Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Marantz Model 19 Scope

Does anyone know anything about these ? I know the basics but there are details missing from the print, LIKE THE PINOUT of the CRT !

I can see though (thank you Drs Budrous and Stewart) so I can see the thicker wires, those are pretty much at cathode potential, -500 volts. I can also find the deflection plates and with the centering make the DC voltages equal, still no display.

Unless there's something I missed I need to get into the grid and focus voltages and if those are all there, the CRT is bad ?

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT. Even people with experience on these things, how many receivers had built in scopes ? I saw one in another brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even very few models.

I got the other problems fixed, it had a fault on the one power amp board and a bad transistor on the tone amp board which is by the way stuck to the chassis with double sided foam tape ! For what they charged fro these things, foam tape ? And you should see the PITA it is to remove, I was thinking "This board it gonna break", but it didn't.

What you really need is a Fein cutter with an L shaped blade. (they are normally used to cut windshields out of cars)

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.
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Default Marantz Model 19 Scope

wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print, LIKE THE PINOUT of the CRT !

I can see though (thank you Drs Budrous and Stewart) so I can see the thicker wires, those are pretty much at cathode potential, -500 volts. I can also find the deflection plates and with the centering make the DC voltages equal, still no display.

Unless there's something I missed I need to get into the grid and focus voltages and if those are all there, the CRT is bad ?

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT. Even people with experience on these things, how many receivers had built in scopes ? I saw one in another brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even very few models.

I got the other problems fixed, it had a fault on the one power amp board and a bad transistor on the tone amp board which is by the way stuck to the chassis with double sided foam tape ! For what they charged fro these things, foam tape ? And you should see the PITA it is to remove, I was thinking "This board it gonna break", but it didn't.

What you really need is a Fein cutter with an L shaped blade. (they are normally used to cut windshields out of cars)

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


Pinouts here :

https://www.radiomuseum.org/tubes/tube_g3-11gj.html

replacement here (bit spendy) :

Ebay item no 254200412600
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Default Marantz Model 19 Scope

In article ,
wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print,
LIKE THE PINOUT of the CRT !


The service manual is available at HiFiEngine.com (free registration
required to download). The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000. According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT.


From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose. They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even
very few models.


Some Macintosh tuners had scopes. Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it. He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim. Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement. I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course). The Pi would capture the data, and then draw it to a 2"
color LCD.



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Default Marantz Model 19 Scope

On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt wrote:
In article ,
wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print,
LIKE THE PINOUT of the CRT !


The service manual is available at HiFiEngine.com (free registration
required to download). The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000. According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT.


From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose. They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even
very few models.


Some Macintosh tuners had scopes. Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it. He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim. Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement. I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course). The Pi would capture the data, and then draw it to a 2"
color LCD.


shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting.


NT
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Default Marantz Model 19 Scope

On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt wrote:
In article ,
wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print,
LIKE THE PINOUT of the CRT !


The service manual is available at HiFiEngine.com (free registration
required to download). The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000. According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT.


From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose. They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even
very few models.


Some Macintosh tuners had scopes. Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it. He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim. Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement. I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course). The Pi would capture the data, and then draw it to a 2"
color LCD.


shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up can
produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm

We have a problem in my industry with 13" colour tubes being over driven
by ignorant people using the wrong HV transformer (from 19" monitors)
and getting the tube into the soft X-ray range...

John :-#(#


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Default Marantz Model 19 Scope

On 27/04/2019 10:48 am, John Robertson wrote:
On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt┬* wrote:
In article ,
┬* wrote:
Does anyone know anything about these ? I know the basics but there
are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download).┬* The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000.┬* According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of automatic
weapons to get a replacement CRT.

┬*From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose.┬* They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had
built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other
than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes.┬* Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It
makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it.┬* He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim.┬* Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement.┬* I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course).┬* The Pi would capture the data, and then draw it to a 2"
color LCD.


shango66 on youtube does some good explanations re CRT emission
problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up can
produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm


We have a problem in my industry with 13" colour tubes being over driven
by ignorant people using the wrong HV transformer (from 19" monitors)
and getting the tube into the soft X-ray range...

John :-#(#


**I've had the odd X-ray and, being an inquisitive chap, I usually
examine the equipment as best as I am able. I've never found an X-ray
machine that operates below 75kV. I recall reading some years ago that
X-rays begin to be a problem at around 20kV. That said, I would imagine
a small tube like the one fitted to the Model 19 (which I also own, BTW)
would operate on a potential of around -500 Volts or so. WAY lower than
5kV.

--
Trevor Wilson
www.rageaudio.com.au

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

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Default Marantz Model 19 Scope

On 2019/04/26 6:59 p.m., Trevor Wilson wrote:
On 27/04/2019 10:48 am, John Robertson wrote:
On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt┬* wrote:
In article ,
┬* wrote:
Does anyone know anything about these ? I know the basics but there
are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download).┬* The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000.┬* According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of
automatic weapons to get a replacement CRT.

┬*From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose.┬* They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had
built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other
than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes.┬* Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It
makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it.┬* He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim.┬* Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement.┬* I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course).┬* The Pi would capture the data, and then draw it to a 2"
color LCD.

shango66 on youtube does some good explanations re CRT emission
problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up
can produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm


We have a problem in my industry with 13" colour tubes being over
driven by ignorant people using the wrong HV transformer (from 19"
monitors) and getting the tube into the soft X-ray range...

John :-#(#


**I've had the odd X-ray and, being an inquisitive chap, I usually
examine the equipment as best as I am able. I've never found an X-ray
machine that operates below 75kV. I recall reading some years ago that
X-rays begin to be a problem at around 20kV. That said, I would imagine
a small tube like the one fitted to the Model 19 (which I also own, BTW)
would operate on a potential of around -500 Volts or so. WAY lower than
5kV.


I wish you were right about 75KV being the minimum voltage to generate
X-rays, but the article suggested otherwise. I'd agree that anything
under 1000V is likely to do anything other than shock you - I've found
nothing so far to challenge that assumption.

The problem with video game repairs with using a 19" flyback on a 13"
tube is the tube is then working at upwards of 25KV, which the specs on
the tube say is dangerous. The maximum safe voltage for these 13" tubes
was around 20KV.

An interesting paper on 6BK4 tubes being driven (60KV) to give off
X-Rays, but it appears they would also generate X-Rays at voltages found
in colour TVs:

http://www.belljar.net/xray.htm

Later 6KB4 tubes had leaded glass it seems.

Well, that is enough time spent on X-Ray production for now. sure looks
like under 1KV is quite safe, and over 20KV it gets interesting.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

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Default Marantz Model 19 Scope

John Robertson wrote:



An interesting paper on 6BK4 tubes being driven (60KV) to give off
X-Rays, but it appears they would also generate X-Rays at voltages found
in colour TVs:

http://www.belljar.net/xray.htm

Later 6KB4 tubes had leaded glass it seems.

Well, that is enough time spent on X-Ray production for now. sure looks
like under 1KV is quite safe, and over 20KV it gets interesting.



** Monochrome CRTs and monitors operated with HT voltages in the range of 16 to 20kV and were made with plain glass while colour CRTs operated at voltages about 5 or 6kV higher and were made with thick leaded glass at the face.

The reason was X-ray generation.

However, seeing small kids sitting less than a metre from colour CRT screens always made me cringe.



..... Phil



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Default Marantz Model 19 Scope

On Sat, 27 Apr 2019 11:59:49 +1000, Trevor Wilson
wrote:

On 27/04/2019 10:48 am, John Robertson wrote:
On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt* wrote:
In article ,
* wrote:
Does anyone know anything about these ? I know the basics but there
are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download).* The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000.* According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of automatic
weapons to get a replacement CRT.

*From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose.* They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had
built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other
than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes.* Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It
makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it.* He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim.* Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement.* I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course).* The Pi would capture the data, and then draw it to a 2"
color LCD.

shango66 on youtube does some good explanations re CRT emission
problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up can
produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm


We have a problem in my industry with 13" colour tubes being over driven
by ignorant people using the wrong HV transformer (from 19" monitors)
and getting the tube into the soft X-ray range...

John :-#(#


**I've had the odd X-ray and, being an inquisitive chap, I usually
examine the equipment as best as I am able. I've never found an X-ray
machine that operates below 75kV. I recall reading some years ago that
X-rays begin to be a problem at around 20kV. That said, I would imagine
a small tube like the one fitted to the Model 19 (which I also own, BTW)
would operate on a potential of around -500 Volts or so. WAY lower than
5kV.


I had an HF modem with a built in scope for tuning.
I still have a 20" colour TV with a CRT, and a 5" colour portable
TV with a CRT.
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Default Marantz Model 19 Scope

On 27/04/2019 3:46 pm, John Robertson wrote:
On 2019/04/26 6:59 p.m., Trevor Wilson wrote:
On 27/04/2019 10:48 am, John Robertson wrote:
On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt┬* wrote:
In article ,
┬* wrote:
Does anyone know anything about these ? I know the basics but
there are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download).┬* The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000.┬* According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of
automatic weapons to get a replacement CRT.

┬*From what I read, it's well beyond that now... you'd need the
services
of at least four demigods, and several falling asteroids to blast one
loose.┬* They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers
had built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other
than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes.┬* Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It
makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it.┬* He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim.┬* Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement.┬* I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course).┬* The Pi would capture the data, and then draw it to a 2"
color LCD.

shango66 on youtube does some good explanations re CRT emission
problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up
can produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm


We have a problem in my industry with 13" colour tubes being over
driven by ignorant people using the wrong HV transformer (from 19"
monitors) and getting the tube into the soft X-ray range...

John :-#(#


**I've had the odd X-ray and, being an inquisitive chap, I usually
examine the equipment as best as I am able. I've never found an X-ray
machine that operates below 75kV. I recall reading some years ago that
X-rays begin to be a problem at around 20kV. That said, I would
imagine a small tube like the one fitted to the Model 19 (which I also
own, BTW) would operate on a potential of around -500 Volts or so. WAY
lower than 5kV.


I wish you were right about 75KV being the minimum voltage to generate
X-rays,


**Read what I wrote. Particularly this point:

"I recall reading some years ago that X-rays begin to be a problem at
around 20kV."


but the article suggested otherwise. I'd agree that anything
under 1000V is likely to do anything other than shock you - I've found
nothing so far to challenge that assumption.


**I've never heard of any issues surrounding X-ray production at
potentials as low as 5kV. And at the several hundred Volts on a Model 19
tube, there is zero chance of a problem.


The problem with video game repairs with using a 19" flyback on a 13"
tube is the tube is then working at upwards of 25KV, which the specs on
the tube say is dangerous. The maximum safe voltage for these 13" tubes
was around 20KV.


**Sure. Colour picture tubes are a known source of X-rays.


An interesting paper on 6BK4 tubes being driven (60KV) to give off
X-Rays, but it appears they would also generate X-Rays at voltages found
in colour TVs:

http://www.belljar.net/xray.htm

Later 6KB4 tubes had leaded glass it seems.

Well, that is enough time spent on X-Ray production for now. sure looks
like under 1KV is quite safe, and over 20KV it gets interesting.


**Which is pretty much what I said.


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On Saturday, 27 April 2019 01:48:25 UTC+1, John Robertson wrote:
On 2019/04/26 4:32 p.m., tabbypurr wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt wrote:
In article ,
wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download). The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000. According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT.

From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose. They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes. Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it. He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim. Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement. I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course). The Pi would capture the data, and then draw it to a 2"
color LCD.


shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up can
produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm

We have a problem in my industry with 13" colour tubes being over driven
by ignorant people using the wrong HV transformer (from 19" monitors)
and getting the tube into the soft X-ray range...

John :-#(#


I guess it's largely been answered Depends what voltage you're running at, how much boost & how much leeway you have with xray production. I would not consider EHT boosting until other options were exhausted. A 500v tube is not an issue though.

Medical x-rays use much higher voltages so the rays are harder, ie penetrate more.


NT
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On Saturday, April 27, 2019 at 1:46:37 AM UTC-4, John Robertson wrote:
On 2019/04/26 6:59 p.m., Trevor Wilson wrote:
On 27/04/2019 10:48 am, John Robertson wrote:
On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt┬* wrote:
In article ,
┬* wrote:
Does anyone know anything about these ? I know the basics but there
are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download).┬* The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000.┬* According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of
automatic weapons to get a replacement CRT.

┬*From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose.┬* They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had
built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other
than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes.┬* Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It
makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it.┬* He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim.┬* Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement.┬* I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course).┬* The Pi would capture the data, and then draw it to a 2"
color LCD.

shango66 on youtube does some good explanations re CRT emission
problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up
can produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm


We have a problem in my industry with 13" colour tubes being over
driven by ignorant people using the wrong HV transformer (from 19"
monitors) and getting the tube into the soft X-ray range...

John :-#(#


**I've had the odd X-ray and, being an inquisitive chap, I usually
examine the equipment as best as I am able. I've never found an X-ray
machine that operates below 75kV. I recall reading some years ago that
X-rays begin to be a problem at around 20kV. That said, I would imagine
a small tube like the one fitted to the Model 19 (which I also own, BTW)
would operate on a potential of around -500 Volts or so. WAY lower than
5kV.


I wish you were right about 75KV being the minimum voltage to generate
X-rays, but the article suggested otherwise. I'd agree that anything
under 1000V is likely to do anything other than shock you - I've found
nothing so far to challenge that assumption.

The problem with video game repairs with using a 19" flyback on a 13"
tube is the tube is then working at upwards of 25KV, which the specs on
the tube say is dangerous. The maximum safe voltage for these 13" tubes
was around 20KV.

An interesting paper on 6BK4 tubes being driven (60KV) to give off
X-Rays, but it appears they would also generate X-Rays at voltages found
in colour TVs:

http://www.belljar.net/xray.htm

Later 6KB4 tubes had leaded glass it seems.

Well, that is enough time spent on X-Ray production for now. sure looks
like under 1KV is quite safe, and over 20KV it gets interesting.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."


You triggered an old (dormant) memory. Back in the 1970s, certain GE portable TVs had a recall campaign because of excessive X-Ray emissions. GE opted to replace the glass HV rectifier with a leaded rubber jacket tube instead of building a new HV cage to retrofit the chassis. Swapping the lead coated rectifier tube took 3 minutes, and 2:50 of that was pulling off the plastic rear cover and reinstalling. I'm pretty sure I still have one of those leaded rectifier tubes somewhere.
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Thanks, it might help. However the tube socket is wired to a set of wires that do down to a socket on the board. There is no way to tell for sure the connections aren't changed from what you would get straight at the base of the tube. I haven't found a decent page on the CRT in the manual, in fact it says something like "provisional" as if they weren't quite sure whose tubes they going to use.

Having the pinout, even in low resolution is better than nothing.
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"I've been dealing with a slightly similar problem myself... I bought a CTS service monitor whose scope is working-but-dim. Fortunately it has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a local source for a used tube (and there are online sources as well). "

Have you tried boosting the filament voltage ? For one it is the best way to extend the life of a CRT, rather than rejuvinating. I wouldn't recommend that for a CRT unless it was in a TV, the color CRTs pull quite a bit of current and guess where it all comes from - the cathodes.

But scope cathodes don't get loaded heavily. they can be just as bright as a tube pulling 20 times more current easily because they are not generating a raster.

If it turns out to be weak emission in this tube I am not exactly sure how to boost the filament voltage. It seems to run off a resistive divider, but for a small tube which is a RAY type tube not a raster type it is sufficient. But then doing anything in that circuit might do something to the G1 bias or whatever.

Thing is also figuring out how to actually test the thing if/when all the other possibilities are eliminated...
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"shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting. "

I'll have to look into that. Nobody in their right mind would try to save an old CRT by boosting the main accelerating voltage.

First I will try the grid bias, if that does it fine, that is IF that is the problem and it isn't some other fault.

Thing is I just heard from the customer that he scope used to work, he actually found the burning -500 rectifier. There are no shorts currently, the new rectifier is doing fine in there.

But no trace.


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"** Monochrome CRTs and monitors operated with HT voltages in the range of 16 to 20kV and were made with plain glass while colour CRTs operated at voltages about 5 or 6kV higher and were made with thick leaded glass at the face."

"The reason was X-ray generation."


I believe that for whatever reason they started using barium for that. That was from a CRT rebuilder. We had, after the tube days, a new rating on CRTS, bars. On the bell of the tube there were either one, two or three bars right in the glass. the three bars were the only ones we could legally use in most of the newer delta gun sets. The older ones would work but well, we use the three bar tubes when called for. When they got to inline guns, even the original GE ones, (Sony was still first) they all has three bar glass.

If I remember correctly the three bar tubes were good up to 35KV.

"However, seeing small kids sitting less than a metre from colour CRT screens always made me cringe."


Kids here more like ┬Ż metre. I wonder what the physiological effects could have been. Well, it seems more people in my age group wear glasses but can we attribute that to that ? Not so sure.

I remember them saying that Xrays dropped due to gravity, though I kinda doubt it. Maybe as much as any photon would but there is no evidence I can't find now that it is any more than that miniscule drop. But they sold people on floor model TVs with it.

Actually thing about it is I would rather have a TV at or below eye level. In fact people have their monitors set at an upward angle which reflects more ambient light. I avoid that but have found that some edge lit LCD screens like in laptops simply are not designed for that.

Needless to say, this Xray **** is a hijack because this thing only has 500 volts. You get real Xrays out of that voltage maybe I will kiss your ass on public square and give you ┬Ż an hour to draw a crowd. (no beans and no mooning)
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On Sunday, 28 April 2019 20:16:35 UTC+1, wrote:
NT:

"shango66 on youtube does some good explanations re CRT emission problem fixing. Though I don't remember him discussing EHT boosting. "


I'll have to look into that. Nobody in their right mind would try to save an old CRT by boosting the main accelerating voltage.


Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it?


NT
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"Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it? "

Well you got lucky. High voltage components are particularly prone to failure even at their rated voltage and you may not have had problems, but I bet out of 10 times at least 7 would be a problem.

Another thing is what did you do about deflection sensitivity ?

How do you know it did not result in excessive Xray emission ? Piece of plywood and some photographic film in a dark room ?
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On Monday, 29 April 2019 04:03:25 UTC+1, wrote:
NT:

"Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it? "


Well you got lucky. High voltage components are particularly prone to failure even at their rated voltage and you may not have had problems, but I bet out of 10 times at least 7 would be a problem.


There is a small failure rate at the original voltage. TV parts are generally run well below parts mfrs' rated voltage to improve reliability, eg 25kV on a 40kV part, 15kV on a 25kV part. Failure rate climbs as you apply more, but it only takes a small boost, 5-10%, and the increase in failures is not great for that much. But yes it's there. However the key phrase is when all else fails. 90% beats 0% by a long way.

Cleaning the EHT stuff always helps, dirt degrades insulation capability..

Another thing is what did you do about deflection sensitivity ?


Raise B+ the same amount. In TVs the easiest way is just to raise B+ across the board.

How do you know it did not result in excessive Xray emission ? Piece of plywood and some photographic film in a dark room ?


The OP has a 500v tube. Otherwise look up the datasheet for the CRT, they're often run below rated v.

You can also use a counter. It can't measure all the tube's output, but it can measure background, and relative original & boosted outputs. Then you know what %age the increase is and can see if that's within requirements.


NT
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On Friday, April 26, 2019 at 1:22:32 PM UTC-4, wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print, LIKE THE PINOUT of the CRT !

I can see though (thank you Drs Budrous and Stewart) so I can see the thicker wires, those are pretty much at cathode potential, -500 volts. I can also find the deflection plates and with the centering make the DC voltages equal, still no display.

Unless there's something I missed I need to get into the grid and focus voltages and if those are all there, the CRT is bad ?

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT. Even people with experience on these things, how many receivers had built in scopes ? I saw one in another brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even very few models.

I got the other problems fixed, it had a fault on the one power amp board and a bad transistor on the tone amp board which is by the way stuck to the chassis with double sided foam tape ! For what they charged fro these things, foam tape ? And you should see the PITA it is to remove, I was thinking "This board it gonna break", but it didn't.

What you really need is a Fein cutter with an L shaped blade. (they are normally used to cut windshields out of cars)

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


Have you tried boosting the filament voltage ? For one it is the best way to extend the life of a CRT, rather than rejuvinating. I wouldn't recommend that for a CRT unless it was in a TV, the color CRTs pull quite a bit of current and guess where it all comes from - the cathodes.


A common trick to boost filament voltage as well as grid voltage was through the use of aftermarket transformer 'CRT boosters'...Basically a dongel that was inserted between the crt socket and the crt pins. Been so long, I forget how they were sized, and am sure you would be hard pressed to find one nowadays...



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On 2019/04/29 10:28 a.m., three_jeeps wrote:
On Friday, April 26, 2019 at 1:22:32 PM UTC-4, wrote:
Does anyone know anything about these ? I know the basics but there are details missing from the print, LIKE THE PINOUT of the CRT !

I can see though (thank you Drs Budrous and Stewart) so I can see the thicker wires, those are pretty much at cathode potential, -500 volts. I can also find the deflection plates and with the centering make the DC voltages equal, still no display.

Unless there's something I missed I need to get into the grid and focus voltages and if those are all there, the CRT is bad ?

From what I hear you would need a SWAT team and a bunch of automatic weapons to get a replacement CRT. Even people with experience on these things, how many receivers had built in scopes ? I saw one in another brand once but can't remember what it was, maybe a Kenwood ? Other than that only Marantz and then even very few models.

I got the other problems fixed, it had a fault on the one power amp board and a bad transistor on the tone amp board which is by the way stuck to the chassis with double sided foam tape ! For what they charged fro these things, foam tape ? And you should see the PITA it is to remove, I was thinking "This board it gonna break", but it didn't.

What you really need is a Fein cutter with an L shaped blade. (they are normally used to cut windshields out of cars)

Anyway, thanks in advance for anything useful on this matter. It makes a big difference in the value of the unit.


Have you tried boosting the filament voltage ? For one it is the best way to extend the life of a CRT, rather than rejuvinating. I wouldn't recommend that for a CRT unless it was in a TV, the color CRTs pull quite a bit of current and guess where it all comes from - the cathodes.


A common trick to boost filament voltage as well as grid voltage was through the use of aftermarket transformer 'CRT boosters'...Basically a dongel that was inserted between the crt socket and the crt pins. Been so long, I forget how they were sized, and am sure you would be hard pressed to find one nowadays...


These were a simple step-up auto-transformer designed for 50/60Hz. I
have one or two lying around my shop and any old radio/TV museum would
have a pile of them I'm sure.

John :-#)#

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On 4/29/19 12:50 PM, John Robertson wrote:

These were a simple step-up auto-transformer designed for 50/60Hz. I
have one or two lying around my shop and any old radio/TV museum would
have a pile of them I'm sure.


That's all well and good, but those had one of 4-5 common TV picture
tube plug/socket pairs. I seriously doubt you could find one with the
matching connectors for a ******* CRT.

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That's all well and good, but those had one of 4-5 common TV picture
tube plug/socket pairs. I seriously doubt you could find one with the
matching connectors for a ******* CRT.

I just looked on E-bay - a number of crt boosters are available. One would have to compare pinouts/sockets (for location & form factor) to see if they match. In the event they didn't match, one could break apart the sockets to expose the crimped wires and then individually mate them to the pins on the crt (and the original socket as well).
It would save a little time as compared to rolling your own.

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On Monday, 29 April 2019 19:48:36 UTC+1, three_jeeps wrote:
That's all well and good, but those had one of 4-5 common TV picture

tube plug/socket pairs. I seriously doubt you could find one with the
matching connectors for a ******* CRT.

I just looked on E-bay - a number of crt boosters are available. One would have to compare pinouts/sockets (for location & form factor) to see if they match. In the event they didn't match, one could break apart the sockets to expose the crimped wires and then individually mate them to the pins on the crt (and the original socket as well).
It would save a little time as compared to rolling your own.


With most TVs it's easier to put an extra turn on the LOPTF


NT
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On 27/04/2019 11:59, Trevor Wilson wrote:
On 27/04/2019 10:48 am, John Robertson wrote:
On 2019/04/26 4:32 p.m., wrote:
On Friday, 26 April 2019 22:45:21 UTC+1, Dave Platt┬* wrote:
In article ,
┬* wrote:
Does anyone know anything about these ? I know the basics but there
are details missing from the print,
LIKE THE PINOUT of the CRT !

The service manual is available at HiFiEngine.com (free registration
required to download).┬* The scope-module schematic is on page 62 of
the original and the tube ponout is given.

The scope V901 is "CRT with 13-pin Nixie base", Marantz part number
337-1000.┬* According to one article I read elsewhere, it's originally
a Siemens D3-II GJ.

After all of these years, I wouldn't be surprised if the cathode were
worn out (low emission) or the CRT has become gassy.

From what I hear you would need a SWAT team and a bunch of
automatic weapons to get a replacement CRT.

┬*From what I read, it's well beyond that now... you'd need the services
of at least four demigods, and several falling asteroids to blast one
loose.┬* They're probably mostly in the hands of owners of Marantz
receivers in that series, being preserved against a Time Of Need.

Even people with experience on these things, how many receivers had
built in scopes ? I saw one in another
brand once but can't remember what it was, maybe a Kenwood ? Other
than that only Marantz and then even
very few models.

Some Macintosh tuners had scopes.┬* Mac seems to have used a more
common/popular tube variety (a 3RP series), for which there are still
some used-but-good tubes available and even a few Chinese-build
clones.

Anyway, thanks in advance for anything useful on this matter. It
makes a big difference in the value of the unit.

One guy who wrote, said that he'd sold a Model 19, and had also sold a
new-old-stock replacement CRT he had for it.┬* He got more for the CRT
than for the receiver.

I've been dealing with a slightly similar problem myself... I bought a
CTS service monitor whose scope is working-but-dim.┬* Fortunately it
has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a
local source for a used tube (and there are online sources as well).

I was thinking of trying to cons up a solid-state replacement.┬* I
think one could probably be made by using a Raspberry Pi or similar
processor as a core, hooked to a reasonably fast (audio-speed)
two-channel SPI-based ADC which would sample the horizontal and
vertical deflection voltages (suitably attenuated and centered of
course).┬* The Pi would capture the data, and then draw it to a 2"
color LCD.

shango66 on youtube does some good explanations re CRT emission
problem fixing. Though I don't remember him discussing EHT boosting.


NT


Aren't you going to run the risk of X-Ray production if the EHT is
increased beyond a reasonable point? The link below says 5KV and up
can produce X-Rays:

https://www.nde-ed.org/EducationReso...generators.htm


We have a problem in my industry with 13" colour tubes being over
driven by ignorant people using the wrong HV transformer (from 19"
monitors) and getting the tube into the soft X-ray range...

John :-#(#


**I've had the odd X-ray and, being an inquisitive chap, I usually
examine the equipment as best as I am able. I've never found an X-ray
machine that operates below 75kV.


The lower keV x-rays are not useful for diagnostic purposes, because for
example, 10keV photons would be totally absorbed in your body, (still
very probably damaging your DNA), and basically none of it would make it
through to the cassette with the intensifying screen (fluorescent stuff)
and film, so it does not help with making an image of your innards. So,
to maximise the benefit and minimise the harm, medical x-ray machines
use relatively high voltages and are also required to include a filter
equivalent to a certain thickness of aluminium in the beam path between
the tube and the patient. This filter removes the lowest energy photons
(that are useless and harmful because they would be totally absorbed in
your body) without causing too much loss of the higher energy photons
that are still harmful but are also potentially useful because they have
some chance of passing through you and making an image.

All vacuum tubes will generate photons internally with some energy. Any
photons shorter in wavelength than roughly 300nm can damage your DNA,
and that corresponds to only a few volts on the anode. Whether the
vacuum tube will emit hazardous photons externally depends on whether
the photons can pass through the vacuum envelope of the tube. I would be
quite careful at 5kV or even below 5kV, if there is absolutely no
shielding other than a thin glass envelope. Whilst the tube envelope may
attenuate the x-rays by a large factor, on the other hand the anode
current, tube-to-human distance and exposure time with e.g. a RF
amplifier being serviced, might be much less favourable than in the case
of a medical x-ray. Medical x-rays usually use a few milliamps for a
second or less. Big amplifiers may run several hundreds of milliamperes
for hours. The other thing to be aware of is that many Geiger counters
are very (or totally) insensitive to 5keV photons. Whilst the Geiger
counter may tick furiously with the accelerating voltage set at 40kV,
and fall completely silent as the voltage is turned down to 5kV, that
does not necessarily mean that the x-rays have stopped, it might just
mean that they are now at a wavelength that the counter cannot detect.



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Default Marantz Model 19 Scope

On 5/4/19 9:29 AM, Chris Jones wrote:
So, to maximise the benefit and minimise the harm, medical x-ray
machines use relatively high voltages and are also required to include a
filter equivalent to a certain thickness of aluminium in the beam path
between the tube and the patient.


While working at ScanRay (airport baggage equipment) it was a
"you learn something new, everyday" when I learned they used
aluminum for lenses.
Unless you work with this stuff, it just doesn't occur to you.

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
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Default Marantz Model 19 Scope

On 05/05/2019 01:00, Fox's Mercantile wrote:
On 5/4/19 9:29 AM, Chris Jones wrote:
So, to maximise the benefit and minimise the harm, medical x-ray
machines use relatively high voltages and are also required to include
a filter equivalent to a certain thickness of aluminium in the beam
path between the tube and the patient.


While working at ScanRay (airport baggage equipment) it was a
"you learn something new, everyday" when I learned they used
aluminum for lenses.
Unless you work with this stuff, it just doesn't occur to you.


I'd never heard of any refractive optics for x-rays. I did read
something about mirrors for x-ray telescopes, but they were supposedly
very inefficient and only worked at glancing? grazing? angles. And of
course diffraction gratings can be made from crystals, and sometimes
they bend a crystal to focus a certain wavelength on a spot. Apart from
that I thought it was all basically just casting shadows.
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