Question Regarding Vertical Centering - 2465B
Is there a way to center just the text display independently of the trace centering in the 2465B? The both bottom and top lines of text are displaced several mm upward making the top text a bit hard to see if looking at it from a slightly elevated position. There's a section that describes vertical centering but not sure if that applies to the trace only or both. If there's a way to simply recenter the text without disturbing any calibrations for the trace, etc., I'd like to do that. If not, and the one procedure covers both text and traces, then I'll just follow that one but thought I'd ask first.
Thanks,
Barry - N4BUQ
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Re: Updated SG504 Head 2 Head comparison
Some OEMs use 50 ohm BNC connectors for video, because they are harder to damage. Look at the photos of the two types and you will see the differences.
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Show quoted text
-----Original Message----- From: "'Craig Sawyers' c.sawyers@... [TekScopes]" <TekScopes@...>
Sent: Mar 24, 2016 2:41 AM
To: TekScopes@...
Subject: RE: [TekScopes] Re: Updated SG504 Head 2 Head comparison
To this day I do not believe you can buy a true 50 ohm BNC connector. They are more like 51 or 52
ohms. It is even worse with 75 ohm BNCs. I've tested several chassis sockets on the market using TDR
(7S12/S52/S6) and there are significant reflections within the connector body. Must try the same with
50 ohm ones.
Craig
Michael A. Terrell
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Re: Another SG504 Head variant- results.
I should have said, no SMA launchers I have used are 0.8mm.
I need the 1.6mm version though, as the PCB design accommodates both the BNC mod and the SMA launcher, the 0.8mm clearance is required to maintain the double sided ground plane perimeter. Otherwise, I'll need more vias, which is avoidable with this approach.
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Re: Another SG504 Head variant- results.
Good observations, Dennis.
The FR4 is 0.8mm, so there's a little standoff with the SMA launcher. No 0.8mm SMA launchers I know of.
The PCB perimeter gap you see is 0.050", not 0.100". Now since the SMA launcher is grounded at all 4 points the net 'inductance' increase derives from 0.0125" ....which is too small for significant phase effects at 1.050 Ghz.
I built another 'experimental' SMA unit. But I couldn't get the performance as good as the first. I got +/- 0.07dB over the range vs +/- 0.05dB. I fab the boards (PCB trace etch tolerance) and then there's component & connector tolerances and soldering thickness variations (which affects inductance a little).
What I am seeing is a little bit of VSWR 'ripple' across the span, equivalent to around one complete sine wave; (+/- .02dB worth.)
But I suppose I am splitting hairs as there's always a bit of performance difference between parts.
The positive outcome though is I reduced the component count by one using PCB capacitance parasitics to do the 'tuning' and got a bit more ground plane % coverage out of it as well as a more solid mechanical assembly.
I'll build one more SMA unit to nail down the dimensions of the parasitic cap, but it's around 0.25pF based on the permittivity of the 0.8mm FR4.
I'll put up the extra SMA units on Ebay, as tuned units. There doesn't seem to be any fundamental performance gains in using the SMA vs the BNC at 1Ghz. There is miniaturization and better build convenience by not converting the BNC connector into a launcher.
As it stands the stock PCB design can use both the BNC launcher mod. and the stock SMA Launcher with no alterations or 'nibbling' etc. Similarly, the latest compact enclosure accommodates both varieties.
I'm taking pics as I go along to do the build blog for the DIY page.
Ancel
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Re: Agilent 85024A and Tektronix 492AP
Yes, you can made a external power supply for the 85024A, the supply voltage for the probe is -12.6V +/- 20% and 15V +/- 20%, otherwise?may damage the probe ( there are regulator inside the box of probe ),
As I saw on the group posted information ,there are replacement for the power plug ( R&S 468-958 ) with some modification ,but not the socket ?
From: "ea7ee@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Monday, April 4, 2016 3:32 PM
Subject: [TekScopes] Re: Agilent 85024A and Tektronix 492AP
? Thank You Tony!
I'm better to make a external power supply, it is easy and I would use the probe with other spectrum analysers.
A simple wall AC power with 16V AC and a chinese supply for audio preamplifier with LM337 and LM317 will do.. HI HI...
Regarding the 492BP question, I will try some dip combinations in memory card to see if it will work. I need the counter function although it have poor resolution... +-5KHz at 2GHz... Oh my good!!! I will need a microwave counter, :-( to test microwave PLLs...
Regards
Manuel
EA7EE
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Re: 7904 excessive vertical drift
Swapping the inputs should reverse the direction of drift if the problem is the channel switch and leaves the Y amplifier closer to its normal operating point.
My 7904 (B103172) has the single channel switch IC U625. I had to remove the A7 board to swap the IC and strictly speaking I do not know if the problem was the part, its pins, or having re-seated the four Peltola connectors on the back of the A7 board. One day I should swap the original back in to check.
Roger
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Re: Agilent 85024A and Tektronix 492AP
Thank You Tony!
I'm better to make a external power supply, it is easy and I would use the probe with other spectrum analysers.
A simple wall AC power with 16V AC and a chinese supply for audio preamplifier with LM337 and LM317 will do.. HI HI...
Regarding the 492BP question, I will try some dip combinations in memory card to see if it will work. I need the counter function although it have poor resolution... +-5KHz at 2GHz... Oh my good!!! I will need a microwave counter, :-( to test microwave PLLs...
Regards
Manuel
EA7EE
|
Re: 2220 POST displays a large X on the screen
I would have hoped for something like the Sad Mac diagnostic screen
made up of a pair of Xs and a caret. If I ever design a DSO or
anything which uses a vector display, that is what I am going to use.
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On 03 Apr 2016 23:47:32 -0700, you wrote: The ROM versions are:
09109 2220 160-3975-13
and
09110 2200 160-3976-13
The X certainly acts as an "I'm not well" indicator, even if not intended. The image of a capacitor with an X though it would be even better. I'm sure you are right about the glitches on the 5V rail.
I'm intrigued at the thought of adding CRT readout as in the 2221. I wonder if it's just a case of different ROMs, which of course are made from unobtanium, so just fanciful thinking!
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Re: 2246 Horizontal Drive problem.
I am not sure what I was looking at when I posted that the two
horizontal amplifier designs were the same except for the transistors.
Whatever it was, I cannot find it now that I am looking for details to
suggest modern replacements for the MOSFET transistors.
There are no modern replacements for the original VP0116 and VN1316
MOSFETs that Tektronix used. The closest I was able to find are the
readily available ZVP2120G and ZVN2120G and they should work just
fine; they have a little more capacitance and a little more gain.
They use the surface mount SOT223 case which is large enough to work
with. A metal heat sink needs to be soldered to the large drain tab
and the gate, source, and drain leads on the other side can be
extended using small lengths of wire so they can be mounted in the
original locations.
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On Mon, 4 Apr 2016 14:27:50 +1000, you wrote: Many thanks for the reply and advice.
s
|
Re: 2220 POST displays a large X on the screen
The ROM versions are:
09109 2220 160-3975-13
and
09110 2200 160-3976-13
The X certainly acts as an "I'm not well" indicator, even if not intended. The image of a capacitor with an X though it would be even better. I'm sure you are right about the glitches on the 5V rail.
I'm intrigued at the thought of adding CRT readout as in the 2221. I wonder if it's just a case of different ROMs, which of course are made from unobtanium, so just fanciful thinking!
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Re: 7904 excessive vertical drift
If it is the channel switch, then disconnecting the vertical inputs to
the vertical CRT amplifier should remove the drift and remove some
doubt about where the problem is.
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On Mon, 4 Apr 2016 00:15:45 +0200, you wrote: Hi, years ago I experienced drift in my 7904 and it was caused by one of
the vertical channel switch ICs
on board A7. After exchanging the board the drift was no more.
G?ran
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Re: 2246 Horizontal Drive problem.
Many thanks for the reply and advice.
s
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Re: 2465B U400 Availability?
Chuck, Here's the thing, the +10V supply is a reference. It is there
for comparators, and the DAC to use as well, a reference. Nobody is allowed to draw significant current from the 10V
reference, and nobody is allowed to apply a variable load
to the reference. The sum total load on the 10V reference
is around 5 to 10ma. The highest individual load on it is a 10K resistor. The loads
are invariant, and in places where it is necessary to protect
the 10V reference's noise level, the load end of the 10V reference
will have a tantalum capacitor to ground. An example is the
DAC's reference. The DAC is a noisy thing, what with all the
switching it does. It has a tantalum to keep it from polluting
the 10V reference. Adding 330uf as a filter to the reference will only serve to
make it difficult for the reference's regulator to perform
properly. The leakage current of your 330uf capacitor could
very well come close to being as high as the intended load
for the supply. The leakage current for nichicon UHE capacitors is specified as no more than the maximum of 0.01CV or 3uA. In this case, that maximum is 0.01 * 0.010 * 10 = 0.001mA which should be an acceptable current draw. Especially since the older capacitors probably had a larger leakage factor so the actual difference is probably much smaller. Or possibly better than the original. I think you were chasing ground noise on your scope's ground
lead, not noise on the 10V reference line.. In my case, I don't think so. I carefully grounded the probe and checked the ground. The fact that the noise was substantially reduced after the modifications further indicates that I wasn't chasing ground noise. The fact that adding the filter capacitor to the 10V source voltage substantially reduced the noise on all of the other voltages validates my point about the other references "copying" the noise on the 10V source. I actually made the modification in stages. Initially, it was only the 10V source and 150uF. I then increased the other filters to 150uF. When that worked, I increased all of the values to get my final results. You state that upping a whole cluster of capacitors from 3 to
10 times their nominal value won't hurt anything. That is true,
no part will blow up. But you need to look at more than just
load issues. Will raising the capacitance of this, or that
load on the supply lower the feedback response corner for a
regulator? Doing so could put the regulator into an unstable state where
it will slowly oscillate... possibly with a period of dozens of
seconds. While I wouldn't have seen a very small oscillation with a period of dozens of seconds, otherwise I haven't seen any appearance of oscillation. Most regulators (and there is only one actual integrated regulator involved - the 7912) can accept large output capacitors. And the discrete regulators appear to be ok as well. Most regulators that oscillate only do so in a narrow load range. Once a minimum has been met, and that range avoided, large output capacitors are only an issue for the initial surge current which is not a problem in this case. Since regulators typically feed other circuits with an unknown number of bypass capacitors, the effective output capacitance can be fairly high. So excessive sensitivity to high output capacitance is generally not a good idea when designing a regulator. I could be wrong, and a problem will occur further down the road. If that happens, I can simply reduce the capacitance. I am convinced that cleaning up the power supply for almost any circuit is a good idea. More noise in a circuit is rarely a good thing. Mike -Chuck Harris 2465bct@... [TekScopes] wrote:
Barry,
I found the same sort of thing on my 2465BCT. Everything was within
specification, but there was a lot of noise that was not power line related.
There was / is one which does have some power line related ripple, but well
within specification (I don't remember which, off-hand). It was also laced
with noise in addition to the power line ripple.
When I examined the schematic, I found that the +10v supply does NOT have an
output filter. It then feeds in as a reference to most of the remaining supply
voltages. What happens is that every one of those attempts to duplicate the
noise on the +10v supply.
I wasn't happy with that so I modified my A2A1 board slightly and my noise is
much, much better. What I did was, first and most important, to put a 330uF
capacitor across VR1293 to clean up the +10v supply. That helps a lot. Then I
also increased the filtering capacitors across the board. The result is much
cleaner supply voltages. The supply voltage with power line ripple still has
it, but the ripple is now clean and not overlaid with a lot of noise. Here are
the changes and parts that I used. They should be the same for your board.
A2A1 C1220 290-0939-00 10uF +100-10% 100V UHE2A121MHD6 120uF 100V 20% 105c 0.64
A2A1 C1240 290-0939-00 10uF +100-10% 100V UHE2A121MHD6 120uF 100V 20% 105c 0.64
A2A1 C1260 290-0942-00 100uF +100-10% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 C1280 290-0942-00 100uF +100-10% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 C1300 290-0942-00 100uF +100-10% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 C1330 290-0942-00 100uF +100-10% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 C1350 290-0942-00 100uF +100-10% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 C1400 290-0943-02 47uF 20% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 C1402 290-0943-02 47uF 20% 25V UHE1E331MPD 330uF 25V 20% 105c 0.46
A2A1 VR1293 Add capacitor across to filter 10v output. UHE1E331MPD 330uF 25V 20% 105c 0.46
Note that the increase in capacitance for these filters is not a problem. It
does NOT affect the scope startup or operation. The reason why is because 1)
the scope limits the start up current flow using the thermal resistors and 2)
the scope sequences the start up based on the rise in voltages. Between those
two circuit features, the scope is protected against an increased surge
current and the start up sequencing still works. Since I have made these
changes, I have never seen a startup issue from the scope nor have I blown a
fuse.
To remove the power line ripple from the one remaining voltage would probably
require substantially increasing the main capacitors on A3 - C1021 and C1022.
Those are originally 290uF and most people replace them with 330uF. The
problem there is size. Because they are high voltage (200v) they are fairly
large and there isn't much room for larger capacitors on A3. Possibly an
inductor could be added between the output voltage and ground, but that might
also be difficult due to space.
Mike
Regarding ripple measurement: When measuring (using the 2445), I don't
exactly see what appears to be PS ripple, but lots of low-level noise (when
viewed with LINE triggering). I assume that's CPU and/or other digital
noise. It presents itself as a band of about 5mV. Is this normal? I have
a 10x probe inserted into J119 and the ground clip attached to one of the
heat-sink fins on one of the Uxxx modules. I'd think this "noise" shouldn't
be getting back into the rails but perhaps it's normal (or, perhaps,
something wrong with the way I'm measuring it)?
One of the rails (I don't remember exactly which one and will have to
check again to find that out) exhibited a small "double blip" that appeared
to me like it's coming from a typical unfiltered full-wave bridge but it was
only a few mV. Not sure if that's normal but I think it was within tolerance.
|
Re: 2465B U400 Availability?
I may be better off seeing if it's just measurement "sloppiness" that's giving me those readings.
Pertinent article:
PIN 7 on J119 is ground and a much shorter path than using the ground lead clipped to a heatsink. It's worth seeing if I can eliminate some of that noise with better measurement techniques rather than trying to fix something that may not be broken.
Thanks,
Barry - N4BUQ
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Show quoted text
----- Original Message ----- From: "David davidwhess@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Sunday, April 3, 2016 2:48:40 PM
Subject: Re: [TekScopes] Re: 2465B U400 Availability?
When making low level measurements, do a sanity check by applying the
probe tip to the same location as the ground clip and then to a ground
near the measurement location. If the noise still shows up, then
either the ground clip is too long or common mode noise is traveling
between the DUT and oscilloscope via their power line ground
connections. Another thing to check is that probe, ground lead, and
test lead positioning does not affect the measurement.
On Sun, 3 Apr 2016 14:10:20 -0400 (EDT), you wrote:
...
Regarding ripple measurement: When measuring (using the 2445), I don't
exactly see what appears to be PS ripple, but lots of low-level noise (when
viewed with LINE triggering). I assume that's CPU and/or other digital
noise. It presents itself as a band of about 5mV. Is this normal? I have
a 10x probe inserted into J119 and the ground clip attached to one of the
heat-sink fins on one of the Uxxx modules. I'd think this "noise"
shouldn't be getting back into the rails but perhaps it's normal (or,
perhaps, something wrong with the way I'm measuring it)?
One of the rails (I don't remember exactly which one and will have to check
again to find that out) exhibited a small "double blip" that appeared to me
like it's coming from a typical unfiltered full-wave bridge but it was only
a few mV. Not sure if that's normal but I think it was within tolerance.
...
|
Re: 2465B U400 Availability?
Would it make sense to put a small value capacitor at/near the output of the various rails - particularly the 10V rail - to kill some of that noise?
Thanks,
Barry - N4BUQ
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Show quoted text
----- Original Message ----- From: "2465bct@... [TekScopes]" <TekScopes@...>
To: "Barry n4buq@... [TekScopes]" <TekScopes@...>
Sent: Sunday, April 3, 2016 1:33:51 PM
Subject: Re: [TekScopes] Re: 2465B U400 Availability?
Barry,
I found the same sort of thing on my 2465BCT. Everything was within
specification, but there was a lot of noise that was not power line related.
There was / is one which does have some power line related ripple, but well
within specification (I don't remember which, off-hand). It was also laced
with noise in addition to the power line ripple.
When I examined the schematic, I found that the +10v supply does NOT have an
output filter. It then feeds in as a reference to most of the remaining
supply
voltages. What happens is that every one of those attempts to duplicate the
noise on the +10v supply.
I wasn't happy with that so I modified my A2A1 board slightly and my noise is
much, much better. What I did was, first and most important, to put a 330uF
capacitor across VR1293 to clean up the +10v supply. That helps a lot. Then I
also increased the filtering capacitors across the board. The result is much
cleaner supply voltages. The supply voltage with power line ripple still has
it, but the ripple is now clean and not overlaid with a lot of noise. Here
are
the changes and parts that I used. They should be the same for your board.
A2A1 C1220 290-0939-00 10uF +100-10% 100V UHE2A121MHD6
120uF 100V 20% 105c 0.64
A2A1 C1240 290-0939-00 10uF +100-10% 100V UHE2A121MHD6
120uF 100V 20% 105c 0.64
A2A1 C1260 290-0942-00 100uF +100-10% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 C1280 290-0942-00 100uF +100-10% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 C1300 290-0942-00 100uF +100-10% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 C1330 290-0942-00 100uF +100-10% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 C1350 290-0942-00 100uF +100-10% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 C1400 290-0943-02 47uF 20% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 C1402 290-0943-02 47uF 20% 25V UHE1E331MPD
330uF 25V 20% 105c 0.46
A2A1 VR1293 Add capacitor across to filter 10v output. UHE1E331MPD
330uF 25V 20% 105c 0.46
Note that the increase in capacitance for these filters is not a problem. It
does NOT affect the scope startup or operation. The reason why is because 1)
the scope limits the start up current flow using the thermal resistors and 2)
the scope sequences the start up based on the rise in voltages. Between those
two circuit features, the scope is protected against an increased surge
current and the start up sequencing still works. Since I have made these
changes, I have never seen a startup issue from the scope nor have I blown a
fuse.
To remove the power line ripple from the one remaining voltage would probably
require substantially increasing the main capacitors on A3 - C1021 and C1022.
Those are originally 290uF and most people replace them with 330uF. The
problem there is size. Because they are high voltage (200v) they are fairly
large and there isn't much room for larger capacitors on A3. Possibly an
inductor could be added between the output voltage and ground, but that might
also be difficult due to space.
Mike
Regarding ripple measurement: When measuring (using the 2445), I don't
exactly see what appears to be PS ripple, but lots of low-level noise (when
viewed with LINE triggering). I assume that's CPU and/or other digital
noise. It presents itself as a band of about 5mV. Is this normal? I have
a 10x probe inserted into J119 and the ground clip attached to one of the
heat-sink fins on one of the Uxxx modules. I'd think this "noise"
shouldn't
be getting back into the rails but perhaps it's normal (or, perhaps,
something wrong with the way I'm measuring it)?
One of the rails (I don't remember exactly which one and will have to
check again to find that out) exhibited a small "double blip" that appeared
to me like it's coming from a typical unfiltered full-wave bridge but it
was
only a few mV. Not sure if that's normal but I think it was within
tolerance.
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Re: 7904 excessive vertical drift
Hi, years ago I experienced drift in my 7904 and it was caused by one of
the vertical channel switch ICs
on board A7. After exchanging the board the drift was no more.
G?ran
[Non-text portions of this message have been removed]
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Re: Another SG504 Head variant- results.
Hi Ancel,
I have a question about this latest version. I looked at the pictures and
the edge launched SMA connector looks "odd" on two accounts:
1) As near as I can tell the PC board must be about half as thick as the PC
board the SMA connector was designed fort. All the edge launch SMA
connectors I have ever seen are designed for a 0.064" (0.162cm) PC Board so
it mates directly to the PC board surface (top and bottom) allow for tight
coupling to the ground plane. It is hard to tell for sure from the photos
but it appears you are using PC Board that is about 0.032" (0.081cm)
2) It is usually good RF practice to run the copper ground plane right up to
the SMA connector. Your copper stops about 0.1" before the edge the SMA
connector is on. That would cause some reflections, particularly at very
high frequencies in the GHz region since there is no microstrip at that
point. This gap may not be important at 1GHz but it just seems like good
practice to avoid dielectric gaps in the microstrip.
Dennis Tillman W7PF
toggle quoted message
Show quoted text
-----Original Message-----
Sent: Saturday, April 02, 2016 3:41 PM
Subject: [TekScopes] Re: Another SG504 Head variant- results.
I did the SMA build and the cal.
The SMA variant is up there with the best BNCs (+/- 0.04dB) with one
notable difference.
Less deviation within the stated flatness range. So, overall the amplitude
curve is smoother and contains no sudden resonances, albeit small ones which
don't affect the peak to peak results.
It is possible that the signal flow changes made to accommodate the new 4-40
clamped housing could have had some impact on this, but I suspect the SMA
integrity helped a bit. See the Excel data.
------------------------------------
Posted by: mosaicmerc@...
------------------------------------
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Re: UK practical help with pulse generator
Hi all,
I still have several dozen BFR 90 here, NOS, original Siemens.
If someone is interested in building this generator....
Regards, Jochen DH6FAZ
Am 03.04.2016 um 09:32 schrieb 'Craig Sawyers' c.sawyers@... [TekScopes]:
toggle quoted message
Show quoted text
> Hi David,
> No need to host the NBS Reference Level Pulse Generator article on
your site.
> It is already on the internet at
>
>
> Dennis Tillman W7PF
I downloaded it, skim read and tried to save - only to find that I
already had it!
Did you spot the co-author was James Andrews, founder of Picosecond
Pulse Labs - which he sold to
Tektronix a couple of years ago?
And that the rather critical BFR90 transistor and 5082-2835 Schottky
have been discontinued by
Vishay and HP/Agilent for the comfort and convenience of the customer.
Although eBay is your friend
if you are determined to build the unit.
Craig
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Re: 2220 POST displays a large X on the screen
Maybe the X is the "capacitors expired" indicator, or maybe if the caps were that bad, some glitching in the supplies confused the brain into turning it on sometimes.
Ed
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Re: Tpe 130 L-C meter calibration using only a 300 pF cap.
Yes, the 130 is quite a nice LC meter. I got one a few years ago, and found it to be in very close (<1-2% about as good as I could resolve on the meter) agreement with some pretty good reference caps, as was. Not bad for a 50-60 year old instrument. I've gathered up some spare tubes and other maintenance stuff for it, and plan to make some special probes to go with it. I found that you can extend the measurement point out from the DUT port connector by up to 2-3 feet if you use 75 ohm cable, and still have enough offset range to zero it. I did some experiments measuring scope input C with this setup - it works great as long as the R is high like the 1 megohm standard inputs.
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Michael A. Terrell
Yiu On Tony C
David Hess
G?ran Krusell