----- Original Message -----

From: Ed Breya

To: TekScopes@...

Sent: Monday, March 18, 2013 9:54 PM

Subject: [TekScopes] Re: Could please any one give a clue about this nice pulsed line generator??

?

The simplest and most likely to work way to extend the line is just using more .141 semi-rigid line. If you have any RG-8 cables - the big stuff - and an adapter for N to SMA, it should definitely work better than RG-58 since it will have much lower loss, and maybe comparable to .141.

There is a slightly more compact possible alternative, but I don't know yet. For one of my pulser designs, I had planned to try a section of scope vertical delay line in differential mode, with the avalanche operation between the oppositely charged lines, then transformer-coupled into a nonlinear transmission line edge compressor. I have the line mounted mechanically in a plug-in only, but not yet rigged for any experiments.

The 7000 series appear to all (I don't know about the 7104) use the same stuff, which looks like it's made with bare copper conductors and outer foil, with HDPE dielectric. It's supposedly about 100 ohms differential, but may act as about 50 ohms common-mode with the conductors tied, or maybe with one conductor grounded to the foil. I found that the outer foil has a longitudinal gap so that it doesn't totally enclose the conductors, so it may behave strangely as a single line - it's really optimized for differential use.

If you happen to have any pieces of delay line or 7000 carcasses available, you may want to experiment with it. I'm curious about how it would act with different wiring arrangements, what the true impedance is, and whether it's low enough in loss for pulser applications. It's heavier than the .141 cable, but on the other hand, it doesn't have silver plated conductors, and the HDPE isn't as good as PTFE. Maybe it's comparable then - the larger size offsetting the lossier materials. Or maybe not.

It's also possible to extend the pulse width arbitrarily by terminating and feeding the charge line at the distal end with a 50 ohm source (at the charge voltage!), but it is much more complicated than the normal method. The power dissipation can quickly get out of hand, and the commutation must be provided by additional circuitry, since there's no reflection from the line.

For the immediate purpose, I'd recommend just using more cable.

For the actual scope measurements, you should have some good coaxial attenuators, or a step attenuator, to knock the level down some. The average pulser power is no problem, but the peak voltage may cause all sorts of strange effects by turning on protection devices and ringing the front-end parasitics.

Ed

--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" wrote:
>
> Today the Pulse Gen come to live, after replace the weak Q100 transistor by selected from what ever transistor I have in my shop..the winner was a npn switching "MPSH10".
> The rise time seems to be right on my unfinished to cal high frequency response 2465B scope..paradoxical..I brought this Gen in order to Cal my scopes ..now I haven`t a calibrated scope in this high impulse picosecond domain..to test this Gen..a dog chasing his tail!!!
> The only I can do is an act of "believe" in avalanche physic & Tek circuit implementation.
>
> As you people warning early, make an extension transmission line from common RG58...work but the pulse is not flat, the decay near linearly along his width..about 80ns.
> Any suggestion about how to make/obtain 15 feet of very good coax cable??? .
> Also please could any one post a pic on what is expected to see on a 2465B once connected to this Gen, about rise time and flatness?.
>
> --- In TekScopes@..., "iglesia_cristiana_arpas_eternas" wrote:
> >
> > The Generator arrive today from USA to my Argentine door!!! .
> >
> > Unfortunately not work fine.
> > Rt=1,67nS (instead 300pS)
> > Width pulse= 5,84nS (wave exponential decay instead rectangular pulse)
> > Max out= 3,5V (instead 25V)
> > Rep Rate=15Mhz (instead 50 or 100Khz)
> >
> > The ratio of different att step, seems to be good.
> > Probability arise that my previous intuition about bipolar avalanche transistor burned out come truth.
> >
> > Perhaps the out pulse I see is not else than the trigger pulse passing trough a short avalanche transistor.
> > Any way, this nice generator will be fixed (tomorow)....all kind of help & advice will be welcome.
> > Gabriel...from the Holly land of Francisco Pope!!..God bless all of Us.
> >
> >
> > --- In TekScopes@..., "iglesia_cristiana_arpas_eternas" wrote:
> > >
> > > Here the link to this almost new pulsed generator, at first glance is a
> > > transmission line pulser with 300ps ..but no model or number at all.
> > > I just brought it with the hope work right...but a good service manual
> > > will be very appreciated and gratefully.
> > > Link to Pulse Gen.
> > > <> > > 2112187?autorefresh=true&pt=LH_DefaultDomain_0&hash=item3a7e99ce3b&nma=t\
> > > rue&si=w4%252BkkAkTYIq9sTkPYLC8H98HEpU%253D&orig_cvip=true&rt=nc&_trksid\
> > > =p2047675.l2557>
> > >
> > > Regards Gabriel.
> > >
> >
>

Today the Pulse Gen come to live, after replace the weak Q100 transistor by selected from what ever transistor I have in my shop..the winner was a npn switching "MPSH10".
The rise time seems to be right on my unfinished to cal high frequency response 2465B scope..paradoxical..I brought this Gen in order to Cal my scopes ..now I haven`t a calibrated scope in this high impulse picosecond domain..to test this Gen..a dog chasing his tail!!!
The only I can do is an act of "believe" in avalanche physic & Tek circuit implementation.

As you people warning early, make an extension transmission line from common RG58...work but the pulse is not flat, the decay near linearly along his width..about 80ns.
Any suggestion about how to make/obtain 15 feet of very good coax cable??? .
Also please could any one post a pic on what is expected to see on a 2465B once connected to this Gen, about rise time and flatness?.

--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@> wrote:

The Generator arrive today from USA to my Argentine door!!! .

Unfortunately not work fine.
Rt=1,67nS (instead 300pS)
Width pulse= 5,84nS (wave exponential decay instead rectangular pulse)
Max out= 3,5V (instead 25V)
Rep Rate=15Mhz (instead 50 or 100Khz)

The ratio of different att step, seems to be good.
Probability arise that my previous intuition about bipolar avalanche transistor burned out come truth.

Perhaps the out pulse I see is not else than the trigger pulse passing trough a short avalanche transistor.
Any way, this nice generator will be fixed (tomorow)....all kind of help & advice will be welcome.
Gabriel...from the Holly land of Francisco Pope!!..God bless all of Us.


--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@> wrote:

Here the link to this almost new pulsed generator, at first glance is a
transmission line pulser with 300ps ..but no model or number at all.
I just brought it with the hope work right...but a good service manual
will be very appreciated and gratefully.
Link to Pulse Gen.
<;
2112187?autorefresh=true&pt=LH_DefaultDomain_0&hash=item3a7e99ce3b&nma=t&#92;
rue&si=w4%252BkkAkTYIq9sTkPYLC8H98HEpU%253D&orig_cvip=true&rt=nc&_trksid&#92;
=p2047675.l2557>

Regards Gabriel.

Okay, here's my report on the loss of center frequency on a 7L13 plugin (digest #7424), albeit a bit late. I had to put together a parts order (Thanks to the tip from 'crippo2', Vernonia Northern, right next door here in Oregon has many Tek parts in stock.) and they just got here today, very quickly I might add. 'David' Hess's advice on control line 'E', it should have been appx. 4 volts, and was at nearly 7 volts. Thanks David for your tips, they were very welcome. U2145 was indeed out to lunch, it's plus and minus supplies were fine. Due to internal issues it allowed pin 6 to swing above the expected 4 volts. R & R the LM311 and viola, the DVM circuit was once again functional. This was the second issue this module had since its arrival from a seller on Ebay. I just love the 'phrase' "We don't know how it works, so it's being sold As-Is", translated: "It's broke, and it don't work". HiHi The first was a shorted tantalytic in the +15 volt rail. Once that was replaced,
the machine worked but no center frequency display, LED or on screen. So... a sincere Thanks to David for your help, you were spot on. I kept thinking something downstream was causing the issue, compounded by my non-familiarity with the DVM to begin with. I was thinking 'Frequency counter', when I was dealing with a Digital Voltage Meter, ya live and learn.

73,
~Michael - AF7U

--- In TekScopes@..., David <davidwhess@...> wrote:

On Mon, 11 Mar 2013 06:35:34 -0000, "Michael" <af7u@...> wrote:

This post is a follow up from post #7360, and my 7L13 with center frequency LED readout all zeros. I am a bit further along with my investigation. I now understand the operation 'somewhat' more. I have looked over the diagrams and taken some voltage readings, I also understand the basic DVM logic and readout operation which sends data to the LCD and the CRT. I have an article from a Jan, 1975 '73' magazine which talks about the Fairchild 3814 digital voltmeter. I must admit I am not too clear on the 'Analog' section of the meter. On board 'A2100', diagram 12, the input to pin 2 of U2110 comes from plug P2540 pin 4. Looking over the A2500 board shows that pin 4 goes to chassis ground. Why would pin 2 from U2110 go all the way back to A2500 to reach chassis ground.

U2110 (LM308 style low bias current bipolar operational amplifier) is
configured as a differential amplifier. The signal ground that the
tuning voltage uses may not be at quite the same potential as the
signal ground that the readout uses so the differential amplifier
subtracts the difference. The differential amplifier will also
subtract low frequency noise between the grounds.

Anyway, the A2000 board seems to be working, albeit the frequency of the clock oscillator is not 200kHz as the diagram shows, it is running at 153.7kHz, though amplitude is good at 5 volts, I would think that would affect calibration but not operation. Back on A2100, the tuning control voltage at R2104 is good, it swings from + - 9.6 volts. The output of U2110 swings + - 10.7 volts. The DCPL Supply rails 15, -15, and 5 volts are all good. The reference voltage at the cathode of VR2115 (Zener) is 3.1, not the 3.3 volts is shows. Voltage at TP 2100, (output of U2130) is 11.65, a bit higher than the listed 11.3 volts. The voltages around the N-channel FET (Q2120) is Drain = 3.37 volts, Source = -3.1 volts, and Gate = -3.5 volts, are those in the ball park?

Those voltages all sound good to me and they are mostly the ones I
would have asked you to measure. In the worst case they add up to a
calibration problem and not a complete failure.

Needless to say there is NO signals present, waveform, 1, 2, 3, and 4 are all missing. Lines 'E' and 'F' are both quiet, the voltages on 'E' are 7.08 volts, on 'F' the voltage is 5.12 volts which swings a bit higher when I adjust center frequency, up to 5.44 volts. Of course 'E' has no signal as would be expected without drive from U2145 there is nothing to trigger the multivibrator U2030 on board A2000 sending a signal back up line 'F'. I keep thinking of this in terms of a frequency counter, I keep thinking there should be a driving input signal. I try to keep in mind it's a voltmeter, and keep in mind the circuit description given in the manual. It describes a ramp signal coming from the output of U2110, I don't understand that statement. The 'Tune' voltage is just a DC voltage, plus to minus. The minus input of U2120 goes to chassis ground??? What 'RAMP' are they speaking about?

E is 7 volts? That is quite a trick since the pull-up resistor
(R2149) is connected to +5V and the output of U2145 (LM311 style
comparator) is wired open collector (pin 1 is the emitter of the
output transistor and wired to ground) so it can only pull down and
not pull up. On the receiver side, U2010D is part of a 74L04 and also
has a 5 volt supply voltage so even if it failed, it can not pull up
to 7 volts

U2145 (LM311) is probably bad but you might want to look for a bad
socket or open trace. Nothing should be able to make its output go to
7 volts except an open on pin 4 or failed part.

The operational amplifiers and comparator are all TO-99 8 pin metal
cans which are difficult to find these days. If you can not find
metal cans, I would try replacing them with 8 pin DIP parts which
conveniently have the same pinout. I have done this before by cutting
the DIP leads short and soldering little wires to them. Cutoff 1/4
watt resistor leads work well.

Texas Instruments still sells TO-99 LM311 comparators but they are $10
each.

U2010 may be damaged as well. I think it can be replaced without
problems with a 74LS04 or even a 74HCT04 which are both more common.

If you have to order the LM311, pick up an LM308 and 74L04 replacement
as well just in case. The LM308 operational amplifiers can be
directly replaced with the Linear Technology LT1008. An LT1012 or
lots of other devices can be used if you pull the compensation
capacitor. JFET or MOSFET input devices should work as well.

Lastly the manual's circuit description on page 5-10 talks about a positive going ramp from U2110, aren't these just DC levels, what 'Ramp' are they talking about?

I think the ramp they talk about is the output of U2140 (another
LM308) which is configured as an integrator. The frequency (and
slope) of the ramp is proportional to the measured voltage.

Okay, I see there are a lot of questions here. I had better post this and hope for the best. It's a great 7L13, it works well, but without a 'Center' frequency display, it's pretty much just a toy. Also, I do appreciate the feedback~!~ I am not accustom to working on test equipment, my experience has been mostly all in Hi-Fi, but this has been very interesting.

I had to add a few pages of the 7L13 manual to my book of stuff I do
not have so it took a bit longer to respond to your post. The 7000
series spectrum analyzers look like fun. I will have to keep an eye
out for one.

On Mon, 11 Mar 2013 06:35:34 -0000, "Michael" <af7u@...> wrote:

This post is a follow up from post #7360, and my 7L13 with center frequency LED readout all zeros. I am a bit further along with my investigation. I now understand the operation 'somewhat' more. I have looked over the diagrams and taken some voltage readings, I also understand the basic DVM logic and readout operation which sends data to the LCD and the CRT. I have an article from a Jan, 1975 '73' magazine which talks about the Fairchild 3814 digital voltmeter. I must admit I am not too clear on the 'Analog' section of the meter. On board 'A2100', diagram 12, the input to pin 2 of U2110 comes from plug P2540 pin 4. Looking over the A2500 board shows that pin 4 goes to chassis ground. Why would pin 2 from U2110 go all the way back to A2500 to reach chassis ground.

U2110 (LM308 style low bias current bipolar operational amplifier) is
configured as a differential amplifier. The signal ground that the
tuning voltage uses may not be at quite the same potential as the
signal ground that the readout uses so the differential amplifier
subtracts the difference. The differential amplifier will also
subtract low frequency noise between the grounds.

Anyway, the A2000 board seems to be working, albeit the frequency of the clock oscillator is not 200kHz as the diagram shows, it is running at 153.7kHz, though amplitude is good at 5 volts, I would think that would affect calibration but not operation. Back on A2100, the tuning control voltage at R2104 is good, it swings from + - 9.6 volts. The output of U2110 swings + - 10.7 volts. The DCPL Supply rails 15, -15, and 5 volts are all good. The reference voltage at the cathode of VR2115 (Zener) is 3.1, not the 3.3 volts is shows. Voltage at TP 2100, (output of U2130) is 11.65, a bit higher than the listed 11.3 volts. The voltages around the N-channel FET (Q2120) is Drain = 3.37 volts, Source = -3.1 volts, and Gate = -3.5 volts, are those in the ball park?

Those voltages all sound good to me and they are mostly the ones I
would have asked you to measure. In the worst case they add up to a
calibration problem and not a complete failure.

Needless to say there is NO signals present, waveform, 1, 2, 3, and 4 are all missing. Lines 'E' and 'F' are both quiet, the voltages on 'E' are 7.08 volts, on 'F' the voltage is 5.12 volts which swings a bit higher when I adjust center frequency, up to 5.44 volts. Of course 'E' has no signal as would be expected without drive from U2145 there is nothing to trigger the multivibrator U2030 on board A2000 sending a signal back up line 'F'. I keep thinking of this in terms of a frequency counter, I keep thinking there should be a driving input signal. I try to keep in mind it's a voltmeter, and keep in mind the circuit description given in the manual. It describes a ramp signal coming from the output of U2110, I don't understand that statement. The 'Tune' voltage is just a DC voltage, plus to minus. The minus input of U2120 goes to chassis ground??? What 'RAMP' are they speaking about?

E is 7 volts? That is quite a trick since the pull-up resistor
(R2149) is connected to +5V and the output of U2145 (LM311 style
comparator) is wired open collector (pin 1 is the emitter of the
output transistor and wired to ground) so it can only pull down and
not pull up. On the receiver side, U2010D is part of a 74L04 and also
has a 5 volt supply voltage so even if it failed, it can not pull up
to 7 volts

U2145 (LM311) is probably bad but you might want to look for a bad
socket or open trace. Nothing should be able to make its output go to
7 volts except an open on pin 4 or failed part.

The operational amplifiers and comparator are all TO-99 8 pin metal
cans which are difficult to find these days. If you can not find
metal cans, I would try replacing them with 8 pin DIP parts which
conveniently have the same pinout. I have done this before by cutting
the DIP leads short and soldering little wires to them. Cutoff 1/4
watt resistor leads work well.

Texas Instruments still sells TO-99 LM311 comparators but they are $10
each.

U2010 may be damaged as well. I think it can be replaced without
problems with a 74LS04 or even a 74HCT04 which are both more common.

If you have to order the LM311, pick up an LM308 and 74L04 replacement
as well just in case. The LM308 operational amplifiers can be
directly replaced with the Linear Technology LT1008. An LT1012 or
lots of other devices can be used if you pull the compensation
capacitor. JFET or MOSFET input devices should work as well.

Lastly the manual's circuit description on page 5-10 talks about a positive going ramp from U2110, aren't these just DC levels, what 'Ramp' are they talking about?

I think the ramp they talk about is the output of U2140 (another
LM308) which is configured as an integrator. The frequency (and
slope) of the ramp is proportional to the measured voltage.

Okay, I see there are a lot of questions here. I had better post this and hope for the best. It's a great 7L13, it works well, but without a 'Center' frequency display, it's pretty much just a toy. Also, I do appreciate the feedback~!~ I am not accustom to working on test equipment, my experience has been mostly all in Hi-Fi, but this has been very interesting.

I had to add a few pages of the 7L13 manual to my book of stuff I do
not have so it took a bit longer to respond to your post. The 7000
series spectrum analyzers look like fun. I will have to keep an eye
out for one.

The Generator arrive today from USA to my Argentine door!!! .

Unfortunately not work fine.
Rt=1,67nS (instead 300pS)
Width pulse= 5,84nS (wave exponential decay instead rectangular pulse)
Max out= 3,5V (instead 25V)
Rep Rate=15Mhz (instead 50 or 100Khz)

The ratio of different att step, seems to be good.
Probability arise that my previous intuition about bipolar avalanche transistor burned out come truth.

Perhaps the out pulse I see is not else than the trigger pulse passing trough a short avalanche transistor.
Any way, this nice generator will be fixed (tomorow)....all kind of help & advice will be welcome.
Gabriel...from the Holly land of Francisco Pope!!..God bless all of Us.


--- In TekScopes@..., "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@> wrote:

Here the link to this almost new pulsed generator, at first glance is a
transmission line pulser with 300ps ..but no model or number at all.
I just brought it with the hope work right...but a good service manual
will be very appreciated and gratefully.
Link to Pulse Gen.
<;
2112187?autorefresh=true&pt=LH_DefaultDomain_0&hash=item3a7e99ce3b&nma=t&#92;
rue&si=w4%252BkkAkTYIq9sTkPYLC8H98HEpU%253D&orig_cvip=true&rt=nc&_trksid&#92;
=p2047675.l2557>

Regards Gabriel.

I'm thinking of buying the parts to refurb my 2465A, but I wanted to know if the parts documented in the 2465B restoration PDF have a good chance of being the same. The service manual I have does not specify the board level component values, so I thought I'd get all the parts before I start the work (once I take it apart I would rather just get the work done). Serial number is B0144xx.



------------------------------------

Yahoo! Groups Links

----- Original Message -----

From: Tom Jobe

To: TekScopes@...

Sent: Monday, March 18, 2013 6:53 PM

Subject: Re: [TekScopes] New 466 owner

?

Because I needed one of those 1/8" plastic flex joints recently and did not have one, I extended an .050" hex wrench today?and changed those couplers on a 465. I?replaced the two flex joints with two of those 1/8" aluminum couplers from Veronia Northern and it all worked perfectly.

You need to remove the bandwidth shaft and a couple of other small bits?to get good access but it was just a few minute job once the hex wrench was lengthened.

tom jobe...

PS The shaft length on the VAR pot is only .400" or so, and it is fairly stiff to rotate.

?

?

?

----- Original Message -----

From: Dan Aldrich

To: TekScopes@...

Sent: Monday, March 18, 2013 6:04 AM

Subject: [TekScopes] New 466 owner

?

Just picked up a 466 over the weekend. Works fine, but the only
problem was the Var knob on CH 2 is broken. Opened it up and saw it
was the coupler that connects the two shafts that's broken. Is there
a source for the couplers? I might just leave it alone as it looks
like a real pain to get down to the Ch 2 stuff.

Thanks,
-d

?

NI GPIB-PCI

David would that be a? PCI-GPIB IEEE 488.2 183617K-01 Interface Card or a AT-GPIB/TNT IEEE 488.2 card?? The former is ~100 USD and the latter ~30 USD.? It seems my workstation can handle another card.. perhaps using a hammer.

The USB adapter, even on e-bay, is way out of my league. :)

/m

----- Original Message -----

From: Dan Aldrich

To: TekScopes@...

Sent: Monday, March 18, 2013 6:04 AM

Subject: [TekScopes] New 466 owner

?

Just picked up a 466 over the weekend. Works fine, but the only
problem was the Var knob on CH 2 is broken. Opened it up and saw it
was the coupler that connects the two shafts that's broken. Is there
a source for the couplers? I might just leave it alone as it looks
like a real pain to get down to the Ch 2 stuff.

Thanks,
-d

Hi David,
On "my" schematic 34 there is no U1620A or U2 and no D181 or U3.
I found the TL 72 OpAmp.
I have a U900 aa vertical D/A converter an a U1010 as horizontal D/A converter.
Gerhard

--- In TekScopes@..., David <davidwhess@...> wrote:

I assume that the character display works correctly even when the
stored signal has no or a low vertical deflection.

I think you will find the problem around U1620A or U2 on schematic 34.
If reseating those ICs or the A40 connections does not resolve the
problem, then you could swap U2 with a different DG181 like U3 to see
if the problem moves to the horizontal axis. I have read about
reliability problems with the DG181 before.

The TL072 used for U1620 has lots of possible replacements including
the TL082 and any number of other FET and MOSFET input operational
amplifiers.

There could be a bad part in the networks surrounding U1620A.

On Mon, 18 Mar 2013 16:44:53 -0000, "g_kupka" <ghm1@...> wrote:

After a warmup time of approx 2 hours the stored signal is displayed in the stored mode but only with an ampltude of 35% of the applied signal.

Gerhard

--- In TekScopes@..., "g_kupka" <ghm1@> wrote:

I swapped the RAM Board and now the 2nd 7854 has the opt 2D.
The 1st 7854 has still the problem, that it doesn't display the stored signal in the store mode, it shows only a horizontal line.
Where can I find the failure?
Many thanks.
Gerhard

--- In TekScopes@..., "David C. Partridge" <david.partridge@> wrote:

Yes

Dave
-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf Of g_kupka
Sent: 17 March 2013 10:22
To: TekScopes@...
Subject: [TekScopes] How to upgrade a 7854 to opt 2D

I have two 7854.
1st one opt 2D(extended memory):
I can store a signal, but it doesn't show the stored signal in the store mode, it shows only a horizontal line.
2nd one opt 78(P11 CRT):
It works well. Can I upgrade this mainframe to opt 2D by swapping the memory board from the 1st one to the 2nd one?

Gerhard

------------------------------------

Yahoo! Groups Links