Date   
Re: What is the meaning of ULU? Topic was: 7000-series power-hungry plug-ins

 

On Wed, Oct 17, 2018 at 03:37 AM, Tim wrote:


At last years Rickreall ham show I pointed out the funny looking 7000 series
case under a vendors table, but it didn't spark your interest.
I picked it up for 20 bucks and have been wondering ever since what it was
used for.
I created an album located here:
https://groups.io/g/TekScopes/album?id=75949
Yes that's exactly the one I was thinking about. So my memory wasn't so bad after all.
/Håkan

Tektronix 551 Power Supply

johnasolecki@...
 

I recently acquired a very clean Tek 551 oscilloscope I'd like to restore; but it's missing the separate power supply unit.
Anyone have one for sale or know where I might acquire one or is this in the unobtanium category?

Re: 2445/2465 Power Supply Smoking

n2msqrp
 

I just had this happen to my 2445. It is still working but I want to replace the Rifa caps before I proceed. Can anyone recommend a substitute Kemet film capacitor that I can purchase from Mouser or Digikey?

Thanks,

Mike N2MS

Re: 2445/2465 Power Supply Smoking

Chuck Harris
 

I have no great fondness for Kemet... I have replaced too
many of their DIP style dry slug tantalum capacitors.

I replace the RIFA style capacitors with Panasonic ECQ UL X-2 Met Poly
capacitors. Specifically:

Mouser 667-ECQ-U2A683KLA

and if necessary (usually not) the comparable 0.0022, 0.0056 and 0.01uf
caps.

-Chuck Harris

n2msqrp wrote:

I just had this happen to my 2445. It is still working but I want to replace the Rifa caps before I proceed. Can anyone recommend a substitute Kemet film capacitor that I can purchase from Mouser or Digikey?

Thanks,

Mike N2MS



Re: 2445/2465 Power Supply Smoking

n2msqrp
 

Chuck,

Thanks. I will check them out.

Mike N2MS

On October 17, 2018 at 10:50 AM Chuck Harris <cfharris@...> wrote:


I have no great fondness for Kemet... I have replaced too
many of their DIP style dry slug tantalum capacitors.

I replace the RIFA style capacitors with Panasonic ECQ UL X-2 Met Poly
capacitors. Specifically:

Mouser 667-ECQ-U2A683KLA

and if necessary (usually not) the comparable 0.0022, 0.0056 and 0.01uf
caps.

-Chuck Harris

n2msqrp wrote:
I just had this happen to my 2445. It is still working but I want to replace the Rifa caps before I proceed. Can anyone recommend a substitute Kemet film capacitor that I can purchase from Mouser or Digikey?

Thanks,

Mike N2MS




7A13 relay substitution report

Fabio Trevisan
 

Hello guys,
After I got that 7A13 some weeks ago I have been fighting with its inconsistencies as I turn the different range knobs...
As anyone who just purchased something, for a couple of weeks I was still in that denial phase where you believe you're going to track down the problem to one or two major culprits and fix it nice and easy.
Denial phase over.. I came to understand how many different weird behaviors can arise from high impedance attenuators, when their action is switched by unreliable contacts.and, yet, to learn that a poor "make" contact is the least of the problems that can happen, and the worse is when some of the contacts fail to break contact completely (while even being able to make on the other contact).
I came to understand how BAD those relays are (or should I say EVIL?) and decided to just get rid of all of them, so I`m replacing them by modern PCB signal relays... not exactly of the same kind that is mentioned here (https://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_amplifier/amplifier_7A11.htm) repair, linked on the 7A11 page of TekWiki.

Instead, I selected and am already installing some of the ones below:

For the SPDT of the X1/X10 gain circuit (K60 and K61)
OMRON G5V-1 series
https://omronfs.omron.com/en_US/ecb/products/pdf/en-g5v_1.pdf
The up side of the OMRON PCB signal relays is they are characterized for R.F. performance...while the majority of the regular PCB signal relays don't even mention frequency response characteristics.
They can isolate 100MHz down to -45dB, which is the best figure you will get from "normal" PCB signal relays.
Their down side however, is that they're "only" rated to 125VAC / 60VDC, which inside the amplifier circuit is not a problem.

Note: There are signal relays meant for RF that ARE characterized up to 6GHz or so, which can go as low as -85dB @ 100MHz but those are more expensive, and requires specific layout (TL) to meet the specs.

For the DPDTs inside the amplifier circuitry (K47, K48, K480 and K490):
OMRON G6K series: https://omronfs.omron.com/en_US/ecb/products/pdf/en-g6k.pdf
or
OMRON G6J-Y series: https://omronfs.omron.com/en_US/ecb/products/pdf/en-g6j.pdf
They share basically the same R.F. performance of the G5V-1 above and also the shortcoming of the limited switching voltage.

For the input DPDTs (K6, K26, K7, K27) and also for the Vc input switching SPDTs (K10 and K30) (i.e. all relays that are subject to the full input voltage)
NEC / TOKIN EA2 or EB2 series (EB2 is through hole, and EB2 is meant for SMD, but after straightening out the leads, both are the same).
http://www.mouser.com/ds/2/283/relay_ea2_eb2_e-528008.pdf
Note: these ones are a compromise... They were the only ones I could grab that would withstand 250VAC / 220VDC, but they're not characterized whatsoever for H.F. use (although it seems they perform acceptably in that department).
Like these ones (without H.F. characterization) there are many brands and models, including the AXICOM / TE connectivity referred on the 7A11 report linked above.

If you don't care about the inputs being able to withstand 250VAC/220VDC (which is as close as it will get to the 7A13 original specs), you can go for the OMRONs G6K or G6J-Y.

See some pictures of the assemblies here:
https://groups.io/g/TekScopes/album?id=72382
Those are the ones that will replace the K7 / K27 (they are SPDT + SPST N.C.)

Last comment...Attention must be paid, on a relay-by-relay basis, to the polarity of the voltage being applied to each of the coils.
The Tek relays were not polarized (in most of the cases, A.F.A.I.K.), but most of the modern mini relays ARE polarized and they won't engage if fed in reverse.
For instance, the wiring to the coil of K7 need to be the opposite of K27 (both are the X10 input att). Also inverted between K10 and K30 (the Vc input switching).

Rgrds,

Fabio










For the SPDTs

Re: 2445/2465 Power Supply Smoking

Dave Wise
 

Those are rated at 275VAC. That's not much margin for those running 240V mains. Do you have a recommendation there?

Dave Wise

On October 17, 2018 at 10:50 AM Chuck Harris <cfharris@...> wrote:

I replace the RIFA style capacitors with Panasonic ECQ UL X-2 Met Poly
capacitors. Specifically:

Mouser 667-ECQ-U2A683KLA

and if necessary (usually not) the comparable 0.0022, 0.0056 and 0.01uf
caps.

-Chuck Harris

Re: 2445A calibration

maxim.vlasov@...
 

Gentlemen,

I've got 2445a successfully calibrated today! It works fine. In a summary the scope can be calibrated in sessions as Chuck has explained. This is exactly how I did it. One after another calibration routine. And at the and no FAIL 04 any more! It all works.

As promised, I've put the listing inhere:
https://groups.io/g/TekScopes/files/2445a%20FW%20listings%20ROMs/2445a_lo32K.lst

It represents the first 32K of the low 64K EEPROM (there are 4 parts in total). It's more interesting since it has all the facilities, the work area initializer and the messages for the on screen display.
Also the free ROM space is filled by the SW interrupt code. I.e. in the case of the wrong jumping SW interrupt will be generated. But SW vector is the same as the RESET. I.e. Tek guys this way tried to debug the FW and see whether it will reset occasionally.

Special thanks to Chuck, Raymond, Siggi, Harvey, Mark, Craig!

P.S As a side reading found an interesting HP journal issue from 1987 explaining about how they have built their boxes:
www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1987-04.pdf
Article starts on the page 12. They say about the UI concept similar to LA box, which is a totally different product. The memory layout and system/SW/FW architecture is covered. Though it could be interesting....

Re: 7A13 relay substitution report

 

Hi Fabio,
I think we will all benefit from your adventure into replacing the Tek relays.
If you get stuck and cannot find an appropriate substitute at any point contact
me off list at dennis at ridesoft dot com and I will try to help however I can.

Dennis Tillman W7PF

-----Original Message-----
From Fabio Trevisan
Sent: Wednesday, October 17, 2018 9:00 AM
Subject: [TekScopes] 7A13 relay substitution report

Hello guys,
After I got that 7A13 some weeks ago I have been fighting with its
inconsistencies as I turn the different range knobs...
As anyone who just purchased something, for a couple of weeks I was still
in that denial phase where you believe you're going to track down the
problem to one or two major culprits and fix it nice and easy.
Denial phase over.. I came to understand how many different weird
behaviors can arise from high impedance attenuators, when their action is
switched by unreliable contacts.and, yet, to learn that a poor "make"
contact is the least of the problems that can happen, and the worse is
when some of the contacts fail to break contact completely (while even
being able to make on the other contact).
I came to understand how BAD those relays are (or should I say EVIL?) and
decided to just get rid of all of them, so I`m replacing them by modern
PCB signal relays... not exactly of the same kind that is mentioned here
(https://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_7000_series_a
mplifier/amplifier_7A11.htm) repair, linked on the 7A11 page of TekWiki.

Instead, I selected and am already installing some of the ones below:

For the SPDT of the X1/X10 gain circuit (K60 and K61) OMRON G5V-1 series
https://omronfs.omron.com/en_US/ecb/products/pdf/en-g5v_1.pdf
The up side of the OMRON PCB signal relays is they are characterized for
R.F. performance...while the majority of the regular PCB signal relays
don't even mention frequency response characteristics.
They can isolate 100MHz down to -45dB, which is the best figure you will
get from "normal" PCB signal relays.
Their down side however, is that they're "only" rated to 125VAC / 60VDC,
which inside the amplifier circuit is not a problem.

Note: There are signal relays meant for RF that ARE characterized up to
6GHz or so, which can go as low as -85dB @ 100MHz but those are more
expensive, and requires specific layout (TL) to meet the specs.

For the DPDTs inside the amplifier circuitry (K47, K48, K480 and K490):
OMRON G6K series: https://omronfs.omron.com/en_US/ecb/products/pdf/en-
g6k.pdf
or
OMRON G6J-Y series: https://omronfs.omron.com/en_US/ecb/products/pdf/en-
g6j.pdf
They share basically the same R.F. performance of the G5V-1 above and also
the shortcoming of the limited switching voltage.

For the input DPDTs (K6, K26, K7, K27) and also for the Vc input switching
SPDTs (K10 and K30) (i.e. all relays that are subject to the full input
voltage) NEC / TOKIN EA2 or EB2 series (EB2 is through hole, and EB2 is
meant for SMD, but after straightening out the leads, both are the same).
http://www.mouser.com/ds/2/283/relay_ea2_eb2_e-528008.pdf
Note: these ones are a compromise... They were the only ones I could grab
that would withstand 250VAC / 220VDC, but they're not characterized
whatsoever for H.F. use (although it seems they perform acceptably in that
department).
Like these ones (without H.F. characterization) there are many brands and
models, including the AXICOM / TE connectivity referred on the 7A11 report
linked above.

If you don't care about the inputs being able to withstand 250VAC/220VDC
(which is as close as it will get to the 7A13 original specs), you can go
for the OMRONs G6K or G6J-Y.

See some pictures of the assemblies here:
https://groups.io/g/TekScopes/album?id=72382
Those are the ones that will replace the K7 / K27 (they are SPDT + SPST
N.C.)

Last comment...Attention must be paid, on a relay-by-relay basis, to the
polarity of the voltage being applied to each of the coils.
The Tek relays were not polarized (in most of the cases, A.F.A.I.K.), but
most of the modern mini relays ARE polarized and they won't engage if fed
in reverse.
For instance, the wiring to the coil of K7 need to be the opposite of K27
(both are the X10 input att). Also inverted between K10 and K30 (the Vc
input switching).

Rgrds,

Fabio



--
Dennis Tillman W7PF
TekScopes Moderator

Re: 2445/2465 Power Supply Smoking

 

Dave

These are the ones I supply - X1 440VAC rated - at Mouser.
I use Vishay wherever possible - may cost a bit more, but reliability is my first priority.
594-222233810683

The other film caps should be Y2 and DC rated.

For full details of all the parts in the kit, check my Spreadsheet in the Files Section.
No guesswork, everything is proven functional.

https://groups.io/g/TekScopes/files/2018%20July%20-%202445%202465%20Capacitor%20list

Re: 2445A calibration

 

On Wed, Oct 17, 2018 at 10:05 PM, <maxim.vlasov@...> wrote:


P.S As a side reading found an interesting HP journal issue from 1987
explaining about how they have built their boxes:
www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1987-04.pdf
Article starts on the page 12. They say about the UI concept similar to LA
box, which is a totally different product. The memory layout and system/SW/FW
architecture is covered. Though it could be interesting....
Also, don't miss the very relevant article on software reliability starting at page 35...

Raymond

Re: Tektronix 551 Power Supply

bobkrassa
 

The 551 is a great scope and was in production for quite some time. There is a 551 power supply on ebay that has been listed for quite some time (I have no connection with the seller and know nothing about them.) . The price seems way too high but you might see if you can contact the seller for a "buy it now" at a reasonable price. Be aware that you will still need the interconnecting cable unless you or this seller have one. Maybe someone on this group has an extra. Stan Griffiths says in his book that the interconnecting cable can be built. You will need to acquire the proper end connectors but they should be available.

Bob Krassa ACØJL

Re: 2445A calibration

Siggi
 

On Wed, 17 Oct 2018 at 16:05 <maxim.vlasov@...> wrote:

I've got 2445a successfully calibrated today! It works fine. In a summary
the scope can be calibrated in sessions as Chuck has explained. This is
exactly how I did it. One after another calibration routine. And at the and
no FAIL 04 any more! It all works.
Awesome, congratulations!
This has been one of the more epic repair threads I've seen here recently,
it was fun to see some of the firmware disassembled. Super-fun to see the
firmware matched my calculation to within 2/4096.
Did you measure the +1.36/-1.24V references after your repair (and DAC
re-calibration)? I'd be most interested to know what the final values of
those reference voltages were against the centered +1.25/-1.24 DLY REF
output.
Apparently 0.5% from the calculated value is too far out, but the -1.25V
value on the schematics is still 0.25% out - the truth is out there!

I'm sure your 244A will give you decades of faithful service from here. My
2467 is my go-to for general spelunking because it operates like it's part
of my anatomy. The digital scopes only come out at need.

Re: 2445A calibration

Tom Gardner
 

On 17/10/18 02:24, maxim.vlasov@... wrote:
It would be good to hear from someone who was coding the boxes @TEK about how the things were. However, the absence of the C compilers didn't stop the Tek to have so many different product lines. Also in embedded world of 80s using Prolog, Pascal, Modula, LISP to code the emedded applications was done routinely.
And more... Both Tek and HP used Smalltalk embedded in test instruments. Plus Tek also produced Smalltalk workstations.

Re: 2445A calibration

Harvey White
 

On Wed, 17 Oct 2018 13:05:05 -0700, you wrote:

Gentlemen,

I've got 2445a successfully calibrated today! It works fine. In a summary the scope can be calibrated in sessions as Chuck has explained. This is exactly how I did it. One after another calibration routine. And at the and no FAIL 04 any more! It all works.
Congradulations.

As promised, I've put the listing inhere:
https://groups.io/g/TekScopes/files/2445a%20FW%20listings%20ROMs/2445a_lo32K.lst

It represents the first 32K of the low 64K EEPROM (there are 4 parts in total). It's more interesting since it has all the facilities, the work area initializer and the messages for the on screen display.
Also the free ROM space is filled by the SW interrupt code. I.e. in the case of the wrong jumping SW interrupt will be generated. But SW vector is the same as the RESET. I.e. Tek guys this way tried to debug the FW and see whether it will reset occasionally.

Special thanks to Chuck, Raymond, Siggi, Harvey, Mark, Craig!
You're welcome. You used which disassembler to do this?

Mine produces a different output, but it's not designed to create a
disassembled -> assembler listing (although I could tweak it so it
could), but it's designed to disassemble something so you can get an
idea of what it does to reverse engineer the program and then write it
in another language.

oh, and I wouldn't have written it that way (with the SWI). SWI is
fine, but the handler needs to just do a jmp to self, leaving the
stack intact. That way you have return addresses and the like to look
at. If all it does is reset, then that's fine, and somewhat
protective, but you never know why it did it.

Harvey


Harvey


P.S As a side reading found an interesting HP journal issue from 1987 explaining about how they have built their boxes:
www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1987-04.pdf
Article starts on the page 12. They say about the UI concept similar to LA box, which is a totally different product. The memory layout and system/SW/FW architecture is covered. Though it could be interesting....




Re: Random noise on LV power rails

skv1958@...
 

Just loud thinking...when jitter starts in some circuit, sudden current draw changes may cause sudden voltage changes, which may appear as noise. What are the amplitudes of these noises on power rails? You may also want to check ripple specifications and bypass capacitors. My two cents on this problem, apart from the mention of some failing pots earlier...

Shailendra

Re: Random noise on LV power rails

Brendan
 

On Wed, Oct 17, 2018 at 07:16 PM, <skv1958@...> wrote:


While trying to figure out what is going on with my 468 I decided to monitor the -8V and 15V supply DC coupled. When the trace starts to jitter there is noise on both of them. Not ripple, it almost looks like a digital signal. What would cause that? This has been a pretty cool trouble shooting experience.

Just loud thinking...when jitter starts in some circuit, sudden current draw
changes may cause sudden voltage changes, which may appear as noise. What are
the amplitudes of these noises on power rails? You may also want to check
ripple specifications and bypass capacitors. My two cents on this problem,
apart from the mention of some failing pots earlier...

Shailendra
I ordered new filter caps today. I'm unable to get any capacitance reading from C926 15V unregulated line. I'm hoping that will cure the issues. The caps will be here Friday. I already have the old caps out, while I was in there I replaced all the bridge rectifiers also. I replaced all the small caps in the storage power supply today and will do the big caps when they come. Figured I may as well give it the full treatment.

Re: 2445A calibration

Harvey White
 

On Wed, 17 Oct 2018 23:53:22 +0100, you wrote:

On 17/10/18 02:24, maxim.vlasov@... wrote:
It would be good to hear from someone who was coding the boxes @TEK about how the things were. However, the absence of the C compilers didn't stop the Tek to have so many different product lines. Also in embedded world of 80s using Prolog, Pascal, Modula, LISP to code the emedded applications was done routinely.
And more... Both Tek and HP used Smalltalk embedded in test instruments. Plus
Tek also produced Smalltalk workstations.
Any idea which ones were the TEK ones? I'm primarily interested in
the TM500, 468, and not sure about any other ones.

Disassembling the DM5010 indicates to me disorganized, but mostly
assembly programmed. If there was a high level language in here, it
wasn't obvious to me.

Harvey





Re: 2445A calibration

maxim.vlasov@...
 

On Wed, Oct 17, 2018 at 04:58 PM, Harvey White wrote:


You used which disassembler to do this?
Harvey,

I used IDA (Interactive DisAssembler created by Ilfak Guilfanov. There is a Wiki page), you can see the section of photos in this thread for the screen capture. it's a semi-automated disassembler. You see the bytevector in front of you at the beginning and you manupulate it by instructing it to convert the byte vector to code/data/table of immediate data or vectors. The tool then will try to start from this, go and disassemble the rest. When it's blocked again you go, explore, instruct comment and give the tool a go. So it's an itterative work. It has a long list of features for signature searching in code, text, etc. I use IDA from the end of 90s. It's by far the only tool to re-create the source quality disassembly.

Re: 2445A calibration

maxim.vlasov@...
 

On Wed, Oct 17, 2018 at 02:08 PM, Siggi wrote:


Awesome, congratulations!
This has been one of the more epic repair threads I've seen here recently,
it was fun to see some of the firmware disassembled. Super-fun to see the
firmware matched my calculation to within 2/4096.
Did you measure the +1.36/-1.24V references after your repair (and DAC
re-calibration)? I'd be most interested to know what the final values of
those reference voltages were against the centered +1.25/-1.24 DLY REF
output.
Apparently 0.5% from the calculated value is too far out, but the -1.25V
value on the schematics is still 0.25% out - the truth is out there!
Thank you Siggi. I had no time to re-measure the test points, I'll do it today. But now DAC is centered (pin 13 J119) between -1.250V and 1.250V, which is quite amazing. I hope that the results will converge with the LTSpice simulated values. After changing the op-amp I have noticed that the OPAMP instead producing -8.1V started pulling the -1.25V line more -8.8V. And everything worked after that.