Date   

Re: Tek TDS694C advice pls

 

They don't seem to run excessively hot.
Thanks for the link, John, I'll have a look over there.

There's no heat spreader or anything on top of these chips but they seem to have a solid metal tab underneath.
In my TDS694C, two of them were too hot to touch for even 5 seconds after operating for less than a minute,
hence my theory that the tab has come loose (bad/non-existent solder flow) or the chip has come loose inside, as per one of the theories on the infamous U800 in the 24X5 series.

In my TDS694C, trigger chips for CH1 and 2 don't get very hot. CH3 and especially CH4 do. CH3 has become intermittent, CH4 is dead now. I only got this 'scope very recently and I opened it up because of the trigger problems. Putting a heat sink on top helped a little for a while.
I don't think that a non-cooling-related problem caused these chips to heat up in the first place.

None of the other chips on the acquisition board get very hot. A small fan while open suffices, but for the trigger chips.

Looking at a <= 200 ps edge with either a TDS694C or a 10 GHz+ sampling 'scope makes quite a difference.
With practice, a classic sampling 'scope is not too difficult to use, especially if you know what to expect...

Raymond


Re: Tek TDS694C advice pls

Phil Hobbs
 

My 694C is my favourite scope. (I have 8 in use at the moment, including two 1180x sampling scopes and about 20 plugins.) If I could have only one, it would be the 694C.

With the matching P6249 FET probes, the 694C becomes more or less a general purpose scope. You do have to watch out that you don't blow the probes up with overvoltage, and they're only 20k // 1 pF, but the combo is very powerful.

Cheers

Phil Hobbs


Re: Tek TDS694C advice pls

John Miles
 

TDS 694Cs are decent scopes for the money, and they're also new enough to
avoid the infamous Tek capacitor plague. See
http://www.eevblog.com/forum/testgear/least-expensive-but-reliable-used-mark
et-scope-with-at-least-1-ghz/msg791170/#msg791170 for more on the trigger
chips.



They don't seem to run excessively hot as long as you either keep the cover
on the scope or aim a fan at the acquisition board when servicing it with
the power on. Two or three minutes without cooling would make me nervous on
behalf of the front end chips. The trigger hybrids are far from the hottest
ones on the board...



They aren't the greatest 3 GHz scopes on the planet, but they are the
cheapest, and they're far nicer to work with than any sampling scope.



-- john, KE5FX



From: TekScopes@... [mailto:TekScopes@...]
Sent: Monday, April 11, 2016 3:01 AM
To: TekScopes@...
Subject: [TekScopes] Re: Tek TDS694C advice pls





The TDS694C is a 3GHz, 10 GS/s Real Time-only 'scope. It is best suited for
one-shot applications and because of that is often used in combination with
a Logic Analyzer, which provides the trigger signal.

Unfortunately, the TDS694C tends to suffer from overheating trigger ASICs,
eventually causing their destruction. It contains four of them; one for each
channel. It seems that their bottom (heat sinking) tab is not correctly
fixed/soldered to the PCB - or the chip separates from the tab...

Hi-jacking the thread: If anyone can provide me with a few of these
unobtanium chips (156-8278-00), I'd be very much obliged....

Classic sampling 'scopes are well suited to judging repetitive signals,
including pulse edge shape. A 7000 mainframe with an S-6 or better yet, an
S-4 vertical input head, provides 11 or 14 GHz BW. I prefer the S-4 mostly
because it has an internal trigger pickoff, which is easier to work with and
avoids distortion caused by extra (splitting) cabling if there's no separate
trigger signal. Generally, because there's no delay line, for pulse work you
need a pretrigger signal (or an accurate separate delay).

Using such a setup in a 7854 is a real treat.

Raymond


Re: Tek TDS694C advice pls

 

Using such a setup in a 7854 is a real treat.
Another good option is using a variable persistence mainframe but any (low-bandwidth) 7000 mainframe will do.

Raymond


Re: Tek TDS694C advice pls

 

The TDS694C is a 3GHz, 10 GS/s Real Time-only 'scope. It is best suited for one-shot applications and because of that is often used in combination with a Logic Analyzer, which provides the trigger signal.

Unfortunately, the TDS694C tends to suffer from overheating trigger ASICs, eventually causing their destruction. It contains four of them; one for each channel. It seems that their bottom (heat sinking) tab is not correctly fixed/soldered to the PCB - or the chip separates from the tab...

Hi-jacking the thread: If anyone can provide me with a few of these unobtanium chips (156-8278-00), I'd be very much obliged....

Classic sampling 'scopes are well suited to judging repetitive signals, including pulse edge shape. A 7000 mainframe with an S-6 or better yet, an S-4 vertical input head, provides 11 or 14 GHz BW. I prefer the S-4 mostly because it has an internal trigger pickoff, which is easier to work with and avoids distortion caused by extra (splitting) cabling if there's no separate trigger signal. Generally, because there's no delay line, for pulse work you need a pretrigger signal (or an accurate separate delay).

Using such a setup in a 7854 is a real treat.

Raymond


Re: Tek TDS694C advice pls

mosaicmerc
 

TDS694C isn't a sampling scope though, it's a real time one shotter.


Re: 2221 100MHz Scope repair project

Stuart Barker
 

Hi Leo
From my own recent experience of fixing a 2220 I would suggest as a matter of course replacing all the low voltage PSU electrolytics. On my scope 7 of the 9 Sangamo 840mic 12V were bulging and at least two measured as being leaky, see the photos I posted under a 2220 post.


best of luck with the repair.
Stuart


Re: Tek TDS694C advice pls

 

Sampling oscilloscopes are not good for general use; where they shine
is applications that require either the highest bandwidth or best
overload recovery. Almost all sampling oscilloscopes also require a
pretrigger signal.

Both types of oscilloscopes will require 50 ohm probes. You will not
find high impedance passive probes on any oscilloscope input faster
than 300 to 500 MHz and passive probes high impedance probes at those
frequencies do not perform well compared to low-z probes which are
easy enough to make on the spot for work up to about 1 GHz.

On 10 Apr 2016 19:16:21 -0700, you wrote:

Hi , In my research for a higher bandwidth scope option, I have placed this item on my wish list.
I see it uses 50 Ohm probes only.

Is there anyone on the forum with advice on this Scope as a high bandwidth option vs sampling scopes etc?

thx


Re: Tek 2216 Opt 1M RAM Mfg/mfg PN (U2708, '09, '11, '12)?

 

The Tektronix Common Parts Design Catalog or at least the one commonly
available online does not include Tektronix IC part numbers higher
than 156-1843-00 so it will not be of any help.

That leaves reverse engineering the schematic to see what part would
be appropriate and I have never seen the 2216 service manual. Maybe
we can get something from the memory organization.

I am confused by your description. The user manual says that the 2216
has either 16k or optional 128k record lengths per channel. Assuming
one x8 SRAM per channel since you mention four memory ICs and 8 bit
records although lots of old Tektronix DSOs use 16 bit records with 8
bit digitizers, that would be 16k x 8 = 128kbit SRAM or 128k x 8 =
1Mbit SRAM. Depending on who made it, I think that means either a
62128 or 621024 type of part number for the larger 1Mbit SRAMs.

What is the part number for the four smaller SRAMs used in the 2216?

The larger SRAMs are suppose to replaced the smaller ones, right?

On Mon, 11 Apr 2016 01:36:21 +0000, you wrote:

Any ol' Tek service people out there that can help with a part question on the Tek 2216 (H prefix SN)?

The service manual has typos regarding the Option 1M RAM on the A7 Processor board. I'm looking for the correct mfg/PN for the higher capacity U2708, '09, '11 and '12. The upgrade should be from a 32KB to a 128KB SRAM. The PCB suggests a 32 pin DIP with 0.4" between rows. The manual lists Tek PN 156-4367-00.

I'd appreciate knowing the proper mfg/mfg PN for this part.

Thanks in advance,

Don


Tek TDS694C advice pls

mosaicmerc
 

Hi , In my research for a higher bandwidth scope option, I have placed this item on my wish list.
I see it uses 50 Ohm probes only.



Is there anyone on the forum with advice on this Scope as a high bandwidth option vs sampling scopes etc?


thx


Tek 2216 Opt 1M RAM Mfg/mfg PN (U2708, '09, '11, '12)?

DON CRAMER <donlcramer@...>
 

Any ol' Tek service people out there that can help with a part question on the Tek 2216 (H prefix SN)?

The service manual has typos regarding the Option 1M RAM on the A7 Processor board. I'm looking for the correct mfg/PN for the higher capacity U2708, '09, '11 and '12. The upgrade should be from a 32KB to a 128KB SRAM. The PCB suggests a 32 pin DIP with 0.4" between rows. The manual lists Tek PN 156-4367-00.

I'd appreciate knowing the proper mfg/mfg PN for this part.

Thanks in advance,

Don


Tek 2216 Opt 1M RAM Mfg/mfg PN (U2708, '09, '11, '12)?

DON CRAMER <donlcramer@...>
 

Any ol' Tek service people out there that can help with a part question on the Tek 2216 (H prefix SN)?

The service manual has typos regarding the Option 1M RAM on the A7 Processor board. I'm looking for the correct mfg/PN for the higher capacity U2708, '09, '11 and '12. The upgrade should be from a 32KB to a 128KB SRAM. The PCB suggests a 32 pin DIP with 0.4" between rows. The manual lists Tek PN 156-4367-00.

I'd appreciate knowing the proper mfg/mfg PN for this part.

Thanks in advance,

Don


Re: 2235A PSU troubleshooting

Steve
 

I found the culprit, C942, I hope this will help someone. Thanks


Re: Bandwidth measurement.

ditter2
 

Bill,
The reason a leveled sine source is used to measure bandwidth rather than rise time of a fast step is to locate any "suck outs", which usually result from a resonance, that might appear somewhere in the passband. These would have an effect on the pulse shape of the step, but the effect may be too small to be easily seen in the waveform.

A leveled sine source is the easiest way to make this measurement, but if you lack one, any oscillator can be used if you can monitor the output level. This can be done using a RF power meter. To remove the effects of cable reflections, the amplitude should be measured as close to the scope input as possible. This can be done using a power divider at the end of the cable, with one end feeding the scope input, the other driving the power head of the power meter. You may have difficulty getting enough voltage to verify the higher V/div settings, but usually you won't find a problem that effects the frequency response with these, so they can be verified for attenuation accuracy only using a LF source, with the BW measurements at a lower V/Div setting. (This assumption is valid up through a few hundred MHz, but not with the 50 ohm inputs of multi GHz scopes. Verifying BW flatness of these is a challenge.)

- Steve

---In TekScopes@..., <wah_1003@...> wrote :

Hello Everyone:


I have been a member of the group for a few years now and always enjoy the posts, the combined experience here is awesome. I recently read a post that said the number of scopes to have was "one more", I agree. If it was not for the size of my work area I would have many more. Right now I have a Fluke Scopemeter, a Tek 2246A, two Tek 475s, a Tek 7904 and a small HP mainframe with a 8558B spectrum analyzer. I also have the normal potpourri of supporting equipment - probes, calibrators, etc. There always seems to be something missing.


The 7904 is a funny story. I had absolutely no room on my bench for something else, so I convinced myself I needed a Tek ScopeMobile cart to "put my hand tools in". Just a few weeks later I got a 7904 to put on top of it and then the unstoppable flow of plugins began. I still have a few extenders I got from John Griessen that I need to put together. Now I think I have really run out of space but you never know.


Now for my real question: One day I was using one of my 475s and there was a strange kind of popping noise and the trace went wild. After some diagnosis there was one large filter cap that had opened up. Since it was so hard to get to (you have to really take most everything out of these to get to the big caps) I replaced them all and also changed all of the incandescent lamps to LEDs with built-in internal dropping resistors. After this I was looking forward to using all of my equipment to re-calibrate the scope. Everything worked out fine but I had a question about the bandwidth test.


First of all one thing I do lack is an SG503/SG504 but if I did I was curious about what should be done if the test shows that the bandwidth is constrained? All of the other adjustments have variable pots and caps that are used to get it back into spec but if the bandwidth is not right what course of action would you take? Seems like the problem could literally be anywhere.


My second question is: Do you really need the leveled sine wave generators to determine bandwidth? Wouldn't just a really good measurement of the risetime be sufficient? I have a TD pulser.


Thank you for your time and keep up the good work,
Bill


Re: a sick 576 (and it's owner) needs help

Ed Breya
 

I may not get the whole picture here, but it seems from the messages so far that you put a resistor across the C-E terminals, but get unexpected results on the 576, then you went so far as to measure the current with a current probe. Now you believe the display appears to simply show the slope due to the current range sensing resistor. Right?

I did not see any mention of checking the voltage across the C-E terminals - only the actual current with a probe, and no mention of checking it without any device between the terminals. I suspect the problem may be a switch signal routing failure, and/or a possible short between the C-E terminals. This part would be simple to check - just run it without any DUT attached to confirm that no current flows as the voltage goes up. Also, check for proper right-left select switch operation, and the B-E mode switch too.

You should confirm that no current flows through the DUT when it shouldn't, and some definitely goes through when it should, and that there's voltage drop across it. If this is the case, then a C-E terminal short is unlikely, so there has to be a switching problem or maybe loss of a connection somewhere allowing the wrong signal to be displayed - maybe a lost ground connection, for example. Another possibility may be a broken switch, where one section or contact is stuck or out of sync with the rest of it.

Ed


Re: 465 oscilloscope problem

Siggi
 

On Sun, 10 Apr 2016 at 17:35 'Tewell, Kevin' tewell.ka@... [TekScopes] <
TekScopes@...> wrote:

The serial number is above 250000
Excellent I see you've noted this before and I missed it - such are the
perils of the centithread :).
I've gone ahead and bought the relevant manual from Artek so that we can be
on the same page - so to speak.


Re: 465 oscilloscope problem

Tewell, Kevin <tewell.ka@...>
 

The serial number is above 250000

Sent from my BlackBerry 10 smartphone.
From: Sigurður Ásgeirsson siggi@... [TekScopes]
Sent: Friday, April 8, 2016 10:17 AM
To: TekScopes@...
Reply To: TekScopes@...
Subject: Re: [TekScopes] 465 oscilloscope problem




On Thu, 7 Apr 2016 at 21:47 'Tewell, Kevin' tewell.ka@... [TekScopes] <
TekScopes@...> wrote:



I have a digital multimeter this one.


http://www.amazon.com/gp/aw/d/B000JKMTDM/ref=mp_s_a_1_sc_7?qid=1460078645&sr=8-7-spell&pi=SL75_QL70&keywords=digital+multimeter+madtech

That looks like a decent enough DMM.
I have a power supply up to 60 volts and a few amps.
Is this a proper lab supply - e.g. does it have a current limit, or just
settable voltage?

I bought the mantel and downloaded it.
Good, unfortunately I don't have a copy of the same manual, so we can't
talk in page numbers, nor can I be sure that you have the same version of
the document I'm going to be looking at, but I'm sure we can make tihs work.

Incidentally, what's the serial number of your scope? This matters because
Tek made changes and improvements over time, and the serial number can tell
us which version of a manual or of a schematic to look at.


I still have the two capacitors out of the scope and I put the meter on
like you said and I still get .9 ohms and I switched the probes and still
get .9 ohms. This is with one lead on test ground and one on the 55 volt
test lead. ‎
Where exactly are you measuring this?

In the power supply schematic (it's numbered schematic 12) I see a test
point labelled TP1536, is that where you're measuring?
If you're measuring this on the point in the schematic labeled "+55V
(UNREG)", then I'd say your resistance reading is likely normal.

So, if you haven't been measuring the resistance of TP1536 to and from
ground, then please measure that and report.

Where I get in trouble is I don't know the terminology dummy
resistor,consumers, bridge rectifier etc...I have to look them up. ‎
Yups, that's how you start. Starting with an oscilloscope repair is fairly
ambitious, but the documentation in the service manuals is so wonderful
that it's not a totally preposterous thing to do (IMHO).

The bridge rectifier is what turns AC to DC, it's the same rectifier for
the 55V and the 120V supplies in your scope - CR1611 on schematic diagram
12. Since your scope is blowing fuses, the bridge rectifier is one of the
natural suspects, as they can fail to a short.

"Consumer" here means everything that uses the 55V power supply, e.g. the
power supply is the producer, and the other boards in the scope are the
consumers.

The first order of business is to figure out whether problem is in the
power supply, or whether it's in one of the consumers, so let's get that
underways.

Good luck!


Re: a sick 576 (and it's owner) needs help

Bene's Mails
 

Yes, current is flowing definitively!

I had not much time the last days to make more measurement, but as I had
redone my measures, I found out, that the perfect describing of the failure
is: my 576 is measuring it’s own sensing shunts. I got perfectly the UI
trace of the series resistance of the collector current sensing circuit. I
proof that with DMM and a TCP202A directly clamped around the Black on white
wire which connects the current return connection from the test fixture with
the vertical switch assembly.



The big problem is, that I can not assume any other root cause of that
behavior as a wrong connection anywhere in the circuit between the shunts
and the vertical amplifier. But I can not imagine where. I checked all
connections between Vertical switch, Mode switch and Display Switch assy as
it was clear by the schematics in the manual without a result.



Tomorrow I will pack the 576 into my car and ask our last tracer guru Helmut
Hoevel here in Germany for help as he is now back from sickness. Maybe he
has a guess.

Von: TekScopes@... [mailto:TekScopes@...]
Gesendet: Donnerstag, 31. März 2016 19:46
An: TekScopes@...
Betreff: [TekScopes] Re: a sick 576 (and it's owner) needs help





Are you sure the current is flowing? I would first put a meter in series
with CE resistor in current mode and measure the current to make sure it was
what it should be then figure out why the voltage across current sense
resistor isn't making into the vert.


Re: 2465 channel two acts as I am going through low pass filter

almus_kenter
 

Yes I can hear the relays clicking away.

Thanks for the info--- I will try and
fix it in the next week or so.


Re: 2465 channel two acts as I am going through low pass filter

Siggi
 

On Sun, 10 Apr 2016 at 09:45 akenter@... [TekScopes] <
TekScopes@...> wrote:

Just checked R across BNC of channel two:

it is open regardless of DC/AC switch.

Channel one toggles between 1M and open (DC:AC)

Is this an easy fix?
It's most likely fixable - do you hear the relay click when you toggle
AC/GND/DC coupling? My 2430 had attenuators that were all over the place -
some of the relay pivots were stuck due to corrosion, and some of the
contacts weren't making contact. See <
https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/501546574> for
the guts of the attenuators.

It's not as hard as it looks at first blush to get the CH1/2 attenuators
out.
From memory you need to get the front bezel off and get the front panel
switch board out.
You then need to pull the screws that hold the attenuators in place. Two
(IIRC) each to the front, a metal bar running across them, and one each
(IIRC) screw you access from the inside of the front-panel cavity pulling
them into the main board.
You then need to desolder two connections, one to the preamp, one to a
trimcap, and they'll lift straight off the board.

To get at the contacts into you just need to undo the screws holding the
shielding on, and then the screws holding the plastic bracket on.
I used IPA and DeOxit on the contact fingers (be careful with those) and on
the contact points on the ceramic substrate. I think perhaps using DeOxit
isn't the best of ideas if IPA will do the trick.