Date   

Sphere's 2021 Holiday Stuff Season is officially open....

 

My apologies for the delay, but a lot of items had to be edited, discounted, re-worked, added and deleted, so it just wasn't possible to keep the page open during all that chaos. Hopefully you will like the new look and feel, I tried to improve the navigation, parts association and appearance wherever I could. There are some new categories, Surprises (kind of speaks for itself), Scopes (I put them all in one place for easier browsing), and SMD Reels (for those who are SMD fans). I will be updating every day or so, the top red banner will tell you when.

https://www.sphere.bc.ca/test/stuffday.html

please let me know if you want to see something specific I have left out, you can email me directly.
all the best to everyone for the upcoming holidays.

-walter & susan
(walter2 -at- sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/index.html


Re: Continuing Problems with 7704A Display

n4buq
 

Hi Ozan,

I'm getting 153.5V at C4201. If 156V is expected, then that might be a symptom of other issues.

I disconnected P4212 and P4213 and measured the voltage across the inner conductors. That shows 118.2VAC. I measured that with my Fluke 27 which _should_ be okay at that frequency (the meter is spec'd up to 30kHz).

I haven't measured the differential voltage between P313's pin 1 and pin 2 but I'm pretty sure the individual voltages are correct with respect to ground.

I'm not sure what that all might indicate but it's what I measured.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Ozan" <ozan_g@erdogan.us>
To: "tekscopes" <TekScopes@groups.io>
Sent: Monday, October 11, 2021 10:55:26 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
Hi Barry,
There is a possibility that T4201 is not generating high enough voltage. As
others pointed out even when collector of Q4115 is as low as it can go you are
not able to get low enough (or high in absolute sense) cathode voltage.

What voltage do you measure across C4201 at +150V terminal? +156V is expected.

T4201 voltage depends on what comes from J4212 and J4213. If you have access to
those terminals each should show about ~ 100Vpp 20kHz signal according to the
schematic,

54V setting that matters for T4201 is in the lower unit, sheet <8>, it is the
+54V adjustment R3143. Differential voltage at connector P313 pins 1 and 3
should be 109.1V according to the schematic.

741 could still be bad since you are measuring 0.8V at pin2. If R4120 measures
470k (i.e. it is not faulty) there is too much current coming out of pin2.
However, replacing the 741 may not fix the real problem.
Ozan


On Mon, Oct 11, 2021 at 08:29 AM, n4buq wrote:


+54V was about +53V. I set it properly and tweaked -50V (was -50.1V).
Virtually no change with the ability to set -2960V and the voltage at
Q4105/Q4115 is still at about 0.5V.

I presume that since the HV multiplier is a X14 and the anode voltage is
supposed to be 21kV, then the input to the multiplier (from
T4201) should be 1500V RMS @~20kHz. So far, I haven't found this stated
empirically so would like confirmation on it. Furthermore, from there, the
doubler circuit should yield 3kV. Is that correct?

Until I get the replacement 741, I'm not sure what else I can check.

Thanks,
Barry - N4BUQ


Re: 7B50 - No Sweep

n4buq
 

Hi Roger,

I tried the things you mention and I get no hint of a trace. The RESET button's light is never on.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Roger Evans via groups.io" <very_fuzzy_logic=yahoo.com@groups.io>
To: "tekscopes" <TekScopes@groups.io>
Sent: Friday, October 15, 2021 10:26:54 AM
Subject: Re: [TekScopes] 7B50 - No Sweep
Barry,

Following from Albert's suggestion that Lockout may be preventing the sweep from
starting, can you try the following.

Select a slow sweep speed eg 0.5 seconds /div.

With a suitable trigger signal present set the trigger level so that the trigger
light is off.

Set the sweep mode to Single Sweep and press the Reset button, the reset light
should stay on. Single sweep reset 'should' reset all the stages of the
lockout / holdoff circuitry.

Turn the trigger level to the point where the sweep should trigger. Do you see
a single slow sweep?

Just for clarity, with Auto sweep enabled do you see anything at all on screen?

Regards,

Roger



Re: Continuing Problems with 7704A Display

n4buq
 

I was mistaken. The 630NA is NOT listed - just the 625NA, 630, and 630A.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "n4buq" <n4buq@knology.net>
To: "tekscopes" <TekScopes@groups.io>
Sent: Friday, October 15, 2021 11:26:50 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
Dave,

I see an "HVP 2" file. That manual mentions using that probe with a Triplett
630NA on the 500V scale.

Unfortunately, I'm not sure what the model number is for my probe. I've never
found anything on it to indicate the model.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Daveolla via groups.io" <grobbins=netflash.net@groups.io>
To: "tekscopes" <TekScopes@groups.io>
Sent: Friday, October 15, 2021 10:28:21 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
The manual for the EICO HV probe is on BAMA (boat
anchor manual archive) google it .It lists the
various resistors in the probe depending on
which input resistance VTVM you have. I think the
file is named "HVP 1"....... unless I changed my file name).
Dave

At 04:49 AM 10/15/2021, you wrote:
The odd ratio is because these probes were
designed for analog VTVMs. These meters had an
input resistance of 9 MOhm and used an 1 MOhm
series resistor inside the X1 probe, making
a total of 10 MOhm input resistance. Since
this arrangement forms a 9/10 attenuator the
meter scales are drawn taking this in account so
the measurements are ok. The HV probe has a
resistor whose value is the right one for an
instrument with 9 MOhm input resistance that is
calibrated to show 1.0 when the true input
voltage is 0.9. If you use this HV probe with a
digital meter with 10 MOhm input resistance you
need to to do the math to have the real value.

An alternative is to make an adapter box to be
inserted between the HV probe and the meter.
This adapter just consists of an attenuator to
further divide the probe output and the ratio
has to be chosen to give a total attenuation of
10000, including the probe resistor, so you can
use a lower range (which is not a problem with a
DVM) and you will get the right measurement
without doing any math other than multiplying
the value by 10000. Part of one resistor of the
attenuator should be variable so you can calibrate the ratio.

I hope this is understandable (English is not my
mother language) but if it is not clear and you are interested, jusk ask.

Regards,

Ignacio EB4APL


El 12/10/2021 a las 15:47, n4buq escribió:
John,

It appears the 90M string works quite well and gives me an easy 10:1 ratio.

After seeing that the 1R09G was giving me odd
results at higher voltages, I removed the
resistor, cleaned it thoroughly with IPA, and
reassembled it without touching the body of the
resistor. After that, 1000V on the calibrator
showed 9.09V which is the 110:1 it should be
(actually, the Fluke waffled between 9.09V and
9.10V and reducing the calibrator voltage by
about 0.5% caused it to settle at 9.09V). I
don't know if a less-than-clean resistor was
the root cause, but it did seem to make that measurement what it should be.

Since 10:1 is a much easier ratio to work with
and I'm not likely to need something for higher
that 10kV, I'm considering making a probe out
of some PVC pipe; however, I don't know how
safe PVC is at higher voltages and need to
research that a bit before deciding to use
it. If not PVC pipe, I'm not sure what other
means I could use to make the probe. Nylon?

Anyway, thanks for the pointers/suggestions!

Apologies to the list if this has gone too far
off topic. If so, please let me know. I tend to get "wordy" at times. :(

Thanks,
Barry - N4BUQ



On 10/11/2021 9:32 AM, n4buq wrote:
Hi Albert,

Lacking a very precise way to measure
voltages of that magnitude, I'm using a
Triplett 630NA on the 6000V scale. I have an
old EICO HV probe but I'm unsure
what it's comprised of; however, I used it
with my voltage calibrator set to
1000V and derived a multiplication factor to use with my Fluke 25. While
that's all a bit crude, both measurement methods read pretty close to each
other. That said, I'm seeing a maximum
voltage of -2900V and that's with R4123
set to maximum CW rotation.

When I was experimenting with injecting
voltages where U4110's pin 6 normally
sets it, I could get the collector voltages at Q4105/Q4115 anywhere between
0.5V and 100V but TP4221 didn't appear to move - at least not that I could
detect on the analog meter.

I'll check the voltage at R4211/R4209/C4208 and report back later today.

Thanks again!
Barry - N4BUQ






Re: Continuing Problems with 7704A Display

n4buq
 

Dave,

I see an "HVP 2" file. That manual mentions using that probe with a Triplett 630NA on the 500V scale.

Unfortunately, I'm not sure what the model number is for my probe. I've never found anything on it to indicate the model.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Daveolla via groups.io" <grobbins=netflash.net@groups.io>
To: "tekscopes" <TekScopes@groups.io>
Sent: Friday, October 15, 2021 10:28:21 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
The manual for the EICO HV probe is on BAMA (boat
anchor manual archive) google it .It lists the
various resistors in the probe depending on
which input resistance VTVM you have. I think the
file is named "HVP 1"....... unless I changed my file name).
Dave

At 04:49 AM 10/15/2021, you wrote:
The odd ratio is because these probes were
designed for analog VTVMs. These meters had an
input resistance of 9 MOhm and used an 1 MOhm
series resistor inside the X1 probe, making
a total of 10 MOhm input resistance. Since
this arrangement forms a 9/10 attenuator the
meter scales are drawn taking this in account so
the measurements are ok. The HV probe has a
resistor whose value is the right one for an
instrument with 9 MOhm input resistance that is
calibrated to show 1.0 when the true input
voltage is 0.9. If you use this HV probe with a
digital meter with 10 MOhm input resistance you
need to to do the math to have the real value.

An alternative is to make an adapter box to be
inserted between the HV probe and the meter.
This adapter just consists of an attenuator to
further divide the probe output and the ratio
has to be chosen to give a total attenuation of
10000, including the probe resistor, so you can
use a lower range (which is not a problem with a
DVM) and you will get the right measurement
without doing any math other than multiplying
the value by 10000. Part of one resistor of the
attenuator should be variable so you can calibrate the ratio.

I hope this is understandable (English is not my
mother language) but if it is not clear and you are interested, jusk ask.

Regards,

Ignacio EB4APL


El 12/10/2021 a las 15:47, n4buq escribió:
John,

It appears the 90M string works quite well and gives me an easy 10:1 ratio.

After seeing that the 1R09G was giving me odd
results at higher voltages, I removed the
resistor, cleaned it thoroughly with IPA, and
reassembled it without touching the body of the
resistor. After that, 1000V on the calibrator
showed 9.09V which is the 110:1 it should be
(actually, the Fluke waffled between 9.09V and
9.10V and reducing the calibrator voltage by
about 0.5% caused it to settle at 9.09V). I
don't know if a less-than-clean resistor was
the root cause, but it did seem to make that measurement what it should be.

Since 10:1 is a much easier ratio to work with
and I'm not likely to need something for higher
that 10kV, I'm considering making a probe out
of some PVC pipe; however, I don't know how
safe PVC is at higher voltages and need to
research that a bit before deciding to use
it. If not PVC pipe, I'm not sure what other
means I could use to make the probe. Nylon?

Anyway, thanks for the pointers/suggestions!

Apologies to the list if this has gone too far
off topic. If so, please let me know. I tend to get "wordy" at times. :(

Thanks,
Barry - N4BUQ



On 10/11/2021 9:32 AM, n4buq wrote:
Hi Albert,

Lacking a very precise way to measure
voltages of that magnitude, I'm using a
Triplett 630NA on the 6000V scale. I have an
old EICO HV probe but I'm unsure
what it's comprised of; however, I used it
with my voltage calibrator set to
1000V and derived a multiplication factor to use with my Fluke 25. While
that's all a bit crude, both measurement methods read pretty close to each
other. That said, I'm seeing a maximum
voltage of -2900V and that's with R4123
set to maximum CW rotation.

When I was experimenting with injecting
voltages where U4110's pin 6 normally
sets it, I could get the collector voltages at Q4105/Q4115 anywhere between
0.5V and 100V but TP4221 didn't appear to move - at least not that I could
detect on the analog meter.

I'll check the voltage at R4211/R4209/C4208 and report back later today.

Thanks again!
Barry - N4BUQ





Re: 7B50 - No Sweep

Roger Evans
 

Barry,

Following from Albert's suggestion that Lockout may be preventing the sweep from starting, can you try the following.

Select a slow sweep speed eg 0.5 seconds /div.

With a suitable trigger signal present set the trigger level so that the trigger light is off.

Set the sweep mode to Single Sweep and press the Reset button, the reset light should stay on. Single sweep reset 'should' reset all the stages of the lockout / holdoff circuitry.

Turn the trigger level to the point where the sweep should trigger. Do you see a single slow sweep?

Just for clarity, with Auto sweep enabled do you see anything at all on screen?

Regards,

Roger


Re: Continuing Problems with 7704A Display

Daveolla
 

The manual for the EICO HV probe is on BAMA (boat anchor manual archive) google it .It lists the various resistors in the probe depending on which input resistance VTVM you have. I think the file is named "HVP 1"....... unless I changed my file name).
Dave

At 04:49 AM 10/15/2021, you wrote:
The odd ratio is because these probes were designed for analog VTVMs. These meters had an input resistance of 9 MOhm and used an 1 MOhm series resistor inside the X1 probe, making a total of 10 MOhm input resistance. Since this arrangement forms a 9/10 attenuator the meter scales are drawn taking this in account so the measurements are ok. The HV probe has a resistor whose value is the right one for an instrument with 9 MOhm input resistance that is calibrated to show 1.0 when the true input voltage is 0.9. If you use this HV probe with a digital meter with 10 MOhm input resistance you need to to do the math to have the real value.

An alternative is to make an adapter box to be inserted between the HV probe and the meter. This adapter just consists of an attenuator to further divide the probe output and the ratio has to be chosen to give a total attenuation of 10000, including the probe resistor, so you can use a lower range (which is not a problem with a DVM) and you will get the right measurement without doing any math other than multiplying the value by 10000. Part of one resistor of the attenuator should be variable so you can calibrate the ratio.

I hope this is understandable (English is not my mother language) but if it is not clear and you are interested, jusk ask.

Regards,

Ignacio EB4APL


El 12/10/2021 a las 15:47, n4buq escribió:
John,

It appears the 90M string works quite well and gives me an easy 10:1 ratio.

After seeing that the 1R09G was giving me odd results at higher voltages, I removed the resistor, cleaned it thoroughly with IPA, and reassembled it without touching the body of the resistor. After that, 1000V on the calibrator showed 9.09V which is the 110:1 it should be (actually, the Fluke waffled between 9.09V and 9.10V and reducing the calibrator voltage by about 0.5% caused it to settle at 9.09V). I don't know if a less-than-clean resistor was the root cause, but it did seem to make that measurement what it should be.

Since 10:1 is a much easier ratio to work with and I'm not likely to need something for higher that 10kV, I'm considering making a probe out of some PVC pipe; however, I don't know how safe PVC is at higher voltages and need to research that a bit before deciding to use it. If not PVC pipe, I'm not sure what other means I could use to make the probe. Nylon?

Anyway, thanks for the pointers/suggestions!

Apologies to the list if this has gone too far off topic. If so, please let me know. I tend to get "wordy" at times. :(

Thanks,
Barry - N4BUQ



On 10/11/2021 9:32 AM, n4buq wrote:
Hi Albert,

Lacking a very precise way to measure voltages of that magnitude, I'm using a
Triplett 630NA on the 6000V scale. I have an old EICO HV probe but I'm unsure
what it's comprised of; however, I used it with my voltage calibrator set to
1000V and derived a multiplication factor to use with my Fluke 25. While
that's all a bit crude, both measurement methods read pretty close to each
other. That said, I'm seeing a maximum voltage of -2900V and that's with R4123
set to maximum CW rotation.

When I was experimenting with injecting voltages where U4110's pin 6 normally
sets it, I could get the collector voltages at Q4105/Q4115 anywhere between
0.5V and 100V but TP4221 didn't appear to move - at least not that I could
detect on the analog meter.

I'll check the voltage at R4211/R4209/C4208 and report back later today.

Thanks again!
Barry - N4BUQ


Re: Continuing Problems with 7704A Display

n4buq
 

Ignacio,

Thanks for that information. I might make an adapter with an appropriate resistor to complete a proper 1000:1 divider. For now, I think I'm okay with the 90M string with the 10M input to form a 10:1 ratio. That seems to be working well enough. I just need to make a better method of mounting it into a probe, etc.

There's absolutely nothing wrong with your English. It is perfectly understandable. I only wish I had alternate-language skills as good as yours!

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "EB4APL" <eb4apl@gmail.com>
To: "tekscopes" <TekScopes@groups.io>
Sent: Friday, October 15, 2021 4:49:47 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
The odd ratio is because these probes were designed for analog VTVMs.
These meters had an input resistance of 9 MOhm and used an 1 MOhm series
resistor inside the X1 probe, making a  total of 10 MOhm input
resistance. Since this arrangement forms a 9/10 attenuator the meter
scales are drawn taking this in account so the measurements are ok. The
HV probe has a resistor whose value is the right one for an instrument
with 9 MOhm input resistance that is calibrated to show 1.0 when the
true input voltage is 0.9. If you use this HV probe with a digital meter
with 10 MOhm input resistance you need to to do the math to have the
real value.

An alternative is to make an adapter box to be inserted between the HV
probe and the meter. This adapter just consists of an attenuator to
further divide the probe output and the ratio has to be chosen to give a
total attenuation of 10000, including the probe resistor, so you can use
a lower range (which is not a problem with a DVM) and you will get the
right measurement without doing any math other than multiplying the
value by 10000. Part of one resistor of the attenuator should be
variable so you can calibrate the ratio.

I hope this is understandable (English is not my mother language) but if
it is not clear and you are interested, jusk ask.

Regards,

Ignacio EB4APL


El 12/10/2021 a las 15:47, n4buq escribió:
John,

It appears the 90M string works quite well and gives me an easy 10:1 ratio.

After seeing that the 1R09G was giving me odd results at higher voltages, I
removed the resistor, cleaned it thoroughly with IPA, and reassembled it
without touching the body of the resistor. After that, 1000V on the calibrator
showed 9.09V which is the 110:1 it should be (actually, the Fluke waffled
between 9.09V and 9.10V and reducing the calibrator voltage by about 0.5%
caused it to settle at 9.09V). I don't know if a less-than-clean resistor was
the root cause, but it did seem to make that measurement what it should be.

Since 10:1 is a much easier ratio to work with and I'm not likely to need
something for higher that 10kV, I'm considering making a probe out of some PVC
pipe; however, I don't know how safe PVC is at higher voltages and need to
research that a bit before deciding to use it. If not PVC pipe, I'm not sure
what other means I could use to make the probe. Nylon?

Anyway, thanks for the pointers/suggestions!

Apologies to the list if this has gone too far off topic. If so, please let me
know. I tend to get "wordy" at times. :(

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "John Kolb" <jlkolb@jlkolb.digitalspacemail17.net>
To: "tekscopes" <TekScopes@groups.io>
Sent: Tuesday, October 12, 2021 7:07:55 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
You can easily extend the measurement range of your Fluke 25 by putting
10 Mohms of resistance in series with the meter, and just multiply the
reading by 2.

Put several resistors in series as few resistors are rated for 1 KV.
Measure 1000V from your calibrator direct and with the series string of
R. Adjust the R value until the reading is exactly half.

Done carefully, this should be nearly as accurate as the Fluke alone,
and certainly more accurate than the 630.

You could go for a 20M string for a 3:1 ratio, but going any higher
would add whatever error might exist between th 1 KV and the 320V ranges
of your fluke.

I'm a day behind on reading emails, so may be replying with comments
others have already said.

John KK6IL



On 10/11/2021 9:32 AM, n4buq wrote:
Hi Albert,

Lacking a very precise way to measure voltages of that magnitude, I'm using a
Triplett 630NA on the 6000V scale. I have an old EICO HV probe but I'm unsure
what it's comprised of; however, I used it with my voltage calibrator set to
1000V and derived a multiplication factor to use with my Fluke 25. While
that's all a bit crude, both measurement methods read pretty close to each
other. That said, I'm seeing a maximum voltage of -2900V and that's with R4123
set to maximum CW rotation.

When I was experimenting with injecting voltages where U4110's pin 6 normally
sets it, I could get the collector voltages at Q4105/Q4115 anywhere between
0.5V and 100V but TP4221 didn't appear to move - at least not that I could
detect on the analog meter.

I'll check the voltage at R4211/R4209/C4208 and report back later today.

Thanks again!
Barry - N4BUQ

----- Original Message -----
From: "Albert Otten" <aodiversen@concepts.nl>
To: "tekscopes" <TekScopes@groups.io>
Sent: Monday, October 11, 2021 11:09:57 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
I removed U4110 and injected a voltage from an adjustable power supply at end
of R4112 (effectively, pin 6 of U4110) and was able to get 73V (+/- a few
volts as it isn't exactly stable) at the collectors of Q4105/Q4115; however,
I'm now wondering if U4110 is truly bad or whether it's simply not getting the
correct inputs. I was also monitoring TP4221 as I did that and it didn't have
very much effect.
Hi Barry,

It would be much more informative when you report those TP4221 voltages. With
that +73 V the TP voltage should also become about 70 V more positive (compared
with near zero volts at the collectors as when U4110 is in use). And once more
a again about 70 V more positive when you create about +150 V at the
collectors.
Can you verify that the voltage at R4211/R4209/C4208 is almost equal to the
collectors voltage?

Albert




--
El software de antivirus Avast ha analizado este correo electrónico en busca de
virus.
https://www.avast.com/antivirus




Re: Continuing Problems with 7704A Display

EB4APL
 

The odd ratio is because these probes were designed for analog VTVMs. These meters had an input resistance of 9 MOhm and used an 1 MOhm series resistor inside the X1 probe, making a  total of 10 MOhm input resistance. Since this arrangement forms a 9/10 attenuator the meter scales are drawn taking this in account so the measurements are ok. The HV probe has a resistor whose value is the right one for an instrument with 9 MOhm input resistance that is calibrated to show 1.0 when the true input voltage is 0.9. If you use this HV probe with a digital meter with 10 MOhm input resistance you need to to do the math to have the real value.

An alternative is to make an adapter box to be inserted between the HV probe and the meter. This adapter just consists of an attenuator to further divide the probe output and the ratio has to be chosen to give a total attenuation of 10000, including the probe resistor, so you can use a lower range (which is not a problem with a DVM) and you will get the right measurement without doing any math other than multiplying the value by 10000. Part of one resistor of the attenuator should be variable so you can calibrate the ratio.

I hope this is understandable (English is not my mother language) but if it is not clear and you are interested, jusk ask.

Regards,

Ignacio EB4APL

El 12/10/2021 a las 15:47, n4buq escribió:
John,

It appears the 90M string works quite well and gives me an easy 10:1 ratio.

After seeing that the 1R09G was giving me odd results at higher voltages, I removed the resistor, cleaned it thoroughly with IPA, and reassembled it without touching the body of the resistor. After that, 1000V on the calibrator showed 9.09V which is the 110:1 it should be (actually, the Fluke waffled between 9.09V and 9.10V and reducing the calibrator voltage by about 0.5% caused it to settle at 9.09V). I don't know if a less-than-clean resistor was the root cause, but it did seem to make that measurement what it should be.

Since 10:1 is a much easier ratio to work with and I'm not likely to need something for higher that 10kV, I'm considering making a probe out of some PVC pipe; however, I don't know how safe PVC is at higher voltages and need to research that a bit before deciding to use it. If not PVC pipe, I'm not sure what other means I could use to make the probe. Nylon?

Anyway, thanks for the pointers/suggestions!

Apologies to the list if this has gone too far off topic. If so, please let me know. I tend to get "wordy" at times. :(

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "John Kolb" <jlkolb@jlkolb.digitalspacemail17.net>
To: "tekscopes" <TekScopes@groups.io>
Sent: Tuesday, October 12, 2021 7:07:55 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
You can easily extend the measurement range of your Fluke 25 by putting
10 Mohms of resistance in series with the meter, and just multiply the
reading by 2.

Put several resistors in series as few resistors are rated for 1 KV.
Measure 1000V from your calibrator direct and with the series string of
R. Adjust the R value until the reading is exactly half.

Done carefully, this should be nearly as accurate as the Fluke alone,
and certainly more accurate than the 630.

You could go for a 20M string for a 3:1 ratio, but going any higher
would add whatever error might exist between th 1 KV and the 320V ranges
of your fluke.

I'm a day behind on reading emails, so may be replying with comments
others have already said.

John KK6IL



On 10/11/2021 9:32 AM, n4buq wrote:
Hi Albert,

Lacking a very precise way to measure voltages of that magnitude, I'm using a
Triplett 630NA on the 6000V scale. I have an old EICO HV probe but I'm unsure
what it's comprised of; however, I used it with my voltage calibrator set to
1000V and derived a multiplication factor to use with my Fluke 25. While
that's all a bit crude, both measurement methods read pretty close to each
other. That said, I'm seeing a maximum voltage of -2900V and that's with R4123
set to maximum CW rotation.

When I was experimenting with injecting voltages where U4110's pin 6 normally
sets it, I could get the collector voltages at Q4105/Q4115 anywhere between
0.5V and 100V but TP4221 didn't appear to move - at least not that I could
detect on the analog meter.

I'll check the voltage at R4211/R4209/C4208 and report back later today.

Thanks again!
Barry - N4BUQ

----- Original Message -----
From: "Albert Otten" <aodiversen@concepts.nl>
To: "tekscopes" <TekScopes@groups.io>
Sent: Monday, October 11, 2021 11:09:57 AM
Subject: Re: [TekScopes] Continuing Problems with 7704A Display
I removed U4110 and injected a voltage from an adjustable power supply at end
of R4112 (effectively, pin 6 of U4110) and was able to get 73V (+/- a few
volts as it isn't exactly stable) at the collectors of Q4105/Q4115; however,
I'm now wondering if U4110 is truly bad or whether it's simply not getting the
correct inputs. I was also monitoring TP4221 as I did that and it didn't have
very much effect.
Hi Barry,

It would be much more informative when you report those TP4221 voltages. With
that +73 V the TP voltage should also become about 70 V more positive (compared
with near zero volts at the collectors as when U4110 is in use). And once more
a again about 70 V more positive when you create about +150 V at the
collectors.
Can you verify that the voltage at R4211/R4209/C4208 is almost equal to the
collectors voltage?

Albert




--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.
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tektronix dpo7254

oliver johnson
 

I have a dpo7254 that has issues , booting issues where scope freezes and I would also like to change to a ssd drive , can soneon tell me where I can get a copy of the original disks that come with the scope for these types of issue where a fresh install is needed, thanks


Re: Type 284 Pulse Generator strange output.

Tom Lee
 

Yes, ignore the non-terminated result -- it's confounded by uncontrolled transmission line effects. When you do terminate properly, notice that you get measurements that are independent of the (infinitely-faster-than-your-scope) pulsers. The result is a legitimate risetime measurement of your scope. That 4.5ns corresponds to a bit over 75MHz bandwidth, at least from the approximation that Mike cites.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/14/2021 21:19, Jared Cabot via groups.io wrote:
On Fri, Oct 15, 2021 at 02:58 AM, Michael Perkins wrote:

Folks,
Risetime and bandwidth are related by a simple relation: BW= 0.35/
risetime. For a 350 MHz bandwidth, the risetime needs to be 1nS. For a 60
MHz bandwidth, you should expect a 5.83 nS risetime.
Mike
Checking again:
The Leo Bodnar pulser is giving me 5.4nS at 1.7VP-P on Channel 1 and 2 on the 60MHz TDS210. So basically spot on (a tiny bit over performing, which is nice).
If I terminate it into 50 ohms, it gives me 4.5nS at 860mVP-P.
The (terminated) Tek 284 is giving me 4.5nS at 240mVP-P on Channel 1 and 2 on the 60MHz TDS210.

I'll call it good, at least the scope is meeting it's rated specs.


On Thu, Oct 14, 2021 at 05:13 PM, Albert Otten wrote:

The Tek peaks at a couple hundred millivolts or so, the Leo Bodnar peaks at
around 5 volts.
All 3 pulsers at Bodnars website (at this moment) have 1.2 V pp max. So which
model are you referring to?
Attenuators will degrade the pulse form somewhat but perhaps you can try
attenuators to test both pulsers at the same scope sensitivity.
Albert
Yep, I'm reading 1.7V P-P, A classic late night typo on my part... :D




Re: Type 284 Pulse Generator strange output.

Jared Cabot
 

On Fri, Oct 15, 2021 at 02:58 AM, Michael Perkins wrote:


Folks,
Risetime and bandwidth are related by a simple relation: BW= 0.35/
risetime. For a 350 MHz bandwidth, the risetime needs to be 1nS. For a 60
MHz bandwidth, you should expect a 5.83 nS risetime.
Mike
Checking again:
The Leo Bodnar pulser is giving me 5.4nS at 1.7VP-P on Channel 1 and 2 on the 60MHz TDS210. So basically spot on (a tiny bit over performing, which is nice).
If I terminate it into 50 ohms, it gives me 4.5nS at 860mVP-P.
The (terminated) Tek 284 is giving me 4.5nS at 240mVP-P on Channel 1 and 2 on the 60MHz TDS210.

I'll call it good, at least the scope is meeting it's rated specs.


On Thu, Oct 14, 2021 at 05:13 PM, Albert Otten wrote:


The Tek peaks at a couple hundred millivolts or so, the Leo Bodnar peaks at
around 5 volts.
All 3 pulsers at Bodnars website (at this moment) have 1.2 V pp max. So which
model are you referring to?
Attenuators will degrade the pulse form somewhat but perhaps you can try
attenuators to test both pulsers at the same scope sensitivity.
Albert
Yep, I'm reading 1.7V P-P, A classic late night typo on my part... :D


Re: 7B50 - No SweepCR262

Mark Vincent
 

Barry,

Nothing stands out yet what is the problem. Start checking d-c voltages. Something will be off. This is what I would do. I see R313 is to a switched voltage. See if you get the -15V on one end of that resistor. This is a point to check. Sometimes writing down voltages to compare has to be done when enough numbers are needed. There may be someone else in this group that may have had the same problem and can tell you what that problem was.

The 741 in the scope would have been the first thing I would have put in to see if that was the problem. I have had this number give problems in the past. The string(s) of resistor(s) can be checked to see if they are too far out of tolerance. I know it is unlikely, check the 470,000 ohm resistor on the input with the IC out. The inverter control and B+ adjust pots affect each other. You may have said what the voltages at the + and - inputs are. They should be almost zero. That IC gives the appearance of a transconductance circuit by the two resistors from the output to ground. I not stating this is the type of circuit, only looking similar. I have no other ideas of the two problems you have. Further information from you will help.

Mark


Re: 577 D2 Display Issues

Zentronics42@...
 

I can confirm that the tube is a direct transplant however I do not know about the HV board. I used a 5110 to replace in the tube in one of my 577's no modification needed.

Zen

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of gmilliorn@gmail.com
Sent: Thursday, October 14, 2021 9:25 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 577 D2 Display Issues

Cleaning the contamination everywhere, and replacing the pots in the 577 HV driver did not fix the display, so I managed to get a rackmount 5110 at auction.
It has a crisp stable display.

Looking inside, I see that the display half is nearly literally the top half of the 577 D2, just as Andy mentioned. The only differences I see are the calibrator loop and that the connections to the HV board are directly wired instead of pin connectors (cost savings, I guess).

Given the soot that was all over my HV board, I'm inclined to perhaps just transplant the tube and the board. The schematics seem identical, unless I'm missing something I'd only have to convert the cables to connector pins. Has anyone tried that as well?


Re: 7B50 - No SweepCR262

n4buq
 

Mark,

No need to apologize! I have benefitted from your advice here many times and would not think you're trying to mislead anyone. I'm sure I could have given more information that would have helped you analyze the problems.

Since LOCKOUT may also be an issue, I started looking at TP436, TP434, TP432, and TP416. None of those have any activity on them. They're either stuck HI or LO but not other signal is present on those. I presume that's why LOCKOUT is holding off the sweep but I'm not sure yet.

Regarding the 741, unfortunately that hasn't made any difference. I'm seeing about -2915V as a maximum negative voltage. Something else must be going wrong but haven't done much other analysis on that yet. BTW, my scope is an earlier serial number and I think would have had the 670-1855-00 HV board; however, mine has a 670-1855-01 board in it. I presume that shouldn't matter and may even be a good thing but thought I'd mention it.

Thanks again for all your help.
Barry - N4BUQ

----- Original Message -----
From: "Mark Vincent" <orangeglowaudio@gmail.com>
To: "tekscopes" <TekScopes@groups.io>
Sent: Thursday, October 14, 2021 7:58:56 PM
Subject: Re: [TekScopes] 7B50 - No SweepCR262
Barry,

I apologize for the mistake I made in the diagnostics. I went by the initial
statement and previous problems I had. Albert is is right about asking about
TP725. Thank you Albert about inquiring about this test point. Knowing that
first, I would have given a different answer.That having a small signal will
eliminate CR262 as a problem. The other two transistors being on will make it
appear the second CR to be bad. That may not be so. See if the switch is dirty
or something else is making these turn on. The second CR may still be good. I
have NO intentions of intentionally misleading anyone on this group.

Let us know if the new 741 in your 7704A makes a difference in the high voltage
once you get it installed. I have prayed you will get your 7704A and plugins
working to your satisfaction. I know you will be so happy having a working
scope and plugins. Please do not think I will ever knowingly mislead you or
anyone else on this group.

Mark



Re: 577 D2 Display Issues

@gmilliorn
 

Cleaning the contamination everywhere, and replacing the pots in the 577 HV
driver did not fix the display, so I managed to get a rackmount 5110 at auction.
It has a crisp stable display.

Looking inside, I see that the display half is nearly literally the top half of the 577 D2,
just as Andy mentioned. The only differences I see are the calibrator loop and that the
connections to the HV board are directly wired instead of pin connectors (cost savings,
I guess).

Given the soot that was all over my HV board, I'm inclined to perhaps just transplant
the tube and the board. The schematics seem identical, unless I'm missing something
I'd only have to convert the cables to connector pins. Has anyone tried that as well?


Re: 7B50 - No SweepCR262

Mark Vincent
 

Barry,

I apologize for the mistake I made in the diagnostics. I went by the initial statement and previous problems I had. Albert is is right about asking about TP725. Thank you Albert about inquiring about this test point. Knowing that first, I would have given a different answer.That having a small signal will eliminate CR262 as a problem. The other two transistors being on will make it appear the second CR to be bad. That may not be so. See if the switch is dirty or something else is making these turn on. The second CR may still be good. I have NO intentions of intentionally misleading anyone on this group.

Let us know if the new 741 in your 7704A makes a difference in the high voltage once you get it installed. I have prayed you will get your 7704A and plugins working to your satisfaction. I know you will be so happy having a working scope and plugins. Please do not think I will ever knowingly mislead you or anyone else on this group.

Mark


Re: 7B50 - No Sweep

Albert Otten
 

Hi Barry,
Yes, this activates the trigger lights, but just to be sure I asked you about TP275. So TD CR262 is no longer suspect.
The reason for TD CR299 not firing can also be that Lockout is active via Q296 and Q293.
Albert

On Thu, Oct 14, 2021 at 08:22 PM, n4buq wrote:


Albert,

I'll have to check but I think I recall that TP275 is correct - or, at least,
shows a waveform similar to what's shown on the schematic. I presume that's
what's allowing the TRIG'D lamp to work, correct?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Albert Otten" <aodiversen@concepts.nl>
To: "tekscopes" <TekScopes@groups.io>
Sent: Thursday, October 14, 2021 12:25:13 PM
Subject: Re: [TekScopes] 7B50 - No Sweep
On Thu, Oct 14, 2021 at 04:56 PM, n4buq wrote:
The waveform at TP262 appears normal; however, I don't see that waveform at
the collector of Q266 and I presume I should(?).
Barry, the collector of Q266 should show just a weak signal because Q273 is
driven common base.
What is TP275 showing?
Albert


Re: 7B50 - No Sweep

n4buq
 

Albert,

I'll have to check but I think I recall that TP275 is correct - or, at least, shows a waveform similar to what's shown on the schematic. I presume that's what's allowing the TRIG'D lamp to work, correct?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Albert Otten" <aodiversen@concepts.nl>
To: "tekscopes" <TekScopes@groups.io>
Sent: Thursday, October 14, 2021 12:25:13 PM
Subject: Re: [TekScopes] 7B50 - No Sweep
On Thu, Oct 14, 2021 at 04:56 PM, n4buq wrote:
The waveform at TP262 appears normal; however, I don't see that waveform at
the collector of Q266 and I presume I should(?).
Barry, the collector of Q266 should show just a weak signal because Q273 is
driven common base.
What is TP275 showing?
Albert



Re: Type 284 Pulse Generator strange output.

Michael Perkins
 

Folks,
Risetime and bandwidth are related by a simple relation: BW= 0.35/
risetime. For a 350 MHz bandwidth, the risetime needs to be 1nS. For a 60
MHz bandwidth, you should expect a 5.83 nS risetime.
Mike

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On Thu, Oct 14, 2021 at 10:46 AM Tom Lee <tomlee@ee.stanford.edu> wrote:

By the way, I've been assuming that you're properly terminating both
pulsers. Improper terminations can make a big difference.
(I didn't pay close attention to the thread, so sorry if this was
already discussed.)

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/14/2021 09:43, Tom Lee wrote:
Hi Jared,

The pulsers have rise times that are much, much faster than your
scope's, so any differences between the pulsers can't be seen by your
scope (which is why one needs a fast scope to resolve details of a
fast input signal). So what you see cannot be attributed to the
pulsers -- you're seeing your scope's limitations, not differences in
details in input pulse shape. As far as your scope is concerned, it is
being driven by infinitely fast pulses. It doesn't matter if one
pulser is "doubly infinitely" fast compared to the other.

-- Cheers,
Tom





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