[NJARC] Museum Needs CRT

Sat Mar 25 20:35:33 EDT 2017

Well, the good news is that I got an entire wall-o-crap sorted out in the
search for that CRT:

[image: Inline image 1]

The BETTER news is that - despite the odds - I finally found it:

[image: Inline image 2]

[image: Inline image 3]

[image: Inline image 4]

And yes, it's a 'shortie.'  I hadn't recalled that it was considerably
shorter than a standard 3" CRT, but it is.  Untested, but judging by the
visual condition of the screen, it appears to be unused.

-- Dave

On Sat, Mar 25, 2017 at 3:29 PM, David Sica <dave at sicaproductions.com>
wrote:

> I can never keep the technical information on most subjects in my head
> like some people seem to be able to do, so I went to look for it. Here's
> what I came up with quickly:
>
> http://www.antiqueradios.com/forums/viewtopic.php?t=122582
>
> http://www.thevalvepage.com/teletech/crt_rej/crt_rej.htm
>
> The Raytronic "CRT Beamer" is known by some as the Cadillac of CRT
> testers/rejuvinators, and by others as a heavy-handed CRT killer.  I just
> got a NIB one; restoring it should be about as easy as it gets as there are
> only 7 parts inside that will likely need to be changed out.
> http://www.myvintagetv.com/Apple%20PDF%20files/Raytronic%20Manual.pdf
>
> Google will, as usual, bring up more info that you're likely to ever want.
>
> As I'm sure you know, it's fairly difficult to burn out a filament with
> even a moderately extreme overvoltage, so although there's risk involved,
> it's not as much as people intuitively expect.  In rebuilding CRTs at the
> Early Television Museum, I believe that 6.3 volt tubes were run at twice
> that voltage for a considerable period of time during cathode activation.
> The issue of stripping off active cathode material is, however, a different
> story and one I don't currently know much about.
>
> Have you tried running the tube on a brightener (either a commercial
> product or a jerry-rigged version?)  I believe that most of these boost the
> filament voltage from the nominal 6.3 to around 8 or 9. You can easily
> simulate this using a separate transformer or power supply to see what
> happens.
>
> Usually folks resort to rejuvenation when the original tube is deemed no
> longer usable.  Since the one we have there is, as I understand it,
> weak-but-usable, I'd proceed with great caution, as you have.
>
> I poked through a few cubic yards of treasure, but haven't found my stash
> of 3RP1s yet.  I will put a bit more time into the hunt later today.  Wish
> me luck and send a search dog if I don't show up tomorrow.
>
> -- Dave
>
>
>
>
> On Sat, Mar 25, 2017 at 1:41 PM, Al Klase <ark at ar88.net> wrote:
>
>>

> Hi Dave,
>>
>> Please dig out an 3RP1 if you can.
>>
>> I took a shot at rejuvenating the one here without much success.
>>
>>
>>
>> I ran 9 VDC on the heater for an hour, pulling 20 mA from a 140 VDC
>> supply through a 4.7K resistor.  Then turned off the DC, and reduced the
>> heater to 6 VDC for half an hour.  Display doesn't seem much brighter, and
>> I felt like I never detected an increase in emission.  Do I need to draw
>> more current?
>>
>> Do any of you have a handle on this procedure?
>>
>> Thanks,
>> Al
>>
>> On 3/24/2017 2:39 PM, David Sica wrote:
>>
>> I'm pretty sure I have a couple of 3RP1s lying around.   As a
>> "don't-force-it-get-a-bigger-hammer" substitute for the Pilot TV CRT, I
>> pick them up whenever I run across one inexpensively.
>>
>> The trick, as usual, will be to actually locate it in the endless piles
>> of radio merriment in the basement.
>>
>> Have you considered rejuvenating the existing tube or wiring in a
>> brightener?  There's a decent chance that one or the other of those tricks
>> will help, possibly for quite a while.
>>
>> I expect to be at InfoAge on Sunday afternoon; I'll let you know if I
>> find one and if I do, I'll leave it at the museum for you.
>>
>> -- Dave Sica
>>
>> On Fri, Mar 24, 2017 at 12:16 PM, Al Klase <ark at ar88.net> wrote:
>>
>>>
>>> _________________________________________________________
>>> Folks,
>>>
>>> Last week the RTM received a generous donation of Marantz stereo
>>> equipment, including a 10B tuner.  This is a timely event as we're getting
>>> ready to rearrange the displays to highlight recorded music.
>>>
>>> The 10B cost $650 in 1965 which is about 5 Grand in today's cash. It's a
>>> thing of beauty.  Looks like military electronics on the inside.  After
>>> clearing away five decades of grime and a little TLC it works quite well.
>>> See: http://www.ar88.net/audio/10B%20Scope.m4v
>>>
>>> Of course the built-in oscilloscope is the best part, but I had to shoot
>>> that video in a darkened room.  We need a new CRT.
>>>
>>> It's a 3" CRT known variously as DG-32, 3RP1, or CV2431.  It's shorter
>>> than the common 3BP1, and operates at lower voltage.  I can buy one for
>>> about $65, but thought I'd ask the group first.
>>>
>>> The donation also included a Model 7 preamp, an 8B power amp, two large
>>> speakers, and an Ampex home-sized tape deck.  Cool stuff!
>>>
>>> Check your junk boxes,
>>> Al
>>>
>>> --
>>> Al Klase – N3FRQ
>>> Jersey City, NJ
>>> http://www.skywaves.ar88.net/
>>>
>>
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