'Osculation' ???? (Sorry, couldn't resist it !!!) Tim On Wed, 9 Sep 2020 at 00:52, fauffing via groups.io <fauffing= [email protected]> wrote: I believe I've narrowed the issue to the probe tip, as you've suggested.
Seems hitting it with a shot of cold air will calm the oscillation for a
short period of time. The probe tip seems to be an amplifier microcircuit
in the P6249 with 4 capacitors. The microcircuit had some red/rust color
material on the traces, and I am leaning to corrosion as a potential
contributor to the problem. Capacitors or microchip degradation may also be
contributors. The tip is very well contained within the housing, and easily
destroyed in attempting removal. There is a small, maybe 1/8" hole in the
housing covered by a piece of tape. The traces of the circuit can be
accessed at this point, with the remainder of the microcircuit well
contained in the housing. It does not seem to be easily repairable. I have
not been able to make further progress, and am not willing to sacrifice my
remaining two probes, as even with the osculation, they are usable at
higher frequencies.
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Re: 7D20 with unknown options or mods
Chuck,
The 7D20T did not require anything extra from the 7D20. Any production 7D20 will function in the T package without modification. You could add the rear access cable for the GPIB that had a companion mod for the R7603. The mainframe for the 7D20T has the necessary 7k interface, rear GPIB wiring and power in a TM5003 skin (the notorious modular package system (MPS)).
Regards,
Clark Foley
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Re: Strange Tek2440 issue
Ok, here's where I'm at.
ALL of the electrolytics, except the two big ones in the back, have been replaced. I tested them and they were all good with very low ESR so I'll toss them in a box for now.
Q870 and Q879 have been replaced. Had to order these.
All resistors in the 5V Regulator have been checked and are all well within spec.
The few small caps (.001uf) were also checked and are right on.
Problem still exists.
Before I was toying around with the idea of hanging an external 5V supply on it. I did try that last week and it did NOT do it and according to the meter on the supply, it wasn't really drawing much current from it - less than 100ma.
Tomorrow I'll go thru the supply again and take more measurements, there were a few points I was looking at and couldn't remember if I checked them and if so what they were. So tomorrow I'll check them and take pictures and better notes.
That's it for tonite.
Vince.
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On 09/02/2020 02:50 PM, Siggi wrote: On Wed, Sep 2, 2020 at 2:07 PM Vince Vielhaber <vev@...> wrote:
I had actually done that last nite, but didn't have the parts layout
handy to see which probe was on which pin (I had them on the diodes>.
Here they are with voltage measurements:
Uh, this makes no sense to me.
The base of Q870 should be pulled toward +15V unreg through R864(? hard to
read on the schematic), and the two op amps shunt it towards ground when
they detect too high voltage or too high current, respectively. Whichever
of pins 1/7 is lower is the op-amp in control of the output.
... time passes ...
Yeah, still doesn't make sense to me. I'm going to guess that either the
op-amps are (pins 1/7 are) reversed on the schematic, or that your channel
designations are.
Even so, it still doesn't make sense, as the voltage-control op-amp starts
dialing more voltage (Channel 2 normal at 5.54V rises to 16.94V), while the
current limit op-amp goes on the limit (Channel 1 normal at 16.76V dips to
6.16V). What doesn't make sense here is that the current control op-amp is
dialing a voltage that exceeds the voltage control's usual/normal voltage.
I haven't done the maths, but as there's a bias on the current limit
op-amp's feedback input, it might be that it's simply kicking in because
the output voltage has sagged.
I think you need to look further afield, how's the +8V rail doing,
the +-15V rails, raw and regulated? How is the -5V rail doing? Any other
rails you can find...
If you can't find a bad rail, start looking at the biasing for Q870 & Q879,
have the resistors drifted? If R864(?) or R478 have drifted significantly
upward, that'd explain why the transistors can't meet the current demand.
If the biasing is OK, you need to look at the transistors themselves. If
their gain is down, that'd also explain things. You can measure the base
current to Q879 indirectly by the voltage drop over its base resistor. Even
looking at what's happening on Q870's emitter under collapse - is that
transistor going to saturation, indicating that Q879 is dozing off on the
job?
Good luck!
--
K8ZW
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I am having issues with a 2445 Oscilloscope that is not showing the A horizontal sweep. The ¡°B¡± sweep appears when the B delayed time base is used. The readout shows some dots on the bottom line of text on the CRT. And the A sweep appears to have a starting dot which is offset to the left of the CRT.
I had wondered if the 2445 has issues with the horizontal output hybrid (as the ¡°A¡± sweep is offset to the left) or the Z-axis hybrid (as there are dots on the CRT). As the ¡°B¡± sweep and readout appears however this seems to imply that the horizontal output hybrid may be working? I am not sure is there could be a failure mode of the horizontal output hybrid which results in the ¡°A¡± sweep not appearing.
I have swapped the ¡°A¡± and ¡°B¡± sweep hybrids which did not resolve the issue.
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I believe I've narrowed the issue to the probe tip, as you've suggested. Seems hitting it with a shot of cold air will calm the oscillation for a short period of time. The probe tip seems to be an amplifier microcircuit in the P6249 with 4 capacitors. The microcircuit had some red/rust color material on the traces, and I am leaning to corrosion as a potential contributor to the problem. Capacitors or microchip degradation may also be contributors. The tip is very well contained within the housing, and easily destroyed in attempting removal. There is a small, maybe 1/8" hole in the housing covered by a piece of tape. The traces of the circuit can be accessed at this point, with the remainder of the microcircuit well contained in the housing. It does not seem to be easily repairable. I have not been able to make further progress, and am not willing to sacrifice my remaining two probes, as even with the osculation, they are usable at higher frequencies.
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Re: Tek TDS694C advice pls
On Tue, Sep 8, 2020 at 11:25 PM, Bruce Griffiths wrote:
Wrong, when calculating the impedance of a parallel R +C the 90 degree phase
shift should be taken into account.
The input impedance is actually closer to 550 ohms.
You're of course absolutely correct about the numbers in my example, Bruce. My approximation is only valid if R >> 1/(2 * pi * f * C), in which case R as a parallel R may be ignored. In my example it obviously isn't. My "calculation" gave a wrong result, as you indicate. My example would yield about 550 Ohm, as you say, and a phase angle of - 56 degrees. Thanks for waking me up! The main point that I was making, i.e. it's not so much the R but the C-dominated Z that makes the P6249 the better choice at high frequencies, remains valid of course. Raymond
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Re: Tek TDS694C advice pls
Wrong, when calculating the impedance of a parallel R +C the 90 degree phase shift should be taken into account.
The input impedance is actually closer to 550 ohms.
Bruce
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On 09 September 2020 at 07:56 Raymond Domp Frank <hewpatek@...> wrote:
On Tue, Sep 8, 2020 at 09:21 PM, Ray wrote:
On second read I checked the specs of the P6249.??So it is active (Fet) and
has higher input resistance (20 kohm) then the P6158 (1 kohm)So the P6249 will
do less loading of the measured circuit.
At higher frequencies the P6249 is a lighter load than the P6158, not because of its 20 kOhm parallel resistance vs. the P6158's 1 kOhm, but because its input capacity is significantly lower (< 1 pF) vs. the P6158's (1.5 pF).
Because of the much lower input capacitance of the P6249, its impedance decreases much slower than that of the P6058 with increasing frequency.
Be aware that at 160 MHz, the input Z of the P6249's input capacitance (if 1 pF) is around 1 kOhm, the same as the P6158's input-R. Input-R is unimportant at higher frequencies, as always with parallel capacitances. The input-Z of the P6158 at 160 MHz is about 670 Ohm, parallelled with 1 kOhm, so 400 Ohm.
Raymond
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Re: Tek TDS694C advice pls
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Thank you Raymond, learned something new today.RaySent from my T-Mobile 4G LTE device------ Original message------From: Raymond Domp FrankDate: Tue, Sep 8, 2020 14:56To: [email protected];Cc: Subject:Re: [TekScopes] Tek TDS694C advice plsOn Tue, Sep 8, 2020 at 09:21 PM, Ray wrote:
On second read I checked the specs of the P6249.??So it is active (Fet) and
has higher input resistance (20 kohm) then the P6158 (1 kohm)So the P6249 will
do less loading of the measured circuit.
At higher frequencies the P6249 is a lighter load than the P6158, not because of its 20 kOhm parallel resistance vs. the P6158's 1 kOhm, but because its input capacity is significantly lower (< 1 pF) vs. the P6158's (1.5 pF). Because of the much lower input capacitance of the P6249, its impedance decreases much slower than that of the P6058 with increasing frequency. Be aware that at 160 MHz, the input Z of the P6249's input capacitance (if 1 pF) is around 1 kOhm, the same as the P6158's input-R. Input-R is unimportant at higher frequencies, as always with parallel capacitances. The input-Z of the P6158 at 160 MHz is about 670 Ohm, parallelled with 1 kOhm, so 400 Ohm. Raymond
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Re: Tek TDS694C advice pls
On Tue, Sep 8, 2020 at 09:21 PM, Ray wrote:
On second read I checked the specs of the P6249.??So it is active (Fet) and
has higher input resistance (20 kohm) then the P6158 (1 kohm)So the P6249 will
do less loading of the measured circuit.
At higher frequencies the P6249 is a lighter load than the P6158, not because of its 20 kOhm parallel resistance vs. the P6158's 1 kOhm, but because its input capacity is significantly lower (< 1 pF) vs. the P6158's (1.5 pF). Because of the much lower input capacitance of the P6249, its impedance decreases much slower than that of the P6058 with increasing frequency. Be aware that at 160 MHz, the input Z of the P6249's input capacitance (if 1 pF) is around 1 kOhm, the same as the P6158's input-R. Input-R is unimportant at higher frequencies, as always with parallel capacitances. The input-Z of the P6158 at 160 MHz is about 670 Ohm, parallelled with 1 kOhm, so 400 Ohm. Raymond
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Re: Tek TDS694C advice pls
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On second read I checked the specs of the P6249.??So it is active (Fet) and has higher input resistance (20 kohm) then the P6158 (1 kohm)So the P6249 will do less loading of the measured circuit.RaySent from my T-Mobile 4G LTE device------ Original message------From: fauffing via groups.ioDate: Tue, Sep 8, 2020 07:19To: [email protected];Cc: Subject:Re: [TekScopes] Tek TDS694C advice plsHave you used the P6158 probes with this scope, and if you have, what are the drawbacks of the P6158 compared to the P6249? Thanks, - Frank
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Re: Help Troubleshooting 466, No +15VDC
There are a number of tricks.? One is to put a current limited supply on the +15.? Adjust the supply to +15 volts and the current limit to roughly between 50 ma to 100 ma.? Look for the lowest voltage across each capacitor.? Suspect the ones with the lowest voltage drop.? Bear in mind that in a parallel string fed from one end, the bad one and all the ones in the string after that would have the same voltage.
Another would be to take a current trace probe (HP made one), feed the line with a pulse train, and then see where all the current is going.
The third method is the LED test.? In a dark room, look to see what capacitor lights up like a dim LED, the dull red glow may be something you could observe.? Ditto if you had an infrared camera.? If there are any filter resistors (Tektronix frequently used a 10 ohm series resistor for isolation), check for damage.
Oh, and disconnecting boards to try to isolate to a particular board isn't a bad idea.
Harvey
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On 9/7/2020 3:18 PM, Sparky wrote: This 466 worked great for years, then suddenly I smelled something burning, and the fan stopped. All low voltages good on interface board, *except* for +15VDC. Reads about 4VDC, (and about 4 ohms to ground with power off....). If I leave power on past about 15 sec, I can smell something burning again, so I only power up long enough the check the voltages.
I'm thinking tantalum cap, but wondering a good way to isolate the offender? Assume the the +15VDC goes all over the scope, to other boards, so would be a bear to lift all tant caps one at a time. Thinking of breaking the trace somewhere near the PS source. Any other tips or likely suspects?
Thanks in advance!
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Re: Tek TDS694C advice pls
Frank, Ray, I recently needed to measure some 600 MHz clock signals and the folks I was working with were not convinced that probe and scope bandwidth was so important, so I came up with this data. It's not directly related to Frank's question, but maybe of some value. I don't have a TDS694, instead, a TDS684B, and somewhat different probes. This info covers most of the systems I have. Sorry for the crude formatting, I can provide an Excel file if anyone is interested, contact me off list at pvhengineering at g mail dot com Tom Bowers PVH Engineering OSCILLOSCOPE SYSTEM BANDWIDTH, SCOPE AND PROBE OPTIONS SCOPE Scope BW Scope Tr PROBE Probe BW Probe Tr System BW System Tr Comment TDS684B 1000 MHz 0.35 nS P6205 750 MHz 0.467 nS 600 MHz 0.583 nS Active probe, +/- 10V, 1M ,2pF, +/- 40 V Max TDS684B 1000 MHz 0.35 nS P6156 3500 MHz 0.100 nS 961 MHz 0.364 nS Passive Probe, 10X, 500 ohm (1x, 20x, 100x) 15V RMS TDS684B 1000 MHz 0.35 nS P6056 3500 MHz 0.100 nS 961 MHz 0.364 nS Passive Probe, 10X, 500 ohm, 9V Max TDS684B 1000 MHz 0.35 nS P6245 1500 MHz 0.233 nS 832 MHz 0.420 nS Active probe, +/- 8V, 1M <1pF, +/- 8V Max TDS684B 1000 MHz 0.35 nS P6057 1500 MHz 0.233 nS 832 MHz 0.420 nS Passive Probe, 100X, 5000 ohm, 21V Max TDS684B 1000 MHz 0.35 nS P6201 900 MHz 0.388 nS 669 MHz 0.523 nS Active probe, 10X , 1M <1.5pF, +/- 6V Max 7904/7A19 500 MHz 0.70 nS P6201 900 MHz 0.388 nS 437 MHz 0.800 nS Active probe, 10X , 1M <1.5pF, +/- 6V Max TDS684B 1000 MHz 0.35 nS P6137 400 MHz 0.875 nS 371 MHz 0.942 nS Passive Probe, 10X, 10M, 10.8pF 500V Max TDS684B 1000 MHz 0.35 nS P6106 250 MHz 1.40 nS 243 MHz 1.433 nS Passive Probe, 10X, 10M, 11.2pF (2 Meter) 500V Max 7904/7A19 500 MHz 0.70 nS P6106 250 MHz 1.40 nS 223 MHz 1.565 nS Passive Probe, 10X, 10M, 8.7pF (1 Meter) 500V Max 7904/7A26 200 MHz 1.75 nS P6106 250 MHz 1.40 nS 156 MHz 2.241 nS Passive Probe, 10X, 10M, 13.2pF (3 Meter) 500V Max 7904/7A26 200 MHz 1.75 nS P6046 100 MHz 3.50 nS 89.4 MHz 3.913 nS Active Differential, 1x to 1mV/Div, 25 V Max TDS684B 1000 MHz 0.35 nS P6006 70 MHz 5.0 nS 69.8 MHz 5.012 nS Passive Probe, 10X, 10M, 8.5pF (6 Foot) 600V Max Note: Active probes are very fragile! On Tue, Sep 8, 2020 at 6:19 AM fauffing via groups.io <fauffing= [email protected]> wrote: Have you used the P6158 probes with this scope, and if you have, what are
the drawbacks of the P6158 compared to the P6249?
Thanks,
- Frank
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Re: Tektronix TDS3PRT Printer
To reply to my own message again , the TDS3PRT printer I purchased from an overseas seller arrived yesterday, but without instructions or accessories. Upon examination I found the platen knob to be frozen; however, after disassembling the unit for inspection, and gradually rocking the knob back and forth, the platen finally broke free. I think this problem arose from a long period of disuse.
At that point I found the Sony UPP-110S 110 mm wide print roll I had hoped to work was too large in diameter for the printer. But after unwinding about two-thirds of the paper to a separate mandrel, so as to reduce the diameter to about 1-1/8-inches, the roll fit the printer. It should be possible to salvage the balance of the paper by refilling the core when the roll is depleted. The Sony UUP-110S paper I tried is their standard thermal printer paper used for printers in medical equipment such as ultrasound scanners. They offer two glossier versions: UUP-110HD and UUP-110HG. I have a roll of the latter, but have not tried it yet. As far as I can ascertain, the originally intended Tektronix print rolls no longer available from any source.
When installed in my TDS3052B the print driver for the TDS3PRT seemed to be automatically selected, and the printer worked fine, except there seemed to be no obvious way of cutting the paper after images are printed. Yet, I might have missed something. Also, I am wondering if there is a need for periodic maintenance, such as cleaning the print head. If anyone has access to the manual or instructions, perhaps they can clarify these issues.
Bruce, KG6OJI
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Re: 1S1 sampling unit; (also 7B53AN & 7A18 plugins)
The only non-Tektronix scope that can accept Tektronix letter- and 1-series plugins is the Lavoie clone AFAIK.
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Re: Tek TDS694C advice pls
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Frank,Wow a fellow TDS694C owner at last.I never get anwers when I ask about this scope.Well don't have your probe type .I got these and they work for what I use them for (up to 148 mhz.62456205Both are fet probes.About the 6158The 6158 probe is x 20. Limit is 22 v rms, low input impedance.Alas it goes to 3 ghz.So it all depends on what you intend is.The goid thing is that they where designed for this scope series.RaySent from my T-Mobile 4G LTE device------ Original message------From: fauffing via groups.ioDate: Tue, Sep 8, 2020 07:19To: [email protected];Cc: Subject:Re: [TekScopes] Tek TDS694C advice plsHave you used the P6158 probes with this scope, and if you have, what are the drawbacks of the P6158 compared to the P6249? Thanks, - Frank
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Re: WTD - P6201 Probe tips (Tek P/N 206-0200-00)
On Tue, Sep 8, 2020 at 02:36 PM, Phil Pemberton wrote:
At least one, ideally two.
Hi Phil, I have (found) two of the tiny screw-in probe tips, NOS, that I can part with. How about a (free) NOS witch hat (015-0135-00) for your P6201 or do you have one?
How much are you asking for the probe tips?
When I purchased components from Japan in a previous life, Japanese vendors asked for an "idea price". So, can you give an idea price? Let's take this off-group. Raymond
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Re: Lot of 10 scopes (400s & 2400s) with 5 scopemobiles
I asked the gentleman in question to plug in the 2465B, 2465, and the second 2445 to take a picture and see if there were a visible screen. He said no. I again wrote back to say it would take 5 minutes. Still no.
I'm 400 miles away. The nobs and such are worth something to people in this group but I would be leery of whatever.
Personal opinion, larry
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Re: 7D20 with unknown options or mods
As I recall, there was a variation of the 7D20 that was called
the 7D20T, that fit in its own chassis, and was used in conjunction
with computers to gather data.
A picture is shown on page 338 of the 1984 TEK Products catalog.
-Chuck Harris
Richard Steedman wrote:
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I have a 7D20 with a couple of modifications or options added. Can anyone provide some information about these?
The first is a board sitting on top of board A11 above the vacant IC sockets U1230, U1330 and U1430. It has a connector P200, connected to J100 on the CCD board A5. It has three ICs - a dual 4-input NOR gate, a quad analog switch/mux and a dual op-amp. One of the 7D20 photos on Barry Johnson's website looks like it has the same mod [()]().
The second is a small board sitting behind the front panel in-between boards A6 and A7. It's connector has flying leads soldered directly to pins of the CCD chips on the underside of board A5.
I have posted photos [here](/g/TekScopes/album?id=253175).
The 7D20 has a serial number in the B085000's and is running firmware F1.03. Any insights gratefully appreciated!
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Re: WTD - P6201 Probe tips (Tek P/N 206-0200-00)
On 08/09/2020 11:57, Raymond Domp Frank wrote: Hi Phil,
I'm pretty certain I have a few, NOS. How "many" do you need?
Shipment from the Netherlands to the UK.
Let me know if not found locally.
Raymond At least one, ideally two. NL->UK shipping is fine, I can't see that being too expensive! How much are you asking for the probe tips? I've found a few ebay listings in the US but either the price or the shipping tends to be the killer (or both). Thanks, -- Phil. philpem@...
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Help Troubleshooting 466, No +15VDC
This 466 worked great for years, then suddenly I smelled something burning, and the fan stopped. All low voltages good on interface board, *except* for +15VDC. Reads about 4VDC, (and about 4 ohms to ground with power off....). If I leave power on past about 15 sec, I can smell something burning again, so I only power up long enough the check the voltages.
I'm thinking tantalum cap, but wondering a good way to isolate the offender? Assume the the +15VDC goes all over the scope, to other boards, so would be a bear to lift all tant caps one at a time. Thinking of breaking the trace somewhere near the PS source. Any other tips or likely suspects?
Thanks in advance!
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Raymond Domp Frank
ebrucehunter