Date   

Re: Self-check reliability on 2465

Siggi
 

On Sun, 22 May 2016 at 14:20 Ryan Stasel rstasel@uoregon.edu [TekScopes] <
TekScopes@yahoogroups.com> wrote:

Timebase var knob does not work. Good call. And interesting.

Would that board be unplugged somehow during a calibration? I'm wondering
if tech just threw it all back together and didn't hook everything back up.
That seems unlikely, I can't think of any reason to pull out the
front-panel board during calibration. It's pretty easy to pull the
front-panel out to see what's up - IIRC you just undo the screws around the
bezel, pull the bezel off, and then the front-panel will pull right out.
I can't see that anything else but the front-panel VAR board would be at
fault, as the -1.25V/+1.36V references are used by the cursor controls and
sundry other pots.
Maybe the scope took a faceplant and either wrecked the pots, or else
pulled that board out of it's socket?


Re: Self-check reliability on 2465

R. Stasel
 

Hold off and trig work

Ryan Stasel
IT Operations Manager, SOJC
University of Oregon

Sent from my iPhone

On May 22, 2016, at 11:41, laser92awd@yahoo.com<mailto:laser92awd@yahoo.com> [TekScopes] <TekScopes@yahoogroups.com<mailto:TekScopes@yahoogroups.com>> wrote:



I don't see a reason why it should be disconnected during cal, unless that scope was "repaired" by putting two broken scopes together and had some "screws leftover" (i.e. not quite complete job). Check all the connectors again, though just to be sure hopefully the trig level and holdoff knobs work, these also require the DAC "ADC" to work much like the VAR knobs.


Re: Self-check reliability on 2465

bc
 

I don't see a reason why it should be disconnected during cal, unless that scope was "repaired" by putting two broken scopes together and had some "screws leftover" (i.e. not quite complete job). Check all the connectors again, though just to be sure hopefully the trig level and holdoff knobs work, these also require the DAC "ADC" to work much like the VAR knobs.


Re: Self-check reliability on 2465

R. Stasel
 

Timebase var knob does not work. Good call. And interesting.

Would that board be unplugged somehow during a calibration? I'm wondering if tech just threw it all back together and didn't hook everything back up.

Thanks!

Ryan Stasel
IT Operations Manager, SOJC
University of Oregon

Sent from my iPhone

On May 22, 2016, at 11:09, Sigur?ur ?sgeirsson siggi@undo.com<mailto:siggi@undo.com> [TekScopes] <TekScopes@yahoogroups.com<mailto:TekScopes@yahoogroups.com>> wrote:



On Sun, 22 May 2016 at 13:47 Ryan Stasel rstasel@uoregon.edu<mailto:rstasel@uoregon.edu> [TekScopes] <
TekScopes@yahoogroups.com<mailto:TekScopes@yahoogroups.com>> wrote:

Okay, so, the var knobs don't seem to do anything, but I do feel them go
into the detents... so this is probably the real issue. Do the var knobs pull
out, or are they just rotate? Is there anything that would make the scope
ignore those pots?

The VAR knobs are just pots, but they're mounted on a second circuit board
from the rest of the front panel controls.
Does the timebase (horizontal) VAR control work? If not, I'd suspect the
second front-panel board has connection issues. If it does, I'd look toward
A5U2418, which is one of the pot scanning MUXes.
You can measure the value of the pots directly on the A5 board at either
end of R2513/R2514 - see circuit diagram <2> Analog Control. They should
span a range from -1.25V to 1.36V as you turn them from one side to the
other.


Good call. I did check them, but was very confused when they didn't seem
to do anything.
It's always the little things - many thanks to <laser92awd@yahoo.com<mailto:laser92awd@yahoo.com>> for
pulling this one back from the brink :).


Re: TDS 754D

Siggi
 

On Sun, 22 May 2016 at 12:38 david.wilson92@yahoo.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:



http://www.tek-parts.com/shopexd.asp?id=13094

Here is the link I found of the similar hybrid to the TDS 380, if you look
at the pictures it appears to be a one sided board I think
I'm not sure. If you look at this repair thread <
http://www.antiqueradios.com/forums/viewtopic.php?f=8&;t=216792>, you'll see
that Matthew is repairing the 50Ohm termination resistor on the underside
of the hybrid. While there aren't any soldered components on the underside,
I suspect you'll find your bad series resistance as one of those (thick
film?) resistors there.


Re: Self-check reliability on 2465

Siggi
 

On Sun, 22 May 2016 at 13:47 Ryan Stasel rstasel@uoregon.edu [TekScopes] <
TekScopes@yahoogroups.com> wrote:

Okay, so, the var knobs don’t seem to do anything, but I do feel them go
into the detents… so this is probably the real issue. Do the var knobs pull
out, or are they just rotate? Is there anything that would make the scope
ignore those pots?

The VAR knobs are just pots, but they're mounted on a second circuit board
from the rest of the front panel controls.
Does the timebase (horizontal) VAR control work? If not, I'd suspect the
second front-panel board has connection issues. If it does, I'd look toward
A5U2418, which is one of the pot scanning MUXes.
You can measure the value of the pots directly on the A5 board at either
end of R2513/R2514 - see circuit diagram <2> Analog Control. They should
span a range from -1.25V to 1.36V as you turn them from one side to the
other.


Good call. I did check them, but was very confused when they didn’t seem
to do anything.
It's always the little things - many thanks to <laser92awd@yahoo.com> for
pulling this one back from the brink :).


Re: 585A Not Powering On

Daniel Koller
 

You;re welcome!  And great news.  Have fun using them now.   I eventually fixed all my plug-ins.  then if one fails I just swap and fix it later.
Dan

On Sunday, May 22, 2016 12:33 PM, "alex_brinister@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com> wrote:



  Hi Dan, I took your advise on reading the manual of the 545A. I got familiar with the delay triggering and I was able to highlight a portion of a waveform and then expand it using the "B intensified by A" and "A delayed by B" controls. I have to say, that's really cool. I never imagined that could be done on an analog scope. Very cool!



The 585A... works. On Friday, when I did tests, I found that the waveform I observed when the calibrator was off was not there anymore. Furthermore, after reading the manual for the 545A, I got more familiar with what the stability control did. With that knowledge, I was able to get a free sweep on the 585A. Just no vertical deflection. After making measurements, I only found one measurement that was a bit off. The plate voltage of the V1094 is higher than it should be. The manual says 170 V, I measured 215 V. Other than that, all components checked out and all voltages checked out.


I thought I would try another plugin, perhaps a more native one than a 500-series through the Type 81. I popped an 82 in there and lo and behold, everything works. I was confused why this 82 worked and the one I tried at the beginning didn't. It turned out that I didn't pay attention to the plugin circuitry; three 6DJ8's and a few transistors were missing from the plugin! No wonder it didn't work! I also found out that neither the Type 81 and the Type 81A I have worked. Furthermore, two CA plugins that I tried with the 81's didn't work either, along with a 1A6. I am kind of suspicious of the 81's. Is it possible that they could have destroyed the plugins in some way?


I played with the delay triggering on the 585A today just to make sure it was okay. I haven't yet tried any of the external horizontal input stuff yet but I'll get to it. Everything seems to check out. Some of the switches don't make good contacts and deform the waveform. The switch where I see this most is the 5x multiplier, which cases the waveform to disappear and leaves just the spots in the middle of the CRT. If it is wiggled around and forced to stay in a place in it's sweep just before the end, the light comes on and the magnification actually occurs. When I get the Deoxit, it should help with that problem. It seems to me that this oscilloscope works.


Thank you for your help,
Alex Brinister



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


Re: Self-check reliability on 2465

R. Stasel
 

On May 22, 2016, at 8:18 AM, TekScopes@yahoogroups.com<mailto:TekScopes@yahoogroups.com> wrote:


On Sun, 22 May 2016 at 10:53 laser92awd@yahoo.com<mailto:laser92awd@yahoo.com> [TekScopes] <
TekScopes@yahoogroups.com<mailto:TekScopes@yahoogroups.com>> wrote:

Incidentally, was playing with my 2465: if I have the VAR adjustment
turned down all the way CCW, I get ~1.7 divisions (which is strikingly
close to 1.5 divisions) on the 0.4V cal signal with 10x probe and
10mV/division (the readout should say ">10mV" when you have the VAR turned
CCW)... You should have VAR turned all the way CW when working with the
graticule.
This is a great point - check the position of the VAR pots, they want to be
in the detent. There should be an indication in the readout, if the scope
believes they're out of detent - the indication will read something like
CH1: *>*1V.

If they're in detent, but the scope doesn't think they are, it may be as
simple as bad or intermittent pots, or we may need to look at the pot
scanning on the A5 board.

PS: as you see, everyone loves a troubleshooting thread :).

Okay, so, the var knobs don’t seem to do anything, but I do feel them go into the detents… so this is probably the real issue. Do the var knobs pull out, or are they just rotate? Is there anything that would make the scope ignore those pots?

That IS what I see. The vertical cursors only show “ratio” they don’t seem to show volts. =/

Good call. I did check them, but was very confused when they didn’t seem to do anything.

Thanks!

-Ryan Stasel


Re: 585A Not Powering On

Albert Otten
 

Hi Alex,

When I bought and first used my 585A in about 1980 I was exited that I could scroll in detail through all individual TV lines while B was triggered by the TV frame pulses.
You will be amazed by the linearity of the delay time dial and circuitry. Or stated otherwise, by the linearity of time difference measurements with the 10 turn dial.

Albert


Re: TDS 754D

David Wilson
 

http://www.tek-parts.com/shopexd.asp?id=13094

Here is the link I found of the similar hybrid to the TDS 380, if you look at the pictures it appears to be a one sided board I think


Re: 585A Not Powering On

Alex Brinister
 

Hi Dan, I took your advise on reading the manual of the 545A. I got familiar with the delay triggering and I was able to highlight a portion of a waveform and then expand it using the "B intensified by A" and "A delayed by B" controls. I have to say, that's really cool. I never imagined that could be done on an analog scope. Very cool!



The 585A... works. On Friday, when I did tests, I found that the waveform I observed when the calibrator was off was not there anymore. Furthermore, after reading the manual for the 545A, I got more familiar with what the stability control did. With that knowledge, I was able to get a free sweep on the 585A. Just no vertical deflection. After making measurements, I only found one measurement that was a bit off. The plate voltage of the V1094 is higher than it should be. The manual says 170 V, I measured 215 V. Other than that, all components checked out and all voltages checked out.


I thought I would try another plugin, perhaps a more native one than a 500-series through the Type 81. I popped an 82 in there and lo and behold, everything works. I was confused why this 82 worked and the one I tried at the beginning didn't. It turned out that I didn't pay attention to the plugin circuitry; three 6DJ8's and a few transistors were missing from the plugin! No wonder it didn't work! I also found out that neither the Type 81 and the Type 81A I have worked. Furthermore, two CA plugins that I tried with the 81's didn't work either, along with a 1A6. I am kind of suspicious of the 81's. Is it possible that they could have destroyed the plugins in some way?


I played with the delay triggering on the 585A today just to make sure it was okay. I haven't yet tried any of the external horizontal input stuff yet but I'll get to it. Everything seems to check out. Some of the switches don't make good contacts and deform the waveform. The switch where I see this most is the 5x multiplier, which cases the waveform to disappear and leaves just the spots in the middle of the CRT. If it is wiggled around and forced to stay in a place in it's sweep just before the end, the light comes on and the magnification actually occurs. When I get the Deoxit, it should help with that problem. It seems to me that this oscilloscope works.


Thank you for your help,
Alex Brinister


Re: TDS 754D

David Wilson
 

http://www.tek-parts.com/shopexd.asp?id=13094

Here is the link to the one sided attenuator module I was talking about, does it appear one sided to you?


Re: TDS 754D

David Wilson
 

I did some searching and found H2452J for the attenuators

As for the 380 attenuators, I might use the 754D to probe around on them. I did a search on the 380 attenuators recently and found pictures of a similar attenuator noticing that all the circuits appeared on one side of the board (single sided). Maybe I don't need to pull the attenuators off as I already have access to everything and removal proved to be difficult for some reason with the solder joints. But could give desoldering another try thought.

Are some attenuators single sided I wonder?


Re: Self-check reliability on 2465

Siggi
 

On Sun, 22 May 2016 at 10:53 laser92awd@yahoo.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:

Incidentally, was playing with my 2465: if I have the VAR adjustment
turned down all the way CCW, I get ~1.7 divisions (which is strikingly
close to 1.5 divisions) on the 0.4V cal signal with 10x probe and
10mV/division (the readout should say ">10mV" when you have the VAR turned
CCW)... You should have VAR turned all the way CW when working with the
graticule.
This is a great point - check the position of the VAR pots, they want to be
in the detent. There should be an indication in the readout, if the scope
believes they're out of detent - the indication will read something like
CH1: *>*1V.

If they're in detent, but the scope doesn't think they are, it may be as
simple as bad or intermittent pots, or we may need to look at the pot
scanning on the A5 board.

PS: as you see, everyone loves a troubleshooting thread :).


Re: Self-check reliability on 2465

bc
 

Incidentally, was playing with my 2465: if I have the VAR adjustment turned down all the way CCW, I get ~1.7 divisions (which is strikingly close to 1.5 divisions) on the 0.4V cal signal with 10x probe and 10mV/division (the readout should say ">10mV" when you have the VAR turned CCW)... You should have VAR turned all the way CW when working with the graticule.

Oh, yeah, using a true RMS voltmeter is not going to show 0.4V on the cal signal of course (you'll have to guesstimate the duty cycle and multiply), it's not exactly the right tool, but should get you in the ball park. 1.5 vs 4 divisions is not in the right ball park.


Re: Self-check reliability on 2465

bc
 

1.002815M ohms for 1M ohm, isn't this 0.28% error not 2.8% (unless you meant the resistance is 1.02815M ohms)? Same with 0.998073M is 0.19% off (unless you meant resistance is 0.98073M ohms)? At 0.28% and 0.19% these don't sound too far off what they should be.

BTW, when you have 1.5 divisions on the 0.4V cal signal at 0.1V/division, if you use the cursors, how many volts do they measure? I guess versus the graticule it's basically pot adjustments, but if the cursors are wrong, then that's an EAROM constant.

Also make sure you check against another scope or true RMS voltmeter or something if you can.


Re: Self-check reliability on 2465

Siggi
 

On Sun, 22 May 2016 at 09:06 David davidwhess@gmail.com [TekScopes] <
TekScopes@yahoogroups.com> wrote:

On Sun, 22 May 2016 12:34:27 +0000, you wrote:

The 2465 is mostly drive-by-wire, in that all kinds of gain and timing
factors are set by the CPU. Both the CH1/CH2 and the CH34 preamps have
voltage-controlled variable gain, as a case in point.
The preamps have a 0.1/0.5 volt/div attenuation setting but no gain
control for variable gain or calibration explaining their poor +/-10%
accuracy specification. In theory the overall vertical gain could be
adjusted but the 2465 series uses this facility otherwise.
Ah - you're quite right of course. The GA3/4 inputs to the CH3/4 preamps
are digital, I'd mistaken them for analog control. The CH1/2 preamps do,
however, have variable gain.
I don't think this changes anything for the diagnosis, nor prognosis? The
fact that CH3/4 gain is good would seem to eliminate everything from the
channel switch forwards.

Ryan: the channel switch is a potential suspect because it has separate
gain stages for the CH1/2 and the CH3/4/5 sides. If you look for a document
named "tek_made_sm.pdf", inside you'll find a die with a designation of
"203-0211-90". This is what's inside U400.
I'd eliminate the analog control first, because there's seemingly very
little that can go wrong with the channel switch that's repairable. The
biasing supplies and resistors are about the only possibility aside from
U400 itself :/.



__._,_.


Re: Self-check reliability on 2465

 

On Sun, 22 May 2016 12:34:27 +0000, you wrote:

...

The 2465 is mostly drive-by-wire, in that all kinds of gain and timing
factors are set by the CPU. Both the CH1/CH2 and the CH34 preamps have
voltage-controlled variable gain, as a case in point.
The preamps have a 0.1/0.5 volt/div attenuation setting but no gain
control for variable gain or calibration explaining their poor +/-10%
accuracy specification. In theory the overall vertical gain could be
adjusted but the 2465 series uses this facility otherwise.


Re: Tek 2215

Jay
 

I just picked up a Fluke 1900A frequency counter for really cheap.. My questions is what can I use all this equipment for when the calibration process is complete ?? Do I need any more equipment ??



Oh I meant to ask can I just check the calibration with 10 Mhz instead of using the 60 Mhz ???
Cause wouldn't it show error on lower frequencies since I want to say they use the same calibration pot ?? >For horizontal calibration there are several different adjustments for
different sets of ranges. There are also some adjustments for
horizontal linearity at the highest sweep speeds.
Could I use a 100mhz crystal and use some attenuators to get around 50 Mhz signal ???






Also could I build a couple of these 10x Attenuator and be on the calibration ??
#91: Basic RF Attenuators - Design, Construction, Testing - PI and T style - A Tutorial https://www.youtube.com/watch?v=A5gGeV7CiQ0 https://www.youtube.com/watch?v=A5gGeV7CiQ0
Yes, the needed square wave frequency for vertical calibration should
be as low as possible so physical construction of the attenuators is
not difficult. If the attenuators and termination are built with
precision resistors, then calibration of the attenuators themselves
may not be necessary. I figured that cause I am trying to limit the amount of money I am spending on calibration cause it seem like a endless cycle..


Re: Self-check reliability on 2465

Siggi
 

On Sun, 22 May 2016 at 00:40 Ryan Stasel rstasel@uoregon.edu [TekScopes] <
TekScopes@yahoogroups.com> wrote:

So, just got back to this, and indeed, for Channels 1 and 2, I get 1.5
divisions for the .4V cal signal when set to 100mv/div (when scope set to
AC coupling on channel). Channels 3 and 4 appear fine, though they don’t
have the attenuators. The time base calibration looks dead-on though.
The 2465 is mostly drive-by-wire, in that all kinds of gain and timing
factors are set by the CPU. Both the CH1/CH2 and the CH34 preamps have
voltage-controlled variable gain, as a case in point.
The analog control voltages are derived on the A5 board in a single DAC,
then multiplexed through some 4051 analog switches followed by S&H op-amps.
I think we can assume your DAC is working fine, but it'd be good to check
the 10V reference on the A5 board, as well as the -1.25V and 1.36V test
points (TP503/TP504) on A5.


Checking the input resistance, both 1 and 2 show open on AC, on DC they
are both off by a “bit”. Channel 1 shows 1.002815M (~2.8% high), and
Channel 2 shows 0.998073 (~2% low).
This is out of spec - the spec is 0.5%. However this might be simple a
measurement error. There's likely some leakage current out of the preamp
inputs, so to get an accurate reading, measure the resistance from center
to ground, and then from ground to center. The average of those readings
ought to be in spec.
Also, there are two 10X attenuator stages in the attenuator hybrid, so you
need to measure this for all the major attenuation steps (relay clicks).
This is neither here nor there, as contact problems produce gross error, so
I think we can assume for the moment that your attenuators are fine.

So I’d assume the scope is indeed completely out of cal for channels 1 and
2.
Do channels 1 & 2 agree to a high degree, or are they out by significantly
different amounts?
I think there are three possibilities:

1. The scope is out of cal.
2. There's a problem with the analog control voltages, most likely in A1
U160/U170.
3. There's a problem with the CH1/2 signal path, most likely A1U400.

I find it somewhat hard to believe that the scope would have been left in
the state it is by a failed calibration, unless there was a hardware fault
that caused it to fail calibration in the first place.

I did find and interesting manual done by the US Army on calibrating these
guys (
http://electroniccalibrators.tpub.com/TB-9-6625-2293-35/TB-9-6625-2293-350001.htm),
Problem is, I don’t have the calibrator referenced. I have a recently cal’d
ARB, and a Good PSU that I can verify on other scopes…
And you have a second scope - it sounds like?

Any tips on what I should look at/for? Do remember, I just re-capped the
PSU, so maybe there’s a reference voltage that’s off?
If you don't already have a good service manual, then I'd recommend the
Artek Manual scan - it's excellent.

I'd start with the A5 board, by checking the 10.000V/1.36V/-1.25V voltages.
I think they're probably fine, but they're easy to check, and foundational
to everything else working.
Then I'd look at A1U170 and A1U160, which are the DEMUX and S&H for some of
the analog controls. They produces the gain and DC balance voltages for
CH1/2, as well as the CH2 skew and trigger holdoff.
The trigger holdoff is easy to test. You can do it visually with a suitable
input signal. You can count the triggers out the back of the scope, or you
can simply measure the holdoff voltage out of the S&H op-amp.

Each attenuator hybrid in the 2400's has two 10X "hard" attenuation steps.
The 1-2-5 steps in between those are done by varying the gain of the
preamps. It'd help if you establish the relationship between the 1-2-5
steps. If those are totally horked, then perhaps it's simply the variable
gain that's broken. This'd be great, as then I'd expect the scope to drop
into the last cal when you fix it.

I forget where the relays click, but start by going down to 2mV/DIV, then
turn down the sensitivity until you hear the first relay click. Go back
down to the previous gain setting, and check whether that step and the two
below it have a 1-2-5 relationship.

In your shoes, I'd make sure to have a bench fan blowing gently across the
mainboard when you operate it for any length of time out of the chassis.
There are two opinions on whether this is strictly necessary, but I don't
see there could be any harm in it :).

Good luck!


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