Re: 2445 CPU Address line failed
I agree. ? I had so many comebacks for this but the rest of the story explained it. ? Joe ?
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From: TekScopes@... [mailto:TekScopes@...] On Behalf Of victor_j_silva
Sent: Saturday, January 19, 2013 7:02 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2445 CPU Address line failed? ? Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
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Re: 2445 CPU Address line failed
When you break your funny bone, it's real bad.
Don Black.
On 20-Jan-13 12:12 PM, Rob wrote:
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?
I know I was
going to ask if it was a rifle scope…. but
refrained….. now I cannot resist.
?
Sorry as always
for when my funny bone kicks in and thanks as always
for the bandwidth.
?
Rob
?
?
Interesting story, I find this statement a little
humerous:
"In late 2012 a dog next door bit my wife and I
needed a scope"
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Re: 2445 CPU Address line failed
I know I was going to ask if it was a rifle scope…. but refrained….. now I cannot resist. ? Sorry as always for when my funny bone kicks in and thanks as always for the bandwidth. ? Rob
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From: TekScopes@... [mailto:TekScopes@...] On Behalf Of victor_j_silva
Sent: Saturday, January 19, 2013 7:02 PM
To: TekScopes@...
Subject: [TekScopes] Re: 2445 CPU Address line failed? ? Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
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Re: 2445 CPU Address line failed
A rifle scope?
Don Black.
On 20-Jan-13 12:02 PM, victor_j_silva wrote:
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Show quoted text
?
Interesting story, I find this statement a little
humerous:
"In late 2012 a dog next door bit my wife and I needed a
scope"
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Re: scanned: 1958 Tek Personnel
Maybe not.? On page 58 of the 1958 photo album, we find the same photo of Ms. Lusk, with the same calendar.? Perhaps the photo was taken in 1953? ? Also, I got one of the possible years wrong; it would be 1942, not 1943.? But, as Don Black commented, Tek did not yet exist in 1943. ? Regards, ? Tony ?
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From: TekScopes@... [mailto:TekScopes@...] On Behalf Of sipespresso
Sent: Saturday, January 19, 2013 4:07 PM
To: TekScopes@...
Subject: [TekScopes] Re: scanned: 1958 Tek Personnel? ? Thanks. Seems right. -Kurt
--- In TekScopes@..., "Tony Jacobson" wrote:
>
> I see calendars on (PDF) pages 32, 56, 82, 88, and 112. I can't make out a
> year in any of the photos, but the one on page 56 appears to be from
> December, with Christmas on a Friday. This would suggest that photo was
> taken in December of 1943, 1953, 1959, 1964, or 1970. (I don't think it
> would be older or newer than these years.)
>
>
>
> I would put my money on 1959.
>
>
>
> Regards,
>
>
>
> Tony
>
>
>
> From: TekScopes@... [mailto:TekScopes@...] On Behalf
> Of sipespresso
> Sent: Saturday, January 19, 2013 12:12 PM
> To: TekScopes@...
> Subject: [TekScopes] Re: scanned: 1958 Tek Personnel
>
>
>
>
>
> Here is another photo album similar to the one I posted before.
>
>
>
> Can anybody figure out the date of this one? thanks, -Kurt
>
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Re: 2445 CPU Address line failed
Interesting story, I find this statement a little humerous:
"In late 2012 a dog next door bit my wife and I needed a scope"
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Tektronix DMM-4020 Opinions?
Hello: ? I have the opportunity to buy one of these far below the list price. I wonder if anyone has used this DMM, and what were your impressions of it> While I know it is not a Keithly, it seems like a lot of Bench Top DMM the $200.00 I am going to pay for it. ? ? Thanks
Rich
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Re: scanned: 1958 Tek Personnel
Nicely spotted. Pretty good if it's 1943, thats before the company
existed.
Don Black.
On 20-Jan-13 7:18 AM, Tony Jacobson wrote:
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?
I see calendars on (PDF) pages 32,
56, 82, 88, and 112.? I can’t make out a year in any
of the photos, but the one on page 56 appears to be
from December, with Christmas on a Friday.? This would
suggest that photo was taken in December of 1943,
1953, 1959, 1964, or 1970. ?(I don’t think it would be
older or newer than these years.)
?
I would put my money on 1959.
?
Regards,
?
Tony
?
?
?
Here is another photo album similar to the one I
posted before.
Can anybody figure out the date of this one?
thanks, -Kurt
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Re: Bench Built Isolation Transformer
Ah, Dave,
But the electrical system in the US is grounded. What you are
referring to is the ability for the GFCI to work without the
presence of a ground conductor attached to the GFCI. The electrical
system? in the building is a grounded system, defined as neutral
connected to gound at one point for reference, even though a green
or bare ground wire is not present at the receptacle.
Remember, for current to flow there needs to be a complete circuit.
Once an isolation transformer is in a circuit, there is no longer a
current path between sides.
You think this is hard to get a mental picture, Some rural places
used to use a distribution system of 15 to 30 killoVolts three
phase, one phase GROUNDED! This was for lightning protection.
On the opposite side we have Navy ships with neither conductor
connected to ground. No ground reference, just monitors for if a
wire becomes grounded. Gives time to fix the wire without a circuit
going down when it is needed....? And no electrocution hazard until
the first wire becomes grounded, hence the monitors. The GFCI won't
work on this circuit either, just like after a GFCI/RCD.
Frank DuVal
On 1/15/2013 1:52 AM, Dave C wrote:
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?
Stefan,
The GFI works on differential measurement, regardless
the presence of ground.
Here in USA these GFI's are legal to use in an
ungrounded electrical system in residential buildings, as
long as a label is attached to the face plate stating
"ungrounded".?
Dave
-=-=-=-
On 14 January 2013, at 10:41 PM, Stefan Trethan
wrote:
And
obviously it won't work after an isolation
transformer, the GFI
needs a grounded grid.
_
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Re: scanned: 1958 Tek Personnel
Thanks. Seems right. -Kurt
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--- In TekScopes@..., "Tony Jacobson" wrote:
I see calendars on (PDF) pages 32, 56, 82, 88, and 112. I can't make out a
year in any of the photos, but the one on page 56 appears to be from
December, with Christmas on a Friday. This would suggest that photo was
taken in December of 1943, 1953, 1959, 1964, or 1970. (I don't think it
would be older or newer than these years.)
I would put my money on 1959.
Regards,
Tony
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of sipespresso
Sent: Saturday, January 19, 2013 12:12 PM
To: TekScopes@...
Subject: [TekScopes] Re: scanned: 1958 Tek Personnel
Here is another photo album similar to the one I posted before.
Can anybody figure out the date of this one? thanks, -Kurt
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Anybody know the difference between a 475M and 475?
Looking at picking up a Tek 475M oscilloscope locally.? Anybody know how it differs from a regular 475?? Is it just the military model?? Are the specifications the same as the plain 475?? Any opinions as to reliability etc?? Thanks ahead of time.
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Re: Need for Termination Feedthrus
On Sat, 19 Jan 2013 20:19:08 -0000, "Philip" <ndpmcintosh@...> wrote: As I gather up all the stuff I need to test and maintain my newly purchased 2235 I am wondering how necessary it is to use a 50 ohm feedthru termination when sending test and calibration signals into the scope. Can one not construct their own device that perform the same purpose as a factory-built feedthru? A T-connector with a termination on one end will work for oscilloscopes that lack internal switchable terminations which generally only have a bandwidth that extends to 100 MHz anyway. And, can anyone recommend a good book that goes into detail on the theory of construction and operation of oscilloscopes? The ones I have gotten at the library are pretty superficial. Jim Williams' book has a great section on oscilloscope vertical amplifiers among other things:
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Re: 7587 Nuvistor Tetrode Substitutions in the Tektronix 184 Time-Mark Generator
What I think is happening is the control grid circuit is rectifying the positive input peaks to set the bias. A JFET replacement would operate in the same way although I may have to change the grid bias resistor or in the worst case, add a paralleled resistor and capacitor for source biasing. Vacuum tube design is before my time so I am just having fun reverse engineering. The time mark outputs which work fine do most of what I need. The screen grid series resistors are 27K and connect to the 125 volt anode supply so the currents are all about 1.8 milliamps which is well under the 3.6 milliamp maximum. That makes the total cathode current less than half of the 20 milliamp maximum at least on the 20 MHz amplifier. The 50 Mhz and 100 MHz amplifiers operate with self biased grid voltages closer to ground so their anode current should be higher. On later units like mine, the screen grid voltage of oscillator V10 is fixed by a zener diode at about 52 volts. None of the carbon composition resistors I checked were out of tolerance. Of course, everything up to the 100 MHz output *does* work. The 200 MHz doubler at least sort of works but the output looks low and distorted to me. I may try replacing the germanium diodes with 1N270s or RF schottky diodes. The only information I have on the 152-0075-00 diodes Tektronix used is from the Tektronix parts book. On Sat, 19 Jan 2013 18:44:49 -0000, "Ed Breya" <edbreya@...> wrote: Wow - that means the grid currents must be over -100 uA to get that much on 100k grid leak resistors. I don't recall what the screens were hooked to, but I think you should calculate the screen currents too, to see the total cathode currents.
If they only used 5 mA or so plate current, you can easily replicate that with modest JFET and cascode NPN current.
Ed
--- In TekScopes@..., David wrote:
I added a 10 ohm current shunt to the anode circuit of V20, the 20 MHz
amplifier, and used it to test all of the tubes. The anode currents
varied from 4.8 to 5.7 milliamps, the gate voltages varied from -10.3
to -12.6 volts, and the screen grid voltages varied from 72.2 to 76.0
volts except for one 7587 which had a screen voltage of 63.5 volts for
some reason.
That one also had the highest anode current but not the highest grid
voltage. I don't know if that is significant.
I can get 2N5950 JFETs and MPSH11 NPNs cheap at the moment so I will
start off with them.
On Wed, 02 Jan 2013 22:06:30 -0000, "Ed Breya"
wrote:
You may want to try swapping tubes from the other spots too, although it seems they're all biased for the same operating conditions, so should wear at the same rate - but if they are only on when needed for their specific function, then it all depends on the history of use. I think the only one that's always on then, would be the 10 MHz oscillator, so it should have the most wear.
I looked up the 7587 and see that it's rated for 20 mA max cathode current, but there were no charts showing what it should be near zero grid bias - unless the grid current gets pretty high, it doesn't seem that it will make much into 100k. It would be interesting to see what it is if you measure it and the actual plate currents.
I think your cascode version with a JFET and an NPN would be best, since you can then assure cutoff by pulling the base to ground. The double-JFET form won't positively cut off unless you can pull the gate negative, making it more complicated. You will have to watch out for the voltage ratings of the NPN to make sure it can handle the cutoff conditions.
I'd recommend around +15V or so for the bases (via small R so they won't oscillate on their own), and about +25V for the collector supply. Those should work with many types of VHF JFETs and small signal RF NPNs. For parts I'd recommend something like 2N5109 or MPSH10 for the NPN, and a J300 with around 15-25 mA Idss.
Ed
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Need for Termination Feedthrus
As I gather up all the stuff I need to test and maintain my newly purchased 2235 I am wondering how necessary it is to use a 50 ohm feedthru termination when sending test and calibration signals into the scope. Can one not construct their own device that perform the same purpose as a factory-built feedthru?
And, can anyone recommend a good book that goes into detail on the theory of construction and operation of oscilloscopes? The ones I have gotten at the library are pretty superficial.
Thanks,
Phil...
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Re: scanned: 1958 Tek Personnel
I see calendars on (PDF) pages 32, 56, 82, 88, and 112.? I can’t make out a year in any of the photos, but the one on page 56 appears to be from December, with Christmas on a Friday.? This would suggest that photo was taken in December of 1943, 1953, 1959, 1964, or 1970. ?(I don’t think it would be older or newer than these years.) ? I would put my money on 1959. ? Regards, ? Tony ?
toggle quoted message
Show quoted text
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of sipespresso
Sent: Saturday, January 19, 2013 12:12 PM
To: TekScopes@...
Subject: [TekScopes] Re: scanned: 1958 Tek Personnel? ? Here is another photo album similar to the one I posted before.
Can anybody figure out the date of this one? thanks, -Kurt
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Re: R7103 backplane repair
Il 2013-01-19 19:49 Peter Gottlieb ha scritto: Sorry, Yahoo seems to be blocking the image, won't accept my login without
multiple layers of entering captcha codes, and generally being such a pain to
use that its not worth it.
Don't worry, there was no attachment, comes from something wrong with my mail. Fabio.
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It's the isolated type, outer bus wired to GND via a << 1 Ohm resistor. That resistor sits nearly against the bottom panel of the 'scope. I guess that resistor is broken.
Albert
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--- In TekScopes@..., "Alex" wrote:
Is the 547 "CAL OUT" connector from the calibrator supposed to be a normal BNC? According to the schematic it is. But on my 547 it's a "floating" BNC, with the barrel separated from the flange with a plastic ring... I never paid much attention to it until I connected a coax to a 1A4 directly and the trace was very noisy. Then I shorted the cable at the "CAL OUT" end with a key to the scope's chassis and the noise went away. Yet I measure continuity in DC between the chassis and the CAL OUT barrel (without the cable).
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Is the 547 "CAL OUT" connector from the calibrator supposed to be a normal BNC? According to the schematic it is. But on my 547 it's a "floating" BNC, with the barrel separated from the flange with a plastic ring... I never paid much attention to it until I connected a coax to a 1A4 directly and the trace was very noisy. Then I shorted the cable at the "CAL OUT" end with a key to the scope's chassis and the noise went away. Yet I measure continuity in DC between the chassis and the CAL OUT barrel (without the cable).
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David Hess