I'll have to get busy, it's half done. Now green yellow or the hard to get soft white leds that imitate?incandescent?bulbs. thanks for the encouragement.
I've seen members come up with a lot of hacks Paul, but yours seems unique. We would all like to hear about it and maybe see it in action. Sounds very interesting for sure.
Geo
----- Original Message ----- From: paul davis <paulkd4ll@...> To: [email protected] Sent: Sun, 10 Jul 2022 07:13:32 -0400 (EDT) Subject: [CDV700CLUB] Sequencing round led display for behind Victoreen cdv-700
I have a vic with the cut down battery box. I am considering adding a 2.3 inch circular led sequencer board behind the plexiglass meter. I have done this with a Cajoe?geiger kit and a converted linear led chaser kit. You have to convert the 555 chip from astable multivibrator to monostable and adjust the input resistance. The other chip is a 4017. You could see the relative radiation from across the room by how fast the circle spins. Looks similar to an atomic test countdown counter. I was wondering if anyone has tried something similar? Thanks
Re: Sequencing round led display for behind Victoreen cdv-700
I've seen members come up with a lot of hacks Paul, but yours seems unique. We would all like to hear about it and maybe see it in action. Sounds very interesting for sure.
----- Original Message ----- From: paul davis <paulkd4ll@...> To: [email protected] Sent: Sun, 10 Jul 2022 07:13:32 -0400 (EDT) Subject: [CDV700CLUB] Sequencing round led display for behind Victoreen cdv-700
I have a vic with the cut down battery box. I am considering adding a 2.3 inch circular led sequencer board behind the plexiglass meter. I have done this with a Cajoe?geiger kit and a converted linear led chaser kit. You have to convert the 555 chip from astable multivibrator to monostable and adjust the input resistance. The other chip is a 4017. You could see the relative radiation from across the room by how fast the circle spins. Looks similar to an atomic test countdown counter. I was wondering if anyone has tried something similar? Thanks
Sequencing round led display for behind Victoreen cdv-700
I have a vic with the cut down battery box. I am considering adding a 2.3 inch circular led sequencer board behind the plexiglass meter. I have done this with a Cajoe?geiger kit and a converted linear led chaser kit. You have to convert the 555 chip from astable multivibrator to monostable and adjust the input resistance. The other chip is a 4017. You could see the relative radiation from across the room by how fast the circle spins. Looks similar to an atomic test countdown counter. I was wondering if anyone has tried something similar? Thanks
it's good at removing stickers etc, yes but plain Naptha(from the paint/hardware store), or at a higher price, Ronsonol or Zippo lighter fluid is better, and is less messy-and since it leaves no residue, the removed label can even be reinstalled if needed(yes, there ARE cases where this is useful).
another FYI about WD-40, it can be bought by the gallon at Harbor Freight for 1/2 the price of Fastenal, Grainger etc.
It's really good at removing old calibration stickers and goo too.
Geo
----- Original Message ----- From: Geo Dowell <GEOelectronics@...> To: [email protected] Sent: Sun, 10 Jul 2022 11:07:39 -0400 (EDT) Subject: Re: [CDV700CLUB] CD V-720
That's what I use M.K. and it is available at HarborFreightTools.
?FYI WD-40 leave a petrolatum residue.
Geo
----- Original Message ----- From: M. K. <ka2mce@...> To: [email protected] Sent: Sun, 10 Jul 2022 10:54:55 -0400 (EDT) Subject: Re: [CDV700CLUB] CD V-720
This makes sense, BUT if you do this use a contact cleaner that does NOT leave a residue..
So Deoxit is probably not the best choice(it's often the product of choice, but not this time).
One suitable product which is easy to find, is CRC QD Electronic Cleaner.
On Sun, Jul 10, 2022 at 9:14 AM David71 via <dnix71=[email protected]> wrote:
You should buy a can of electronic cleaner/deoxidizer and clean the whole board and selector switch with a toothbrush.
Zinc whiskers can cause all kinds of leakage on a circuit like that and your board looks nasty.
Hi Stephen.? You picture indicates it's a Victoreen 720 model 3A. Attached is the shop manual for that variant, as well as an apdate done to a Vic 715 that addressed some leakage issues..
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
----- Original Message ----- From: Geo Dowell <GEOelectronics@...> To: [email protected] Sent: Sun, 10 Jul 2022 11:07:39 -0400 (EDT) Subject: Re: [CDV700CLUB] CD V-720
That's what I use M.K. and it is available at HarborFreightTools.
?FYI WD-40 leave a petrolatum residue.
Geo
----- Original Message ----- From: M. K. <ka2mce@...> To: [email protected] Sent: Sun, 10 Jul 2022 10:54:55 -0400 (EDT) Subject: Re: [CDV700CLUB] CD V-720
This makes sense, BUT if you do this use a contact cleaner that does NOT leave a residue..
So Deoxit is probably not the best choice(it's often the product of choice, but not this time).
One suitable product which is easy to find, is CRC QD Electronic Cleaner.
On Sun, Jul 10, 2022 at 9:14 AM David71 via <dnix71=[email protected]> wrote:
You should buy a can of electronic cleaner/deoxidizer and clean the whole board and selector switch with a toothbrush.
Zinc whiskers can cause all kinds of leakage on a circuit like that and your board looks nasty.
Hi Stephen.? You picture indicates it's a Victoreen 720 model 3A. Attached is the shop manual for that variant, as well as an apdate done to a Vic 715 that addressed some leakage issues..
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
----- Original Message ----- From: Lenox Carruth <radios@...> To: [email protected] Sent: Sun, 10 Jul 2022 11:03:18 -0400 (EDT) Subject: Re: [CDV700CLUB] CD V-720
?
My experience with these instruments was quite a few years ago but I found that the desiccant is very important.? That would be the first thing that I would try.? Particularly if you are in a humid location which, since it is summer, you probably are.
?
Putting a desiccant package inside never failed to cure the leakage problem for me.
?
Lenox
?
?
?
Does this meter require a desiccant in the can to help reduce the upscale readings?
----- Original Message ----- From: M. K. <ka2mce@...> To: [email protected] Sent: Sun, 10 Jul 2022 10:54:55 -0400 (EDT) Subject: Re: [CDV700CLUB] CD V-720
This makes sense, BUT if you do this use a contact cleaner that does NOT leave a residue..
So Deoxit is probably not the best choice(it's often the product of choice, but not this time).
One suitable product which is easy to find, is CRC QD Electronic Cleaner.
On Sun, Jul 10, 2022 at 9:14 AM David71 via <dnix71=[email protected]> wrote:
You should buy a can of electronic cleaner/deoxidizer and clean the whole board and selector switch with a toothbrush.
Zinc whiskers can cause all kinds of leakage on a circuit like that and your board looks nasty.
Hi Stephen.? You picture indicates it's a Victoreen 720 model 3A. Attached is the shop manual for that variant, as well as an apdate done to a Vic 715 that addressed some leakage issues..
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
My experience with these instruments was quite a few years ago but I found that the desiccant is very important.? That would be the first thing that I would try.? Particularly if you are in a humid location which, since it is summer, you probably are.
?
Putting a desiccant package inside never failed to cure the leakage problem for me.
?
Lenox
?
?
?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Hi Stephen.? You picture indicates it's a Victoreen 720
model 3A. Attached is the shop manual for that variant, as
well as an apdate done to a Vic 715 that addressed some
leakage issues..
Geo
----- Original Message -----
From: Stephen Nelson <steve.motorola.uranium@...>
To: [email protected]
Sent: Sat, 09 Jul 2022 18:58:12 -0400 (EDT)
Subject: [CDV700CLUB] CD V-720
Hello,
I purchased a non working CD V-720, and found the
meter "nuts" were not present which caused the meter to
not show any movement...obviously. After connecting the
meter, it seemed to be ok enough to zero, but..... most
ranges were maxed out which I take as high leakage
current from something dirty. The insides looked pretty
clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were
reduced to a ~0.5R/hr reading on the 1x scale. I cleaned
the glass insulators on the chamber with 99% IPA and a
Qtip and the chamber leakage went down to about 12 R/Hr
on the 10x range.
Looking at the schematics, I see mine is different
from what was published in 1961. I have a 8.2k resistor
across the meter, and the 470k resistor near the
potentiometer is 100K ohms. I am wondering if they made
changes in 1971 when a faint stamp shows CD calibrated
the meter. It looks like my meter was made in 1962 with
"62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of
the PCB (kept dry), and that sorda helped, bringing the
1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty
which is causing the upscale readings, and there is a
leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to
do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to
help reduce the upscale readings?
Thanks for any help, I attached the check results
with and without the chamber, name plate and? one of the
component side. I left them full resolution such that
one can zoom in if need be.
You should buy a can of electronic cleaner/deoxidizer and clean the whole board and selector switch with a toothbrush.
Zinc whiskers can cause all kinds of leakage on a circuit like that and your board looks nasty.
Thanks, David71.
Your comments are right on the subject.
Some nostalgia, RE: the cleaner you mentioned. I remember at trade shows the manufacturers having a fish aquarium filled with the clear stuff, and a completely submerged bare-chassis TV set powered on and operating, to the amazement of the inevitable crowd. We used it by the case at work, a product called "Whiiiish". It came with a special metal sort of Hypo which you screwed on to a potentiometer shaft and a plunger that flushed the pot's insides with the stuff. Safe to say not a day went by without treating at least one police car's two-way radio control head volume and squelch controls with it.
Some nostalgia on metal "whiskers": Back in the early days of earth satellites (maybe '63?), micro-meteors were a concern and electronic PCB's were sort of new and untrusted, so an article was run in a magazine on how the metal whiskers were being employed to combat trace breakages. That was the first time i became of the crystal "whiskers" phenomenon and was literally amazed. Some readers may not know of them even today, here is a link that explains:
Hi Stephen.? You picture indicates it's a Victoreen 720 model 3A. Attached is the shop manual for that variant, as well as an apdate done to a Vic 715 that addressed some leakage issues..
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
Gaseous ionization detectors?are radiation detection instruments used in radiation protection applications to measure ionizing radiation and particle physics to detect the presence of ionizing particles. These detectors are designed to measure the ionization produced when an incident particle traverses some medium and are based on radiation¡¯s ionizing effect. For ionizing radiation to occur, the kinetic energy of particles (photons, electrons, etc.) of ionizing radiation?is sufficient. The particle can ionize?(to form ions by losing electrons) target atoms to form ions. Simply ionizing radiation can knock electrons from an atom.
The basic?gaseous ionization detector?consists of a chamber filled with a suitable medium (air or a special fill gas) that can be easily ionized. The most widely used types of these detectors are based on the effects produced when a charged particle passes through a gas. The operating medium:
should be chemically stable (or inert) so that the moving ionization electrons are not easily captured by the molecules of that medium
should have a low ionization potential (I) value to maximize the amount of ionization produced per energy deposited by any incident particle.
should not be very sensitive to radiation damage so that its response to incident particles does not change markedly with use.
Typical gases used in detectors are?argon?and?helium, although?boron-trifluoride?(BF3) is utilized when the detector is to be used to measure neutrons.?Gaseous ionization detectors?are widely used in nuclear power plants, for the most part, to measure??and?,?, and?. The detectors operate in the ionization, proportional, and Geiger-Mueller regions, with an arrangement most sensitive to the measured radiation type. Neutron detectors utilize ionization chambers or proportional counters of appropriate design. Compensated ion chambers, BF3?counters, fission counters, and proton recoil counters are examples of neutron detectors.
Basic Principle of Gaseous Ionization Detectors
Detectors of ionizing radiation consist of two parts that are usually connected. The first part consists of sensitive material, consisting of a compound that experiences changes when exposed to radiation. The other component is a device that converts these changes into measurable signals.
The?chamber?has a cathode and an anode that are held at some large relative voltage, and the device is characterized by a capacitance determined by the geometry of the electrodes. As ionizing radiation enters the gas between the electrodes, a finite number of ion pairs are formed. The behavior of the resultant ion pairs is affected by the potential gradient of the gas¡¯s electric field and the fill gas¡¯s type and pressure. Under the influence of the electric field, the positive ions will move toward the negatively charged electrode (outer cylinder), and the negative ions (electrons) will migrate toward the positive electrode (central wire). The electric field in this region keeps the ions from recombining with the electrons. Collecting these ions will produce a charge on the electrodes and an electrical pulse across the detection circuit. The average energy needed to produce an ion in the air is about 34 eV. Therefore a 1 MeV radiation completely absorbed in the detector produces about 3 x 104?pairs of ions. However, it is a small signal that can be considerably amplified using standard electronics.
Operating Regions of Ionizing Detectors ¨C Detector Voltage
The relationship between the applied voltage and pulse height in a detector is very complex.?Pulse height?and the number of ion pairs collected are directly related. As was written, voltages can vary widely depending upon the detector geometry, gas type, and pressure. The figure schematically indicates the different?voltage regions?for alpha, beta, and gamma rays. There are six main practical operating regions, where three (ionization, proportional, and Geiger-Mueller region) are useful for detecting ionizing radiation. These regions are shown below. The alpha curve is higher than the beta and gamma curve from the recombination region to part of the limited proportionality region due to the larger number of ion pairs produced by the initial reaction of the incident radiation.
This diagram shows the number of ion pairs generated in the gas-filled detector, which varies according to the applied voltage for constant incident radiation. The voltages can vary widely depending on the detector geometry, gas type, and pressure. This figure schematically indicates the different voltage regions for alpha, beta, and gamma rays. There are six main practical operating regions, where three (ionization, proportional, and Geiger-Mueller region) are useful for detecting ionizing radiation. Alpha particles are more ionizing than beta particles, and gamma rays, so more current is produced in the ion chamber region by alpha than beta and gamma, but the particles cannot be differentiated. Alpha particles produce more current in the proportional counting region than beta. Still, by the nature of proportional counting, it is possible to differentiate alpha, beta and gamma pulses. In the Geiger region, there is no differentiation of alpha and beta as any single ionization event in the gas results in the same current output.
?
Recombination Region.?The electric field is not large enough at low voltage to accelerate electrons and ions. The electrons and ions can recombine soon after they are produced, and only a small fraction of the produced electrons and ions reach their respective electrodes. As the detector voltage increases, however, an increasingly large fraction of the ions produced will reach the electrodes. This increase continues until the ¡°saturation¡± voltage is attained. The operating voltage range where this occurs is referred to as the?recombination region. Detectors are not operated in this region because neither the number of recombinations nor the number of ion pairs initially produced can be determined accurately.
Ionization Region. In the ionization region, an increase in voltage does not cause a substantial increase in the number of ion pairs collected. The number of ion pairs collected by the electrodes equals the number of ion pairs produced by the incident radiation. It is dependent on the type and energy of the particles or rays in the incident radiation. Therefore, in this region, the curve is flat. The voltage must be higher than the point where dissociated ion pairs can recombine. On the other hand, the voltage is not high enough to produce gas amplification (secondary ionization). Detectors in the ionization region operate at a low electric field strength, selected so that?no gas multiplication?occurs, and their current is independent of the applied voltage. They are?preferred for high radiation dose rates?because they have no ¡°dead time,¡± a phenomenon that affects the accuracy of the Geiger-Mueller tube at high dose rates.
Proportional Region. In the proportional region, the charge collected increases with a further increase in the detector voltage, while the number of primary ion pairs remains unchanged. Increasing the voltage provides the primary electrons with sufficient acceleration and energy to ionize additional atoms of the medium. These secondary ions formed are also accelerated, causing an effect known as?Townsend avalanches, which creates a single large electrical pulse. Even though there is a large number of secondary ions (about 103?¨C 105) for each primary event, the chamber is always operated such that the number of secondary ions is?proportional?to the number of primary events. It is very important because the primary ionization is dependent on the type and energy of the particles or rays in the intercepted radiation field. The number of ion pairs collected divided by the number of ion pairs produced by the primary ionization provides the gas amplification factor (denoted by A). The gas amplification in this region can increase the total amount of ionization to a measurable value. The charge amplification process greatly improves the detector¡¯s signal-to-noise ratio and reduces the subsequent electronic amplification required. The?voltage must be kept constant?when instruments are operated in the proportional region.?If a voltage remains constant, the gas amplification factor also does not change. Proportional counter detection instruments are very sensitive to low levels of radiation. Moreover, proportional counters are capable of particle identification and energy measurement (spectroscopy). Different energies of radiation and different types of radiation can be distinguished by analyzing the pulse height since they significantly differ in the primary ionization.
Limited Proportional Region. In the limited proportional region, the gas amplification factor does not continue to increase proportionally to the voltage. Additional ionizations and nonlinear effects cause no proportionality of the output signal to the deposited energy at a given applied voltage. The electric field in the chamber is distorted due to the high positive ion concentration. Free electrons are much lighter than the positive ions; thus, they are drawn toward the positive central electrode much faster than the positive ions are drawn to the chamber wall. The resulting cloud of positive ions near the electrode leads to distortions in gas multiplication. This region is usually avoided as a detection region.
Geiger-Mueller Region. In the Geiger-Mueller region, the voltage and thus the electric field are so strong that secondary avalanches can occur. These avalanches can be triggered and propagated by photons emitted by atoms excited in the original avalanche. Since these photons are not affected by the electric field, they may interact far (e.g., laterally to the axis) from the primary avalanche. The entire Geiger tube is participating in the process. A strong signal (the amplification factor can reach about 1010) is produced by these avalanches with shape and height independently of the primary ionization and the energy of the detected photon. Detectors operated in the Geiger-Mueller region can detect gamma rays and all types of charged particles that can enter the detector. These detectors are known as?Geiger counters. The main advantage of these instruments is that they usually do not require any signal amplifiers. Since the positive ions do not move far from the avalanche region, a positively charged ion cloud disturbs the electric field and terminates the avalanche process. In practice, the termination of the avalanche is improved by the use of ¡°quenching¡± techniques. In contrast to proportional counters, the energy of incident radiation particles can not be distinguished by Geiger counters since the output signal is independent of the amount and type of original ionization.
Discharge Region. Finally, at still higher voltages (above the Geiger-Mueller region), the electric field generates a continuous discharge of the medium, with the chamber no longer being sensitive to any incident ionization. This region is not used for the detection or measurement of ionizing radiation. Suppose the Geiger tube voltage is increased above the end of the plateau. In that case, the count rate increases rapidly until the onset of continuous discharge, where the tube cannot detect radiation and may be damaged.
Types of Detectors of Ionizing Radiation
As a result, there are three basic types of?gaseous ionization detectors, which are categorized according to the voltage applied to the detector:
ionization chambers,
proportional counters,
Geiger-M¨¹ller tubes.
As with other detectors, ionization chambers can be operated in current or pulse mode. In contrast, pulse mode almost always uses proportional counters or Geiger counters. Detectors of ionizing radiation can be used both for activity measurements as well as for dose measurements. The dose can be obtained with knowledge about the energy needed to form a pair of ions.
Hi Stephen.? You picture indicates it's a Victoreen 720
model 3A. Attached is the shop manual for that variant, as
well as an apdate done to a Vic 715 that addressed some
leakage issues..
Geo
----- Original Message -----
From: Stephen Nelson <steve.motorola.uranium@...>
To: [email protected]
Sent: Sat, 09 Jul 2022 18:58:12 -0400 (EDT)
Subject: [CDV700CLUB] CD V-720
Hello,
I purchased a non working CD V-720, and found the
meter "nuts" were not present which caused the meter to
not show any movement...obviously. After connecting the
meter, it seemed to be ok enough to zero, but..... most
ranges were maxed out which I take as high leakage
current from something dirty. The insides looked pretty
clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were
reduced to a ~0.5R/hr reading on the 1x scale. I cleaned
the glass insulators on the chamber with 99% IPA and a
Qtip and the chamber leakage went down to about 12 R/Hr
on the 10x range.
Looking at the schematics, I see mine is different
from what was published in 1961. I have a 8.2k resistor
across the meter, and the 470k resistor near the
potentiometer is 100K ohms. I am wondering if they made
changes in 1971 when a faint stamp shows CD calibrated
the meter. It looks like my meter was made in 1962 with
"62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of
the PCB (kept dry), and that sorda helped, bringing the
1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty
which is causing the upscale readings, and there is a
leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to
do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to
help reduce the upscale readings?
Thanks for any help, I attached the check results
with and without the chamber, name plate and? one of the
component side. I left them full resolution such that
one can zoom in if need be.
Hi Stephen.? You picture indicates it's a Victoreen 720 model 3A. Attached is the shop manual for that variant, as well as an apdate done to a Vic 715 that addressed some leakage issues..
Geo
----- Original Message ----- From: Stephen Nelson <steve.motorola.uranium@...> To: [email protected] Sent: Sat, 09 Jul 2022 18:58:12 -0400 (EDT) Subject: [CDV700CLUB] CD V-720
Hello,
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
Hi Stephen.? You picture indicates it's a Victoreen 720 model 3A. Attached is the shop manual for that variant, as well as an apdate done to a Vic 715 that addressed some leakage issues..
----- Original Message ----- From: Stephen Nelson <steve.motorola.uranium@...> To: [email protected] Sent: Sat, 09 Jul 2022 18:58:12 -0400 (EDT) Subject: [CDV700CLUB] CD V-720
Hello,
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
I purchased a non working CD V-720, and found the meter "nuts" were not present which caused the meter to not show any movement...obviously. After connecting the meter, it seemed to be ok enough to zero, but..... most ranges were maxed out which I take as high leakage current from something dirty. The insides looked pretty clean compared to others with battery leakage damage.
I removed the chamber and the leakage currents were reduced to a ~0.5R/hr reading on the 1x scale. I cleaned the glass insulators on the chamber with 99% IPA and a Qtip and the chamber leakage went down to about 12 R/Hr on the 10x range.
Looking at the schematics, I see mine is different from what was published in 1961. I have a 8.2k resistor across the meter, and the 470k resistor near the potentiometer is 100K ohms. I am wondering if they made changes in 1971 when a faint stamp shows CD calibrated the meter. It looks like my meter was made in 1962 with "62" on the meter and a 62 date code on the vacuum tube.
I scraped off the flux residue on the solder side of the PCB (kept dry), and that sorda helped, bringing the 1x leakage currents to show ~0.25 R/hr on the 1x scale.
I am thinking the glass insulators are still dirty which is causing the upscale readings, and there is a leakage path on the PCB or switch somewhere.
Questions:
What was the 470K -> 100K resistor mod supposed to do?
What is the resistor across the meter for?
Does this meter require a desiccant in the can to help reduce the upscale readings?
Thanks for any help, I attached the check results with and without the chamber, name plate and? one of the component side. I left them full resolution such that one can zoom in if need be.
Re: No.4- CD V-700 Shop Manual ENi ......... WHEW! FINALLY! The missing and most important shop manual for ENi CDV-700! Includes the retrofit version data.
----- Original Message ----- From: Ed Garrett <garrett_ew@...> To: [email protected] Sent: Thu, 09 Jun 2022 13:46:12 -0400 (EDT) Subject: Re: [CDV700CLUB] No.4- CD V-700 Shop Manual ENi ......... WHEW! FINALLY! The missing and most important shop manual for ENi CDV-700! Includes the retrofit version data.
Thanks for posting Geo.
Thank you, thank you, thank you Steve and Tanner.
Christmas certainly came early this year.
Fellow old school collector and refurber.
Ed / KJ7LSI
On 6/9/2022 8:40 AM, Geo Dowell wrote:
Now in FILES under CDV-700 Shop Manuals folder.
Many thanks to members Steve and Tanner in U.K. for dredging this up!
Like always, it's a team effort!
Geo
Re: No.4- CD V-700 Shop Manual ENi ......... WHEW! FINALLY! The missing and most important shop manual for ENi CDV-700! Includes the retrofit version data.
Many thanks to members Steve and Tanner in U.K. for dredging this
up!
Like always, it's a team effort!
Geo
No.4- CD V-700 Shop Manual ENi ......... WHEW! FINALLY! The missing and most important shop manual for ENi CDV-700! Includes the retrofit version data.
ebay has become the digital internet junk yard.? sometimes you find a gem, but you have to sort through a lot of junk.? eBay wants $$$ through seller fees and advertising.? As always, buyer beware.? and know who you are dealing with.??
David71
Ed Garrett
Michael C