Re: How to calibrate a frequency counter (on the cheap)
Thanks for all of the very helpful replies!
What about a non-Thunderbolt GPS receiver that only outputs a 1 pps signal and has no provision for a 10 MHz output? For example, a receiver that has integrated the antenna and receiver into one little mushroom-shaped module.
Would that be another example of a unit that might have significant jitter - and therefore cannot be relied upon if you are striving for accuracy at the 1 part in 10^12 level?
Patrick Wong AK6C
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Show quoted text
--- In TekScopes@..., David <davidwhess@...> wrote:
I asked about this not long ago on the time-nuts@... mailing
list.
Most receivers have a fixed frequency oscillator driving the
numerically control oscillators so the 1pps output has significant
sawtooth jitter because of limited timing resolution. The better
timing receivers that work this way report the difference between the
1pps output and the calculated 1pps value so external correction can
be applied.
The Thunderbolt design is different in that the 10 MHz reference
frequency itself that drives the numerically controlled oscillators is
phase locked to GPS time so the PPS output only has random jitter
error.
On Mon, 15 Oct 2012 17:38:38 -0400, "Tom Miller"
<tmiller11147@...> wrote:
Usually the 1 pps comes from the 10 MHz (or some higher reference) but they are both common.
Tom
----- Original Message -----
From: Geoff Blake
To: TekScopes@...
Sent: Monday, October 15, 2012 5:19 PM
Subject: Re: [TekScopes] Re: How to calibrate a frequency counter (on the cheap)
If I understand correctly, the 20nS spec. of the 1ppS signal is
relative to time, not frequency, in other words, it means that the 1
ppS pulse is within 20nS of GPS (I think) time once the delays are
taken out. It is rather like saying your clock is one minute slow, but
looses only one second a week. The accuracy of the 1 ppS period is the
same(ish) as the 10MHz, i.e. ~ parts in 10-^12 from which it is
derived, and is quite suitable to look at Rb sources.
At least, I think so.
Geoff
On 15 October 2012 22:02, Patrick Wong <patwong3@...> wrote:
>
>
> After seeing this post, I looked into the specs of various GPS receivers.
>
> I note that the Thunderbolt is rated at 1 part in 10^12 accuracy with respect to the 10 MHz signal that it produces - can't beat that unless you have your own cesium standard. Apparently this requires the Thunderbolt to do some averaging over a day, to reach that accuracy.
>
> However the 1 pps signal is rated at much lower accuracy, within 20 ns. I believe that this translate to an error of up to 0.2 Hz at 10 MHz. Is my analysis correct?
>
> Therefore, it seems to me that using the 1 pps signal as a real-time reference to adjust a rubidium oscillator is not helpful unless you know the Rb oscillator was off by more than 0.2 Hz to begin with.
>
> I recently bought an HP 5335A which can read out frequency up to 1.3+ GHz to 11 digits, and this has caused me to become interested in an effective way to reference my rubidium frequency standard as well as the built in 10 MHz standard within the HP 5335A. Right now the difference between the two is around 0.01 Hz which reflects ~1 part in 10^9...
>
> I guess I also will look for a Trimble Thunderbolt or equivalent.
>
> Patrick Wong AK6C
>
> --- In TekScopes@..., "denyhstk" <denyhstk@> wrote:
>>
>> About 2 years ago, I picked up a Rubidium oscillator on ebay for around $60. Put it in a box with power and convection ventilation. Picked up a Garmin miniature hockey puck sized GPS receiver for $59 (I think it was either direct or an Amazon purchase). Only problem is the Garmin put out a 1pps signal and I was not in the mood to get fancy with this.
>>
>> I ran the 10MHz Rubidium into an HP 3336B and generated a much lower frequency at the output of the synthesizer. Both the lower frequency (can't recall, maybe 10kHz) and 1PPS were run into a scope, triggered on one and the timebase adjusted for a shorter and shorter interval as my adjustments of the Rubidium got closer.
>>
>> After a few hours, I think I had it between 10^-9 and 10^-10 (an estimate by observing the rate of drift of the two).
>>
>> At that point I called it a day and haven't checked since.
>>
>> Den
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
--
#################################################
Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
<geoff@...> or <melecerties@...>
Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
and even on the NAS. Avoiding Micro$oft like the plague.
#################################################
|
Re: How to calibrate a frequency counter (on the cheap)
I asked about this not long ago on the time-nuts@... mailing list. Most receivers have a fixed frequency oscillator driving the numerically control oscillators so the 1pps output has significant sawtooth jitter because of limited timing resolution. The better timing receivers that work this way report the difference between the 1pps output and the calculated 1pps value so external correction can be applied. The Thunderbolt design is different in that the 10 MHz reference frequency itself that drives the numerically controlled oscillators is phase locked to GPS time so the PPS output only has random jitter error. On Mon, 15 Oct 2012 17:38:38 -0400, "Tom Miller" <tmiller11147@...> wrote: Usually the 1 pps comes from the 10 MHz (or some higher reference) but they are both common.
Tom
----- Original Message -----
From: Geoff Blake
To: TekScopes@...
Sent: Monday, October 15, 2012 5:19 PM
Subject: Re: [TekScopes] Re: How to calibrate a frequency counter (on the cheap)
If I understand correctly, the 20nS spec. of the 1ppS signal is
relative to time, not frequency, in other words, it means that the 1
ppS pulse is within 20nS of GPS (I think) time once the delays are
taken out. It is rather like saying your clock is one minute slow, but
looses only one second a week. The accuracy of the 1 ppS period is the
same(ish) as the 10MHz, i.e. ~ parts in 10-^12 from which it is
derived, and is quite suitable to look at Rb sources.
At least, I think so.
Geoff
On 15 October 2012 22:02, Patrick Wong <patwong3@...> wrote:
>
>
> After seeing this post, I looked into the specs of various GPS receivers.
>
> I note that the Thunderbolt is rated at 1 part in 10^12 accuracy with respect to the 10 MHz signal that it produces - can't beat that unless you have your own cesium standard. Apparently this requires the Thunderbolt to do some averaging over a day, to reach that accuracy.
>
> However the 1 pps signal is rated at much lower accuracy, within 20 ns. I believe that this translate to an error of up to 0.2 Hz at 10 MHz. Is my analysis correct?
>
> Therefore, it seems to me that using the 1 pps signal as a real-time reference to adjust a rubidium oscillator is not helpful unless you know the Rb oscillator was off by more than 0.2 Hz to begin with.
>
> I recently bought an HP 5335A which can read out frequency up to 1.3+ GHz to 11 digits, and this has caused me to become interested in an effective way to reference my rubidium frequency standard as well as the built in 10 MHz standard within the HP 5335A. Right now the difference between the two is around 0.01 Hz which reflects ~1 part in 10^9...
>
> I guess I also will look for a Trimble Thunderbolt or equivalent.
>
> Patrick Wong AK6C
>
> --- In TekScopes@..., "denyhstk" <denyhstk@...> wrote:
>>
>> About 2 years ago, I picked up a Rubidium oscillator on ebay for around $60. Put it in a box with power and convection ventilation. Picked up a Garmin miniature hockey puck sized GPS receiver for $59 (I think it was either direct or an Amazon purchase). Only problem is the Garmin put out a 1pps signal and I was not in the mood to get fancy with this.
>>
>> I ran the 10MHz Rubidium into an HP 3336B and generated a much lower frequency at the output of the synthesizer. Both the lower frequency (can't recall, maybe 10kHz) and 1PPS were run into a scope, triggered on one and the timebase adjusted for a shorter and shorter interval as my adjustments of the Rubidium got closer.
>>
>> After a few hours, I think I had it between 10^-9 and 10^-10 (an estimate by observing the rate of drift of the two).
>>
>> At that point I called it a day and haven't checked since.
>>
>> Den
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
--
#################################################
Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
<geoff@...> or <melecerties@...>
Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
and even on the NAS. Avoiding Micro$oft like the plague.
#################################################
|
Re: How to calibrate a frequency counter (on the cheap)
Usually the 1 pps comes from the 10 MHz (or some higher reference) but they
are both common.
?
Tom
?
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Show quoted text
----- Original Message -----
Sent: Monday, October 15, 2012 5:19
PM
Subject: Re: [TekScopes] Re: How to
calibrate a frequency counter (on the cheap)
?
If I understand correctly, the 20nS spec. of the 1ppS signal is
relative
to time, not frequency, in other words, it means that the 1
ppS pulse is
within 20nS of GPS (I think) time once the delays are
taken out. It is
rather like saying your clock is one minute slow, but
looses only one
second a week. The accuracy of the 1 ppS period is the
same(ish) as the
10MHz, i.e. ~ parts in 10-^12 from which it is
derived, and is quite
suitable to look at Rb sources.
At least, I think
so.
Geoff
On 15 October 2012 22:02, Patrick Wong <patwong3@...>
wrote:
>
>
> After seeing this post, I looked into the specs
of various GPS receivers.
>
> I note that the Thunderbolt is rated
at 1 part in 10^12 accuracy with respect to the 10 MHz signal that it produces
- can't beat that unless you have your own cesium standard. Apparently this
requires the Thunderbolt to do some averaging over a day, to reach that
accuracy.
>
> However the 1 pps signal is rated at much lower
accuracy, within 20 ns. I believe that this translate to an error of up to 0.2
Hz at 10 MHz. Is my analysis correct?
>
> Therefore, it seems to
me that using the 1 pps signal as a real-time reference to adjust a rubidium
oscillator is not helpful unless you know the Rb oscillator was off by more
than 0.2 Hz to begin with.
>
> I recently bought an HP 5335A which
can read out frequency up to 1.3+ GHz to 11 digits, and this has caused me to
become interested in an effective way to reference my rubidium frequency
standard as well as the built in 10 MHz standard within the HP 5335A. Right
now the difference between the two is around 0.01 Hz which reflects ~1 part in
10^9...
>
> I guess I also will look for a Trimble Thunderbolt or
equivalent.
>
> Patrick Wong AK6C
>
> --- In TekScopes@...,
"denyhstk" wrote:
>>
>> About 2 years
ago, I picked up a Rubidium oscillator on ebay for around $60. Put it in a box
with power and convection ventilation. Picked up a Garmin miniature hockey
puck sized GPS receiver for $59 (I think it was either direct or an Amazon
purchase). Only problem is the Garmin put out a 1pps signal and I was not in
the mood to get fancy with this.
>>
>> I ran the 10MHz
Rubidium into an HP 3336B and generated a much lower frequency at the output
of the synthesizer. Both the lower frequency (can't recall, maybe 10kHz) and
1PPS were run into a scope, triggered on one and the timebase adjusted for a
shorter and shorter interval as my adjustments of the Rubidium got
closer.
>>
>> After a few hours, I think I had it between
10^-9 and 10^-10 (an estimate by observing the rate of drift of the
two).
>>
>> At that point I called it a day and haven't
checked since.
>>
>>
Den
>
>
>
>
>
------------------------------------
>
> Yahoo! Groups
Links
>
>
>
--
#################################################
Geoff Blake, G8GNZ
JO01fq: Chelmsford, Essex, UK
<geoff@...> or <melecerties@...>
Using
Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
and even on the NAS.
Avoiding Micro$oft like the
plague.
#################################################
|
Re: How to calibrate a frequency counter (on the cheap)
If I understand correctly, the 20nS spec. of the 1ppS signal is relative to time, not frequency, in other words, it means that the 1 ppS pulse is within 20nS of GPS (I think) time once the delays are taken out. It is rather like saying your clock is one minute slow, but looses only one second a week. The accuracy of the 1 ppS period is the same(ish) as the 10MHz, i.e. ~ parts in 10-^12 from which it is derived, and is quite suitable to look at Rb sources. At least, I think so. Geoff On 15 October 2012 22:02, Patrick Wong <patwong3@...> wrote:
After seeing this post, I looked into the specs of various GPS receivers.
I note that the Thunderbolt is rated at 1 part in 10^12 accuracy with respect to the 10 MHz signal that it produces - can't beat that unless you have your own cesium standard. Apparently this requires the Thunderbolt to do some averaging over a day, to reach that accuracy.
However the 1 pps signal is rated at much lower accuracy, within 20 ns. I believe that this translate to an error of up to 0.2 Hz at 10 MHz. Is my analysis correct?
Therefore, it seems to me that using the 1 pps signal as a real-time reference to adjust a rubidium oscillator is not helpful unless you know the Rb oscillator was off by more than 0.2 Hz to begin with.
I recently bought an HP 5335A which can read out frequency up to 1.3+ GHz to 11 digits, and this has caused me to become interested in an effective way to reference my rubidium frequency standard as well as the built in 10 MHz standard within the HP 5335A. Right now the difference between the two is around 0.01 Hz which reflects ~1 part in 10^9...
I guess I also will look for a Trimble Thunderbolt or equivalent.
Patrick Wong AK6C
--- In TekScopes@..., "denyhstk" <denyhstk@...> wrote:
About 2 years ago, I picked up a Rubidium oscillator on ebay for around $60. Put it in a box with power and convection ventilation. Picked up a Garmin miniature hockey puck sized GPS receiver for $59 (I think it was either direct or an Amazon purchase). Only problem is the Garmin put out a 1pps signal and I was not in the mood to get fancy with this.
I ran the 10MHz Rubidium into an HP 3336B and generated a much lower frequency at the output of the synthesizer. Both the lower frequency (can't recall, maybe 10kHz) and 1PPS were run into a scope, triggered on one and the timebase adjusted for a shorter and shorter interval as my adjustments of the Rubidium got closer.
After a few hours, I think I had it between 10^-9 and 10^-10 (an estimate by observing the rate of drift of the two).
At that point I called it a day and haven't checked since.
Den
------------------------------------
Yahoo! Groups Links
-- ################################################# Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK <geoff@...> or <melecerties@...> Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc and even on the NAS. Avoiding Micro$oft like the plague. #################################################
|
Re: How to calibrate a frequency counter (on the cheap)
After seeing this post, I looked into the specs of various GPS receivers.
I note that the Thunderbolt is rated at 1 part in 10^12 accuracy with respect to the 10 MHz signal that it produces - can't beat that unless you have your own cesium standard. Apparently this requires the Thunderbolt to do some averaging over a day, to reach that accuracy.
However the 1 pps signal is rated at much lower accuracy, within 20 ns. I believe that this translate to an error of up to 0.2 Hz at 10 MHz. Is my analysis correct?
Therefore, it seems to me that using the 1 pps signal as a real-time reference to adjust a rubidium oscillator is not helpful unless you know the Rb oscillator was off by more than 0.2 Hz to begin with.
I recently bought an HP 5335A which can read out frequency up to 1.3+ GHz to 11 digits, and this has caused me to become interested in an effective way to reference my rubidium frequency standard as well as the built in 10 MHz standard within the HP 5335A. Right now the difference between the two is around 0.01 Hz which reflects ~1 part in 10^9...
I guess I also will look for a Trimble Thunderbolt or equivalent.
Patrick Wong AK6C
toggle quoted message
Show quoted text
--- In TekScopes@..., "denyhstk" <denyhstk@...> wrote:
About 2 years ago, I picked up a Rubidium oscillator on ebay for around $60. Put it in a box with power and convection ventilation. Picked up a Garmin miniature hockey puck sized GPS receiver for $59 (I think it was either direct or an Amazon purchase). Only problem is the Garmin put out a 1pps signal and I was not in the mood to get fancy with this.
I ran the 10MHz Rubidium into an HP 3336B and generated a much lower frequency at the output of the synthesizer. Both the lower frequency (can't recall, maybe 10kHz) and 1PPS were run into a scope, triggered on one and the timebase adjusted for a shorter and shorter interval as my adjustments of the Rubidium got closer.
After a few hours, I think I had it between 10^-9 and 10^-10 (an estimate by observing the rate of drift of the two).
At that point I called it a day and haven't checked since.
Den
|
I have no clue. They are in a bin marked something like "5V T-1" and when tested were more like 75mA instead of 60mA. The place is Gateway Electronics near St. Louis but they do not have them listed on their web page. On Mon, 15 Oct 2012 16:48:58 -0400, "Tom Miller" <tmiller11147@...> wrote: The Mouser lamps are rated for 100k hours. What are the ones you found rated for?
Tom
----- Original Message -----
From: David
To: TekScopes@...
Sent: Monday, October 15, 2012 4:37 PM
Subject: Re: [TekScopes] Re: 7B92 No Auto trigger
For the 5 volt T-1 lamps Tektronix used for their illuminated
switches, these are what I was going to order until I found a less
expensive supply of them at a local electronics store:
On Mon, 15 Oct 2012 20:20:54 -0000, "baltimora86" <acuffe@...>
wrote:
>Thanks for your suggestions. I will check them and post back as soon as I have a chance (probably later tonight). I can't believe how much time I'm spending on this plug in, but it's so close to working, and I can't leave a puzzle unfinished.
>
>Assuming I get it working, I need to replace most of the light bulbs. Is there are known good source for the tiny bulbs used to illuminate the buttons?
>
>--- In TekScopes@..., "Albert" <aodiversen@...> wrote:
>>
>> pdf page 26, calibration steps j and k. Albert
>>
>> > How to adjust the bias current (also for the other TDs) is undoubtedly described in the Calibration procedure. I didn't read that part (yet).
|
The Mouser lamps are rated for 100k hours. What are the ones you found
rated for?
?
Tom
?
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Show quoted text
----- Original Message -----
Sent: Monday, October 15, 2012 4:37
PM
Subject: Re: [TekScopes] Re: 7B92 No Auto
trigger
?
For the 5 volt T-1 lamps Tektronix used for their illuminated
switches,
these are what I was going to order until I found a less
expensive supply
of them at a local electronics store:
On
Mon, 15 Oct 2012 20:20:54 -0000, "baltimora86" <acuffe@...>
wrote:
>Thanks
for your suggestions. I will check them and post back as soon as I have a
chance (probably later tonight). I can't believe how much time I'm spending on
this plug in, but it's so close to working, and I can't leave a puzzle
unfinished.
>
>Assuming I get it working, I need to replace most
of the light bulbs. Is there are known good source for the tiny bulbs used to
illuminate the buttons?
>
>--- In TekScopes@...,
"Albert" wrote:
>>
>> pdf page 26,
calibration steps j and k. Albert
>>
>> > How to adjust
the bias current (also for the other TDs) is undoubtedly described in the
Calibration procedure. I didn't read that part (yet).
|
For the 5 volt T-1 lamps Tektronix used for their illuminated switches, these are what I was going to order until I found a less expensive supply of them at a local electronics store: On Mon, 15 Oct 2012 20:20:54 -0000, "baltimora86" <acuffe@...> wrote: Thanks for your suggestions. I will check them and post back as soon as I have a chance (probably later tonight). I can't believe how much time I'm spending on this plug in, but it's so close to working, and I can't leave a puzzle unfinished.
Assuming I get it working, I need to replace most of the light bulbs. Is there are known good source for the tiny bulbs used to illuminate the buttons?
--- In TekScopes@..., "Albert" <aodiversen@...> wrote:
pdf page 26, calibration steps j and k. Albert
How to adjust the bias current (also for the other TDs) is undoubtedly described in the Calibration procedure. I didn't read that part (yet).
|
Thanks for your suggestions. I will check them and post back as soon as I have a chance (probably later tonight). I can't believe how much time I'm spending on this plug in, but it's so close to working, and I can't leave a puzzle unfinished.
Assuming I get it working, I need to replace most of the light bulbs. Is there are known good source for the tiny bulbs used to illuminate the buttons?
toggle quoted message
Show quoted text
--- In TekScopes@..., "Albert" <aodiversen@...> wrote:
pdf page 26, calibration steps j and k. Albert
How to adjust the bias current (also for the other TDs) is undoubtedly described in the Calibration procedure. I didn't read that part (yet).
|
Re: two 453 scopes for sale
It would be nice if EVERYBODY?would ALWAYS remember to include their location in their "have" listings.
It's a little frustrating for us stateside folks; a lot more so for people in Europe.
73 Jim N6OTQ
From: Jon
To: TekScopes@...
Sent: Monday, October 15, 2012 12:57 PM
Subject: [TekScopes] two 453 scopes for sale
Hi, I have? two? type 453 scopes for sale both? do not work but are good for parts.? I? asking? $35 for each one and actual shipping. pics avalable? on request thanks? Jon ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: ? ? <*> Your email settings: ? ? Individual Email | Traditional <*> To
change settings online go to: ? ? ? ? (Yahoo! ID required) <*> To change settings via email: ? ? TekScopes-digest@... ? ? TekScopes-fullfeatured@...<*> To unsubscribe from this group, send an email to: ? ? TekScopes-unsubscribe@...<*> Your use of Yahoo! Groups is subject to: ? ?
|
pdf page 26, calibration steps j and k. Albert
toggle quoted message
Show quoted text
How to adjust the bias current (also for the other TDs) is undoubtedly described in the Calibration procedure. I didn't read that part (yet).
|
(continued)
Hi Andy,
I think I addressed your last message also, actually I saw too late that I replied to a new message from you.
Albert
|
Re: How to calibrate a frequency counter (on the cheap)
On 14/10/12 01:55, David wrote:
The 1992 I got was fully functional except for the front panel
buttons, which are a common failure point for these counters. It only
has the TCXO and no GPIB so I am now on the prowl for a better
oscillator, although not strictly necessary since it has an external
reference in, and the GPIB port.
There's a HK based ebay seller who does a Micro Crystal OXCO in a 14 DIP package, see item #310380778466 - just over $25. I put one of these in a 1991 that had a faulty TCXO and it seems pretty good. If you remove the TCXO from it's PCB you will even find that provision is made for smaller footprint oscillators, including the 14 DIP package so it will actually drop straight in. There isn't provision for the control voltage if you do that but it wouldn't be difficult to mount a multi-turn trimmer on the board. I made up a small replacement board so that I could still adjust the oscillator via the back panel. No connection with the seller except as a satisfied customer.
|
5030 Dual Beam Scope Instruction Manual in Excellent
condition ¨C Free to a good home
All you pay is for the package and the shipping cost to
CONUS only.
?
Contact me off list please
?
Chris HJ
?
?
|
Hi Andy,
My previous comments need correction. I did measurements now in my 7904A and in this 'scope the whole trace intensity was influenced by the plugin's pot. Then I saw and remembered a jumper for "7900" vs "all other". Didn't try. Maybe that's it!
My description of the Delay Time signal is applicable only when the delayed sweep is "triggerable after delay", so Level in out position. Then the increase in bias of the TDs CR940 and CR950 after end of delay is clearly visible, and stays in effect until both TD's switch to the high level at the next (delayed) trigger event.
With Level pushed in CR968 keeps Q948 in saturation; CR940 remains in the low state all the time. Since (I suppose) you have the problem in this situation the fault might be in the circuit around TD CR364. This TD should switch to the high state at end of delay. Maybe R364 is adjusted for a too high bias current for this TD, forcing the TD in it's high state too early.
I took the delaying sweep saw tooth from TP408 and triggered the test 'scope from that signal. CR364 can be probed at TP365.
How to adjust the bias current (also for the other TDs) is undoubtedly described in the Calibration procedure. I didn't read that part (yet).
Hope this helps.
Albert
|
Hi,
I have two type 453 scopes for sale both do not work but are good for parts. I asking $35 for each one and actual shipping. pics avalable on request
thanks Jon
|
Re: Beautiful 556 setup on Ebay
I guess we are lucky he understed the qunatity. The 556 uses 17 6DJ8 tubes, not 12.
It went fast - hopefully to someone who appreaciated it as a scope. Too bad I did not see it in time - I have a good friend who lives in the same city.
-Steve
toggle quoted message
Show quoted text
--- In TekScopes@..., Brad Thompson <brad.thompson@...> wrote:
On 10/15/2012 12:02 AM, sipespresso wrote:
I have no affiliation with the seller.
<snip> Hello, Kurt and the group-- The sad part of the is its prominent mention of
"...12 6DJ8 vacuum tubes....", which might appeal
to an audiophile who would kill the whole whale
for a few ounces of ambergris.
73--
Brad AA1IP
|
Re: Who Bought the 1L20 on eBay?
Bummer.? How about using one of these:
(no
connection to seller - just an example of a tracking YIG) ?and run it off the sweep?
Dan
From: Craig Sawyers
To: TekScopes@...
Sent: Monday, October 15, 2012 12:06 PM
Subject: RE: [TekScopes] Re: Who Bought the 1L20 on eBay?
?
> Given an operating 5xx scope, $150 might qualify as your cheapest route to
a
> 4 GHz SA. However IMO it's still not a good "value" as a working
instrument
> for quantitative work, as opposed to a novel collector's item. The 1L20 is
> functionally primitive.
And that is right on both counts. They are useable, but are pre-YIG, so are
beset by spurs and images. You need to keep your wits about you when
interpreting the display.
Craig
|
Hi Albert,
It's good to know the intensity problem may not be significant. I'll ignore it for now.
I tried what you suggested, and discovered that the delayed trigger has other problems. The delayed trigger level has no effect on the display. Also, even with the delayed trigger source set to external (with no input) the display remains the same. I would expect the intensified portion to disappear completely in this case (as it does on my 7B53). Is it possible that the delayed sweep is somehow being triggered by the main trigger?
It's beginning to look like the original problem is still there, but that the failure mode changed. Remember that auto trigger started working spontaneously after I attempted to pull up the voltage at TP421 which directly connects to the tunnel diode in the delayed trigger circuit. Maybe one of the tunnel diodes is bad, or failed due to my earlier test. I had intended to pull up the sweep gate voltage at Q486 to try to unblank the display, rather than mess with the tunnel diode circuit, but I picked the wrong test point by mistake.
Thanks,
Andy
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Show quoted text
--- In TekScopes@..., "Albert" <aodiversen@...> wrote:
Hi Andy,
2 and 3. As mentioned before by David, the brightness in Intensified mode depends very much on the main frame as well.
The *un*intensified portion should listen to the plugin's Intensity pot. I tried my 7B92 in a 7704A and I also couldn't make the unintensified portion visible. I think to remember that such was also the case in other main frames, while the 7B92A had better control in this respect.
I verified operation of the plugin's pot with the delay time multiplier near maximum and with the intensified portion positioned to the right off screen (with Hor Pos). Then I could safely increase the MF Intensity for a visible unintensified portion and see the effect of the plugin's pot. Since your delay time doesn't work, try to position the intensified portion to the left off screen. Or, display slightly more than one waveform cycle at the CRT, push *out* the bottom left LEVEL button (3 lights will burn then), and set the level such that the intensified portion starts near the end of the sweep. Then move the trace to the right such that the intensified portion is off screen.
Albert
To
|
Re: Interesting fault in 535A
Sorry, Morris, I didn't notice where you were.
Carry on.
Dave Wise
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-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf Of Morris
Sent: Friday, October 12, 2012 7:27 PM
To: TekScopes@...
Subject: [TekScopes] Re: Interesting fault in 535A
Thanks for the offer Dave, but after adding shipping down here
to Oz I'm sure the local or ebay prices are not too bad in comparison.
Regards,
Morris
--- In TekScopes@..., David Wise <david_wise@...> wrote:
No explanation, Morris, but I'd like to remind all that I have
a bag 6.8nF/4kV and 10nF/4kV polyester film caps that make
fine replacements for the HV BB's. I'm only asking $0.50 each;
that's a break-even price. I have more than I will ever use.
Dave Wise
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David Hess