Date   

Re: Looking at a broken 2440

Harvey White
 

On Thu, 19 Jul 2018 14:02:28 -0700, you wrote:

I think I'm going to pass it up. I need to start being selective on my scope choices. I think my next scope will be one I really want. Which is a 2467 or 7104 with a MCP CRT.
I have a 7104. I use it only when I need the MCP or the 1 GHZ
bandwidth. That requires either a direct coax input or a 1 GHz probe
(and, for that matter, something where the bandwidth is needed).

Having one, I wouldn't give it up. Not having one, I'd wonder if I
need it. (mostly my use would be digital stuff, and looking at pulses
there. I've got an HP 16702B that helps here).

Harvey




On Thu, Jul 19, 2018 at 01:23 PM, goran parezanovich wrote:


Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .


<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas




Re: My "new" Tek 485 with opt 4

Artekmedia <manuals@...>
 

The 1982 catalog lists Option 04 for the 485 indeed as EMC option
-DC
manuals@...

On 7/19/2018 4:25 PM, Reginald Beardsley via Groups.Io wrote:
I just got a nicely refurbished 485 which lists "opt4" under the SN. I could find no information despite several searches. I was surprised at how little information there was at the w140.com/Tekwiki. My 465 manual says opt 4 is EMI environmental. Is that true of the 485 also?

It came with a CD of the service manual, but I'd like to get a nice hard copy original if anyone has one they are willing to part with. I can offer a 465 and RM45 manuals in good condition in exchange.


--
Dave
Manuals@...
www.ArtekManuals.com


Re: Looking at a broken 2440

Craig Cramb
 

The 2400 series digital are pretty cool. What I’ve dealt with over the years of repairing them is yes the NVRAM batteries can be failed which adds up to replacement recalibrate. . But rebuilding the PS isnt too bad. You just need all the caps. Disassemble the scope remove PS module. Disassemble the rack assembly from off the PS and then replace the caps. Yes this is a process but can work out ok. The other issue with the 2400 digital I have dealt with is the CRT being shorted out. So right now I have 4 2400 digital scopes with shorted CRT removed and disposed of. So buying a cheap scope thinking repair will be apiece of cake isn’t always true. Many hours of work and unobtainable parts can be required to fix. Which is now you have to buy two scopes to maybe fix one. I currently have a nice working 2467 in my inventory if you are deciding to go another route.


My "new" Tek 485 with opt 4

Reginald Beardsley
 

I just got a nicely refurbished 485 which lists "opt4" under the SN. I could find no information despite several searches. I was surprised at how little information there was at the w140.com/Tekwiki. My 465 manual says opt 4 is EMI environmental. Is that true of the 485 also?

It came with a CD of the service manual, but I'd like to get a nice hard copy original if anyone has one they are willing to part with. I can offer a 465 and RM45 manuals in good condition in exchange.


Re: Looking at a broken 2440

Jeff Woolsey
 

On 7/19/18 1:06 PM, lop pol via Groups.Io wrote:
I'm looking at a 2440 that won't power on for $85. Worth it or not? What is the likelihood of just power supply issues and no IC problems?
Thanks fellas
I'd say that could be likely.  I bought a 2440 at a flea market for
more, and it was stone dead when I got it home.  With the help of people
on this list, I got it running.  The archives should contain the saga. 
It has some small nits that I live with.  I bought a second one with a
self-test failure to use as a parts mule, but the fix for that failure
was trivial...  It's my go-to scope now.

--
Jeff Woolsey {{woolsey,jlw}@jlw,first.last@{gmail,jlw}}.com
Nature abhors straight antennas, clean lenses, and empty storage.
"Delete! Delete! OK!" -Dr. Bronner on disk space management
Card-sorting, Joel. -Crow on solitaire


Re: Looking at a broken 2440

Brendan
 

I think I'm going to pass it up. I need to start being selective on my scope choices. I think my next scope will be one I really want. Which is a 2467 or 7104 with a MCP CRT.

On Thu, Jul 19, 2018 at 01:23 PM, goran parezanovich wrote:


Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .


<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas



Re: Looking at a broken 2440

goran parezanovich
 

Just remembered something - there is also a safety circuit designed to
stop powering up in the case of short for any of DC voltages rails - so
theoretically if there is a short at some other board the unit will not
start and power supply is still working correctly .

<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas



Re: Looking at a broken 2440

goran parezanovich
 

Personally I would offer less - in addition to power supply caps and
possible damage to the traces under the caps there is a possibility
that the NVRAMs will have to be changed ( dead batteries ) .

<-----Original Message----->
From: lop pol via Groups.Io [the_infinite_penguin=yahoo.com@groups.io]
Sent: 7/19/2018 2:04:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking at a broken 2440

?I'm looking at a 2440 that won't power on for $85. Worth it or not?
What is
the likelihood of just power supply issues and no IC problems?
Thanks fellas



Re: OT: Scopes and other electronics on "The Outer Limits"

 

Gentlemen,
The vast majority of comments on this topic are completely lacking any relevance to the TekScopes.

Please stop wasting our bandwidth.

Thank you, Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Jeff Urban
Sent: Thursday, July 19, 2018 9:38 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: Scopes and other electronics on "The Outer
Limits"

I had a boss who made that necessary.

I go in the office, tell him what a job needs, we got it, callem am
tell me if I should do it.

He gets on the phone and I hear "OK, we'll be there with it around
4:00"

"TONY, IT'S 3:30 !"



--
Dennis Tillman W7PF
TekScopes Moderator


Looking at a broken 2440

Brendan
 

I'm looking at a 2440 that won't power on for $85. Worth it or not? What is the likelihood of just power supply issues and no IC problems?
Thanks fellas


Re: OT: Scopes and other electronics on "The Outer Limits"

 

I had a boss who made that necessary.

I go in the office, tell him what a job needs, we got it, callem am tell me if I should do it.

He gets on the phone and I hear "OK, we'll be there with it around 4:00"

"TONY, IT'S 3:30 !"


Re: OT: Scopes and other electronics on "The Outer Limits"

Michael A. Terrell
 

Everyone knows that Scotty always pads the estimated time by a factor of 3.5 to 1.

The Outer Limits episode with the monkey working in something was on Comet TV last night, at midnight.

Michael A. Terrell

-----Original Message-----
From: Dave Seiter <d.seiter@...>
Sent: Jul 19, 2018 4:53 AM
To: "TekScopes@groups.io" <TekScopes@groups.io>
Subject: Re: [TekScopes] OT: Scopes and other electronics on "The Outer Limits"

Well, yeah- but if he had ever failed to get the engines working again at one of those critical junctures...
-Dave

From: Jeff Urban <@JURB>

Except Scotty.


Re: OT: Scopes and other electronics on "The Outer Limits"

Dave Seiter
 

Well, yeah- but if he had ever failed to get the engines working again at one of those critical junctures...
-Dave

From: Jeff Urban <@JURB>
To: TekScopes@groups.io
Sent: Wednesday, July 18, 2018 11:08 PM
Subject: Re: [TekScopes] OT: Scopes and other electronics on "The Outer Limits"

Except Scotty.


Re: OT: Scopes and other electronics on "The Outer Limits"

 

Except Scotty.


Re: 114xx bezzel buttons

Clark Foley
 

Pete,

The keycap has two little tabs that snap over the momentary switch. I will send a photo if you have not resolved this yet. Removing the keycap requires access to the button board because the keycap tabs must be pried carefully from the switch. Installation is easy. You just jam it over the switch, straight in, and the tabs flex and snap into place. By the way, the same keycap is used on the 11K plugins.

Clark


Re: OT: Scopes and other electronics on "The Outer Limits"

Dave Seiter
 

Or anyone who had a red shirt- that was the kiss of death!
-Dave

 new character on Star Trek, but not Uhura, you are dead within the hour. At least it seemed so.


Re: 465B Square Wave problem

 

Couple of questions and a comment.

One, why can't I get the print at w140 ? I went to that Polish site and got it and it is scanned terribly and there are tings missing. Then I went to BAMA and it appears to be the same file but also on the list was "missing pages". None of them seem to have the end of the front end. Where is a good manual for this ? I don't see any TP1 or 2, the PDF I have is 47.4 MB. Is that the same as you got ? If so, can you tell what pages those test points are ? Might help.

Two, your pictures show 2 waveforms, one severely overpeaked and the other severely underpeaked. What is the difference in the settings between the two ? Looks like the attenuator is set the same and both CH 1, are they at different frequencies ?

Now, one of my general rules about troubleshooting is that when it doesn't work right look at the last thing done to it. you did the multiplier which should have no bearing on the peaking. you changed the vertical output board. not if both channels are affected the same way that means the problem is there. If it is different between CH 1 and CH 2 that is a different story. But you only changed the output right ? If both channels display the same there is one thing they have in common.

Both David and Fabio are right, the 5 mV range is where to start. If it displays the same at that setting then get out of the attenuator. (which I call the front end) Forget any adjustments there.

If you find the display the same on both channels down there, whatever compensation is on the output board is the most likely culprit except for the outputs themselves.

Vertical deflection plates on a scope can affect focus, but that means there is an imbalance in the output stage. When you stick a probe on there you just put 10 meg to ground. (I hope you use 10 X except in rare cases when you need all the sensitivity) If that causes a DC offset of only one plate, or a common mode offset in both plates that could be the cause of the problem as well as the compensation problem. But to determine that we need the settings used on your 2 quite different waveforms. there are o clues, no readout on the screen and we can't see the time base, all I think I saw (pretty sure) is that both waveforms are from Channel 1.

If by chance is it intermittent, then it is an intermittent cap that goes shorted and then open when it feels like. Not the most uncommon failure mode in the west. That's where the frequency might help to determine the cause, the higher pF value caps seem a bit more likely to do this. And when it comes to frequency comp they are not using tantalum.

I hope this is of at least some help, so I put it out there. If not just ignore it. but that's the way I would proceed, go to 5 mV and see what that looks like, both channels. And don't try to align it anymore. That is far too much error to be simply in need of alignment.


Re: OT: Scopes and other electronics on "The Outer Limits"

 

On Tue, Jul 17, 2018 at 02:37 PM, David Hess wrote:


I found some of the old Twilight Zone and Outer Limits episodes to be
terrifying as a child. The Zanti Misfits comes to mind.
Something lost with youth. They were better when young and can really get scared. Later they lose some of their bite, or more aptly we lose the ability to feel it. It's almost impossible for a show to even "move" me slightly. Even young it eventually becomes clear that the good guys are not going to die, it is in their contract :-) well there was an exception, if you're Black and a new character on Star Trek, but not Uhura, you are dead within the hour. At least it seemed so.

Had an argument online a while back about the original airing of War Of The Worlds. People got so scared that some of them killed themselves. A guy was claiming there were adequate announcements that it was fiction and there was an argument about it, I wasn't in it yet but it piqued my curiosity. I downloaded the original and scrutinized and I can see why people might think it was real. There were only a couple of announcements it was Wells, they made it look like it was a music show and these were news interruptions. So if you go to the bathroom or something and miss that...

Star Trek had set and setting in the distant future, but much of the Twilight Zone and Outer Limits was set in the present. That probably contributed to its scariness.

I wonder just how much scifi contributed to our interest in science and technology.


Re: tants new vs old

Sergey Kubushyn
 

On Wed, 18 Jul 2018, Craig Sawyers wrote:

Better yet replace them with higher voltage rated ones if they are available. 20V tantalum lasts
forever
on 5V rail as well as 35V one on 15V.
Well, yes. All I'm saying is that I have identical plugins (such as 7A26)
in which at some point Tek went from tant bead to aluminium electrolytic.
So substitution is tried and tested.
That is fine where it is possible. Alas there are places where it is
difficult to make such a replacement. Just for example -- there are some
high capacitance (something like 1,000uF 25V) wet tantalums in 494AP inside
RF enclosures that were used because of much higher capacitance per volume
and it is almost impossible to find an aluminum capacitor that would've fit
into those enclosures even with same capacitance. Trying to find something
of the same size with bigger capacitance to properly replace a tantalum
doesn't make the task any easier :)

And low ESR is not as good for tantalum beads as compared with modern low
ESR aluminium electrolytics designed for switched mode supplies. As an
example an AVX 47uF 35V tantalum bead has an ESR at 100kHz of 0.8 ohms. A
Panasonic FR of the same capacitance, but 25V rated has an ESR of 0.3 ohms
at 100kHz.
There are low-ESR tantalums these days that are even better :) There are
also other considerations like limited life of those aluminum/polymer
capacitors, much higher leakage currents, bigger size etc. For power
supplies those are OK but they won't fit the bill where some unique tantalum
features are needed. And one should not forget that all aluminum capacitors,
polymer or not, are _WOUND_ ones unlike tantalums so they have much higher
inductance.

Properly chosen tantalum essentially lasts forever unlike aluminum which is
also a factor.


I can send you a handful :) They _ALWAYS_ leak sooner or later because of their very chemistry.
They
are filled with sulfuric acid and although silver sulfate has very low solubility it is still not
zero so sooner
or later that nice silver can turns to sieve. And the fact they are almost always used at their
rated
voltage or even above also doesn't make them last longer...
Operating any capacitor at or above its rated voltage is a short term recipe for capacitor death
regardless of chemistry. Even with wet tant, the current recommendation is that for long life the
rated voltage should be at least 1.6 times the operating voltage.

I have dozens of those leaked in 492BP/494AP SAs that I refurbish on a regular basis. The same is
true
for those HP 835xx microwave plugins that I revived quite a few -- I have never seen a single such
plugin that didn't have at least one leaked wet tantalum. The most spectacular was one 83572A
plugin
where sulfuric acid from one big wet tantalum ate off it leads completely, spilled on the
motherboard
and ate a hole through the entire motherboard PCB, through all of its copper and fiberglass
layers.

That is impressive! Were these rubber sealed versions?
They were teflon sealed. But that doesn't matter because vast majority of
them didn't leak through the seal. They had their silver cans eaten through.

The very first sign of imminent failure is intense blackening around
NEGATIVE lead and then case color change under the thermosetting sleeve.
Sulfuric acid etches the can and finds its way out through microscopic (not
even "pinhole") holes first. Capacitor at this stage is still mechanically
sound and most of that miniscule quantity either dries out around hegative
lead or gets trapped inside the plastic sleeve thus changing the case color.
The capacitor is still within its specs at this point but its case is
already seriously weakened and mechanical failure is just around the corner.
And when it finally happens the capacitor simply breaks into pieces and all
sulfuric acid it contained gushes out making a big puddle that eats whatever
it gets in contact with.

The above scenario applies to properly used wet tantalums. Those cheaper
rubber-sealed ones in e.g. 7000-series plugins usually have different
failures mechanism -- they were used at their full rated voltage and even
above and had significant ripple currents running through them so they
overheated and boiling sulfuric acid found its way out through positive
terminal seal way before it got a chance to eat through the silver can.

---
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Re: tants new vs old

Tom Gardner
 

On 18/07/18 09:29, Craig Sawyers wrote:
I have had axial tantalum capacitors leak and destroy nearby PCB traces, specifically
C6246 and C6341 in a Tek 1502 TDR.
Interesting - must check mine. Wonder why they used them only on the +25V rail, which is only used on
the high voltage board, to feed the switching transistors on the primary of the HV transformer, but
regular electrolytics on the other rails? Noted that these wet tants are 30V parts on a 25V rail
(rated = 1.2 rail voltage), so is somewhat close to the wire.
It has only happened in 20% of my 1502s. I seem to have a
fetish for the damn things :)

ISTR the 25V rails are not low current, which might increase
the stress.