Hi,
A pix of the 7x03 prototype as a min load in my A7704 acquisition unit. seems happy.
Jerry Massengale
|
On 02/20/2013 10:36 AM, Dave Daniel wrote: Thanks for letting me know that the original gauge was 24. It sure looks like it is. Does anyone with an original Tek 7K extender confirm that the wires in the custom ribbon cable were 24 gauge except for the coaxes? Thanks, John
|
Re: Now: 50 Ohm attenuator Re: What use for a 640 Ohm 1x Probe?
Well for 100 W into 50 Ohms you will have 70.7V rms or 100 V peak.? If the 'scope can handle that, you don't need an attenuator.? If it can't, you can cobble an attenuator from a pair of resistors that will present a resistance of much higher than 50 Ohms, say at least 5000 Ohms.? So a 4500 Ohm resistor in series with a 500 Ohm resistor will do it for 10:1 but of course they have to be able to dissipate one Watt.
To complicate matters, if the coaxial line to the 'scope is an appreciable fraction of a wavelength (say 10%, which is 1 meter on 10 meters) you will have to deal with the SWR of that section.? So maybe a 100:1 attenuator would be better, using 4950 Ohms and 50 Ohms, with the 50 Ohm unit located right at the oscilloscope input terminal.
If you do that, you must be concerned about the stray capacitance across the 4950
Ohm resistor and, if necessary, compensate for it with a larger capacitance across the 'scope line input.
Generally these refinements won't be necessary for HF but anything higher and it becomes important, gradually.
Bob
|
--- On Wed, 2/20/13, Cliff White wrote:
From: Cliff White
Subject: Now: 50 Ohm attenuator [TekScopes] Re: What use for a 640 Ohm 1x Probe?
To: TekScopes@...
Date: Wednesday, February 20, 2013, 7:14 AM
?
Ok, that's what I thought. What I'm
really trying to do is like this: 100W transmitter into a dummy
load, with a tee in that line going to the scope. Would 10x be
enough? Or should I aim for 100x?
On 02/19/2013 10:50 PM, Bob Albert wrote:
You don't generally
need impedance matching.? The 'scope input won't load a 50
Ohm source much.? I use a 50 Ohm termination without
attenuation and the high impedance of the oscilloscope has
negligible effect.
If you are handling substantial power you will need an
attenuator; the books tell you what the parameters should
be.? For 20 dB attenuation you need 45 Ohms in series and
5 Ohms across the 'scope input.? And of course the 45 Ohm
resistor has to handle the power.
If you are using a 50 Ohm cable, it needs to be in a 50
Ohm circuit, so the attenuator components should be right
at the 'scope.
Bob
--- On Tue, 2/19/13, Cliff White
wrote:
From: Cliff White
Subject: Re: [TekScopes] Re: What use for a 640 Ohm 1x
Probe?
To: TekScopes@...
Date: Tuesday, February 19, 2013, 8:05 PM
?
So, I've
had the idea of building a 50 ohm fixed 10x
attenuator to use inline with a 50 ohm cable.
What kind of impedance matching should I use for
the 1meg ohm on the scope?
On 02/19/2013 07:26 PM, Don Black wrote:
It should be 9 Meg ohms.
Then 90% of the signal is dropped across the
probes 9 Meg and 10% across the scope's 1 Meg
input impedance, giving 10:1 ratio.
The compensating capacitors across them are
adjusted for the same division at high
frequencies to maintain the flat response,
that's hat you're setting when you adjust for
flat square wave with the trimmer.
Don Black.
On 20-Feb-13 12:18 PM, David wrote:
?
On Wed, 20 Feb 2013 00:24:09 -0000,
"Philip" ndpmcintosh@...>
wrote:
>The publication on scope probes
mentioned earlier is good and I am working
my way through it. I already had it in my
document collection and it was on my
reading list.
>
>If I ohm out a 10x 10Mohm probe in the
same way, I get about 10 MOhms. I'll keep
reading though...
I get almost exactly 9.00 MOhms on each of
several different x10
probes within reach.
|
|
Re: 7L13 'Center Frequency' display issue
Also make sure that the 2 boards, A2100 DVM analog board and
A2000, DVM logic & readout board are only connected/touching where they
should. There needs to be a small space (say 1mm or less) between each - a piece
of thin card between the two will suffice. If the boards touch the display can
freeze, you can lose the units digit on the SA (although the 7Kxx readout still
works).? OP is spot on - also remove clean &?reseat the A2000
board actives.
?
Beyond that you need to start looking at the A2100 board &
follow the volts!? The manual gives an excellent description of what should
happen. On the basis that neither readout works, it is more likely the A2100,
analog board you need?to look at.
?
Chris HJ
?
My 7L13 display was cured by pulling and reseating the DIPs on the RO board.
IC pins were visibly tarnished. Symptoms not as complete as yours, but AFAIR the
display would intermittently 'freeze' while tuning continued.
toggle quoted message
Show quoted text
--- In TekScopes@...,
"Michael" wrote: > > Hi all, > I have a 7L13 Spectrum Analyzer
out in the field, it's not in front of me right now but I will pick it up later
this week. I've seen the unit and the 'Center Frequency' LED read-out is stuck,
and reads '0000', also the same value is being sent to the CRT display. The
analyzer is sitting in a 7000 series mainframe and the mainframe works fine in
every other way. In fact, the spectrum analyzer works fine, just the 'Center
Frequency' display stays on zeros. The 'Tuning' works and adjusts correctly. It
is used with a TR-502 and that combination also works, you just don't know where
you are frequency wise. You can place a frequency counter on the AUX out of the
TR-502 and manually scan the bandwidth and read the frequency on the counter. It
appears everything is fine, just the readout is non-functional, or at least
stuck on zeros. I thought it was curious the display in the 7000 is also reading
zeros too. I will have it in front of me next week but I thought I would see if
anyone had any thoughts before I open it up. > > > Thanks
in advance, > ~Michael - AF7U >
o virus found in this
message.
Checked by AVG -
Version: 2012.0.2238 / Virus
Database: 2639/5618 - Release Date: 02/20/13
|
Now: 50 Ohm attenuator Re: What use for a 640 Ohm 1x Probe?
You don't want the scope attenuator to be the dummy load. You can make a simple pick-off tee with the main signal going straight through, with a high resistance tapped off, feeding a termination resistance to make it 50 ohms locally. Then connect that small signal to the scope with coax and termination there too. Of course, the tee structure should be in a transmission line environment, depending on the frequency.
Just set the resistor ratios to give nice numeric relationships so you don't need brain calculations on the fly to interpret what you see. For example, a 100X voltage attenuator would need a 2.475K tap rated for about 2W or more, terminated in 50R locally and 50R at the scope. The extra load would have only a 2 percent effect on the main line impedance. Higher attenuation would need less power rating and have less loading effect - it depends on how much signal you need at the scope, given the application.
Ed
toggle quoted message
Show quoted text
--- In TekScopes@..., Cliff White <cn.white@...> wrote:
Ok, that's what I thought. What I'm really trying to do is like this:
100W transmitter into a dummy load, with a tee in that line going to the
scope. Would 10x be enough? Or should I aim for 100x?
Respectfully,
Cliff White, W5CNW
w5cnw@... <mailto:w5cnw@...>
On 02/19/2013 10:50 PM, Bob Albert wrote:
You don't generally need impedance matching. The 'scope input won't
load a 50 Ohm source much. I use a 50 Ohm termination without
attenuation and the high impedance of the oscilloscope has negligible
effect.
If you are handling substantial power you will need an attenuator; the
books tell you what the parameters should be. For 20 dB attenuation
you need 45 Ohms in series and 5 Ohms across the 'scope input. And of
course the 45 Ohm resistor has to handle the power.
If you are using a 50 Ohm cable, it needs to be in a 50 Ohm circuit,
so the attenuator components should be right at the 'scope.
Bob
--- On *Tue, 2/19/13, Cliff White /<cn.white@...>/* wrote:
From: Cliff White <cn.white@...>
Subject: Re: [TekScopes] Re: What use for a 640 Ohm 1x Probe?
To: TekScopes@...
Date: Tuesday, February 19, 2013, 8:05 PM
So, I've had the idea of building a 50 ohm fixed 10x attenuator to
use inline with a 50 ohm cable. What kind of impedance matching
should I use for the 1meg ohm on the scope?
On 02/19/2013 07:26 PM, Don Black wrote:
It should be 9 Meg ohms. Then 90% of the signal is dropped across
the probes 9 Meg and 10% across the scope's 1 Meg input
impedance, giving 10:1 ratio.
The compensating capacitors across them are adjusted for the same
division at high frequencies to maintain the flat response,
that's hat you're setting when you adjust for flat square wave
with the trimmer.
Don Black.
On 20-Feb-13 12:18 PM, David wrote:
On Wed, 20 Feb 2013 00:24:09 -0000, "Philip" ndpmcintosh@...
</mc/compose?to=ndpmcintosh%40mac.com>>
wrote:
>The publication on scope probes mentioned earlier is good and I
am working my way through it. I already had it in my document
collection and it was on my reading list.
>
>If I ohm out a 10x 10Mohm probe in the same way, I get about 10
MOhms. I'll keep reading though...
I get almost exactly 9.00 MOhms on each of several different x10
probes within reach.
|
Re: Now: 50 Ohm attenuator
> What I'm really trying to do is like this: 100W transmitter into a dummy load, with a tee in that line going to the scope. Would 10x be enough?
?
About ten years ago I built a dummy?load out of some huge 850 ohm?power resistors I?picked up at a hamfest. I?mounted a pair of heavy copper wires like a pair of rails?and then soldered the resistors between them. Instead of putting a UHF?jack, I actually installed about?five feet of coax?terminated?with a UHF plug. I also "built-in" a divide-by-10 probe that comes out to a BNC jack. (The whole thing is installed in a?meatloaf tin that I've flipped over and mounted on a wooden base. I have to tweak the?built-in "probe" if I use it with different scopes, but it works great?for the workebench. It sets up on some shelves to the side and the coax that feeds the dummy load reaches a radio on the bench with not trouble. The output from the built-in probe goes through a smaller piece of coax to the o'scope.
?
My antenna analyzier shows virtuall 1:1 SWR as high as it goes (up to around 150 MHz). I calibrate the probe?just like you would any other probe--using a 1 kHz square wave. Each of the 850 ohm resistors is about the size of a AA?battery and I've run 100 watts into the load for a minute or so without having problems with heating.
?
I used a tee adaptor with my other dummy loads prior to that,? but if you do this type of work often it's nice to have it all built into one dedicated piece of gear.
?
I do also have a 20 dB power attenuator. It is built into?the?case that used to be a low-pass filter?(also picked up at a hamfest). I use it to feed the output into?one of my step attenuators. I've been working on a homebrew spectrum analyzier for years now (work keeps me out of town these days and I rarely get a weekend at the workbench), but the idea was that this would all feed into the?SpecA when that is built.
? 73 de Jim W4JBM
http://www.hamuniverse.com/w4jbm/
"With a soldering iron in one hand, a schematic in the other, and a puzzled look on his face..."
?
|
Re: tektronix 318 logic analyzer probe
| >>?Those probes are fairly rare
That is because most sellers think they are just wires and are scrapped.
|
--- On Wed, 2/20/13, Ed Breya <edbreya@...> wrote:
From: Ed Breya
Subject: [TekScopes] Re: tektronix 318 logic analyzer probe
To: TekScopes@...
Date: Wednesday,
February 20, 2013, 5:23 PM
?
I know what you mean. Those tiny connectors are a PITA. When I first got a 7D01, I searched a lot for the probes, and considered even hard wiring some kind of cables into the front-end to go to reasonably-sized connectors and home-made probes. I had collected for cheap a number of HP and Gould LA probes, and finally even some of those tiny plugs, so I was going to blend it all together. Of course, after all that scrounging, a couple of the real probe kits showed up at a decent price, so I skipped the rest.
Those probes are fairly rare, while 7D01s are not - during the last flea market season I bought several of them at less than five bucks average price.
Ed
--- In TekScopes@..., cleyson@... wrote:
>
> Hi guys
>
> It was quite some time ago but I found a 25 way micro D plug so decided to have a go at building a probe to test out a rebuilt 7D01. It ended up as only 4 channels as I didn't have enough comparators for all 9 inputs. Comparators were GEC Plessey SP9680 in 8-pin DIL package all mounted dead-bug style on some copper clad PCB. Theshold was set with an op-amp and a pot mounted on the PCB and there were some back to back diodes across the comparator inputs. I think the input resistance for each channel was around 10k or so, OK for a logic probe.
>
> As for reliability, wires kept breaking off the micro D connector and after several attempts at resoldering the connector it didn't fit into the 7D01 very well. I gave up out of frustration and the 7D01 has been sitting in a cupboard for about 10 years.
>
> In hindsight I should have used a couple of MC10H124 TTL to ECL translators it would have been much easier.
>
> I might have another go at building a probe in the not to distant future, just have to find some nice dual channel comparators with differential ECL outputs.
>
> Chris
>
> --- In TekScopes@..., Gala Dragos wrote:
> >
> > schematics and pictures pls.
> > I could not find any line receivers that have ecl output, single ended input and trigger on selective voltage.
> >
> > --- On Wed, 2/20/13, David DiGiacomo wrote:
> >
> > From: David DiGiacomo
> > Subject: Re: [TekScopes] Re: tektronix 318 logic analyzer probe
> > To: TekScopes@...
> > Date: Wednesday, February 20, 2013, 5:48 AM
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > ??
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Tue, Feb 19, 2013 at 5:40 PM, cleyson@> wrote:
> >
> > > Hi David
> >
> > >
> >
> > > Fair comment, maybe you could make your own probes but I don't think you could build a 10 channel 1Meg 5pF FET probe for less than the $100 asking price. You need the 25 way micro D connectors, twisted pair cables and a PCB. Been there and done it for a 7D01 and I just ended up with an unreliable and not very usable probe that's at the bottom of the junk box somewhere.
> >
> >
> >
> > If it ever comes up to the top again, it would be really interesting
> >
> > to see the board and hear more about the problems you ran into.
> >
> >
> >
> > It sounds like you were trying to achieve similar performance to the
> >
> > Tek design. If the goal was just to get a 308 working, it seems like
> >
> > a much less ambitious design would be OK. I still wouldn't want to do
> >
> > it, but I think the parts cost would be a lot less than $100.
> >
>
|
Re: tektronix 318 logic analyzer probe
I know what you mean. Those tiny connectors are a PITA. When I first got a 7D01, I searched a lot for the probes, and considered even hard wiring some kind of cables into the front-end to go to reasonably-sized connectors and home-made probes. I had collected for cheap a number of HP and Gould LA probes, and finally even some of those tiny plugs, so I was going to blend it all together. Of course, after all that scrounging, a couple of the real probe kits showed up at a decent price, so I skipped the rest.
Those probes are fairly rare, while 7D01s are not - during the last flea market season I bought several of them at less than five bucks average price.
Ed
toggle quoted message
Show quoted text
--- In TekScopes@..., cleyson@... wrote:
Hi guys
It was quite some time ago but I found a 25 way micro D plug so decided to have a go at building a probe to test out a rebuilt 7D01. It ended up as only 4 channels as I didn't have enough comparators for all 9 inputs. Comparators were GEC Plessey SP9680 in 8-pin DIL package all mounted dead-bug style on some copper clad PCB. Theshold was set with an op-amp and a pot mounted on the PCB and there were some back to back diodes across the comparator inputs. I think the input resistance for each channel was around 10k or so, OK for a logic probe.
As for reliability, wires kept breaking off the micro D connector and after several attempts at resoldering the connector it didn't fit into the 7D01 very well. I gave up out of frustration and the 7D01 has been sitting in a cupboard for about 10 years.
In hindsight I should have used a couple of MC10H124 TTL to ECL translators it would have been much easier.
I might have another go at building a probe in the not to distant future, just have to find some nice dual channel comparators with differential ECL outputs.
Chris
--- In TekScopes@..., Gala Dragos <gala_dragos@> wrote:
schematics and pictures pls.
I could not find any line receivers that have ecl output, single ended input and trigger on selective voltage.
--- On Wed, 2/20/13, David DiGiacomo <daviddigiacomo@> wrote:
From: David DiGiacomo <daviddigiacomo@>
Subject: Re: [TekScopes] Re: tektronix 318 logic analyzer probe
To: TekScopes@...
Date: Wednesday, February 20, 2013, 5:48 AM
??
On Tue, Feb 19, 2013 at 5:40 PM, cleyson@> wrote:
Hi David Fair comment, maybe you could make your own probes but I don't think you could build a 10 channel 1Meg 5pF FET probe for less than the $100 asking price. You need the 25 way micro D connectors, twisted pair cables and a PCB. Been there and done it for a 7D01 and I just ended up with an unreliable and not very usable probe that's at the bottom of the junk box somewhere.
If it ever comes up to the top again, it would be really interesting
to see the board and hear more about the problems you ran into.
It sounds like you were trying to achieve similar performance to the
Tek design. If the goal was just to get a 308 working, it seems like
a much less ambitious design would be OK. I still wouldn't want to do
it, but I think the parts cost would be a lot less than $100.
|
Re: 7L13 'Center Frequency' display issue
My 7L13 display was cured by pulling and reseating the DIPs on the RO board. IC pins were visibly tarnished. Symptoms not as complete as yours, but AFAIR the display would intermittently 'freeze' while tuning continued.
toggle quoted message
Show quoted text
--- In TekScopes@..., "Michael" <af7u@...> wrote:
Hi all,
I have a 7L13 Spectrum Analyzer out in the field, it's not in front of me right now but I will pick it up later this week. I've seen the unit and the 'Center Frequency' LED read-out is stuck, and reads '0000', also the same value is being sent to the CRT display. The analyzer is sitting in a 7000 series mainframe and the mainframe works fine in every other way. In fact, the spectrum analyzer works fine, just the 'Center Frequency' display stays on zeros. The 'Tuning' works and adjusts correctly. It is used with a TR-502 and that combination also works, you just don't know where you are frequency wise. You can place a frequency counter on the AUX out of the TR-502 and manually scan the bandwidth and read the frequency on the counter. It appears everything is fine, just the readout is non-functional, or at least stuck on zeros. I thought it was curious the display in the 7000 is also reading zeros too. I will have it in front of me next week but I thought I would see if anyone had any thoughts before I open it up.
Thanks in advance,
~Michael - AF7U
|
On 02/19/2013 06:40 PM, cleyson@... wrote:> Been there and done it for a 7D01 and I just ended up with an unreliable and not very usable probe that's at the bottom of the junk box somewhere. On 02/19/2013 09:48 PM, David DiGiacomo wrote: If it ever comes up to the top again, it would be really interesting
to see the board and hear more about the problems you ran into. Yes, it could be good for a performance low cost front end on something like this:
|
Now: 50 Ohm attenuator Re: What use for a 640 Ohm 1x Probe?
Ok, that's what I thought. What I'm
really trying to do is like this: 100W transmitter into a dummy
load, with a tee in that line going to the scope. Would 10x be
enough? Or should I aim for 100x?
On 02/19/2013 10:50 PM, Bob Albert wrote:
toggle quoted message
Show quoted text
You don't generally
need impedance matching.? The 'scope input won't load a 50
Ohm source much.? I use a 50 Ohm termination without
attenuation and the high impedance of the oscilloscope has
negligible effect.
If you are handling substantial power you will need an
attenuator; the books tell you what the parameters should
be.? For 20 dB attenuation you need 45 Ohms in series and
5 Ohms across the 'scope input.? And of course the 45 Ohm
resistor has to handle the power.
If you are using a 50 Ohm cable, it needs to be in a 50
Ohm circuit, so the attenuator components should be right
at the 'scope.
Bob
--- On Tue, 2/19/13, Cliff White
wrote:
From: Cliff White
Subject: Re: [TekScopes] Re: What use for a 640 Ohm 1x
Probe?
To: TekScopes@...
Date: Tuesday, February 19, 2013, 8:05 PM
?
So, I've
had the idea of building a 50 ohm fixed 10x
attenuator to use inline with a 50 ohm cable.
What kind of impedance matching should I use for
the 1meg ohm on the scope?
On 02/19/2013 07:26 PM, Don Black wrote:
It should be 9 Meg ohms.
Then 90% of the signal is dropped across the
probes 9 Meg and 10% across the scope's 1 Meg
input impedance, giving 10:1 ratio.
The compensating capacitors across them are
adjusted for the same division at high
frequencies to maintain the flat response,
that's hat you're setting when you adjust for
flat square wave with the trimmer.
Don Black.
On 20-Feb-13 12:18 PM, David wrote:
?
On Wed, 20 Feb 2013 00:24:09 -0000,
"Philip" ndpmcintosh@...>
wrote:
>The publication on scope probes
mentioned earlier is good and I am working
my way through it. I already had it in my
document collection and it was on my
reading list.
>
>If I ohm out a 10x 10Mohm probe in the
same way, I get about 10 MOhms. I'll keep
reading though...
I get almost exactly 9.00 MOhms on each of
several different x10
probes within reach.
|
|
Re: tektronix 318 logic analyzer probe
Hi I'm looking for a pair of P6451's for a LA501and WR501 to make it complete, but I agree 100 is way too much , I'd be a buyer at 50.00ea.
Regards
Dave?
|
|
Re: tektronix 318 logic analyzer probe
| I've found some in the mean while
http://cds.linear.com/docs/en/datasheet/171112f.pdf http://cds.linear.com/docs/en/datasheet/lt685fa.pdf http://www.ti.com/product/lmh7324
|
--- On Wed, 2/20/13, cleyson@... wrote:
From: cleyson@...
Subject: [TekScopes] Re: tektronix
318 logic analyzer probe
To: TekScopes@...
Date: Wednesday, February 20, 2013, 3:50 PM
?
Hi guys
It was quite some time ago but I found a 25 way micro D plug so decided to have a go at building a probe to test out a rebuilt 7D01. It ended up as only 4 channels as I didn't have enough comparators for all 9 inputs. Comparators were GEC Plessey SP9680 in 8-pin DIL package all mounted dead-bug style on some copper clad PCB. Theshold was set with an op-amp and a pot mounted on the PCB and there were some back to back diodes across the comparator inputs. I think the input resistance for each channel was around 10k or so, OK for a logic probe.
As for reliability, wires kept breaking off the micro D connector and after several attempts at resoldering the connector it didn't fit into the 7D01 very well. I gave up out of frustration and the 7D01 has been sitting in a cupboard for about 10 years.
In hindsight I should have used a couple of MC10H124 TTL to ECL translators it would have been much easier.
I might have another go at building a probe in the not to distant future, just have to find some nice dual channel comparators with differential ECL outputs.
Chris
--- In TekScopes@..., Gala Dragos wrote:
>
> schematics and pictures pls.
> I could not find any line receivers that have ecl output, single ended input and trigger on selective voltage.
>
> --- On Wed, 2/20/13, David DiGiacomo wrote:
>
> From: David DiGiacomo
> Subject: Re: [TekScopes] Re: tektronix 318 logic analyzer probe
> To: TekScopes@...
> Date: Wednesday, February 20, 2013, 5:48 AM
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> ??
>
>
>
>
>
>
>
>
>
> On Tue, Feb 19, 2013 at 5:40 PM, cleyson@...> wrote:
>
> > Hi David
>
> >
>
> > Fair comment, maybe you could make your own probes but I don't think you could build a 10 channel 1Meg 5pF FET probe for less than the $100 asking price. You need the 25 way micro D connectors, twisted pair cables and a PCB. Been there and done it for a 7D01 and I just ended up with an unreliable and not very usable probe that's at the bottom of the junk box somewhere.
>
>
>
> If it ever comes up to the top again, it would be really interesting
>
> to see the board and hear more about the problems you ran into.
>
>
>
> It sounds like you were trying to achieve similar performance to the
>
> Tek design. If the goal was just to get a 308 working, it seems like
>
> a much less ambitious design would be OK. I still wouldn't want to do
>
> it, but I think the parts cost would be a lot less than $100.
>
|
Re: tektronix 318 logic analyzer probe
Hi guys
It was quite some time ago but I found a 25 way micro D plug so decided to have a go at building a probe to test out a rebuilt 7D01. It ended up as only 4 channels as I didn't have enough comparators for all 9 inputs. Comparators were GEC Plessey SP9680 in 8-pin DIL package all mounted dead-bug style on some copper clad PCB. Theshold was set with an op-amp and a pot mounted on the PCB and there were some back to back diodes across the comparator inputs. I think the input resistance for each channel was around 10k or so, OK for a logic probe.
As for reliability, wires kept breaking off the micro D connector and after several attempts at resoldering the connector it didn't fit into the 7D01 very well. I gave up out of frustration and the 7D01 has been sitting in a cupboard for about 10 years.
In hindsight I should have used a couple of MC10H124 TTL to ECL translators it would have been much easier.
I might have another go at building a probe in the not to distant future, just have to find some nice dual channel comparators with differential ECL outputs.
Chris
toggle quoted message
Show quoted text
--- In TekScopes@..., Gala Dragos <gala_dragos@...> wrote:
schematics and pictures pls.
I could not find any line receivers that have ecl output, single ended input and trigger on selective voltage.
--- On Wed, 2/20/13, David DiGiacomo <daviddigiacomo@...> wrote:
From: David DiGiacomo <daviddigiacomo@...>
Subject: Re: [TekScopes] Re: tektronix 318 logic analyzer probe
To: TekScopes@...
Date: Wednesday, February 20, 2013, 5:48 AM
??
On Tue, Feb 19, 2013 at 5:40 PM, cleyson@...> wrote:
Hi David Fair comment, maybe you could make your own probes but I don't think you could build a 10 channel 1Meg 5pF FET probe for less than the $100 asking price. You need the 25 way micro D connectors, twisted pair cables and a PCB. Been there and done it for a 7D01 and I just ended up with an unreliable and not very usable probe that's at the bottom of the junk box somewhere.
If it ever comes up to the top again, it would be really interesting
to see the board and hear more about the problems you ran into.
It sounds like you were trying to achieve similar performance to the
Tek design. If the goal was just to get a 308 working, it seems like
a much less ambitious design would be OK. I still wouldn't want to do
it, but I think the parts cost would be a lot less than $100.
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Hi,
I finished building the first prototype of my 7X03 extender/load plugin. I have verififed that its extender function works and am ready to try the min-load function. I have 2 working 7704As and a 7514 to try it on. My goal is to be able to power up the 7704A acquisition unit without the display unit. I want it to be able useful as a min load with the other mainframes. It would be used by itself with full mainframes.
The loads are switched in and out by a 8pdt rotary switch. The +5V and Lamp power have a 4 ohm load on each. The 15V lines each have 20 ohm loads and the 50V lines each have 500ohm loads. Each power has a 10ma led load. The total power with the load inserted should be about 47watts.
Is there a file somewhere that list the power usage of each plugin?
I would like advice on the wisdom of offering this plugin for sale. I think it would be a very useful tool but could be a problem with unwise use. I worry what would happen if someone uses the extender in a mainframe with 3 other plugins and inserts the loads.
I have 2 7X01 extenders that have been my shops models for the last year or so. They are now available as I will keep the first 2 7X03s. I offer them for $100 each plus shipping. They are the same as the 10 7X02s I sold last year but have black faces with white letters and no woven cover for the cable.
Please respond off list.
Jerry Massengale
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Re: P6541 probe (was tektronix 318 logic analyzer probe)
| I've managed to gather a bunch of information of the net about the probes that can fit my logic analyzer.
They have the following part number?010-6451-0x , where x can be any number.
If someone has some probes and is willing to trade please contact me offline.
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Re: IC programmers slightly OT
Thanks Bruce. I'm not in much of a hurry to get a programmer, so I'm looking for a decent one that will fit my budget. I'll look for those too.
Mark
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On 2/19/2013 12:38 PM, Bruce Lane wrote: I'm partial to Advin myself. Alternatively, a decent used Data I/O
programmer.
Happy hunting.
* REPLY SEPARATOR *
On 19-Feb-13 at 10:46 Alexandre Souza - Listas wrote:
Anybody familiar with the Xeltec line of programmers? Good, bad,
indifferent? I see a batch of 'em all the time on Ebay, some going
for
seemingly high prices. Good programers, but I'd buy Elnec
Ops, I have a beeprog from Elnec :)
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Re: 475 Triggering Issue -- Will recent 468 Triggering Issue Thread Help Me?
I haven't followed this thread but noticed that you purchased new TD's and as David says, your adjustments seem to be (quite far) off.
Did you purchase the right TD's? They're not all the same!
Peak currents vary from 1mA to more than 10mA. They need appropriate biase adjustments!
Raymond
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--- In TekScopes@..., David <davidwhess@...> wrote:
If those low profile socket elements are the ones I am thinking of,
they are called Miniserts. I have had at least two incidents now
where a Minisert was open and reseating the lead at least temporarily
fixed the problem.
There is a datasheet for them in the files area:
Q532 (and Q526) are operating as emitter followers. The emitter
voltages for each are low impedance and should be about 0.6 volts
higher than their base voltages at all times. They are just used as
simple voltage buffers.
Trigger B is completely independent from trigger A and is only used if
a sweep mode other than A internal is selected.
From your description I suspect everything is working but that the A
trigger circuit needs to be calibrated:
R534 is used to center the trigger point vertically on the CRT when
R530 is in the middle of its rotation.
R673 adjusts the trigger view vertical positioning on the CRT.
R547 adjusts the trigger level so that it does not change when the
slope is changed.
R565 adjusts the tunnel diode threshold for maximum sensitivity.
On Wed, 20 Feb 2013 02:17:18 -0000, "stan_katz" <stan_katz@...>
wrote:
I know I've let this thread go cold, but I assure members it wasn't out of neglect. For one thing, I was advised to read the manual, and I have been doing so. In the meantime, I had been monitoring the trigger diodes by clipping scope probes on their anodes. I intended on recording waveforms with my digital camera. Alas, I found the camera was fried. Nevertheless, I decided to do some more examination of the Trigger A circuits. I took hold of one of the probes attached to a tunnel diode, intending to disengage it. The instrument was powered on. The probe came off the board, WITH THE TUNNEL DIODE STILL ATTACHED to the probe! The diode had no sign of being soldered in. I turned off the instrument, and pulled on the other tunnel diode, and it came out. No solder. Now it sunk in. Those phosphor/bronze stakes weren't hiding solder pads underneath, they were all sockets! I must have missed that in some FAQ or manual addendum. The only semiconductors soldered in my 475 are small signal
diodes. Who knows if my probes were intermittently yanking out the anode ends of the TDs. I certainly wasn't going to waste members' time by trying to diagnose TD damage. I bit my lip, and purchased two NOS tunnel diodes for $OUCH.00. As least this message would start with good tunnel diodes.
Following David's advise to do a modified 5-40 trigger A calibration from just Channel 1 input lead me nowhere. The scope wouldn't trigger on the 12mv p-p 350khz sine wave I was using to obtain a .32 division height on the CRT. Adjusting R565 had no effect. Lowering the attenuator and filling the screen with the signal also had no effect. I then returned the trigger level to full + ( clockwise ), attenuator down to 50mv, and with the waveform filling the screen, I got trigger lock. I did note, that during the modified 5-40 calibration attempt, there was no sign of the trigger signal with TRIG VIEW depressed. However, with the intentional misadjustments reported above, I could just see some light at the top of the screen in TRIG VIEW. Although I was advised not to start messing with anything but R565, I adjusted R534 in the "misadjusted" state using TRIG VIEW. The waveform came into view, and I could center it. With this set of adjustments, I could now trigger on the 12mv waveform
with the attenuator turned up to .1v so that I could meet the .32 divisions performance called out in 5-40. I thought I was on to something regarding the trigger centering. I esr'ed all the electrolytics in the triggering section. All checked out. A separate check with a VOM didn't show shorted electrolytics. I thought there may be a fault with U520, and given both it, and U720 were both socketed, I swapped them. No change. I haven't been able to find any shorted bypass caps..yet. I replaced Q532, and two resistors that were more than 50% out of spec. No go. One thing that bothers me is that, on the schematic, the emitter of Q532, is pulled up through R535 to +8.2v. I only measure +5.0v. I can't find any errata that verifies my measurement. The 8.2v source is functioning as it is available everywhere else noted on partial A8 schematic with trigger circuit. Trigger level at pin 14 of U520 varies from 1.7v (full + level) to 200mv (full - level). Is this OK? TP526 has a copy of the 12mv
waveform as expected. I'm fixated on the centering circuit, but can go no further. With HORIZ DISPLAY on A LOCK, there shouldn't be any interaction with TRIG B? Right? I suppose trimmer 534 could be bad, but checking that out requires flipping A8. Yeesh! I haven't messed with R673 yet, as my troubleshooting has been with AC coupling only. Should I go there?
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Re: TDS 744A Power Supply Issue - Any Ideas?
I believe all can be repaired thus far. I see no PCB damage.
I've purchased a handful of slightly under-rated fuses (20%). It was a matter of what was available more than anything.
Still waiting on the FETs to come in. At this point, the failure matches the blog suggested before (Q5/Q6 - with Q5 failing and not Q6).
I do not expect to get as lucky and have my debug end at this stage. I still suspect more issues.
From my initial measurements - I thought the voltage readings on the ICs were out of spec. However, ground reference changes (is not always chassis) - so absolute voltages based off of chassis ground are suspect. For ICs - better I measure GND pin to VCC rather than chassis to VCC.
That said, I plan on testing the ICs out of circuit. Will bread-board up a test circuit and verify function. Although I'm looking at bench supplies (w/var current limit and voltage) - those will take a while to purchase so I'll use a wall-wart and v-divs.
I'll also map out what I can for cascaded rails and try to lift all but the rails involved in 400V regulation. I need to isolate 400V and at least get that working without having to worry about failures down the chain.
At least once 400V is back up I can add the rest one by one until I blow a fuse (or not).
Of course, this process would seem more efficient if I stopped "blogging" about each step. I could edit out the messy parts. However, I believe it's instructive/useful to at least one future debugger to leave the warts in.
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--- In TekScopes@..., "baltimora86" <acuffe@...> wrote:
I can tell you from experience with switching power supplies that even replacing the fuse with the correct rating can cause more collateral damage if the power supply isn't fully repaired. Doubling the rating can lead to irreparable damage. If anything, I like to halve the fuse rating for the first test.
I would check/replace everything on the gate of that FET the blew up, and any other power transistors that have failed. If there are any ICs controlling that part of the power supply, replace them. Improper gate/base drive can cause instant failure. Also, loss of regulation can cause some spectacular failures.
--- In TekScopes@..., "circuitsandcode" <circuitsandcode@> wrote:
I used the fused circuit of the meter (10A) which is a little over 2x max current.
--- In TekScopes@..., larrys@ wrote:
"circuitsandcode" <circuitsandcode@> wrote:
Would prefer to have a variable P/S to ramp up voltage - but went for
broke and shorted across the fuse (using multimeter measuring amps)
and Q5 went out in flames. I've since ordered a handful of 2SK1018
parts to replace. Might want to make sure the meter didn't take any collateral damage.
-ls-
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Re: What use for a 640 Ohm 1x Probe?
The usual way to build such a probe is simple and excellent for
measuring very fast sub-nanosecond pulses. It consists of a length
of 50 ohm coax that's terminated in 50 ohms at the scope, either
with a 50 ohm input on the scope (usual on high bandwidth scopes) or
with a separate? termination. At the input end a small, low
inductance resistor is soldered to the center conductor and the
shield twisted into a small tail for the ground connection. The lead
length is kept as small as possible and the leads often soldered
directly to the test points. With a 450 ohm input resistor the probe
divides by ten, a 4950 ohm resistor divides by 100. The input
resistance is 500 and 5000 ohm respectively. This seems very small,
however at high frequencies any capacitive loading is severe, the
reactance of 1 pf at 1 GHz is approx. only 160 ohms. These probes
are quick and cheap and the short leads are essential for reliable
signal coupling; an inch of lead has significant inductance at high
frequencies. Even the most professional engineers with access to the
latest equipment make them up since they are so handy. Incidentally,
the multi thousand dollar many GHz probes are often soldered
directly into the test points to minimize lead inductance. I've
attached the instructions for making a probe, they are often simpler
if a commercial termination is used at the scope end and doesn't
have to be built into the cable. The resistor can be tinier too.
It's a bit of art to make them with a really flat response, suitable
test equipment to check response is valuable, but if made carefully
they are capable of useful performance as is. There was a link to a
you-tube discussion forum a few weeks back on probes that was very
good, if anyone has the link to it, it's worth watching. Tektronix
sold some coax probes like this, I don't know if they still do so. I
have a 100:1 probe that has a switchable 50 ohm termination at the
scope end. For really high frequencies the simple minimalist home
made ones are probably better since the lead length is small. The
ground lead in particular is important and is often a short spike to
touch a ground point.
On the other hand, if you want to look at mid frequencies, use a
standard high impedance 10:1 probe. The low impedance of a coax
cable will load the circuit. An unterminated coax with clip leads is
OK for audio frequencies but has too much capacitance for much
higher than that.
Don Black.
Don Black.
On 20-Feb-13 3:05 PM, Cliff White wrote:
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?
So, I've had the idea of
building a 50 ohm fixed 10x attenuator to use inline with
a 50 ohm cable. What kind of impedance matching should I
use for the 1meg ohm on the scope?
On 02/19/2013 07:26 PM, Don Black wrote:
It should be 9 Meg ohms. Then 90% of the
signal is dropped across the probes 9 Meg and 10% across
the scope's 1 Meg input impedance, giving 10:1 ratio.
The compensating capacitors across them are adjusted for
the same division at high frequencies to maintain the flat
response, that's hat you're setting when you adjust for
flat square wave with the trimmer.
Don Black.
On 20-Feb-13 12:18 PM, David wrote:
?
On Wed, 20 Feb 2013 00:24:09 -0000, "Philip" ndpmcintosh@...>
wrote:
>The publication on scope probes mentioned
earlier is good and I am working my way through it.
I already had it in my document collection and it
was on my reading list.
>
>If I ohm out a 10x 10Mohm probe in the same way,
I get about 10 MOhms. I'll keep reading though...
I get almost exactly 9.00 MOhms on each of several
different x10
probes within reach.
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