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Re: Option 7 for DC-508A

Nenad Filipovic
 

I don't have the original PDF, but I compiled and posted instructions some time ago on the group in a thread named "DC508A Option 7 installation guide":
https://groups.io/g/TekScopes/message/167339
Photos and instruction documents:
https://groups.io/g/TekScopes/files/DC508A%20Option%207%20installation%20guide
https://groups.io/g/TekScopes/album?id=247439

Nenad


[OT] CRT + Vidicon = analog convolution?

 

Hi all,
I have recently stumbled upon the idea of using vidicons and CRTs for
analog convolution. Convolution of a continuous incoming signal (say
audio) with a FIR (finite impulse response) is one way of creating
echo, simulating filters, etc. By far the only method of calculating
convolution nowadays is the DFT (discrete Fourier transform), a form
of the FFT (fast Fourier transform).

I was wondering if anyone used vidicons and can confirm if this scheme
would work.

The first time I heard of vidicons being used together with CRTs was
when I read up on old TV stations and how they converted from 50 to 60
Hz or between line amounts. They essentially filmed a TV, but the
device eventually was an integrated CRT-Vidicon invention where the
CRT and Vidicon both scanned horizontally. However, if you make them
scan at 90 degrees of each other, you can use that for computation.

One way of calculating convolution is as follows. Let's assume for a
second that the signal and the FIR take values from -1 to 1. For every
sample of the signal you have coming in, call that sample s_t, you
start outputting s_t * FIR - you output all samples of the FIR
subsequently, scaled by s_t. So on this sample, you output s_t *
FIR_1, where FIR_1 is the first sample of the FIR. On the next sample,
say s_t+1, you start outputting s_t+1 * FIR, while also continuing to
play back s_t * FIR. So on the second sample you output s_t+1 * FIR_1,
but also s_t * FIR_2.

Let's say you take a CRT and break it up into, say, a grid of 100 x
100 points. Scan them horizontally from top left to bottom right.
Start out in the top left. Wait for a sample of the signal, say s_1,
to come in. Horizontally, you start outputting - using the Z channel
(brightness) - the samples s_1*FIR_1, s_1*FIR_2, etc.

Wait for the next sample to come in, and meanwhile move to the 2nd
line, and start on the second point. When sample s_2 comes in, start
outputting s_2*FIR_1, s_2*FIR_2, until you hit the end of the line,
which is s_2*FIR_99. Then wrap around to the start of the line 2
(without advancing to line 3), and output s_2*FIR_100.

So on the nth scan line, you start outputting at the nth "pixel". On
the 100th scan line, you start at the 100th pixel. Then you wrap
around to the first line and start on the 1st pixel.

Next for the Vidicon. Orient it towards the CRT, but at an angle of 90
degrees. So it should be scanning vertically, top to bottom, left to
right, starting from the top left, and ending on the bottom right. It
has scan columns rather than scan rows.

For every sample you have coming in, as you are outputting the
relevant row to the CRT, scan a single column. You can start before
the row is done outputting, because all previous rows are done, and as
for the latest row, you only care about the home pixel (the pixel that
is first put on the screen, ie for the nth line it's the nth pixel).
While scanning this, sum up the brightness over your whole scan, and
that's your output. That just calculated a convolution between the FIR
and the incoming signal. It's a 100-point convolution. Cool, right?

Here's an even cooler thing. Nothing says you have to make the FIR
have as many points as there are rows. You can make the FIR a
continuous signal. Then, you can scan that 100-row image using more
than 100 columns. Say, scan it at 400 columns. This then just means
that the FIR has a bandwidth 4x higher than the signal it's being
applied to.

And finally, of course you can output different FIR for every incoming
sample (for every incoming row). This would let you eg apply, via
convolution, a parametric filter.

Regarding practical implementation of the CRT output. For simplicity,
I described above a situation where you're outputting horizontal lines
of variable brightness in a raster. However, to preserve the phosphor,
when increasing the Z (brightness) of the trace, you would also add a
little bit of a high-frequency signal, to make the line thicker. The
vidicon and the subsequent averaging circuit will like it just as
well, and probably even better. This way you can prevent incoming hot
spots. Also it doesn't matter if the lines intersect - they might just
as well all be at the same level. However, then the phosphor might get
more hot spots, and the non-linearity of the phosphor brightness vs
cathode current might come into play. The raster was just to
illustrate the structure of the algorithm, but if you need some form
of accuracy, then you might want to keep lines from intersecting, but
at that point, why are you even doing this using a Vidicon?


Re: Tek Scopes on Government deals

Paul McClay
 

Um, anybody near Hughesville PA or ready to roll the shipping dice on a 630lbs pallet of CRTs might want to take a look thru the photos...

... all the photos; there's nearly no duplication.

I'm too lazy to copy out an inventory, but just in case your visual pattern matcher is tuned for scopes: there's a pen plotter in there too.

On Fri, Jan 21, 2022 at 08:53 PM, Bill Higdon wrote:


https://www.govdeals.com/index.cfm?fa=Main.Item&itemid=1511&acctid=19307


Re: Type 106 Adjustment

Stephen
 

On Sat, Jan 22, 2022 at 03:26 AM, tgerbic wrote:


Yes the silicon diode mod. Was wondering if someone in the past had performed
the mod and got it wrong.
Yes, that would be great if someone who has already done it successfully could share their experience. Just in case someone, for whatever reason, has to do it some day.

Cheers


Re: Tek Scopes on Government deals

Dave Seiter
 

Brings back memories of what got me started with Tek scopes- two pallets of mostly 7K scopes from a Telogy auction.  I got them for $50 each, the only bidder, because there were a few obviously dead items, like the 7104 and a few others with broken CRTs on the top of the stacks.  Lots of 7104s and 7488s, mostly 100% working or easily repairable.
$500 seems a bit much, but if they're following the R2 regs, and the scopes are working, could be good for someone.
-Dave

On Friday, January 21, 2022, 06:53:59 PM PST, Bill Higdon via groups.io <willard561@...> wrote:

https://www.govdeals.com/index.cfm?fa=Main.Item&itemid=1511&acctid=19307


Re: Tek Scopes on Government deals

Bill Higdon
 


Tek Scopes on Government deals

Bill Higdon
 


Re: Help needed finding a connector as used in TDS scopes.

Jared Cabot
 

Unfortunately the Champ part (1-1734099-0) won't fit as the staggering of the pins is opposite to the footprint on the PCB.

Here is the underside of that part:
https://i.imgur.com/DGVLdeO.jpg

Here is the top of the PCB it needs to fit into:
https://i.imgur.com/C3FEtuA.jpg


Re: Type 106 Adjustment

tgerbic
 

Yes the silicon diode mod. Was wondering if someone in the past had performed the mod and got it wrong.


Re: Help needed finding a connector as used in TDS scopes.

Jim Ford
 

I'll take Amp/Tyco/TEConnectivity over Molex any day.  From bad experiences with Molex.         Jim Ford Sent from my T-Mobile 4G LTE Device

-------- Original message --------From: Bruce Lane <kyrrin@...> Date: 1/21/22 6:02 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Help needed finding a connector as used in TDS scopes.     Indeed I do. Those are actually made by at least three different companies: Tyco/AMP, Hirose Electric and Molex. They're 1.27mm pitch on the contact spacing, and DigiKey has a generous selection at this link.     Here's one example of a mating part, for the one in your picture, from DigiKey.https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/1-1734037-0/1121339     That should help you track down what you need. Happy tweaking.On 21-Jan-22 08:04, Jared Cabot via groups.io wrote:> Hi all,>> as part of repairing a couple TDS600/700 series scopes, I need to source a few connectors.> Does anyone know what this connector is and where I can find some? I can't see any markings on it to even get me started..>> https://i.imgur.com/UBmmtoZ.jpg>> Thanks!>>> >>-- Bruce Lane, ARS KC7GRkyrrin@..."Quando Omni Flunkus Moritati" (Red Green)


Re: Option 7 for DC-508A

Greg Muir
 

I unfortunately don’t have any documentation on this option but you might gain a little information by going here:

https://groups.io/g/TekScopes/topic/dc508_help_with_photos_option/30289354

Greg


Re: Help needed finding a connector as used in TDS scopes.

Bruce Lane
 

Indeed I do. Those are actually made by at least three different companies: Tyco/AMP, Hirose Electric and Molex. They're 1.27mm pitch on the contact spacing, and DigiKey has a generous selection at this link.

    Here's one example of a mating part, for the one in your picture, from DigiKey.

https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/1-1734037-0/1121339

    That should help you track down what you need. Happy tweaking.

On 21-Jan-22 08:04, Jared Cabot via groups.io wrote:
Hi all,

as part of repairing a couple TDS600/700 series scopes, I need to source a few connectors.
Does anyone know what this connector is and where I can find some? I can't see any markings on it to even get me started..

https://i.imgur.com/UBmmtoZ.jpg

Thanks!



--
Bruce Lane, ARS KC7GR
kyrrin@...
"Quando Omni Flunkus Moritati" (Red Green)


Re: Help needed finding a connector as used in TDS scopes.

durechenew@...
 

Seems close (not significant differences) with 1-1734099-0, used in TDS3000.

https://www.ebay.ca/itm/163591113538

TT


Option 7 for DC-508A

 

Does anyone happen to have a PDF of the instructions that accompanied the Tektronix 040-0789-00 field modification kit for adding Option 7 to the DC-508 or DC-508A counters?

Bruce, KG6OJI


Re: What is it about Z-axis amps?

 

Where I wrote "pin #4 of U1560" I should have written "pin #9 of U1560"; I mis-traced the long parallel tracks on the schematic.

-- Jeff Dutky


Re: TDS380 Jerky Response with Measurements Turned On

Harvey White
 

Shouldn't be a factor, adding an extra display that exactly replicates the internal display is just paralleling signals.

If the external display could be written to separately, then it would be CPU intensive.

Harvey

On 1/21/2022 5:15 PM, David Templeton wrote:
How are you displaying on that monitor? , I presume it must have a secondary output, could that be a factor?





Re: Type 106 Adjustment

Stephen
 

On Fri, Jan 21, 2022 at 04:39 PM, <Zentronics42@...> wrote:

Interleaved.


The DSA602A should work though it is being pushed to the practical limit. It
will not be able to do amplitude measurement based on the -3db limit and being
in the upper range of the falling curve. Wave shape should be accurate.
However the time base in the DSA is plenty fast once it kicks in to sampling
mode. That is also a good point. The DSA is a sampling scope so you are good
to go there. I will take some measurement on my 106 with the DSA so we have
something to compare to.
Yes, please do.

The DSA will kick in and out of sampling >mode based. on the time base settings. This is not bad just they way they implemented the
function in the 90's era (I think for the DSA)

But Stephen is correct the waves forms of the fast rise should look exactly
like the fast fall just inverted something is definitely wrong on the fast
rise board.
Thanks. If you have seen the latest pictures after I switched around Q103 and Q124, things look much, much better.
I wouldn’t mind see how flat the entire first half of the fast + waveform is on yours. Because although mine is now looking less funky, the hump is still there, albeit a bit less pronounced.

At this point I’m trying to determine if I should try to make it flatter.


Ill be back in the lab tonight if there is anything that I can do to help the
cause.

Zen
Thank you Eric, you’ve always been m, like many others, very humble and helpful, and your YouTube channel helped me bring this 106 back to life.

Regards,


Re: Wanted: Tektronix 067-0645-0X TM 500 flexible extender (or equivalent)

fiftythreebuick
 

Soon as I figure out how to send you a photo I'll get it on the way!


Re: TDS380 Jerky Response with Measurements Turned On

Dave Voorhis
 

I don’t own a TDS380 so I don’t have a basis of comparison, but it looks completely normal to me. I would expect measurements to consume some CPU horsepower, with a corresponding slowdown or latency elsewhere.

On 21 Jan 2022, at 20:11, Richard Peterson <saaber1@...> wrote:

Any thoughts? Normal?


Re: TDS380 Jerky Response with Measurements Turned On

Richard Peterson
 

Any thoughts? Normal?

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