Date   

Re: Tek 2246 issues

Alex
 

Besides recapping, and while you are there (at the power supply board), one of the highest priority preventive work for any of the 224x scopes (2245, 2246/A, 2247A, and 2252), is to replace all the rectifier diodes on the LV power supply board (total 17 diodes) that have either ZM or ZS marked on them as they are well known to get leaky after some time and might fail. Original part number is 152-0400-00 (MB2501), and a good replacement would be to use MUR160 600V 1Amp 50nS diodes (Mouser PN 821-MUR160). Do not use regular 1N400x diodes.

Good luck.
Alex


2440 PSU trouble

oiledllamas@...
 

Hi, I recently bought a 2440+2402 combination that appears to have never been used really. The 2402 won't boot from my floppy, but I don't know anything about msdos, and both are issues for later. The 2440 boots up, but with a blurry CRT that cannot be adjusted out. The 15V rail is reading 14.14V, which I assume is the problem. I have checked (out of circuit) R576, R757, CR757, CR583, and CR576, in addition to replacing U570 (op amp), all to no avail. What should I check or replace next? I was thinking replace U579 (voltage regulator). The resistance from the 15V test point to ground is 211ohms, which appears to be normal considering the other rail resistances to ground. I suppose the next test would be the low voltage power supply board with nothing plugged into it. Any ideas as to what could cause this? The schematic is on drawing 23 in the service manual, and principles of operation on page 3-98.


Re: OT: Datron Wavetek 4920 AVMS manuals

 

Thank you, I've uploaded them to the Datron-Wavetek group files area, so please delete the rar file from the Tekscopes file area.

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of udtmang via groups.io
Sent: 03 August 2021 20:39
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: Datron Wavetek 4920 AVMS manuals

uploaded to files area


Re: OT: Datron Wavetek 4920 AVMS manuals

Michael J Wallace
 

uploaded to files area


D11 CRT

Michael J Wallace
 

Looking for a new or used D11 crt part number is
154-0634-10
other numbers on label are
57336
21-3
New or used is fine as long as it works, unless someone can point me to an acceptable replacement for a single beam storage crt, i dont really need storage

Thank you.


Re: 184 marker generator problems

Tom Gardner
 

On 04/08/21 08:15, Morris Odell wrote:
Hi all,

I'm trying to repair a 184 that appears to have suffered at the hands of a previous owner. The delay line has no ferrite beads and is not working but that's not such a big deal as it can be bridged to allow markers to get through even if they are not coincidental.

The immediate problem is in the 10 MHz to 2 MHz (0.1 uS to 0.5 uS) divider. This is a charge pump circuit where each cycle of the 10 MHz reference input pumps a little bit of charge out of a fixed 15 pf ceramic cap into a storage cap (39 pf in parallel with a 9-50 pf ceramic trimmer) and when it gets to a certain voltage after 5 pulses it triggers a blocking oscillator using a 2N964 high frequency Ge pnp to provide 2 MHz pulses. In my unit it divides by a larger number than 5 even at the extreme of the trimmer cap setting. That indicates either that the storage cap has gone high or the 15 pf cap is too low in value. Alternatively one of the two isolating diodes might have too much reverse leakage which is probably more likely than a ceramic cap drifting. The 2N964 tests OK and temporarily replacing it with a high frequency Si transistor doesn't make much difference. Either way it will be difficult to replace the appropriate bits. That divider affects all the other marker frequencies which are unstable and incorrect.

Before I unplug lots of wires to the board, replace diodes and disconnect the delay line I wonder whether anyone else has encountered this problem or has any advice about it. There's no rush as I'll be busy with other stuff for a couple of days anyway.
It might also be that there is too little charge being put onto the 15pF capacitor, perhaps due to a (carbon composition) resistor being too high.

Tacking a resistor in parallel with a suspect resistor could be a way of testing that without removing the board.


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Roger M
 

Keith ... The TekWiki page regarding the 12AU6 leaves obvious bread crumbs
for a path to the selection process underlying the 157-0050 . Please note that no
words are sprinkled around about gain or linearity.
So go to
https://w140.com/tekwiki/wiki/12AU6
..and look for the links on "tube aging procedure" and "selection and checking procedure".
You'll find two PDF's that contain info on a raft of TEK tubes.

In the end no magic tricks appear to have been performed.

FWIW: It caught my eye that the hand written notes in the "selection" PDF are a match with
red pencil originals in one of two binders I obtained from Stan Griffiths' estate, and I'm darn
glad to see the information has been previously copied for the educational enjoyment of all.

Roger Marin
Canby, OR


184 marker generator problems

Morris Odell
 

Hi all,

I'm trying to repair a 184 that appears to have suffered at the hands of a previous owner. The delay line has no ferrite beads and is not working but that's not such a big deal as it can be bridged to allow markers to get through even if they are not coincidental.

The immediate problem is in the 10 MHz to 2 MHz (0.1 uS to 0.5 uS) divider. This is a charge pump circuit where each cycle of the 10 MHz reference input pumps a little bit of charge out of a fixed 15 pf ceramic cap into a storage cap (39 pf in parallel with a 9-50 pf ceramic trimmer) and when it gets to a certain voltage after 5 pulses it triggers a blocking oscillator using a 2N964 high frequency Ge pnp to provide 2 MHz pulses. In my unit it divides by a larger number than 5 even at the extreme of the trimmer cap setting. That indicates either that the storage cap has gone high or the 15 pf cap is too low in value. Alternatively one of the two isolating diodes might have too much reverse leakage which is probably more likely than a ceramic cap drifting. The 2N964 tests OK and temporarily replacing it with a high frequency Si transistor doesn't make much difference. Either way it will be difficult to replace the appropriate bits. That divider affects all the other marker frequencies which are unstable and incorrect.

Before I unplug lots of wires to the board, replace diodes and disconnect the delay line I wonder whether anyone else has encountered this problem or has any advice about it. There's no rush as I'll be busy with other stuff for a couple of days anyway.

Thanks,

Morris


Re: What do you do when you get a call from AUSTRALIA

Randy Newman
 

Dear Dennis. SO very glad to hear that you are ok.
I just want to say that I have very much appreciated all your work here on this forum.
As I am into the latter portion of my EE career, I am finding that the number of at-work acquaintances and friends is diminishing. I’m in That demographic. That being the case, I am appreciative of relationships, both near and far.

Have to run, but just wanted to offer a word of encouragement, and say thanks. More later, hopefullly via PM.
Randy Newman.


Re: OT (again, but different)

Milan Trcka
 

Ken,
I have been in the field of development, qualification, and production of med instrumentation for some 17 years. I share your pain. All I could suggest is to go through prototype(s) test and "letter to file" route while documenting that the replacement is every way identical to the old one. If the LED is not a "critical" or "life support" component (established reliability, exact wavelength and intensity, tight specs, etc), and form-fit-function can be be proven, perhaps as an indicator, it should work. If the LED is a part of, say, pulse oximeter sensor, it may be a bit harder. problem. Updated Hazard Analysis would help. Either way, is is a bit of work. EOL is a pain. Planning for EOL is a major part of the game. Been there, done that...


Re: File /wavbtek.rar uploaded #file-notice

Tom Lee
 

There is lots of freeware that does the job. My favorite happens to be 7zip, but that’s one option among many.

Cheers
Tom

Sent from my iThing, so please forgive brevity and typos

On Aug 3, 2021, at 15:52, Roy Morgan <k1lky68@gmail.com> wrote:

I looked up the.rar file format but am still confused.

Is opener software free, easy to use, and widely used among our list members??

Roy Morgan
K1LKY Western Mass

On Aug 3, 2021, at 3:42 PM, TekScopes@groups.io Notification <noreply@groups.io> wrote:
The following files have been uploaded to the Files area of the TekScopes@groups.io group.

/wavbtek.rar
_._,_




Re: File /wavbtek.rar uploaded #file-notice

Dave Daniel
 

Yes, there free .rar decoders for Windows.

DaveD

On Aug 3, 2021, at 19:36, Paul Amaranth <paul@auroragrp.com> wrote:

It's not my favorite format but an unrar command is available freely for Linux.
I would assume you can find one for Windows as well

Paul

On Tue, Aug 03, 2021 at 06:52:42PM -0400, Roy Morgan wrote:
I looked up the.rar file format but am still confused.

Is opener software free, easy to use, and widely used among our list members??

Roy Morgan
K1LKY Western Mass

On Aug 3, 2021, at 3:42 PM, TekScopes@groups.io Notification <noreply@groups.io> wrote:
The following files have been uploaded to the Files area of the TekScopes@groups.io group.

/wavbtek.rar
_._,_

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows





Re: File /wavbtek.rar uploaded #file-notice

David Holland
 

7-Zip will open RARs under Windows.

https://www.7-zip.org/

David

On Tue, Aug 3, 2021 at 7:36 PM Paul Amaranth <paul@auroragrp.com> wrote:

It's not my favorite format but an unrar command is available freely for
Linux.
I would assume you can find one for Windows as well

Paul

On Tue, Aug 03, 2021 at 06:52:42PM -0400, Roy Morgan wrote:
I looked up the.rar file format but am still confused.

Is opener software free, easy to use, and widely used among our list
members??

Roy Morgan
K1LKY Western Mass

On Aug 3, 2021, at 3:42 PM, TekScopes@groups.io Notification <
noreply@groups.io> wrote:
The following files have been uploaded to the Files area of the
TekScopes@groups.io group.

/wavbtek.rar
_._,_

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows






Re: File /wavbtek.rar uploaded #file-notice

Paul Amaranth
 

It's not my favorite format but an unrar command is available freely for Linux.
I would assume you can find one for Windows as well

Paul

On Tue, Aug 03, 2021 at 06:52:42PM -0400, Roy Morgan wrote:
I looked up the.rar file format but am still confused.

Is opener software free, easy to use, and widely used among our list members??

Roy Morgan
K1LKY Western Mass

On Aug 3, 2021, at 3:42 PM, TekScopes@groups.io Notification <noreply@groups.io> wrote:
The following files have been uploaded to the Files area of the TekScopes@groups.io group.

/wavbtek.rar
_._,_
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: File /wavbtek.rar uploaded #file-notice

Roy Morgan
 

I looked up the.rar file format but am still confused.

Is opener software free, easy to use, and widely used among our list members??

Roy Morgan
K1LKY Western Mass

On Aug 3, 2021, at 3:42 PM, TekScopes@groups.io Notification <noreply@groups.io> wrote:
The following files have been uploaded to the Files area of the TekScopes@groups.io group.

/wavbtek.rar
_._,_


OT (again, but different)

ken chalfant
 

Greetings,

Kindly forgive this way off topic message.

My day job is in medical capital equipment manufacturing (not as rewarding as one might think).

A big part of my job is solving EOL (End Of Life) component issues with a system that has been successfully in production for a long time.

Recently we were advised that three of the components we use (SMD LED’s) had gone out of production. We were not offered an end of life buy opportunity.

Because it is a PMA (Pre-MArket Approval) medical product even changing to the manufacturer’s recommended replacement is a staggering amount of man hours and documents.

We are trying every source and the brokers we know, but so far we have only found one of the three.

Can anybody suggest a source for the following two part numbers?

Avago (Broadcom) Red SMD LED: ALMD-EG3D-VZ002 (1,000 - 1,500 pieces)

Avago (Broadcom) Amber SMD LED: ALMD-EL3D-VX002 (1,000 - 1,500 pieces)

Thanks for your time and the use of our bandwidth.

Regards,

Ken


File /wavbtek.rar uploaded #file-notice

TekScopes@groups.io Notification <noreply@...>
 

The following files have been uploaded to the Files area of the TekScopes@groups.io group.

By: udtmang@...

Description:
wavtek 4920 stuff


Re: Does the 5L4N small grey knob exist elsewhere?

 

On Tue, Aug 3, 2021 at 06:03 PM, Victor wrote:


In my 5L4N manual (Instruction Manual - printing JAN 1975) the MULTR/MNL part
number appears to be 366-1608-00.
As far as can see #1 on the exploded drawing which is 366-1608-00
is the CAL knob with red top. The MULTR/MNL is #7. I agree that the
7 looks almost as a 1 on the drawing but the clue is how many of
each P/N is used i.e.1 of 366-1608-00 and 6 of 366-1540-00.

Hakan, do you know if the "Instruction Manual"s available for sale are the full service manual for the 5L4N?
I don't know about any manual available for sale but if the P/N is 070-1733-00 then it is the full manual.
Last revision date is July 1982.

/Håkan


Re: Tek 2246 issues

Mark Vincent
 

nmi8080,

If you have enough skill and knowledge, recap it yourself. I do not know your skill level. The power supply should be redone. The electrolytics on the secondary side can be raised in value, e.g. 1000mfd to 1500mfd, 39mfd to 56mfd, etc.. The main input filter, 270mfd can be 390mfd. The electrolytics in the preregulator circuit need replacing as well. The 4,7mfd ones can be a 50V 5% film type. The types I have found to be the best in life, lowest ESR and are high temperature are Nichicon ULD, UHE, UCA/S/Y and LGR (this last one would be for the main filter >270mfd). The film types can be Kemet, Wima , etc.. After replacing the caps, adjust the 7,5V adj.. That should make the other voltages correct. I am looking at the schematic, I do not own this model.

Change ALL RIFA caps! These are usually in a clear amber colour case. Use X1 and Y1 types as replacements. The X1 and Y1 can be X2 and Y2 if you want to use a higher voltage rating for these. These are on the mains input and may be a few in the primary of the power oscillator.

If there is a battery in it for any type of backup, replace it. I do not know if an axial can be installed. If so, a larger capacity one is better, e.g. 2,4A/hr. If not, find the largest capacity that will work. The larger capacity will give a longer life before needing replacing. A weak/dead battery can cause weird problems. Refrain from replacing ICs in the logic circuits until a new battery is installed. You may need to use it a couple of times after replacing the battery for everything to work right. I have seen this in my 2440.

After replacing the above parts, clean contacts, make sure it is working then calibrate it, if needed. The beam finder switch should also be cleaned. That being dirty will cause display problems.

All these parts are available from Mouser.

Mark


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Renée
 

Keith, Dave and Tom-

Keith I appreciate your view on the tubes as I acquired a 575 and it is in need of some tubes. By sheer visual, the magic gas has left, and white is not the best colour for tubes.

So Please keep this info coming so I may continue to learn and not make mistakes previously made by those that have gone before me, and in fact have far more knowledge than I.

The knowlede that is available here is tremendous. Thank you all.
back to listening..ehhhh...reading/watching
Renée
BTW my 575 was stored in a barn and looks like it was outside for a winter too. currently stored inside at a friends place awaiting me and resurrection.

On 8/3/21 7:13 AM, Keith wrote:
Hi Dave, Hi Tom,

Yes, I understand what you're saying, and I certainly respect your input and cautions. You make a lot of sense. Please forgive my fast and loose description - as "tube testing" is a sort of careless shorthand phrase. I'm guilty of using it for both for my Hickok and for a variety of custom fixtures I often gin up that manipulate tubes in ways that let one quantify all kinds of interesting things.

re: 157-0050-00 12AU6 selected tubes in a 575

Skipping over all the discussion of what the magic parameter might be, it would seem to me that Tek would have most likely to have been looking for a.) a strong similarity in linearity of the four "selected tubes" over a fairly wide range of operation, and b.) a predetermined value for a certain amount of desired gain when popped into a circuit with certain not so easy to adjust parameters. I say this because the circuit gain and differential balance and D.C. balance all appear to be reasonably adjustable at R434, R459, and R456.

Not to be disrespectful here, but these three parameters had to be adjustable, because the 575 originally had to accommodate a generic 12AU6 in all these spots! That's because Tek built the 575 this way for TEN YEARS (1957-1967). They sold at least many thousands of 575 like this before they issued the Miracle Max 12AU6. Why the change in 1967 and again in 1973?

I think the whole thing goes to ease of calibration.

A careful read of the text of 1973's Mod M12361 comes to mind here, Back before Mod 12361 came about, Tek apparently didn't care what kind of 12AU6 you put in the horizontal and vertical amplifiers. The caveat was that you had to then be prepared to chase accurate calibration on the various step generated ranges. That was done in part by manually tweaking R445 and R465 resistors on the ceramic strips. (those are the pre-1967 nominally 3.3m shunt resistors for R347 and R447). Practically speaking, this might mean soldering and re-soldering fairly awkwardly located resistors on the fragile ceramic strips. Not impossible, but certainly also likely to cause drift to the precision 60k shunt resistors R447/347, and potential damage to the ceramic strips - if done over and over.

I admit this is a guess, but strong hints at this reasoning are revealed in two places. The first is in the 1959 factory calibration procedure. (See 575-3, top of page, correcting differential balance errors by replacing R345/445 by using "...standard RMA resistance values from 3.3 to 10M."). Second - and more revealing - there's the 1973 production modification M12361, page 3. There, they TELL you to use an 8.2m resistor with the special tubes and even supply the resistor in the kit. O.K. Great, slap in an 8.2m and the magic tubes, calibrate and you're happy, right? But wait! Besides the Miracle Max tubes and the "selected 8.2m resistor" in the M12361 kit, they also continue to include what is basically a cleaned up version of the old 1959 calibration procedure, with R345/445 "tweaking" instructions as page 3 of the kit instructions. Hmmm... why?

Clearly, for the 1967/73 mod, they've picked tubes with a certain narrow range of gain and linearity and essentially warranted that these special tubes ALMOST always work right with an 8.2m resistor shunting R347/447. This mostly eliminates the fussy soldering and re-soldering of something between 3.3m and 10m...at least for most people. But Tek does seem to admit (by including p3, 1973 mod kit) that you might still have to tweak for your scope...even WITH the special 157-0050-00 12AU6. Like I said, Miracle Max "mostly calibrated! I said MOSTLY!"

THAT, in my opinion is why the 157-0050-00 tubes are special. I don't think the magical qualities themselves are difficult to identify...Tek just didn't spell out the gain and linearity specifications. How hard can that be? Put a Miracle Max in the circuit. Measure the performance over ten steps. Stick in a generic 12AU6, compare. Not rocket science.

Now for sure, I'm not claiming to be anywhere near as smart as you guys, OR those guys at Tek. In fact, I'm positively a cave man by comparison. Further, I know precious little about the secret life of transistors...but I do know tubes a little. I know that there are ways to make fixtures and/or use circuits that exist in a way that will quantify every single one of what must be a strictly limited set of tube performance similarities. Tek did it, so have lots of other folks...and even a lowly troglodyte like me does that fairly regularly for my own amateurish reasons. Bottom line, at the end of the day there are only so many possible parameters. Tek wasn't BUILDING these tubes. Even the gods at Tek can't make tubes have parameters that tubes simply don't have...and even with pentodes there are only so many of them.

In this case, we have the circuit. We know the input signal. We have the optimized values that are known to work for a "calibrated" tube. We have example of the calibrated tube. In fact, I have about nine of the special 12AU6 with a Tek decal on it. Three seem to me to be worn out, two are marginal, four appear NOS in the box. Then, I have several other NOS "non-magical" 12AU6 which can be compared to the TEK magic reference tube in the calibrated circuit.

Color me a dunce, but with all these clues and proofs, reverse engineering to measure Tek's secret tube performance parameters can't be that fussy. I don't have to invent or guess, I only have to measure all reasonable parameters in a working circuit and gather the numbers from qualified new, qualified worn-out, and non-qualified tubes. Make a spreadsheet. The X factor should pop right out.

I'm certainly not claiming to be the man, but somebody's eventually going to have to figure this out, since those miracle max branded Tek 157-0050 12AU6 must be getting fairly scarce? Otherwise, what do we do when the last one is used up? Throw away our 575 because we can't get four good 157-0050-00? (or go back the the 1959 hunt-and peck model of calibration, i suppose?)

But again, bless you guys, I appreciate the cautions and for sure I won't do anything stupid. And, if all else fails, I guess I can always stick the last of my stock of special Miracle Max Tektronix 12AU6 in there and call it a day.



respectfully,

Keith
coolblueglow




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