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Lucifer[_6_] Lucifer[_6_] is offline
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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.