Pilot Radio Company made a three inch black and white television in the
late 1940's early 1950's. It was the first television to break the
$100.00 price tag, on the low side. It's CRT IIRC was a 3RP4 with P4
phosphor. These sets are highly prized by collectors, including myself.
I have one currently under restoration, with a good CRT. Unfortunately
many of these sets do NOT have good CRT's. and the folks who have them
have resorted to using the 3RP1's and this of course is adding to their
shortage. Making clocks with them is also adding to their shortage,
along with the collector crowd.
Ira.
On 10/29/2025 4:25 PM, Tom Katt wrote:
They are hard to find for some reason lol. I stumbled upon them by
accident even though I was searching for 3RP1's. Mine just arrived
today - well packaged and factory sealed boxes. I haven't hooked them
up yet, but they are obviously new and look nice so I do not expect
any issues.
LOT OF 3 Oscilloscope Vacuum Tube 3RPI-A | eBay
<https://www.ebay.com/itm/235029032080>
On Wednesday, October 29, 2025 at 12:11:58 AM UTC-4
[email protected] wrote:
Tom,
Can you post a link to the eBay listing for the 3RP1A tubes? I
was not able to find it searching with the “I” or “1”, looking in
both current and completed listings.
Thanks,
Randy
On Oct 28, 2025, at 6:15 AM, TomJ <[email protected]> wrote:
Forgot to mention - if anyone else is considering a crt clock
project, brand new Chinese 3RP1A tubes are available from US
sellers on eBay (3 for $85 shipped). But they are listed with
the letter "I" instead of the numeral "1" - the eBay
search doesn't pick up on that, so they are easily overlooked. I
think these are the same ones that Sphere used to sell.
On Tue, Oct 28, 2025 at 6:07 AM TomJ <[email protected]> wrote:
On Mon, Oct 27, 2025 at 4:31 PM Mac Doktor
<[email protected]> wrote:
Note that over at the GeigerCounters group talking about
building negative HV power supplies can get you banned.
A couple of people found that out the hard way after
having been warned. The -900V supplies in Geiger
counters are grandfathered in, of course, and the
currents are very low.
Certainly, the voltages involved are no joke and can be
lethal. CRT voltages typically are very low current as well,
but I suspect still very dangerous. Though it seems a bit
nanny-state' to ban legitimate scientific discussions - you
can just as easily discover mortality working on your car or
a home appliance.
In any event, I also received a very informative email from
the gentleman at Sgitheach... My understanding is that the
crt tube doesn't really care - it comes down how you want to
design your circuit. Having the high potential at the cathode
makes the deflection circuit easier to implement because the
voltages are lower. BUT, if you desire to incorporate some
kind of intensity modulation or Z axis, you now have to
manage that end with high voltages. The end result from a
performance perspective will be the same.
Thanks for the insight!
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