TekScopes@groups.io

Re: Using the SA 7L13 and the TR502 to calibrate a filter with 75 ohm impedance.

You can build it at home, it is just a 2 resistor pad. Google for minimum loss adapter.

Regards,

Ignacio EB4APL

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El 12/03/2021 a las 16:09, Attilio escribió:
Hello everybody,
I would like to calibrate a VHF band pass filter using the tracking generator TR503 (converted to TR502) and the SA 7L13 in the mainframe 7613, but I have the problem that they have a characteristic impedance of 50 ohm while the filter has input and output impedance of 75 ohm . How can I do ?
I have seen on the internet a 50 to 75 ohm BNC adapter (5.7 dB attenuation) but it is quite expensive.

Thanks for the attention
-- Cheers
Attilio

-- 
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.

Using the SA 7L13 and the TR502 to calibrate a filter with 75 ohm impedance.

#180244

Hello everybody,
I would like to calibrate a VHF band pass filter using the tracking generator TR503 (converted to TR502) and the SA 7L13 in the mainframe 7613, but I have the problem that they have a characteristic impedance of 50 ohm while the filter has input and output impedance of 75 ohm . How can I do ?
I have seen on the internet a 50 to 75 ohm BNC adapter (5.7 dB attenuation) but it is quite expensive.

Thanks for the attention
-- Cheers
Attilio

Re: Broke my TDS3000B

#180243

I've no idea what I should be looking for and those pins are mighty small
and close together.Oh yes, thats not easy. 

I was thinking about checking if the lines are totally stuck or are looking normal, i.e. change state every now and then.
Or if a line is moving a little when you switch below 400us... things like that, to confirm or not if the ASIC really has a problem.

cheers
Martin

Re: Broke my TDS3000B

#180242

Eight of them - I've checked everything now using the stereo microscope.

D.

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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Martin
Sent: 12 March 2021 13:20
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

How many Tantalums did you replace on that board? 
How sure are you that there is no problem with a solder joint on or around
one of these?

cheers
Martin

Re: Broke my TDS3000B

#180241

I've no idea what I should be looking for and those pins are mighty small
and close together.

Show quoted text

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Martin
Sent: 12 March 2021 13:28
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

Just one more thing... (Columbo)

Can you check the suspect lines with a another scope?
Do they look stuck? Is there any correlation with good/bad behaviour of the
TDS?

cheers
Martin

Re: Broke my TDS3000B

#180240

Just one more thing... (Columbo)

Can you check the suspect lines with a another scope?
Do they look stuck? Is there any correlation with good/bad behaviour of the TDS?

cheers
Martin

Re: Broke my TDS3000B

#180239

How many Tantalums did you replace on that board? 
How sure are you that there is no problem with a solder joint on or around one of these?

cheers
Martin

Re: Broke my TDS3000B

#180238

I have no clue as the IC's in question are custom ASICs.

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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Martin
Sent: 12 March 2021 11:29
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

Hi David,

were you able to verify the type of pin that you shorted, or presumably
shorted? I mean if its a supply line (low impedance), or inputs or 3 state
or whatever? In my experience digital logic is rather robust and it was rare
to cook a chip just by shorting one of its pins to another, even to GND or
VCC. 

cheers
Martin

Re: Broke my TDS3000B

#180237

Hi David,

were you able to verify the type of pin that you shorted, or presumably shorted? I mean if its a supply line (low impedance), or inputs or 3 state or whatever? In my experience digital logic is rather robust and it was rare to cook a chip just by shorting one of its pins to another, even to GND or VCC. 

cheers
Martin

Re: Broke my TDS3000B

#180236

And the  bad news is - it's still broken ?

D.

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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of David C. Partridge
Sent: 12 March 2021 10:20
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

I went in and checked over and partially redid the cleanup under the
microscope yesterday pm.  Still need to put back together and test.

D.

Re: [Tek 485] No intensity control

#180235

I'm waiing a delivery from Mouser including 2N3565 transistors, 1N4152 diodes and capacitors.

Will get back when I'll receive it and change CR1539, CR1534, C1537, Q1544.

Jose

Re: Broke my TDS3000B

#180234

I went in and checked over and partially redid the cleanup under the
microscope yesterday pm.  Still need to put back together and test.

D.

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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of John Miles
Sent: 12 March 2021 08:04
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

I've since removed the splatter but now any horizontal sweep rate fasterthe
400uS breaks up into a mess, and autoset doesn't work right.  I'm thinking
I've probably killed it  >:(Are you sure you  got *all* the solder?

-- john, KE5FX

Re: Broke my TDS3000B

#180233

I've since removed the splatter but now any horizontal sweep rate fasterthe
400uS breaks up into a mess, and autoset doesn't work right.  I'm thinking
I've probably killed it  >:(Are you sure you  got *all* the solder?

-- john, KE5FX

Re: TDS544A with strange display #photo-notice

#180232

If you look at the fourth image in the photo album where the bottom right 'button' is active then the artifact appears on the very top line of the scan, presumably displayed on the following field.  The artifact is also triggered by the symbol for the rotary control knob but only where the approximation to the circle extends to the very last pixel on the scan line.

This suggests a way to reliably look at the video signal where it is displaying the artifact.  You can trigger from FSYNC or VSYNC, it would be interesting to see if the artifact was on all four fields or just one.  You then use delayed sweep to select the first scan line and depending on the polarity and timing of the vertical sync pulses you may need to change the delay for the different trigger options.  So now you can trace the video signal from the RAMDAC through to the output of the video amplifier at the clipping diodes CR560, CR568.  The video amplifier has a lot of high frequency peaking including a few inductive elements so there is plenty of opportunity for it to ring because of a fault or an incorrect video drive signal.

Good hunting!

Regards,

Roger

Re: 2235 AN/USM-488 power supply low voltages

#180231

Im still struggling with this power supply

If I remove the A5 board from the scope the power  supply voltages return to normal and can be adjusted to spec by adjusting R938.   As soon as I plug the A5 board back in the voltages drop to the following levels: and R938 has no affect
+5.2=4.3
+8.6=7.4
-8.6=-7.3
+30=+25.8
+100=+87.8

Also when I adjust the Scale Illumination knob the with of the trace shrinks

Any and all suggestion would be appreciated

R A

Re: Broke my TDS3000B

#180230

All channels equally impacted.  Yes I was referring to the big National Semi IC.  Sweep rates of 400us and slower are just fine.  Anything faster is a total mess.  I see the MPC860 now - right next to the ethernet connector (J910) at the other end of the board.

Is it OK to operate this beastie with covers off for any length of time - loath to inflict further damage that way.

D.

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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of maxim.vlasov@...
Sent: 11 March 2021 22:10
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

TDS3000B are built on the MPC860 PowerQUICC. This is the main CPU. So, it has no boot ROM or the full fledged custom secure bootloader (too old), which is a great advantage for repairman. So, this thing can be sourced and replaced, IMHO.

Are you referring to the big PQFP240 National Semi thingy, right? IMHO, this is not the CPU, it's the ASIC DPO emulator with the ADC/RAM/etc crossbar, ADC clock generator PLL and DMA functionality.

Could you, please, check at which sampling rates you have a garbled response? If you run in X/Y mode, do you have the same stuff? Is it the same when running from the external trigger? Are all the traces garbled or just a subset of channels? Try to remove all the plug-ins and extension cartridges. 
Also it could be the SRAM too (just two chips next to the ASIC). How about the linear power regulators in the vicinity of the tantalum cap? Are they OKAY?
Try to go around the o-scope and check the logic levels around the SRAM and National Semi ASIC. Maybe you can find a burned buffer or something. If it breaks below 400us, it could be the PLL.
I would go around and note the voltages and levels and post it to the forum.
Also the thermal image would be a good indication of something awkward.
You said that built-in self test runs OKAY. But how about running the calibration and service routines, would these fail?

Re: Broke my TDS3000B

#180229

Up-hack is discussed on EEVBLOG.

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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of durechenew via groups.io
Sent: 12 March 2021 00:24
To: [email protected]
Subject: Re: [TekScopes] Broke my TDS3000B

On Thu, Mar 11, 2021 at 11:43 AM, David C. Partridge wrote:

up-hacked to TDS3064B
Hi Dave,
Worked long ago with 3054, loved that scope (some people don't like Tek, I do). Unfortunately I never looked inside one so far (seen something on you tube) and I'm afraid I could be of no help here. It would be interesting though to read if you posted somewhere information about how you "...up-hacked to TDS3064B".
All the good luck (you'll need a lot)
TT

Re: Success! 5S14N becomes 5S14 with readout

#180228

Thanks for taking the time to write it up!

Re: Broke my TDS3000B

#180227

On Thu, Mar 11, 2021 at 11:43 AM, David C. Partridge wrote:


up-hacked to TDS3064B
Hi Dave,
Worked long ago with 3054, loved that scope (some people don't like Tek, I do). Unfortunately I never looked inside one so far (seen something on you tube) and I'm afraid I could be of no help here. It would be interesting though to read if you posted somewhere information about how you "...up-hacked to TDS3064B".
All the good luck (you'll need a lot)
TT

Re: TDS544A with strange display #photo-notice

#180226

On Thu, Mar 11, 2021 at 5:11 PM durechenew via groups.io <durechenew=
[email protected]> wrote:

I'm talking here about the diagrams that, if I'm not wrong, you provided
for TDS544A.
In diagram 22 of CPU/display, there are two RAMDACs, one for monochrome
(U190) and the other for VGA (U199); both take the information from the
same place, O20 (0,...7). U190 provides at the output (pin 25) the frame
synchro signal (white level, black level and blanking level - I'll double
check that). U199 provides RGB color signals for VGA and we know that
information is correct; up to this point nothing could be wrong.
Diagram 23 might be the place where I have the problem; here is TLC434075
getting its data (FS0... FS19) from U400... U404, memories, in turn taking
their data VBA0... VBA8 from U2011 (Diagram 24). Possible that one of those
memories is bad; but where, in all this, is CLEAR MENU, as that command
disables the stripes...
Thanks for sharing your findings and your thinking along the way. I've
never had occasion to drill into the display machinery on these scopes, and
there's clearly a lot of that.


I've seen Siggi's comment. I think shutter is not capable of working at
the line frequency; I don't know if driving such a big surface of LCD
(capacitance is high) at high frequency would be possible... At frame
frequency, not an issue, I guess.
I'm dealing in pure speculation, so please take it with a healthy grain of
salt. I'll say that the output drivers on the LCD shutter board seem pretty
beefy and they drive at 24V, presumably differentially at each panel.

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