Date   

Re: TM500 Mainframe Tester construction master thread.

Andy Warner
 

So far, I have one observation, and one question:
1. observation - digikey BOM has a typo in the reference designators for the 1N4007 diodes. "CR11" should read "CR101".
2. question - if I insert the stops in S3 where the manual suggests on page 2, the index on the knob does not align with the front panel when using the flat on the shaft with the grub screw.
I plan on buzzing the switch out to see what the correct location is, but I thought I would ping the list about the inconsistency as well.

--
Andy


Re: 465/475 Volts/Div range LED swap problem.

Chuck Harris <cfharris@...>
 

When faced with that problem, I usually add a diode
in series with the emitter of the transistor switch.
That allows a "0" to turn the switch off better.

-Chuck Harris

Dave Peterson via groups.io wrote:

Sorry Dave.

The link was to the thumbnail. The full picture can be expanded by finding it in the thread:

https://www.eevblog.com/forum/repair/tektronix-465/msg697587/#msg697587


Not so much theatrics as impatience on my part. I'm cleaning up my LTSpice simulations to upload to the files area, and need to build up a photo album. In the interests of saving on the TekScopes group space usage I need to resize all my pictures by quite a lot.

No need to apologize. Pardon my impishness and impatience.

Yes, the 10x diode stays on weakly. I tried all manner of remedies, but the basic issue is that Q386 needs enough base current to drive the 1X LED, and that current is always enough to cause the 10X LED to start illuminating. I'd just ordered a batch of 100 2N3904's to replace one missing in the scope. So decided to wire one parallel to the 10X LED. I was really trying to minimize the complexity of this solution. This was the best I could come up with.

Posting the LTSpice files now. Want to/will add a writeup PDF too.

Dave

On Saturday, February 20, 2021, 10:11:48 AM PST, Dave Voorhis <voorhis@gmail.com> wrote:

On 20 Feb 2021, at 17:54, Dave Peterson via groups.io <davidpinsf=yahoo.com@groups.io> wrote:

Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image

What's wrong with this picture?
It’s too small to see?

Sorry to be grumpy, but I’m not finding your guessing-game approach much fun. Could you share the problems you’ve found and the solution you’ve developed and, with respect — and unfortunately there’s no write to say this as politely as I would say it in person — please spare us the theatrics?












Re: Help replacing a resistor/inductor in SG503

TomC
 

The ones that failed were rated at 15 volts and were on the 15 volt power lines. Obviously a poor choice as they only lasted 40 or so years before failing. Well, maybe not so bad after all.

I think later revisions went to a 25 volt rating. That's what I used to replace the originals.

Tom

On 2/19/2021 6:54 PM, Harvey White wrote:
GIven that the recommendation of the manufacturers was to minimize the headroom between the working voltage and the rated voltage (to the point where things fail.....)
That's a good idea to replace with higher voltage ratings, but I'm dumping this in here in case someone only hits this thread and doesn't research the older (and similar) ones.
but I can't figure out how to shoehorn FOOM! in here.....
Harvey
On 2/19/2021 9:37 PM, TomC wrote:


On 2/19/2021 5:57 PM, Roy Thistle wrote:
On Fri, Feb 19, 2021 at 04:02 PM, TomC wrote:


To fix, I took a closeup photo of one that hadn't been damaged and counted
turns. There are 47 turns. Found the wire gauge with a micrometer on the wire
from one that was destroyed. Then ordered wire and a supply of carbon comp 10
ohm resistors.

Made up a jig to wind the 47 turns on new 10 ohm resistors. Then soldered the
ends and painted with dope.
As Stan Lee would say, "nuff said!"
Actually, what I failed to say was that I replaced those 4 tantalums, using a higher voltage rating, in every 7A26 I own. Both the ones that had failed short, and the ones that hadn't failed yet.  But that is probably obvious to the people here.







Re: 465/475 Volts/Div range LED swap problem.

Dave Peterson
 


Re: 465/475 Volts/Div range LED swap problem.

Dave Peterson
 

Sorry Dave.

The link was to the thumbnail. The full picture can be expanded by finding it in the thread:

https://www.eevblog.com/forum/repair/tektronix-465/msg697587/#msg697587


Not so much theatrics as impatience on my part. I'm cleaning up my LTSpice simulations to upload to the files area, and need to build up a photo album. In the interests of saving on the TekScopes group space usage I need to resize all my pictures by quite a lot.

No need to apologize. Pardon my impishness and impatience.

Yes, the 10x diode stays on weakly. I tried all manner of remedies, but the basic issue is that Q386 needs enough base current to drive the 1X LED, and that current is always enough to cause the 10X LED to start illuminating. I'd just ordered a batch of 100 2N3904's to replace one missing in the scope. So decided to wire one parallel to the 10X LED. I was really trying to minimize the complexity of this solution. This was the best I could come up with.

Posting the LTSpice files now. Want to/will add a writeup PDF too.

Dave

On Saturday, February 20, 2021, 10:11:48 AM PST, Dave Voorhis <voorhis@gmail.com> wrote:

On 20 Feb 2021, at 17:54, Dave Peterson via groups.io <davidpinsf=yahoo.com@groups.io> wrote:

Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image

What's wrong with this picture?
It’s too small to see?

Sorry to be grumpy, but I’m not finding your guessing-game approach much fun. Could you share the problems you’ve found and the solution you’ve developed and, with respect — and unfortunately there’s no write to say this as politely as I would say it in person — please spare us the theatrics?


Re: Failed Transistor with Low h(FE)?

Chuck Harris <cfharris@...>
 

I have often wondered if many circuit designers
take these "holes" caused by factory robbery into
account when they specify their parts... I never
did, but perhaps the production guys would have
liked me better if I had?

You think you are using a 1K nominal part, +/-5%,
but in reality, your part is really:
[1.05K|0.95K] +/-2.5% of 1K

You thought you bought a one humped dromedary camel,
but Amil the camel dealer came rolling up to your
camp with a two humped bactrain camel, and none of
your saddles will fit.

It puts a completely different spin on a Monte Carlo
analysis on part tolerances.

No wonder HP only used 1% or better parts.

-Chuck Harris


Ed Breya via groups.io wrote:

Chuck wrote: " What I generally
find is that out of 1000's of 5% resistors, not a single one
was within 1% of its nominal value. But, all were within 5%."

These two-lobed distributions are common. The ones that fell in the middle range near 1% were likely separated out and sold as a better grade part, leaving the rest of the distribution (which should be normal) with a hole in the middle.

Ed







Re: 2467B TEST 04 FAIL 02

Chuck Harris <cfharris@...>
 

Sadly, there is no sanctioned way of telling what step
has failed.

You can tell with unsanctioned methods by reading the
NVRAM, and looking at the data bits. The location and
layout of the calibration data is only loosely described
in the maintenance section of the manual. There are 170
14 bit calibration constants in the NVRAM. Each of those
constants has its own checksum, and status bits to tell
if it is in or out of range. All left to us as a mystery
by tektronix.

If you look at the calibration data using the EXER02 function
in the calibration/test menu, you will see each of the
256 RAM locations you can read has the format:

AA DDDD P, where "AA" is the address, "DDDD" is the hex
data for the constant, of which 14 bits are valid, and P is
the parity bit X is even, blank is odd.

The actual locations of this data in the NVRAM have been
found and discussed by others on this group.

I meant one day to take a virgin NVRAM, and read it after
every step of the calibration routine is completed, and
to note the differences in the calibration section of the
NVRAM. I will probably never do so, because I, well, I have
a life, and I just don't care that much....

However, there is nothing stopping one of you from doing
the heavy lifting. I would suggest using what is called
an EPROM emulator, or RAM emulator to save wear on the
NVRAM socket. There will be at least 170 times the data
after a calibration step needs to be compared with the
"virgin" NVRAM data.

Please note that the NVRAM has only 170 calibration constants,
and the entire rest of the NVRAM is used as program storage,
and as a result, is reset every time you fire up the scope.

This is your task should you choose to accept it, good luck
with it! International fame and no fortune await!

-Chuck Harris

tvoshell@cableone.net wrote:

My 2467B >B052xxx suffered two nasties! (The processor board caps exploded and subsequently ate up some of the copper traces near them underneath the solder mask layer. (tough to see)
Also my sram backup died. I was able to get a new recent date code SRAM and it works ok but no cal data now. Also I was able to clean up the cap mess and replace the crummy electrolytic caps with tantalum caps.
I went thru the tek "ADJUSTMENT PROCEDURE" and set everything I could: the really fast horizontal cal's I didn't have gear for. I approximated the top end and pressed the trigger coupling button. I was able to program everything else, or so I thought, but now I am getting a cal limit error TEST 04 FAIL 02. Since the procedure is quite lengthy, with a lot of steps stored, it would be great to know which step of which cal is out of limit.

Is there a way to determine which cal/step is responsible for the error?

All responses are welcome, Thanks
TomV






Re: 465/475 Volts/Div range LED swap problem.

Ozan
 


A properly sized resistor in parallel with the X10 resistor should fix it.
I meant a properly sized resistor in parallel with the X10 LED should fix it.

Ozan

--------

Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image


What's wrong with this picture?

Dave

On Saturday, February 20, 2021, 09:46:09 AM PST, Michael W. Lynch via
groups.io <mlynch003=yahoo.com@groups.io> wrote:

I am sure that more than a few people here and elsewhere would like to hear
more about this.  I am a devotee of Mr. Goldberg myself.

--
Michael Lynch
Dardanelle, AR






Re: 465/475 Volts/Div range LED swap problem.

Ozan
 

The picture is too small to see what is happening but looking at the schematic X10 light bulb supplies the base current of Q396. Either X1 is not lighting up (too small current) or X10 is lighting dimly when X1 is selected depending on what is connected for the LED circuit.

A properly sized resistor in parallel with the X10 resistor should fix it.

Ozan


--------


Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image


What's wrong with this picture?

Dave

On Saturday, February 20, 2021, 09:46:09 AM PST, Michael W. Lynch via
groups.io <mlynch003=yahoo.com@groups.io> wrote:

I am sure that more than a few people here and elsewhere would like to hear
more about this.  I am a devotee of Mr. Goldberg myself.

--
Michael Lynch
Dardanelle, AR






Re: 465/475 Volts/Div range LED swap problem.

Dave Voorhis
 

On 20 Feb 2021, at 17:54, Dave Peterson via groups.io <davidpinsf=yahoo.com@groups.io> wrote:

Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image

What's wrong with this picture?
It’s too small to see?

Sorry to be grumpy, but I’m not finding your guessing-game approach much fun. Could you share the problems you’ve found and the solution you’ve developed and, with respect — and unfortunately there’s no write to say this as politely as I would say it in person — please spare us the theatrics?


Re: 1L10 crystal needed (Newbie)

Michael A. Terrell
 

Joel B Walker wrote:
I posted a picture of the circuit. Perhaps one of you exceptionally intelligent individuals could tell me what the drive level is for this crystal. I tried Lokoselectronics. They are the ones that wouldn't respond to my emails. Bomars website isn't working today. I see that there are SMD crystals available in that frequency range, but they can only be driven with miniscule power levels in the micro watts. This the need to know what the circuit demands of the crystal.
If all else fails, you could use a DDS module with a small controller like the Aurdino Nano, or even smaller to program the DDS on power up. You can not only program the frequency, but the amplitude..


What years were tunnel diodes designed into Tek instruments?

J Hunt
 

The recent discussion about tunnel diodes got me wondering about when they were being designed into Tek instruments.

Questions:

- introduction date and model of the first Tek instrument with tunnel diodes (maybe 1960?)
- last Tek instrument to use tunnel diodes (maybe 1975?)

I bet that Tom Lee and probably some of the Tek engineers (or rebuilders) in this group will know.

John Hunt
Portland, OR

***************************************************
Re: tunnel diodes retrace lines in curve tracer
From: saipan59 (Pete)
Date: Thu, 18 Feb 2021 13:54:46 PST

My understanding is that by the 1970's or so, TD's were obsolete because most of the practical circuits that used them could be done cheaper with modern transistors and IC's.


Re: 465/475 Volts/Div range LED swap problem.

Dave Peterson
 

Here's a hint:

https://www.eevblog.com/forum/index.php?action=dlattach;topic=45906.0;attach=157509;image


What's wrong with this picture?

Dave

On Saturday, February 20, 2021, 09:46:09 AM PST, Michael W. Lynch via groups.io <mlynch003=yahoo.com@groups.io> wrote:

I am sure that more than a few people here and elsewhere would like to hear more about this.  I am a devotee of Mr. Goldberg myself.

--
Michael Lynch
Dardanelle, AR


Re: 465/475 Volts/Div range LED swap problem.

Michael W. Lynch
 

I am sure that more than a few people here and elsewhere would like to hear more about this. I am a devotee of Mr. Goldberg myself.

--
Michael Lynch
Dardanelle, AR


Re: 1L10 crystal needed (Newbie)

Ed Breya
 

The very small or SMD ones at very low frequency ranges are likely the piezo-" tuning fork" type resonators - the 32,768 Hz watch frequency is the most common example. Your 900 kHz crystal requirement is around the traditional borderline of crystal can size changes - about a MHz. I don't know where the borderline is anymore, or how tiny regular crystals can be made nowadays, or how much can be jammed into an SMD package - it's pretty amazing, actually. If you can find any sort of regular crystal at 900 kHz, just try it and see. If you can only find it in a piezo type, it would be best to use it in the normally intended way, in a CMOS gate oscillator.

I still think you should just do the 9 MHz XO divided by 10 thing, and get it over with simply and quickly.

Ed


2467B TEST 04 FAIL 02

Thomas Voshell
 

My 2467B >B052xxx suffered two nasties! (The processor board caps exploded and subsequently ate up some of the copper traces near them underneath the solder mask layer. (tough to see)
Also my sram backup died. I was able to get a new recent date code SRAM and it works ok but no cal data now. Also I was able to clean up the cap mess and replace the crummy electrolytic caps with tantalum caps.
I went thru the tek "ADJUSTMENT PROCEDURE" and set everything I could: the really fast horizontal cal's I didn't have gear for. I approximated the top end and pressed the trigger coupling button. I was able to program everything else, or so I thought, but now I am getting a cal limit error TEST 04 FAIL 02. Since the procedure is quite lengthy, with a lot of steps stored, it would be great to know which step of which cal is out of limit.

Is there a way to determine which cal/step is responsible for the error?

All responses are welcome, Thanks
TomV


Re: Tm500 Extender on eBay

David Sidrane
 

I started a project to build a flexible adapter. The parts cost is not cheap, nor was the crimp tool. I screwed up the AC lines on the layout (do not ask it was dumb) the I ended up having to rework the boards, so they are not usable with out re-work. I wanted to make 3 sets for my CG5011 but after crimping and reworking the first one, they have just sat. I had planed to 3D print cases but my enthusiasm for the project dwindled. If someone wants a project, let me know.

http://www.nscdg.com/tek/tm5x.JPG

David


Re: PG506 vs. PG506A risetime?

 

Hi Jeff,
I got this reply from John Addis. He is the absolutely brilliant designer of many Tektronix ICs, circuits, amplifiers, and the DA1855!
Dennis Tillman W7pF

From: John Addis
Sent: Thursday, February 18, 2021 7:19 PM
To: dennis@ridesoft.com
Subject: RE: LeCroy DA1855A Differential Amplifier

Jeff,

The Preamble 1855 was designed in Beaverton. The LeCroy DA1855A was designed and built by Preamble Instruments in Beaverton until LeCroy bought Preamble Instruments and ultimately changed the 1855A front panel and body color from tan to gray. LeCroy never made the non-A version.

My copy of the Preamble 1855 Operator’s Manual (which should be the same as the LeCroy 1855A) lists the equipment required as PG506A. The PG506 and PG506A are essentially the same for the purpose of adjusting the 1855A. I am responsible for the inconsistency.

Later, my copy says “Pulse generators such as the Tektronix PG506 do not have a slew rate as high as might be encountered in some measurement situations...” There is no “If” at the beginning of the sentence. The intention was to allow additional fine adjustment, not to provide a basic means of adjusting CMRR because some device under test might not have an appropriately long enough pulse to adjust the probes over the entire frequency range. Best to use a flat top fast rise pulse such as the PG506/PG506A.

There are few generators providing a higher amplitude and faster rise pulse. I built one at Preamble that had 150V output with a 1.5ns risetime. I still have it. I don’t remember if that was used in calibration at the Preamble factory or not. That was up to the person calibrating the 1855 or 1855A and probes (Steve Lindberg is still around, and I can provide a phone number if requested). That 1.5ns rise time might make calibration even more difficult to do because you could see much more.

Don’t worry about it. It’s a tough calibration to do, and you can’t make it perfect.

Incidentally, the difference between the Preamble 1855 and 1855A is in the logic board. The A model uses a microprocessor and the non-A uses discrete logic. The A model turns the reference oven off with the power switch, the 1855 does not. The LeCroy version has an additional “Remote” digital interface. The amplifiers and probes are all the same to my knowledge

LeCroy may have made some minor changes in the circuit. For example, if they could not obtain a particular transistor, they may have substituted another. I know of no significant changes to the amplifier over the 19 years or so that the 1855/1855A was in production.

Someday I may release the schematic to the public. I hope you like the instrument. If you ever mess with or calibrate an 1855A itself, there are several unmarked holes in the top panel for input attenuator adjustments. I have a template which names those controls that I could make available. I do not recommend messing with those adjustments unless they are screwed up.

John Addis

-----Original Message-----

From: Dennis Tillman W7pF
Sent: Thursday, February 18, 2021 5:02 PM
To: John Addis
Subject: LeCroy DA1855A Differential Amplifier

Is this the LeCroy Differential Amplifier you designed?

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff Keyzer
Sent: Wednesday, February 17, 2021 10:01 AM
To: TekScopes@groups.io
Subject: [TekScopes] PG506 vs. PG506A risetime?

I have a Lecroy DA1855A differential amplifier with DXC100A probes. I am trying to calibrate the probes. The calibration manual calls for a PG506A "or equivalent" for calibration. They are using both the high amplitude and fast rise outputs of the pulser to adjust LF/HF probe compensation and CMRR.

There is also a paragraph that reads "If pulse generators such as the Tektronix PG506 that do not have a high enough slew rate are encountered in measurement situations..." and then they go on to describe a way of compensating the probes without access to a pulser.

I'm a little confused by their note, and since this the DA1855A a discontinued product I'm not expecting much help from Lecroy. I'm wondering if this is their way of saying that they prefer the PG506A over the PG506?

My question for the group - did the risetime/slew rate change between the PG506 and the PG506A? Would Lecroy have reason to prefer one over the other, or am I misreading their note?








--
Dennis Tillman W7pF
TekScopes Moderator


465/475 Volts/Div range LED swap problem.

Dave Peterson
 

Hi All,

Been working on replacing 465 Volts/Div range bulbs with LEDs. Has anyone here actually done this before?

I've tried searching here and EEVBlog forum, but I've either gotten too many results or no details. Searching for "465 LED" is too general and there's too many off topic results, and "465 volts/div LED" returns two results that yield nothing. Same on EEVBlog. People seem to do it, but don't seem to be doing much beyond straight swap (with current limiting R), or don't reveal what they're doing exactly.

I ran into a surprise, and have worked out a fix. But I never came across this issue looking into it. Does everyone just live with it, or is there another scenario or solution that I'm not finding or thinking of? There's a peculiarity to the 465/475 1X/10X indicator circuit that results in an issue with a straight swap that I'm not willing to live with.

"Atta' boy/girl" for anyone who knows the issue I'm talking about. I'll reveal, but I'm getting my ducks lined up. I want to share my solution including LTSpice schematic/simulation. I think it works nicely, but I'm a classic Rube Goldberg solution expert. I.e. I seem to try the most difficult solutions first. Am I over thinking this? I tried several alternatives before building what I have.

Would like to know how far into the weeds I've gone before I expose myself to withering ridicule.

Thanks,
Dave


Re: 1L10 crystal needed (Newbie)

Joel B Walker
 

I posted a picture of the circuit. Perhaps one of you exceptionally intelligent individuals could tell me what the drive level is for this crystal. I tried Lokoselectronics. They are the ones that wouldn't respond to my emails. Bomars website isn't working today. I see that there are SMD crystals available in that frequency range, but they can only be driven with miniscule power levels in the micro watts. This the need to know what the circuit demands of the crystal.

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