Date   

Re: Maintainance of 2753p and peak drift

Torquil Macdonald Sørensen <torquil@...>
 

On 09/03/2020 00:34, John Miles wrote:
3) I'm experiencing that spectrum peaks are drifting somewhat between
each
sweep when the digital view is activate. For each frequency sweep, a given
peak will have drifted somewhat in one direction, until after a few sweeps
it again appears at around the original position, so it is kind of cyclic.
I think it only happens when the digital view is active. It is more
pronounced for low frequency peaks, maybe because the amount of drift is
absolute in hz/s, not relative to the frequency value. Anyone seen this
before?
Likely normal, depending on the span. Off the top of my head, I don't recall whether it's the first or the second LO that is allowed to drift slightly between sweeps before being relocked, but it's described in the manuals. If you're not getting error messages, you are probably OK.

It wouldn't be a bad idea to go through the LO subsystem calibration in service volume 1. This isn't too time-consuming, and can give you some confidence in the adjustment margins of the various trimpots. But there's also a case to be made for not 'fixing' it if it's not broken.

-- john, KE5FX

Thanks, that is very helpful to know! I guess I will have to have a look
at the other service manuals that I have managed to download
(492/494/496/2754/...) I was not able to find a downloadable service
manual for the 2753, or the 495 with the same frequency range. Would you
happen to know the frequency ranges for the 1st and 2nd LO in this unit?
Surely it is different from the higher frequency units?

I would also like to do some audio work with this unit since it goes
down to 100 Hz, but the peak drift problem is a bit too much at those
low frequencies. I think the peak drift is actually dependent on if I
use the peak locate feature button or not during the sweeping.

But I think the first items that need to be addressed are: noisy fan,
check electrolytics/SMD electrolytics/RIFA capacitors and look at the
state of the battery. The serial number is B030249 and it was apparently
owned by Boeing before, according to the stickers. The latest
calibration was done in 2002.

Torquil


Re: 2465 U950 Z AXIS IC Chip 155-0242-01 Fails After Re-installation

 

PSU first - make sure you’ve got good going in before trying to get good out

Robin
G5HI

On 9 Mar 2020, at 04:22, Don N3DEB via Groups.Io <dbawatsonville=yahoo.com@groups.io> wrote:

 Update. Had some room on my bench and opened this up again.

The U950 wave forms are quite dirty/noisy compared to my good 2465.

Low voltage power supply voltages are all in spec, but P-P ripple is about double the spec on +10, +5, and triple on -15V.

Change PS caps before going further? Or continue looking at the Z-Axis circuit?



Re: Viewing hoods for 7000 series

EJP
 

Err, I'll be doing it for my SC504 today. The 7704 size is just too wide for my printer. I may try to work out how to print it in two parts with a joiner.

EJP


Re: 2465 U950 Z AXIS IC Chip 155-0242-01 Fails After Re-installation

Don N3DEB
 

Update. Had some room on my bench and opened this up again.

The U950 wave forms are quite dirty/noisy compared to my good 2465.

Low voltage power supply voltages are all in spec, but P-P ripple is about double the spec on +10, +5, and triple on -15V.

Change PS caps before going further? Or continue looking at the Z-Axis circuit?


Re: Ringing on 2235 100 volt supply

John G
 

Hi Raymond,
Let me clarify a bit. Table 6.4 in the service manual shows 40.0 P-P Ripple (mv) as the limit on the +100 V supply. I see about 90 mv P-P as pic 1 shows. Scope set at 20mv per div.
If it wasn't for the ringing it would be in spec. I see the same result measuring itself or on another scope. Measured at Test Point W954 which is adjacent to C954.
The thread that I believe is the same issue, but I couldn't find the photos referred to is:
https://groups.io/g/TekScopes/topic/7646253#62131

I added more picts showing the horz sweep problem:
https://groups.io/g/TekScopes/album?id=242594
2 is normal, 3 is after it fails and settles down, 4 is the transition between the 2 states, very erratic sweep. Moving any control, switch or tapping on components doesn't cause it to fail or fix it. Random when it happens, usually about 30 minutes after you turn it on. It will fail for 5 sec to 2 minutes, work properly 10 sec or 30 minutes. Totally random. All other functions seem normal. S/N B024573
Thank You for any light you can shed on these issues.
John


Re: Viewing hoods for 7000 series

Mlynch001
 

On Sun, Mar 8, 2020 at 07:56 PM, EJP wrote:


There is a 3D-printable one at thingiverse.com. It's for a difference Tek
scope but should be trivial to adjust for 7000 series. I'll be doing one
myself for my 7704A this week.

EJP
Yes, If you have access to a 3D printer and can download the STL file from an online source, that would be a great way to do it. I find a lot of these type items on THINGIVERSE.
--
Michael Lynch
Dardanelle, AR


Re: Viewing hoods for 7000 series

EJP
 

There is a 3D-printable one at thingiverse.com. It's for a difference Tek scope but should be trivial to adjust for 7000 series. I'll be doing one myself for my 7704A this week.

EJP


Re: Viewing hoods for 7000 series

Mlynch001
 

Sean,

I have successfully printed glare shields for various models of TEK Scopes that I own and use, including 465/475 + 24XX series as well as Type 576 curve tracers. I design them and use my 3D Printers to produce them to fit as needed. Although I have not done one for the 5000 and 7000 series, it would be a simple matter to produce one of them. I have several 5000 series scopes and a couple of 76xx series that I could also probably use as a pattern for those models that you mentioned. I can send you a picture of what I make. They are not injection molded and not folding, but they do a good job and look quite presentable. If you want more details, contact me off list.

--
Michael Lynch
Dardanelle, AR


Re: Ringing on 2235 100 volt supply

 

On Sun, Mar 8, 2020 at 03:32 PM, John G wrote:


Upon further searching it looks like this is a common problem and no
resolution found. It apparently doesn't cause any problems.
Where did you find this is a common problem (and no resolution found)? I can't make sense of your "90" and "40". What unit? Spec is +/- 3 VDC off.
Unfortunately, settings for your image are unknown.
OTOH, the kind of problem with the 100 V would suggest more problems than an intermittent horizontal problem. Speaking of that, what does that intermittent problem consist of? One in n sweeps missing? The sweep not working on odd dates?

Raymond


Re: Ringing on 2235 100 volt supply

 

On Sun, Mar 8, 2020 at 04:56 AM, John G wrote:


Checking the power supplies, all were in spec except the 100v supply ripple at
90 p-p, spec is 40 p-p.
This certainly is *not* common or even normal for the 100 VDC supply and certainly *not* without negative effects.
Are you really talking about the voltage across e.g. C954?

Raymond


Re: Maintainance of 2753p and peak drift

John Miles
 

1) The unit can store graphs and configuration settings, so it has a
battery. Is there a danger of losing calibration data if the battery fails,
or is it only used for what I mentioned above? I would hate to be forced to
attempt to calibrate of this thing.
No calibration info is stored, only graphs, settings, and macros (for those units that support them).

2) Does the unit contain SMD capacitors that should be changed as soon as
possible to avoid collateral damage od the pcb or other components?
This depends more on the production date than on the model number. See http://www.ke5fx.com/49x_notes.pdf for some suggestions on what to look for.

3) I'm experiencing that spectrum peaks are drifting somewhat between
each
sweep when the digital view is activate. For each frequency sweep, a given
peak will have drifted somewhat in one direction, until after a few sweeps
it again appears at around the original position, so it is kind of cyclic.
I think it only happens when the digital view is active. It is more
pronounced for low frequency peaks, maybe because the amount of drift is
absolute in hz/s, not relative to the frequency value. Anyone seen this
before?
Likely normal, depending on the span. Off the top of my head, I don't recall whether it's the first or the second LO that is allowed to drift slightly between sweeps before being relocked, but it's described in the manuals. If you're not getting error messages, you are probably OK.

It wouldn't be a bad idea to go through the LO subsystem calibration in service volume 1. This isn't too time-consuming, and can give you some confidence in the adjustment margins of the various trimpots. But there's also a case to be made for not 'fixing' it if it's not broken.

-- john, KE5FX


Re: Noob needs help with a 453 no sweep

Albert Otten
 

I hooked up my meter to TP505 and it is .037vdc most of the time but when
the single sweep is reset I have -.027vdc and when the sweep gets triggered
I see -5.vdc on it while the sweep is moving across the screen, even when I
have it set very slow.
Hi Brian,

That's exactly the guessed behavior. The TD gets reset (from "high" negative state to slightly positive)) at the end of the sweep, by action of the Sweep Reset circuit. But that action should be maintained only during retrace (what you probably also can see at very slow sweep speeds) and subsequent during charging of the HoldOff capacitor. It should stop when the Sweep Circuit is switched back to rest state by some high voltage at the HoldOff cap. After this the TD gets armed again by a current just below the current needed to "fire" the TD. This is visible as an only slightly negative voltage because of the IV-characteristics of the TD. Now the TD is triggerable and waits for a trigger signal.
You might get more insight in the sequence of events if you test the working 453 in Normal mode (no signal, slow sweep) and force a trigger by Level rotation.

Albert


Re: Noob needs help with a 453 no sweep

Brian Mathews
 

Hi Roger,

I was not able to work on this until today and I went back through all of
the responses and I found I had not replied to your post here.

I did what you asked here and it does trigger a single sweep when I have it
on single sweep (reset lit) and I move the trigger selector from EXT to
LINE, but only when I have the LEVEL pot in the middle of it's range.

I did try moving the LEVEL to the CW position and then with Reset lit I get
a single sweep when I turn the level control CCW.

I hooked up my meter to TP505 and it is .037vdc most of the time but when
the single sweep is reset I have -.027vdc and when the sweep gets triggered
I see -5.vdc on it while the sweep is moving across the screen, even when I
have it set very slow.

Brian W6BRY




On Wed, Mar 4, 2020, 23:31 Roger Evans via Groups.Io <very_fuzzy_logic=
yahoo.com@groups.io> wrote:

I was trying to specify a very definite sequence to see whether or not the
trigger circuitry was working.

Reset the single sweep with trigger set to external, the single sweep
ready light should stay on.

Move the trigger selector to 'line' without touching the single sweep
reset, the beam should sweep once and the single sweep ready light should
extinguish.

If this works as above then it seems to me that the scope is generating a
trigger pulse and the problem is with the sweep circuitry not resetting
when set to 'normal'. You could be more thorough and set the trigger
selector to normal and move the trigger level to one end of its travel.
Then do the single sweep reset and induce a trigger pulse by moving trigger
level to the other extreme.

There is also the issue as to why there is no sweep when in 'auto' mode
and there is no need for a trigger pulse anyway, but there could well be a
common cause.

Roger




Re: 311-1404-00 concentric potentiometer for (R)7603: Intensity and Readout control

Gregor Lasser
 

Hi Gudjon,

Sure, that is better than no readout, and practically what I have now (I managed to fiddle with the broken off center piece to get the inner potentiometer for the readout adjusted for an ok value.

I just like to be able to turn down the intensity of readout and beam when I have the scope running for longer time as a measure to preserve the CRT.

Greetings,
Gregor

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Gudjon Gudjonsson
Sent: Sunday, March 08, 2020 1:28 PM
To: TekScopes <TekScopes@groups.io>
Subject: Re: [TekScopes] 311-1404-00 concentric potentiometer for (R)7603: Intensity and Readout control

Hi Gregor

I have the same problem with my 7603 and I just replaced it with a resistor and I don't see any downside of a constant intensity readout. I may have missed something important :)

Regards
Gudjon


Re: 311-1404-00 concentric potentiometer for (R)7603: Intensity and Readout control

Gregor Lasser
 

Hi Colin,
Thanks for your fast reply! The original one is 5k/5k with a build in
switch. I will measure all dimensions tonight to see what I actually need.

Greetings,
Gregor

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Colin
Herbert via Groups.Io
Sent: Sunday, March 08, 2020 1:19 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 311-1404-00 concentric potentiometer for (R)7603:
Intensity and Readout control

Hi Gregor,
I have a 311-1430-00 pull which is a dual concentric 5k/50k. I haven't
checked it yet. I guess it's the wrong values, but who knows. I am in
London, UK, so it would be a small task to post it within the UK. Postage to
the US might be a little trickier, but if it isn't anything like you want,
then that doesn't matter.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Gregor
Lasser
Sent: 08 March 2020 18:23
To: TekScopes@groups.io
Subject: [TekScopes] 311-1404-00 concentric potentiometer for (R)7603:
Intensity and Readout control

Hi,

I am currently restoring an R7603 that had a badly bent intensity/readout
potentiometer. With lots of careful bending I was able to get the
potentiometer back to work to the point where I could rotate the beam
intensity control more or less independently of the readout intensity, but
at this point the inner readout intensity axis of the potentiometer became
loose. My attempts to fix this by reshaping the "head" of the axis were not
successful. Otherwise the scope seems to be in good shape, I fixed a few
minor things and coarse alignment of the vertical amplifier brought the beam
and readout back to the center of the screen.

Does anyone have a spare 311-1404-00 concentric potentiometer/switch
assembly for (R)7603, or has a parts 7603 front panel they are willing to
sell? I looked up the typical soureces but they seem to be sold out on that
part.

Greetings,
Gregor


Re: Viewing hoods for 7000 series

Albert Otten
 

Sean,
If it doesn't have to be collapsible it should be easy to construct something yourself I think. Before I had one I simply used a few pieces of cardboard with inward bent edges and taped together. But I needed this mainly for taking photographs.
Albert


Viewing hoods for 7000 series

@0culus
 

Hi all,

I have a 7904A and a 7104 that are my workhorse oscilloscopes, and I also have to deal with harsh overhead lighting so I can see my work. I managed to find a Tektronix collapsible viewing hood, part #016-0260-00 that appears to be a unicorn. It's really more of a shade that keeps the room lights off the o-scope screen. I've never seen another one, and not for lack of looking. I'd like to find another one, or something similar that's compatible with the 7000 series bezels so I don't have to move it between scopes.

Any suggestions?

Thanks!

Sean


Re: 311-1404-00 concentric potentiometer for (R)7603: Intensity and Readout control

Gudjon Gudjonsson
 

Hi Gregor

I have the same problem with my 7603 and I just replaced it with a
resistor and I
don't see any downside of a constant intensity readout. I may have missed
something important :)

Regards
Gudjon


Re: 311-1404-00 concentric potentiometer for (R)7603: Intensity and Readout control

Colin Herbert
 

Hi Gregor,
I have a 311-1430-00 pull which is a dual concentric 5k/50k. I haven't
checked it yet. I guess it's the wrong values, but who knows. I am in
London, UK, so it would be a small task to post it within the UK. Postage to
the US might be a little trickier, but if it isn't anything like you want,
then that doesn't matter.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Gregor
Lasser
Sent: 08 March 2020 18:23
To: TekScopes@groups.io
Subject: [TekScopes] 311-1404-00 concentric potentiometer for (R)7603:
Intensity and Readout control

Hi,

I am currently restoring an R7603 that had a badly bent intensity/readout
potentiometer. With lots of careful bending I was able to get the
potentiometer back to work to the point where I could rotate the beam
intensity control more or less independently of the readout intensity, but
at this point the inner readout intensity axis of the potentiometer became
loose. My attempts to fix this by reshaping the "head" of the axis were not
successful. Otherwise the scope seems to be in good shape, I fixed a few
minor things and coarse alignment of the vertical amplifier brought the beam
and readout back to the center of the screen.

Does anyone have a spare 311-1404-00 concentric potentiometer/switch
assembly for (R)7603, or has a parts 7603 front panel they are willing to
sell? I looked up the typical soureces but they seem to be sold out on that
part.

Greetings,
Gregor


311-1404-00 concentric potentiometer for (R)7603: Intensity and Readout control

Gregor Lasser
 

Hi,

I am currently restoring an R7603 that had a badly bent intensity/readout
potentiometer. With lots of careful bending I was able to get the
potentiometer back to work to the point where I could rotate the beam
intensity control more or less independently of the readout intensity, but
at this point the inner readout intensity axis of the potentiometer became
loose. My attempts to fix this by reshaping the "head" of the axis were not
successful. Otherwise the scope seems to be in good shape, I fixed a few
minor things and coarse alignment of the vertical amplifier brought the beam
and readout back to the center of the screen.

Does anyone have a spare 311-1404-00 concentric potentiometer/switch
assembly for (R)7603, or has a parts 7603 front panel they are willing to
sell? I looked up the typical soureces but they seem to be sold out on that
part.

Greetings,
Gregor