint few pulses as if
they were compressed but they are barely visible

On Thu, 18 Mar 2021, 21:45 Ozan, <ozan_g@erdogan.us> wrote:


I'm in Prague, Czech Republic, Central Europe
Couple of years back I was planning to go to Prague during an Europe trip
but timing didn't work out. Hopefully soon when travel is safe again.

Since our timings are off here are more considerations while you are on
the scope:

Relays K879 and K1242 are on a socket and easy to pull if you are careful.
While putting back pins has to align so that they don't bend. Although I
expect timing to be much worse if they are bad, they are easy to test.
However, the main reason for removing is you can test the timing caps
easily once they are out. If you forget to mark the orientation (like I
did) pinout is 180-degree symmetric as far as I remember.

With the relays out you can test the timing capacitors C1405 and C1404 at
G3/G5 terminals (and equivalent on B side). Just turn the time/div knob to
close the proper switch. Also measure the resistance from each leg to
ground. Although figure shows a floating cap in reality they are caps with
three legs, the outer leg is a shield and connected to ground. On my 485
there was a short between one of the terminals and outer shield (ground).

You can also observe A sweep out at the BNC for linearity.
Ozan








Re: Alert for 519 owners - The significance of the Gold GR Connectors

 

Another lot of 125 ohm connectors on ebay: 333925686202


Re: How to troubleshoot a faulty 7B92A?

Dan G
 

On Thu, Mar 18, 2021 at 07:03 PM, Thierry Delaitre wrote:

The jumper for mainframe selector is on P835 for "other 7000"
This should be correct for your scope. P834/P835 affect the hold-off
timing at fast sweep rates: approximately 1.2 us when set to "7800/7900",
and 2.2 us when set to "other".

I am not sure if the jumper for time/div variable selector should be on P760
(delayed) or P761 (delaying) for the 7704A ?
The choice of delayed or delaying variable selector is unrelated to the mainframe.
I think most users keep this in the "delayed" position so that the variable
control is available in "normal" mode (i.e. when the delaying and delayed
selectors are locked together).

There is nothing showing on the screen when pressing the beam finder button

When the 7B92A module is inserted into the scope, the trace displayed by the
other timebase is vibrating a bit and it can be observed that the position of
the readout is different for the other timebase/input.

Do you have any recommendations on the approach for troubleshooting a 7B92A?
When the time base plug-in is operated in a horizontal slot, the "sweep gate"
signal, the differential positive-going ramp signal, and a host of other control
signals all have to be ok in order to produce a useful display.

If you are reasonably confident that the 7B92A isn't putting out signals that are
so far out that they may damage whatever mainframe slot you plug it into, then
I would suggest the following tests:

- Install the 7B92A in the Left Vertical slot.
- Set the 7B92A to NORM, AC, INT triggering.
- Lock the delaying and delayed selectors on the 7B92A together and
set them to 1 ms/div.
- Install your other (working) time base in a horizontal slot, and set it to
1 ms/div, AUTO, AC, INT triggering.

With this setup, you should be able to get a horizontal line on the screen,
whose vertical position can be set by 7B92A's POSITION control.
(You will need to move it towards the clock-wise end of the range in
order to get the line on the screen.)

If no setting of 7B92A's POSITION will give you a visible trace, then
push the BEAM FINDER to see where it is.

If you do see a trace that you can control with 7B92A's POSITION, then
change the 7B92A triggering to AUTO. Now you should see
diagonal lines on the screen.

The steps described above will tell us whether the 7B92A is able
to drive the differential output signal at all, and will side-step any
potential problems with the Sweep Gate and other control signals.


dan


Re: Alert for 519 owners - The significance of the Gold GR Connectors

Sean Turner
 

S/N 1282 here, has gold plated connectors on the front panel.

Sean


Re: How to troubleshoot a faulty 7B92A?

Harvey White
 

Replies interleaved:


On 3/18/2021 7:03 PM, Thierry Delaitre via groups.io wrote:
Hello

I have a faulty 7B92A that I would like to repair

I have a 7704A as a scope
OK, a little fast for the 7704A but that only shows up on the fastest sweeps.
The jumper for mainframe selector is on P835 for "other 7000"
I think that's right, the other setting may be for a 7854, which makes a difference.  I think it may end up changing where the illumination power comes from.

I am not sure if the jumper for time/div variable selector should be on P760 (delayed) or P761 (delaying) for the 7704A ?
Either is valid.  It depends on how you decided to use it.  You'll get different behaviors, of course.

There is nothing showing on the screen when pressing the beam finder button
And I'll assume that the beam finder works properly with another horizontal plugin.  So it's not the switch.

When the 7B92A module is inserted into the scope, the trace displayed by the other timebase is vibrating a bit and it can be observed that the position of the readout is different for the other timebase/input.
What I'd suspect is that the output of the plugin is out of scope (!), that is, is going between  extremes at the horizontal input stage.  In other words, the plugin is driving the horizontal input of the mainframe badly.


Do you have any recommendations on the approach for troubleshooting a 7B92A?
Check the power supplies first, in case there's too much loading from a bad capacitor.

Look at the output to the scope, it ought to be wrong.

Crosstalk from H to V and between the H channels can happen with the trace deflected off the screen.  A symptom is that you may see the displays (and other trace) wiggle when the 7B92A sweep triggers.  The rate of "wiggle" may vary with the sweep settings.

I'd suspect all of the outputs from the plugin until I have verified that they work.

Harvey



Thanks

Thierry





Re: [HOswap on IO] FS: Panavise vise with circuit board adapter!

Richard R. Pope
 

Hello all,
The Panavise is sold. I appreciate the interest!
GOD Bless and Thanks,
rich!

On 3/18/2021 3:41 PM, Richard R. Pope wrote:
Hello all,
As you all know by now I probably have cancer and I am selling off my possessions to finance my travels around the country. I have for sale one Panavise vise with nylon jaws and a large circuit board holder adapter. $100 plus shipping. Please reply off list. I live in Reedsburg, WI 53959. I prefer Paypal F&F. If you use G&S please add the 4.5% handling fee. Will accept MO, Cashiers Check, and Personal Check (must clear before shipping)!
GOD Bless and Thanks,
rich!




How to troubleshoot a faulty 7B92A?

Thierry Delaitre
 

Hello

I have a faulty 7B92A that I would like to repair

I have a 7704A as a scope

The jumper for mainframe selector is on P835 for "other 7000"

I am not sure if the jumper for time/div variable selector should be on P760 (delayed) or P761 (delaying) for the 7704A ?

There is nothing showing on the screen when pressing the beam finder button

When the 7B92A module is inserted into the scope, the trace displayed by the other timebase is vibrating a bit and it can be observed that the position of the readout is different for the other timebase/input.

Do you have any recommendations on the approach for troubleshooting a 7B92A?

Thanks

Thierry


Re: Type 106

 

On Thu, Mar 18, 2021 at 11:10 PM, Eric wrote:


Teminated in to 50 Ohms
Rise time - 9.2ns
P-P voltage - 13.0 V

Unterminated
Rise time - 350ns
p-p Voltage 72.8 Maxes out Rigol scope
Re. into 50 Ohm:
Be careful not to exceed the 'scope's maximum input on 50 Ohm.
It's not so much the rise time that your Rigol shows, it's the quality of the square wave that makes it useful, especially a flat top and no more than around 5% percent over- and undershoot, otherwise you could use a triggered Jim Williams pulser just as well.

Re. Unterminated:
The maximum safe input voltage of 'scopes is dependent on the input frequency. Check your 'scope's specs. Of course, if you use a 10x probe, it's not as risky.

Raymond


TDS 520A 'parts only'

 

Hi all,
Just acquired via Ebay. Front panel dirty; no fuses blown; one 10 ohm NTC current limiter and two voltage limiting diodes in the PSU needed replacing, also a handful of SMD electrolytics on three panels were around 6 ohms ESR. Replaced with 10u 50V and 47u 16 to 35V standard electrolytics from parts bin.
Finally switched on: result ALL checks passed and nice clear display!
Now all I need is a 500Mhz input connector.


Re: Type 106

Eric
 

I made some measurements on mine I used a crappy cable on purpose to get the worst rise time I could

Teminated in to 50 Ohms
Rise time - 9.2ns
P-P voltage - 13.0 V

Unterminated
Rise time - 350ns
p-p Voltage 72.8 Maxes out Rigol scope

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Stephen
Sent: Thursday, March 18, 2021 12:33 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Type 106

On Thu, Mar 18, 2021 at 05:21 AM, Eric wrote:


Now Raymond has me thinking I might need to check the rise time when I
get back in to the lab tonight on mine make sure my BNC jack did not
roll it off to far. I did the mod because the GR to BNC adaptors are
getting harder and harder to find. Also 12ns rise time is only
29.166Mhz bandwidth so I should be fine there I expect but only
testing will tell. On my 184 I have not had to recap yet but I am
expecting it to play up any time now and will have to how much of a pain in the butt is that going to be?

Eric
I haven’t had to recap it until yesterday... And I’ve had it for quite a while now. It ran without any issues.
Fortunately the bad caps didn’t take anything out in the way. They were not even leaky or anything, they were just DEAD as a door knob. Completely open with no capacitance whatsoever. Well... the 2000uF read about 3nF...
It’s not too much of a pain. Except for the 700uF for which you have to remove the fuse holder to be able to pull it out from underneath. Otherwise it’s pretty straight forward. Make sure to use 105C rated caps though.


Re: Alert for 519 owners - The significance of the Gold GR Connectors

Dave Seiter
 

Ok; my other two 519s have gold plated GR connectors on the front panel.  I don't recall the serial numbers, but IIRC, the one without gold is early-ish, while the other two are mid- to late production.
-Dave

On Thursday, March 18, 2021, 07:51:29 AM PDT, Dennis Tillman W7pF <dennis@ridesoft.com> wrote:

As far as I know none of the 519s had gold on their front panel GR connectors.
You can easily tell the difference between a 50 ohm and a 125 ohm impedance GR connector by looking at the inner conductor whether they are gold or not.
Additionally a 125ohm GR connector will not mate with a 50 ohm GR connector because the inner conductor fingers are the wrong size to mate properly.

Dennis Tillman W7pF





--
Dennis Tillman W7pF
TekScopes Moderator


Re: Replacing a 7000 MF Rear Interface Connector: IS THIS EVEN POSSIBLE?

Harvey White
 

There's a trick to removing contacts, most of which is traditional.  Remove one at a time, and then pull them out while heating the pin from the back.  I use a Metcal desoldering gun. The non traditional trick is to, as needed, take a very long and thin soldering tip, put it in (and through) the hole.  Place the desoldering tip over the soldering tip (a very good guide), and suck out the solder while withdrawing the long thin tip.  It gets very clean results.  I've used this on Chinese made double sided boards.

Harvey

On 3/18/2021 3:20 PM, Ed Breya via groups.io wrote:
Dennis, it is possible to remove those connectors, but it would be a PITA. I've removed large connectors from certain boards with my Hako solder flow/rework machine, but usually for salvaging parts from boards that were to be junked. Sometimes I have removed connectors and other large parts for repair on good boards. It takes great care to tape off the surrounding areas, and to set the solder temperature and pressure just right (to not inject solder through the holes and flood the top of the board), and to work the whole thing around quickly to melt all the connections, without overheating. Most importantly, this can only work on a board that has a flat, clear solder-side, with no big components that can't be taped, or are too tall and interfere with the solder flow. I recall doing this on a 7K interface board years ago, and saving the connectors whole, but the board was probably a junker - I'll take a look and see if I still have it, and remember the process involved.

I think it's easiest and safest to just go ahead and replace the contacts one by one, especially if you have the board out in the open anyway. I did it once in-place on a 7904, but it was only a dozen or so contacts. Like you described, the worst kind is when the contact fingers get bent out of place and then crumpled up.

Ed





Re: 485 super weak brightness control

Ozan
 

I'm in Prague, Czech Republic, Central Europe
Couple of years back I was planning to go to Prague during an Europe trip but timing didn't work out. Hopefully soon when travel is safe again.

Since our timings are off here are more considerations while you are on the scope:

Relays K879 and K1242 are on a socket and easy to pull if you are careful. While putting back pins has to align so that they don't bend. Although I expect timing to be much worse if they are bad, they are easy to test. However, the main reason for removing is you can test the timing caps easily once they are out. If you forget to mark the orientation (like I did) pinout is 180-degree symmetric as far as I remember.

With the relays out you can test the timing capacitors C1405 and C1404 at G3/G5 terminals (and equivalent on B side). Just turn the time/div knob to close the proper switch. Also measure the resistance from each leg to ground. Although figure shows a floating cap in reality they are caps with three legs, the outer leg is a shield and connected to ground. On my 485 there was a short between one of the terminals and outer shield (ground).

You can also observe A sweep out at the BNC for linearity.
Ozan


Re: 485 super weak brightness control

Ondrej Pavelka
 

On Thu, 18 Mar 2021, 20:47 Ozan, <ozan_g@erdogan.us> wrote:


I think we are in a different time zone, I always get the messages as
soon
as a leave the workshop and go home.
I am close to San Francisco, California (more precisely in Silicon Valley
area).

I'm in Prague, Czech Republic, Central Europe



I'm not sure if it's important observation but all the horizontal
calibration is miles out. When I have say both A and B set to 10uS A is
roughly 50% out and B is totally out by 300 or 400%
Just to make sure: Is variable setting of time/div in "cal" position? You
may want to exercise it few times to make sure switch is good.
Yes it is I can see it clearly jump when I engage the switch (push in/out)


I think you measured +50V and it was good. Timing uses +50V for its
current sources so it should be accurate and low ripple.
It's was 49.something and low ripple, I will do more accurate evaluation
tomorrow


These settings use different timing caps:
How much is A/B off in 0.1us to 1ns (I know only B side works 5/2/1ns)
and are all the speeds about same percentage off?
How much is A/B off in 0.2us to 10us and are all the speeds about same
percentage off?
How much is A/B off 20us to 1ms, and are all the speeds about same
percentage off?
How much is A/B off in 2ms and slower speeds, and are all the speeds about
same percentage off?

Are the sweeps linear, if you apply a sine wave does it cross horizontal
axis uniformly?
Yes nice and linear just wrong number of divisions


I will test the rest tomorrow morning

Thanks again for your support and hand holding me through this.
Ondřej



Ozan










Re: 485 super weak brightness control

Ozan
 

I think we are in a different time zone, I always get the messages as soon
as a leave the workshop and go home.
I am close to San Francisco, California (more precisely in Silicon Valley area).

I'm not sure if it's important observation but all the horizontal
calibration is miles out. When I have say both A and B set to 10uS A is
roughly 50% out and B is totally out by 300 or 400%
Just to make sure: Is variable setting of time/div in "cal" position? You may want to exercise it few times to make sure switch is good.

I think you measured +50V and it was good. Timing uses +50V for its current sources so it should be accurate and low ripple.

These settings use different timing caps:
How much is A/B off in 0.1us to 1ns (I know only B side works 5/2/1ns) and are all the speeds about same percentage off?
How much is A/B off in 0.2us to 10us and are all the speeds about same percentage off?
How much is A/B off 20us to 1ms, and are all the speeds about same percentage off?
How much is A/B off in 2ms and slower speeds, and are all the speeds about same percentage off?

Are the sweeps linear, if you apply a sine wave does it cross horizontal axis uniformly?

Ozan


Re: Replacing a 7000 MF Rear Interface Connector: IS THIS EVEN POSSIBLE?

Ed Breya
 

Dennis, it is possible to remove those connectors, but it would be a PITA. I've removed large connectors from certain boards with my Hako solder flow/rework machine, but usually for salvaging parts from boards that were to be junked. Sometimes I have removed connectors and other large parts for repair on good boards. It takes great care to tape off the surrounding areas, and to set the solder temperature and pressure just right (to not inject solder through the holes and flood the top of the board), and to work the whole thing around quickly to melt all the connections, without overheating. Most importantly, this can only work on a board that has a flat, clear solder-side, with no big components that can't be taped, or are too tall and interfere with the solder flow. I recall doing this on a 7K interface board years ago, and saving the connectors whole, but the board was probably a junker - I'll take a look and see if I still have it, and remember the process involved.

I think it's easiest and safest to just go ahead and replace the contacts one by one, especially if you have the board out in the open anyway. I did it once in-place on a 7904, but it was only a dozen or so contacts. Like you described, the worst kind is when the contact fingers get bent out of place and then crumpled up.

Ed


Re: Type 106

Kurt Rosenfeld
 

As far as I know, my 106 has its original case. This is what it looks like:
https://photos.app.goo.gl/uJ2kG29mVRwKTq4F8


Re: Type 106

Stephen
 

If anyone knows of a case for sale, please let me know offline.

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