Comments interspaced.? While I have a 7904, I don't remember these particular problems, but these ideas might help. On 7/8/2020 7:30 PM, Bill Riches via groups.io wrote: My 7904 just stopped working.? I have had it for about 5 years - no problems - used several times a week.
1. No blown fuses No blown fuses says that the bulk supply, rectifiers, and filter capictors are likely ok, but does not say anything about the bulk capacitors not being open.? Check them by looking at ripple on the bulk supply if you have another scope. .2.? Powered with metered Sencore variac -? it draws about 10 watts after initial kick and meter pulses slightly.? I assure it is in pulse mode. It would say that, and it makes sense.? Been there, think I've done that. 3.? High voltage warning light is on and when power is removed it goes out after a few min. Not sure that this is significant, depending on where the HV supply is derived.? Things at this point suggest that you start disconnecting power supply and see if it works.? Note that supply may need a minimum load on one supply to regulate.? Not sure about this. 3. Removed all plugins and it still would not power up. Plugins therefore are not the only problem.? If using a plugin in a working scope brings the supply down, then it's a plugin. ??? 4. Removed ps and checked all caps and diodes for shorts. Then the PS, unless it needs a minimum load, should be ok for shorts.? If it will work without a load, look at the supply that has an adjustment.? It will be a reference supply.? Tektronix liked to use a negative supply.? That must be very close for the other supplies to be within tolerance. 5. Checked resistance readings of supply voltages with ps connected and unconnected - they are close. I think here you need to define "close". The supply generally ticks (in startup mode) when there's too much current drawn.? Something's got to be causing that. I have not checked out ps with 20 volts input and using test scope yet. Go for the test scope.? See if any supply actually gets to the desired voltage before the scope PS shuts down.? Storage scope would be good, but slow sweep and dim light can give you an idea. I would like to rule out ps problems and wonder if any of our group would have a working ps that I could purchase. Nope, not here but it's diagnosable... and fixable, generally. Question is:? what supply is shutting the scope down.? IIRC, there's a resistor from each supply to a summing junction, and then that junction has to be right for the main supply (not bulk) to be running. So your problems can be twofold, one is that there is a supply demanding too much current, another is that there's a supply overvoltage. Since you have a variac, you might want to run the voltage up from zero, looking at the outputs of a supply and the inputs to that regulator.? Until you get to about 80 or 90 volts, you can expect the supplies to be a little under.? If any supply overshoots sufficiently, then you're messing with the overvoltage protection.? SImilarly, look at the overcurrent protection on any supply, it's generally a transistor BE junction across a sense resistor, and that sense resistor in the output of the supply just after the regulator. Watching that voltage (either one) as the supply ticks should show you a lot. Harvey Any help would be appreciated.
73,
Bill, WA2DVU - (good on QRZ)Cape May, NJ609 425 8651
|
My 7904 just stopped working.? I have had it for about 5 years - no problems - used several times a week.
1. No blown fuses.2.? Powered with metered Sencore variac -? it draws about 10 watts after initial kick and meter pulses slightly.? I assure it is in pulse mode.3.? High voltage warning light is on and when power is removed it goes out after a few min.?3. Removed all plugins and it still would not power up.4. Removed ps and checked all caps and diodes for shorts.5. Checked resistance readings of supply voltages with ps connected and unconnected - they are close.
I have not checked out ps with 20 volts input and using test scope yet.
I would like to rule out ps problems and wonder if any of our group would have a working ps that I could purchase.
Any help would be appreciated.
73,
Bill, WA2DVU - (good on QRZ)Cape May, NJ609 425 8651
|
Re: Purpose of Q32 in S-52
On Wed, Jul 8, 2020 at 09:57 PM, Ed Breya wrote:
The question then is what happens past the valley - how much current and
voltage are available to continue up the diode curve, where power dissipation
increases a lot. It depends on the specifics of the circuitry, which could be
figured out if necessary.
This is the situation I had in mind in my post, though written down rather clumsily - incorrectly, actually. There's also the situation where the -12V is - for a short or long period - between say -6V and -12V. The digilog stuff still (mostly) works but the -12V is off by a lot. Can't think the consequences through ATM. Raymond
|
Re: Purpose of Q32 in S-52
Albert,
When the -12.4 V is lost, it's essentially zero V, so the emitters of Q72 and Q74 are effectively grounded through R72, and the long-tail pair cannot provide feedback. Assuming they're Si transistors, the TD voltage can't be high enough to turn Q74 on (unless the actual TD current is very high up its diode curve, and in danger anyway). The -12.4 V emitter feed via R72 makes it able to operate around zero, and without it, it's open-loop.
Ed
|
Re: Purpose of Q32 in S-52
If the -12.4 V supply is lost, the comparator/S-H stops working, and the
amplifier goes open-loop, to whatever maximum current it can deliver, possibly
risking overheating the TD. In this event, Q32 forces the current into ground
instead. Hi Ed, When -12 V is lost, U30B will not conduct and the base of Q72 will have the proper voltage for comparator operation, like in period 2. Hence I think the TD current will not get higher than Ip. As soon as the TD fires the comparator switches Q74 to on and the TD current will drop below the arming current. The voltage at the now isolated base of Q90 will slowly drop. After that different scenarios can be thought of. The comparator may or may not switch back. The danger I think is that the average power might get too large. Albert
|
Re: Purpose of Q32 in S-52
I don't think the TD needs protection, as long as the available bias current can't get too big. Once past the peak current, the TD will switch to valley current and voltage, and should be just fine. The question then is what happens past the valley - how much current and voltage are available to continue up the diode curve, where power dissipation increases a lot. It depends on the specifics of the circuitry, which could be figured out if necessary.
I read the circuit description, and I can see how it may be possible for the bias current to get relatively quite large if things get out of control. The circuit is a sort of auto-leveling system, testing the TD during each cycle, and adjusting the arming current according to its characteristics - pretty slick, I think. The bias generator is an amplifier capable of more current than needed for operation, and its output is controlled by the TD state comparator, in kind of a sample-hold setup, with a simple long-tail pair.
If the -12.4 V supply is lost, the comparator/S-H stops working, and the amplifier goes open-loop, to whatever maximum current it can deliver, possibly risking overheating the TD. In this event, Q32 forces the current into ground instead.
Ed
|
Re: Pallet of scopes for sale
Thank you; I thought so, someone else didn't. I finally have some older
equipment to work on as a hobby this winter. I would have loved to have
had a 500 series scope (other than curve tracer), but it will still be
similar to relive my earlier life - lol. The first scope I ever used was
one of those 500 series (I don't remember which one).
I can remember in Electronics school there was this older gentleman who
maintained all those old scopes. Being arse-holes like we kids were, with
those 500 series scopes the graticules, if I recollect correctly, were on
the blue external screen. We learned that if you put tracing paper under
that blue screen, they didn't focus worth a darn. So the lab teacher would
be called over, he would look and then just give a new scope and that one
would head to the old man. A few hours later, we heard this "OH GOD Dxxx!"
coming from his lab. The lab teacher would break down laughing (knowing
what we did). I really don't think those things could fail on their own,
at least in 1979/1980. Internally, they are electronic art. Gorgeous!
I later ended up getting one from the military surplus, but after my job,
early in life, took me to Cincinnati and had everyday filled, I really
don't remember what happened to it. I think I sold or traded it at a
hamfest, I really don't remember as that was 35-38 years ago. So with the
575, I can re-live a little of my youth, which I pine for. How can you put
a price on that?
toggle quoted message
Show quoted text
On Wed, Jul 8, 2020 at 3:20 PM Chuck Harris <cfharris@...> wrote: Lose money??? for what you got, that was cheap.
You got a very good deal.
-Chuck Harris
David Kuhn wrote:
" While not out of line for a 576 + 2 575s plus misc other stuff it
was not what I would consider a bargain."
I'm the idiot that won the auction. I had a nice vacation out of getting
the equipment and visited the two largest flea markets in the Cincinnati
area, when I was out there over this last weekend.
The was TWO (575s) on the pallot (I thought only one) in addition to the
576. There was a worthless HP Logic Analyser. There was however a nice HP
10K-1.5GHZ Spectrum analyzer and it appears to work and has a great CRT.
Also on the pallot, all those 576 plugin, three TDS420A (I think) with
GPIB ports and Thermal Printers and scope probes. The one I tested in the
hotel room seems noisy on the test square wave probe calibrator, but had a
really good and bright trace trace. It also seemed to go to some
ridiculously high digitation rate for a scope like that. The thermal
printer worked. There also were two no-name brand analog scopes and a Tek
2245 Analog scope that works fine and has a great trace. There is more
stuff in the boxes too. Seemed like foam with a bunch of transistors in it
with the gain documented and a few other things.
I am not sure what I am going to do with all that stuff. For now, it is
getting unloaded into my one shed. Next month, a friend will help clear
out the garage and the industrial shelves and move all the gear to there.
I don't really have a use for it, but if it works, the 576 will sit in the
corner of my large bench and look impressive (if I keep it). I don't know
because of their weight, if I will try to sell the 575's or part them out.
Having them packed and then shipped would probably cost $50 for
professional packing and another $100+ shipping, which no one will want to
pay. So confirming that they work and then parting them out, may be the
best option, but not until I play with them for nostalgia's sake. When I
went to Electronic School in 79-81, they had them and they were old back
then. So I want to admire them inside and out and then figure out what to
do with them. The other scopes should be okay for sale if I want. Heck I
think I paid $400 for NOS for a GPIB interface for a TDS420A that I already
had two/three years ago.
I really don't care if I lose money on these units. We had a blast back
home over the weekend and the excitement of searching through all the stuff
on the pallot.
Plus at the flea markets (with masks of course), my kid got a couple of DS
Games and a sword. Then at Microcenter Mall in Cincinnati, my kid also
picked up a professional microphone and accessories for his future "game
podcasting career" (heh heh heh) and we got a 3D printer to play with for
my wife's crafting.
All, in all, it was a good 4 days. Not a bargain or not, I am happy.
Dave
On Sat, Jun 27, 2020 at 4:08 PM Paul Amaranth <paul@...> wrote:
For those who are interested, the bid closed at $655 + $50.44 buyers
premium + $65.50 tax for a total of $770.94
While not out of line for a 576 + 2 575s plus misc other stuff it
was not what I would consider a bargain.
Paul
On Fri, Jun 19, 2020 at 12:33:59PM -0400, David Kuhn wrote:
" My only hope is that somebody bids it up so it's past my bargain
threshold."
And what do you think that would be? It would be an excuse to take a trip
to Cincy again (about 8 hours from here). I lived there from 1985-2000 and
miss the place.
Dave
On Thu, Jun 18, 2020 at 2:48 PM Paul Amaranth <paul@...> wrote:
I don't need them; I have all the scopes and curve tracers I could
want
and more
projects than I can get to. But Cinci is within driving range and I
hear
the
auction calling ...
My only hope is that somebody bids it up so it's past my bargain
threshold.
Must resist ....
Paul
On Thu, Jun 18, 2020 at 02:33:20PM -0400, Roy Morgan wrote:
On Jun 18, 2020, at 10:14 AM, Bill Higdon via groups.io
<willard561=
[email protected]> wrote:
If you're in the area of the auction it might be interesting I see
2
curve tracers
Ok ok, ¡°THE AREA¡± seems to be Cincinnati Ohio.
Roy
Who will not go there, as such as he¡¯d like to own that stuff!!!!
Roy Morgan
K1LKY since 1958
k1lky68@...
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
!DSPAM:5eece91c223591987219665!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
|
Re: 1240 / 1241 Logic Analyzer Lithium Battery Removal
Hi Andre,
I am probably your original source for the story about how
the Catalyst Research Corp lithium battery made a mess of my
1240. It totaled the multilayer CPU board, so I had to replace
it too.
The same, or a similar cell is used in the RAM cartridges, so
they should be serviced as well.
I replaced mine with a socket, and lithium coin cell that was
the biggest I could find. I should check it out to see if it
is still holding memory, as it has been a while since I made
the swap.
The only thing the cell protects is the setup, so it is safe
to pull the board, and simply replace it. I wouldn't go out
of my way to short circuit the cell, but I wouldn't worry too
much about doing so, either.
-Chuck Harris
Andre D'Amours via groups.io wrote:
toggle quoted message
Show quoted text
Hello Everyone,
I just acquired a very nice 1241 logic analyzer with accessories. I'm aware that the 1240 and 1241 have a potentially nasty Catalyst Research Corp lithium iodine battery that should should be removed before it causes damage. Does anyone have any suggestions on the safe removal of this battery? Is it safe to remove the battery using vacuum de-soldering equipment such as Metcal or Pace? Is a CR-123A in a socket a good replacement for this battery?
Thank you!
Andre
|
Re: Pallet of scopes for sale
Lose money??? for what you got, that was cheap.
You got a very good deal.
-Chuck Harris
David Kuhn wrote:
toggle quoted message
Show quoted text
" While not out of line for a 576 + 2 575s plus misc other stuff it
was not what I would consider a bargain."
I'm the idiot that won the auction. I had a nice vacation out of getting
the equipment and visited the two largest flea markets in the Cincinnati
area, when I was out there over this last weekend.
The was TWO (575s) on the pallot (I thought only one) in addition to the
576. There was a worthless HP Logic Analyser. There was however a nice HP
10K-1.5GHZ Spectrum analyzer and it appears to work and has a great CRT.
Also on the pallot, all those 576 plugin, three TDS420A (I think) with
GPIB ports and Thermal Printers and scope probes. The one I tested in the
hotel room seems noisy on the test square wave probe calibrator, but had a
really good and bright trace trace. It also seemed to go to some
ridiculously high digitation rate for a scope like that. The thermal
printer worked. There also were two no-name brand analog scopes and a Tek
2245 Analog scope that works fine and has a great trace. There is more
stuff in the boxes too. Seemed like foam with a bunch of transistors in it
with the gain documented and a few other things.
I am not sure what I am going to do with all that stuff. For now, it is
getting unloaded into my one shed. Next month, a friend will help clear
out the garage and the industrial shelves and move all the gear to there.
I don't really have a use for it, but if it works, the 576 will sit in the
corner of my large bench and look impressive (if I keep it). I don't know
because of their weight, if I will try to sell the 575's or part them out.
Having them packed and then shipped would probably cost $50 for
professional packing and another $100+ shipping, which no one will want to
pay. So confirming that they work and then parting them out, may be the
best option, but not until I play with them for nostalgia's sake. When I
went to Electronic School in 79-81, they had them and they were old back
then. So I want to admire them inside and out and then figure out what to
do with them. The other scopes should be okay for sale if I want. Heck I
think I paid $400 for NOS for a GPIB interface for a TDS420A that I already
had two/three years ago.
I really don't care if I lose money on these units. We had a blast back
home over the weekend and the excitement of searching through all the stuff
on the pallot.
Plus at the flea markets (with masks of course), my kid got a couple of DS
Games and a sword. Then at Microcenter Mall in Cincinnati, my kid also
picked up a professional microphone and accessories for his future "game
podcasting career" (heh heh heh) and we got a 3D printer to play with for
my wife's crafting.
All, in all, it was a good 4 days. Not a bargain or not, I am happy.
Dave
On Sat, Jun 27, 2020 at 4:08 PM Paul Amaranth <paul@...> wrote:
For those who are interested, the bid closed at $655 + $50.44 buyers
premium + $65.50 tax for a total of $770.94
While not out of line for a 576 + 2 575s plus misc other stuff it
was not what I would consider a bargain.
Paul
On Fri, Jun 19, 2020 at 12:33:59PM -0400, David Kuhn wrote:
" My only hope is that somebody bids it up so it's past my bargain
threshold."
And what do you think that would be? It would be an excuse to take a trip
to Cincy again (about 8 hours from here). I lived there from 1985-2000 and
miss the place.
Dave
On Thu, Jun 18, 2020 at 2:48 PM Paul Amaranth <paul@...> wrote:
I don't need them; I have all the scopes and curve tracers I could want
and more
projects than I can get to. But Cinci is within driving range and I
hear
the
auction calling ...
My only hope is that somebody bids it up so it's past my bargain
threshold.
Must resist ....
Paul
On Thu, Jun 18, 2020 at 02:33:20PM -0400, Roy Morgan wrote:
On Jun 18, 2020, at 10:14 AM, Bill Higdon via groups.io
<willard561=
[email protected]> wrote:
If you're in the area of the auction it might be interesting I see
2
curve tracers
Ok ok, ¡°THE AREA¡± seems to be Cincinnati Ohio.
Roy
Who will not go there, as such as he¡¯d like to own that stuff!!!!
Roy Morgan
K1LKY since 1958
k1lky68@...
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
!DSPAM:5eece91c223591987219665!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
|
Re: Pallet of scopes for sale
" While not out of line for a 576 + 2 575s plus misc other stuff it
was not what I would consider a bargain."
I'm the idiot that won the auction. I had a nice vacation out of getting
the equipment and visited the two largest flea markets in the Cincinnati
area, when I was out there over this last weekend.
The was TWO (575s) on the pallot (I thought only one) in addition to the
576. There was a worthless HP Logic Analyser. There was however a nice HP
10K-1.5GHZ Spectrum analyzer and it appears to work and has a great CRT.
Also on the pallot, all those 576 plugin, three TDS420A (I think) with
GPIB ports and Thermal Printers and scope probes. The one I tested in the
hotel room seems noisy on the test square wave probe calibrator, but had a
really good and bright trace trace. It also seemed to go to some
ridiculously high digitation rate for a scope like that. The thermal
printer worked. There also were two no-name brand analog scopes and a Tek
2245 Analog scope that works fine and has a great trace. There is more
stuff in the boxes too. Seemed like foam with a bunch of transistors in it
with the gain documented and a few other things.
I am not sure what I am going to do with all that stuff. For now, it is
getting unloaded into my one shed. Next month, a friend will help clear
out the garage and the industrial shelves and move all the gear to there.
I don't really have a use for it, but if it works, the 576 will sit in the
corner of my large bench and look impressive (if I keep it). I don't know
because of their weight, if I will try to sell the 575's or part them out.
Having them packed and then shipped would probably cost $50 for
professional packing and another $100+ shipping, which no one will want to
pay. So confirming that they work and then parting them out, may be the
best option, but not until I play with them for nostalgia's sake. When I
went to Electronic School in 79-81, they had them and they were old back
then. So I want to admire them inside and out and then figure out what to
do with them. The other scopes should be okay for sale if I want. Heck I
think I paid $400 for NOS for a GPIB interface for a TDS420A that I already
had two/three years ago.
I really don't care if I lose money on these units. We had a blast back
home over the weekend and the excitement of searching through all the stuff
on the pallot.
Plus at the flea markets (with masks of course), my kid got a couple of DS
Games and a sword. Then at Microcenter Mall in Cincinnati, my kid also
picked up a professional microphone and accessories for his future "game
podcasting career" (heh heh heh) and we got a 3D printer to play with for
my wife's crafting.
All, in all, it was a good 4 days. Not a bargain or not, I am happy.
Dave
toggle quoted message
Show quoted text
On Sat, Jun 27, 2020 at 4:08 PM Paul Amaranth <paul@...> wrote: For those who are interested, the bid closed at $655 + $50.44 buyers
premium + $65.50 tax for a total of $770.94
While not out of line for a 576 + 2 575s plus misc other stuff it
was not what I would consider a bargain.
Paul
On Fri, Jun 19, 2020 at 12:33:59PM -0400, David Kuhn wrote:
" My only hope is that somebody bids it up so it's past my bargain
threshold."
And what do you think that would be? It would be an excuse to take a trip
to Cincy again (about 8 hours from here). I lived there from 1985-2000 and
miss the place.
Dave
On Thu, Jun 18, 2020 at 2:48 PM Paul Amaranth <paul@...> wrote:
I don't need them; I have all the scopes and curve tracers I could want
and more
projects than I can get to. But Cinci is within driving range and I
hear
the
auction calling ...
My only hope is that somebody bids it up so it's past my bargain
threshold.
Must resist ....
Paul
On Thu, Jun 18, 2020 at 02:33:20PM -0400, Roy Morgan wrote:
On Jun 18, 2020, at 10:14 AM, Bill Higdon via groups.io
<willard561=
[email protected]> wrote:
If you're in the area of the auction it might be interesting I see
2
curve tracers
Ok ok, ¡°THE AREA¡± seems to be Cincinnati Ohio.
Roy
Who will not go there, as such as he¡¯d like to own that stuff!!!!
Roy Morgan
K1LKY since 1958
k1lky68@...
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
!DSPAM:5eece91c223591987219665!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows
|
Re: Purpose of Q32 in S-52
Thanks for the replies so far. The common thread is protection of the TD in case of other failures. I was thinking along the same lines, but also thought that one single other failure could do no harm, except perhaps a way too high +15V.
For instance a missing -12.2V would shut down U10 and U20, having the same effect as states 1 and 10-16 in normal operation. Then the TD current supply via R97+R98 would permanently be present while the TD is in the low state. That alone would do no harm I think.
I was also thinking of an interrupted R109 and hence missing -5.1V, -3V and -2.5V. That would have more or less the same effect as a missing -12.2V.
In case the zener VR109 dies (to open circuit) U10 and U20 will be destroyed but Q32 doesn't mind.
Albert
|
Re: Tektronix 2465b Boo Boo
I am of the general opinion that the only reason to buy
a "pre-calibrated" DS1225, is because you are selling your
scope, and you want to fool the potential buyers into
thinking the scope is calibrated.
Kind of the tektronix version of turning back the odometer
on a used car.
I hope he wasn't thinking a pre-calibrated NVRAM is a
legitimate solution to any real problem.
-Chuck Harris
satbeginner wrote:
toggle quoted message
Show quoted text
Putting in a pre-loaded Dallas or Fram will remove the 'not calibrated' indication (?????? or ............), but this will mean the scope from now on is
"Not Calibrated",
only it will not be visible to a user.
The error could be anything from 1% to 15 or more %, depending on the parameter used.
Timebase, Amplitude, Delay, etc.
Putting in a pre-loaded replacement is the ostrich way....
The only real way to go is calibration.
Just my 2cts...
Leo
|
I may be wrong, and Roy can certainly fend for himself,
but he is agreeing with you.
The puzzling results he mentions are the ones you get
when your dead certainty that there are only ones, and
zeros, and nothing in between. Runs into something in
between.
-Chuck Harris
Dave Daniel wrote:
toggle quoted message
Show quoted text
Hmmm.... I don¡¯t mean to be argumentative, but, outside of text books and digital simulators ( e.g., Synopsy VCS, Modelsim, etc.), what real-world circuit is not analog?
On Jul 8, 2020, at 09:51, Roy Thistle <roy.thistle@...> wrote:
On Wed, Jul 8, 2020 at 05:18 AM, Dave Daniel wrote:
Indeed, everything is analog
Probably not necessarily. But, I agree: we tend to want to believe the world is the way we perceive it... and that bias sometimes leads to particularly puzzling results.
|
Re: Tektronix 2465b Boo Boo
Putting in a pre-loaded Dallas or Fram will remove the 'not calibrated' indication (?????? or ............), but this will mean the scope from now on is
"Not Calibrated",
only it will not be visible to a user.
The error could be anything from 1% to 15 or more %, depending on the parameter used.
Timebase, Amplitude, Delay, etc.
Putting in a pre-loaded replacement is the ostrich way....
The only real way to go is calibration.
Just my 2cts...
Leo
|
Re: Tektronix 2465b Boo Boo
On Wed, Jul 8, 2020 at 07:00 PM, Chuck Harris wrote:
The NVRAM swap was the idea of the original poster... not any
of us.
I'm under the impression that the OP thought he'd solve his problem by replacing the NVRAM with a nice, clean one. You're right that he came up with the idea but our reactions didn't make it clear that unless he buys one of those preloaded NVRAMs containing "some general" calibration data, he won't solve his problem that way. BTW, I'm not a believer in the preloaded NVRAMs but of course, I'm biased because I have the equipment and I have calibrated these 'scopes - and I have replaced NVRAMs, both with new ones and with FRAMs. "Preloaded" calibration data may be good enough for some/many, don't know. I'd guess calibration may be 2 - 5% off, right? Raymond
|
Re: Tektronix 2465b Boo Boo
The NVRAM swap was the idea of the original poster... not any
of us.
The only advice given was Exercise 3 by Tom, and an explanation
of how the problem occurs by me.
After he asked what NVRAM to use, I told him, and warned about
trying to remove the old NVRAM using substandard means.
Some of the calibration steps will not allow you to step through
them without making changes... for example: the vertical calibration,
the trigger calibration, the parametric calibration, all do their thing
automagically using the specified voltage coming from your voltage
calibrator.
If the voltage calibrator is not there, the routine will fault with a
bunch of dots, and if you quit early, a bunch of question marks.
I wish there were a way of aborting without making changes, but tek
didn't do that.
Why do I wish that? On more than a few occasions, I have finished a
routine, and with my head running on autopilot, re-entered the just
finished calibration step, requiring me to do it all over again, or
suffer the ???? display.
-Chuck Harris
Raymond Domp Frank wrote:
toggle quoted message
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Please forgive me for asking but I can't quite follow.
The OP told us that his 'scope was working fine but that he hadn't been able to resist the temptation to enable "cal" mode and play around. That resulted in the bottom line with lots of question marks. As far as we know - or hope, the 'scope is still about as much in calibration as before.
He also told us that doing a cal. is no option for him, technologically nor financially.
Where does the advice come from to replace the NVRAM, except for the fact that it may lose its memory soon? It may not for a while if left untouched. If it does during replacement (that has happened before), he won't be able to recover.
Why not just advise the OP to follow Chuck's advice to step through the procedure he started but didn't finish or first do an exercise 3 and hope for the best? When restarting - and finishing the procedure the OP started, he should finish it all the way *without* changing anything, if possible.
After performing his steps, the OP should switch off, then on.
Raymond
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Hmmm.... I don¡¯t mean to be argumentative, but, outside of text books and digital simulators ( e.g., Synopsy VCS, Modelsim, etc.), what real-world circuit is not analog?
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On Jul 8, 2020, at 09:51, Roy Thistle <roy.thistle@...> wrote:
On Wed, Jul 8, 2020 at 05:18 AM, Dave Daniel wrote:
Indeed, everything is analog
Probably not necessarily. But, I agree: we tend to want to believe the world is the way we perceive it... and that bias sometimes leads to particularly puzzling results.
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Re: Tektronix 2465b Boo Boo
Please forgive me for asking but I can't quite follow.
The OP told us that his 'scope was working fine but that he hadn't been able to resist the temptation to enable "cal" mode and play around. That resulted in the bottom line with lots of question marks. As far as we know - or hope, the 'scope is still about as much in calibration as before.
He also told us that doing a cal. is no option for him, technologically nor financially.
Where does the advice come from to replace the NVRAM, except for the fact that it may lose its memory soon? It may not for a while if left untouched. If it does during replacement (that has happened before), he won't be able to recover.
Why not just advise the OP to follow Chuck's advice to step through the procedure he started but didn't finish or first do an exercise 3 and hope for the best? When restarting - and finishing the procedure the OP started, he should finish it all the way *without* changing anything, if possible.
After performing his steps, the OP should switch off, then on.
Raymond
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On Wed, Jul 8, 2020 at 05:18 AM, Dave Daniel wrote:
Indeed, everything is analog
Probably not necessarily. But, I agree: we tend to want to believe the world is the way we perceive it... and that bias sometimes leads to particularly puzzling results.
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Re: Tektronix 2465b Boo Boo
At the risk of contradicting the master of the 2465 scopes -Obi Wan Harris- when I removed my NVRAM chip I used a simple soldapullt solder sucker (albeit one of the good quality ones - EDSYN) and in the end the chip just fell off the board by itself after the last pin was cleared. Even the ground pin was cleared quite easily without using anywhere near excessive heat. Just make sure to first "wet" each joint well with fresh good quality solder (for me that would be Kester 44), and that will make it much easier for the thru holes to be cleared on the first try. So even tough I would agree that a desoldering station is probably the best way to do this job, or at least the one with the least risk to the board, if you are in the middle of nowhere don't be afraid to use simpler methods as long as you are comfortable with it and have the proper expertise in using the desoldering tool of your choice. And be patient, don't rush things making sure every single pin is clear and confirmed loose before you start pulling on the chip. Sometimes the pin can still be slightly stuck even tough the hole looks clear, then you can try wiggling the pin a bit towards the center of the hole and most times it will just break free. Otherwise refill the hole with some more fresh solder and try again. Hope that helps.
BTW get your replacement NVRAM from a reputable place like Mouser (or Digikey), never from Ebay, specially avoid if it comes from Chinaland, as it might be an old relabeled chip with an internal battery that is well past its expiration date. Also get a good quality low profile socket to reinstall the new chip. I got mine from Mouser, one of the machined pin type, although some people say its best not to use this type but rather the convention kind. In any case it worked for me. Good luck with the repair, and please report back your progress.
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Bill Riches
Raymond Domp Frank
satbeginner