Date   

Re: Tek 577 Step Gen & Volt Div knobs skirt pictures needed

Rogerio O
 

Hi Folks,
After working with the photos posted by Daves for a long time I realized that there is a problem about them If one is trying to really mimic the original Tek knob.
That is because in the original knobs, the actual value of the variable is "engraved" in the gray part of the skirt (by not applying gray ink on them) so they are highlighted by the lamp that exists in the case panel.
Of course I it is possible to use the yellow arrow to known the value that has been selected but it would be very nice if we could keep the original feature.
So, any photo posted for that purpose should be taken with the knob out of the instrument and placed over a white surface, so the numbers would appear "white" on the photo.
I am sorry I have missed that until now.
The "bright side" of this is that it is much more easy to have a good lighting condition in this situation.
Regads,
Roger


Re: Looking for sensitive audio RMS meter

Bob Albert
 

Signal to noise ratio is a parameter that applies over a wide range of signals.  Dynamic range is the ratio of the strongest signal that can be handled without excessive distortion, to the weakest.  Distortion includes noise for weak signals.
Bob

On Sunday, May 16, 2021, 11:11:45 AM PDT, cheater cheater <cheater00social@gmail.com> wrote:

On Sun, May 16, 2021 at 1:51 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

Rebonjour Cher Cheater

1/RE noise floor distinguish between Signal to noise ratio and dynamic range
What's the difference?

3/ audio and digital audio noise and achievable noise floor, SNR and dynamic range have been topics of many fine papers.  Especially, reccomend  AES papers by our old friend Louis Fielder of Dolby Laboratoires ~1977, and John Vanderkoy and Stanley Lipschuttz at Guelph U. Waterloo 1970s...1980s
thanks for the tips.


Re: Looking for sensitive audio RMS meter

 

On Sun, May 16, 2021 at 1:51 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

Rebonjour Cher Cheater

1/RE noise floor distinguish between Signal to noise ratio and dynamic range
What's the difference?

3/ audio and digital audio noise and achievable noise floor, SNR and dynamic range have been topics of many fine papers. Especially, reccomend AES papers by our old friend Louis Fielder of Dolby Laboratoires ~1977, and John Vanderkoy and Stanley Lipschuttz at Guelph U. Waterloo 1970s...1980s
thanks for the tips.


Re: PG506 Repair - I had a Great Day today/

tek_547
 

Yesterday I made some measurements so here again is an update of that.
The values that Albert measures around U460 is on my PG506 almost the same;
U460 & U430 pin3 = 8,85V / C420 = 13,36V (switch on DC). Also exact 100V is present.
Unfortunately it didn´t give new insights to solve the problem so I think it's better to let it rest for at least a couple of weeks or so. Because as I said before, the unit is working normal exept the display.

It is a complicated piece of equipment (for me) and trouble shooting is very time consuming with no result till now. Thanks so far for the detailed contributions and also the loads of pictures from Michael, maybe something for the future.
René


Re: Tek 577 Step Gen & Volt Div knobs skirt pictures needed

Rogerio O
 

Thank you for uploading the photos, folks.
Andy the photos of the 577 have a "bright spot" on the left and a shadow on the lower right.
I might be able to correct the bright spot using a photo editor, but it will not be possible to fix the "low light" section since there is not "enough information" there to allow it.
Yes I can wait so you can select another day /opportunity to take another set of photos.
As a suggestion, if you use artificial lighting try to use at least 2 light sources (to avoid the appearance of "shadows").
The lamps could be located slightly off the center axis of the knob since this is the position were the camera should be located
Reading lamps may be useful, but try to put a blank sheet of paper (printer paper or similar) taped to the lamp frame to act as a diffuser.
It will lower the "amount of light" reaching the knob (bad) but it will avoid the formation of bright spots like the ones that are appearing on the left of the picture (good).
Special thanks to you since I know from experience that it is not easy to keep moving a 20kg instrument around in order to get the proper lighting to take pictures....
regards,
Roger


Re: TDS3044B repair

durechenew@...
 

Hello gentlemen,
I reviving this thread because I'm restoring a (heavily) damaged TDS3012 (broken plastic parts all over the place); one question was not asked (and no answer, of course): is a display for 30xxB fully compatible with 30xx?
In need of plastic parts I ordered a front part 3012B (available at a decent price) that included the display and front panel board; before blindly trying them on my 3012 (just to know their status, my scope is - electronically - fully functional and I don't really need them now) I thought asking if someone has already done that would make sense...
Thanks for any answer
TT


Re: Looking for sensitive audio RMS meter

Jean-Paul
 

Rebonjour Cher Cheater

1/RE noise floor distinguish between Signal to noise ratio and dynamic range

2/ Noise floor is a function of bandwidth, noise Spectrum and the limit of thermal noise, a function of the equivalent impedance.

3/ audio and digital audio noise and achievable noise floor, SNR and dynamic range have been topics of many fine papers. Especially, reccomend AES papers by our old friend Louis Fielder of Dolby Laboratoires ~1977, and John Vanderkoy and Stanley Lipschuttz at Guelph U. Waterloo 1970s...1980s


Bon dimanche

Jon


Re: Looking for sensitive audio RMS meter

EJP
 

On Sat, May 15, 2021 at 11:28 PM, cheater cheater wrote:

In my audio amplification chain I have an active analog crossover
which seems to be the source of noise. So for that reason I am looking
for a good way to measure and quantify that noise. The noise is so
high that it is audible in speaker outputs. I
I'm curious why you think you need microvolt resolution in an active crossover application. It is operating at tens of millivolts at least, and noise sources 80dB below that won't be audible in the speaker outputs.

Just wondering.

EJP


Re: Need a CT-3 trigger pick-off for the lab.

stevenhorii
 

On Sat, May 15, 2021, 21:08 Eric <ericsp@gmail.com> wrote:

Does anyone have a CT-3 Trigger pick-off they would be willing to part
with. I am looking to touch up the calibration on a 465B and some 485's.

Thanks
Eric






Tek 114 Pulse Generator

Shaun M
 

Folks:

I have recently refreshed a pair of Type 114 Pulse Generators as follows:

Both have serial numbers > 1680 and so are the latest revision in the manuals that I have
Both had leaky PS filter capacitors (originals from the Apollo era)
Both had carbon composition resistors which had drifted upward out of specification
Both had output amplifier transistors that showed slow rise time and very slow fall time. This caused pulse stretching and rendered the units unfit for calibration. Measured rise/fall times (as a unit) were ~15/55 ns using a 2 GHz scope.

After all the usual component replacements and adjustments, they are both working well and have pulse and square wave rise/fall times well below the 10 ns specification (< 7ns on a 2 GHz scope) given in the Factory Calibration Document. I swapped out NOS 2N2501 output amplifier transistors until I found pairs which gave fast, closely matched rise and fall times.

The as received o/p transistors in these units were not likely original as they either ECG 123A or unmarked/unreadable. I can only conclude that the OEM selected 2N2501’s were replaced at some point just to get the units running without regard to wave shape or rise/fall time.

Shaun M


FS: Tektronix Concept series Measurements and Circuits

Ken Eckert
 

I have a complete set (or pretty close too) of the Tektronix Concept series, Measurements and Circuits. They are in pristine condition, I don't think they were ever read, so no marking, no dog ears.....

I would like to sell them as two sets (unless someone wants both) So all Measurements in one set, all the Circuits in one set.

What I thought that instead of setting a price and possibly juggling competing offers that are the same, send me your offer. Best offer by Sat. morning May 22 takes. That should (hopefully) give everyone a chance to see the offer.

I am in Vancouver, BC local pickup is fine, shipping would be by Canada Post on top of the purchase price.

Tektronix Concept series:

Set 1:

Vertical Amp circuits
Sweep gen circuits
Storage CRTs
Spectrum Analyzer circuits
Sampling oscilloscope circuits
Oscilloscope trigger circuits
TV waveform processing circuits
CRTs
Auto test systems
INFO display concepts

Set 2:

Spectrum Analyzer Measurements
Probe Measurements
TDR Measurements
Biophysics measurements
TV system measurements
Semiconductor Measurements
Engine Analysis measurements


FS: Tek AM503 Current Probe Amplifier

Liam Perkins
 

Damn I dislike G-mail
This:

I have an example so clean it looks like it was never used. $US75.00 plus
postage
I took pix of it and a slew of other stuff, put 'em on a thumb drive
written to from a laptop, then moved them to my daily driver desktop and
Photoshopped them all nice and pretty, left the drive in the machine for a
couple days, forgot I hadn't copied the edited data to my d'top before I
scrubbed the thumb drive and just spent an hour looking for it all. Never
erase anything before AM coffee.
So, pix will be available soon and if anyone wants first dibs before then
ping me off-list.

Was supposed to be a new thread, sorry for the bullocks.

Liam


Re: Looking for sensitive audio RMS meter

Liam Perkins
 

I have an example so clean it looks like it was never used. $US75.00 plus
postage
I took pix of it and a slew of other stuff, put 'em on a thumb drive
written to from a laptop, then moved them to my daily driver desktop and
Photoshopped them all nice and pretty, left the drive in the machine for a
couple days, forgot I hadn't copied the edited data to my d'top before I
scrubbed the thumb drive and just spent an hour looking for it all. Never
erase anything before AM coffee.
So, pix will be available soon and if anyone wants first dibs before then
ping me off-list.

==================

In the matter of 4th order LR xovers: despite Sig's obvious, but to that
point in 1979 completely overlooked, observation that drivers must be
crossed at their -6dB points and -not- at their -3dB points was for me in
1979, revelatory.

How-ev-er he too missed the fact that all drivers are
Electro-Mechano-Acoustic-Composite (ELMAC) bandpass filters with phase
responses that simply must be reckoned.

Along with much else, Heyser realised this and in one of his papers showed
drive units radiating thru air paths delays varying with frequency; in
other words their acoustic centers moved axially wrt their fixed positions.
Almost everyone in this business still misses this.

D'load my paper here:

https://www.pearl-hifi.com/03_Prod_Serv/PR2/Refs/PR_2_Expanded_Info.pdf

and go to 'Sec. 7 - The Crossover' on page 10 of document itself (page 16
in the PDF) to read about what's actually needed to get correct phase
summation -in air- of the drivers' respective outputs. Fig. 7.7 on doc. pg.
15 shows what was done in 1980, which even today seems a mystery to most
loudspeaker designers.

In these days of dual channel FFTs such a measurement is almost trivial,
1980 it took two B & K measuring amplifiers looped thru two 2020 Heterodyne
Filters tuned by a 1022 (tube type) BFO whose sweep range was controlled by
a 4712 Frequency Response Display. A Wavetek 740 Phase Angle Meter watched
the measuring amps' outputs and its DC output vertically drove a beam on a
Tek R5113 Dual Beam Storage scope I bought new in about 1977. Because the
BFO's sweep rate was known and constant the scope's timebase was used to
generate the horizontal sweep.

The 2020s' outputs were spec'd within <1 deg of each other so that Rube
Golberg of an affair actually worked, with B & K Montreal being
sufficiently impressed with the result they bought a pair and used them
across the country to demo their new 2032 25KHz dual channel FFT box.

====================

And with all that, enough with the reminiscences already . . .







On Sat, May 15, 2021 at 6:23 PM cheater cheater <cheater00social@gmail.com>
wrote:

Loved hearing about your friend. Thanks a lot for that.

On Sat, May 15, 2021 at 9:54 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

Liam, I am thinking of John Dunne, the Uk poet and writer of 16th
century.....
Holy Sonnets,..... "Batter my heart, three personed God.....1609"

Julien Dunn was indeed the Jitter man.
Very Sadly Julien was afflicted with leukemia and passed on decades ago.

A moments réflexion on both John Donne the 16th century poet, and Julien
Dunn, a great engineer and audio researcher.

Sorry for the tangential reminisces......

NNNNNN
-73-

Jon












End caps for handle on 453/4 wanted

Mark Vincent
 

I am looking for the two blue round caps that fit on the handle of these
models. I have one that I got that these two were not on it to begin with.
Contact me off list anyone has a pair.

Mark


Need a CT-3 trigger pick-off for the lab.

Eric
 

Does anyone have a CT-3 Trigger pick-off they would be willing to part with. I am looking to touch up the calibration on a 465B and some 485's.

Thanks
Eric


Re: Looking for sensitive audio RMS meter

 

Loved hearing about your friend. Thanks a lot for that.

On Sat, May 15, 2021 at 9:54 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

Liam, I am thinking of John Dunne, the Uk poet and writer of 16th century.....
Holy Sonnets,..... "Batter my heart, three personed God.....1609"

Julien Dunn was indeed the Jitter man.
Very Sadly Julien was afflicted with leukemia and passed on decades ago.

A moments réflexion on both John Donne the 16th century poet, and Julien Dunn, a great engineer and audio researcher.

Sorry for the tangential reminisces......

NNNNNN
-73-

Jon








Re: Looking for Tek T922 HV transformer part number 120-0996-00

 

I have located a whole Tek 922 IF board. Thank you for reading my post.

--
Regards,
Bernie Murphy


7934 Disassembled

Karin Johnson
 

Hi All:
I thought you might want to see what a Tek 7934 looks like when it is taken all apart. The photo was uploaded to the Photos section of this list. This photo was taken 2 days ago, and since then I've made good progress in putting is all back together. All of the front panel switches and cables are connected correctly and scoped out. The top and bottom are mated together, but the remaining cables between top and bottom have yet to be connected.
I am taking this very slowly and so far so good. Of course the final test will be, does it work. On the faulty power supply issue that started all of this madness, there is also some good progress.

It turns out there was a short on one of the main switching transistors. Q40. There is a small insulated bushing that fastens this transistor to the heat sink. The heat sink is not at ground potential, it floats at the negative terminal of the bridge rectifier which is fed from the AC line. the external finned heat sink is at ground but there is a a mylar insulator sheet between the external fins and the power supply sub-chassis. It took me several days to work up enough courage to start removing components. It also turns out that my previous post about a faulty programmable unijunction transistor was INCORRECT. The symptom overall was that the inverter would not start. Troubleshooting the power supply showed that with a negative lead on TP46 and the positive lead on the cathode of CR38 the voltage would never rise above 10 volts DC. I am using a 7A22 differential plug in with my Tek 7603 to make these measurements. I finally lifted the cathode end of CR49 and the path to the short was detected, because now the voltage on the cathode of CR38 would rise above the previously mentioned 10 volts. It was also confirmed with ohm meter readings.
All of this troubleshooting is being done with a variac feeding the AC line to the 7934 power supply. The variac is very important to limit the line voltage and prevent the supply from going into tick mode. All of the loads are disconnected while I am testing.
One very important thing that I didn't pay to much attention to, caused me to overlook these transistors in the first place. The troubleshooting steps listed in the service manual, specifically indicate to remove Q34 and Q40 and test them separately, I did in circuit ohm meter tests and it did not show the short. The short is actually a high resistance short, just enough to prevent the starting circuit from working, but not enough to detect via in circuit ohm meter testing.
Lesson for self. Read the service manual and follow it religiously.

Onward and Upward,

Karin


Re: Persuading a 7S12 to play nice with a 7934.

Richard Steedman
 

While you hunt for your extenders, I've been taking a bunch of observations and have written up my findings in a PDF posted here. I have just one of John Griessen's flexible extenders and put my vertical amp on that which let me probe the left interface board of the 7S12 in situ. I've also gone back through the various manuals and written up the documentation discrepancies as I see them. One thing that was confusing me previously is that the page on Karl's wiki describing the 7000 series plug-in interface had incorrect voltage levels for pin B7. The wiki stated that B7 and A16 were both 0V/+5V but that's not the case. Checking the actual Tek documentation revealed B7 to be spec'ed as -0.6V/+1.1V with a +/-0.2V tolerance. So the signal from my 7934 is well with spec - the 7S12 just can't deal with it. I've corrected the wiki. If you read my document you'll see that another issue with the NPN transistor is its slow switch-off time, due to lack of a Baker-clamp in the circuit. I might try substituting it with a 2N2369 which has gold doping and faster switch-off time and see if that improves things.


Re: Looking for sensitive audio RMS meter

Jean-Paul
 

Liam, I am thinking of John Dunne, the Uk poet and writer of 16th century.....
Holy Sonnets,..... "Batter my heart, three personed God.....1609"

Julien Dunn was indeed the Jitter man.
Very Sadly Julien was afflicted with leukemia and passed on decades ago.

A moments réflexion on both John Donne the 16th century poet, and Julien Dunn, a great engineer and audio researcher.

Sorry for the tangential reminisces......

NNNNNN
-73-

Jon

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