Hi
£55 is expensive - you should be able to get them for £30.
Have you tied the deflection plates to A2 for testing purposes or left
them floating? They should be tied to A2.
Can you turn the brightness pot down to fully extinguish the dot? If not
you need to be able to.
Grahame
On 25/11/2023 18:28, Max DN wrote:
@Grahame
Thanks for the suggestion. I didn't know about CV2302 DH3-91, I see
Langrex is selling it for £55 on eBay.
Yes, my voltages were off. I have made some changes:
Cathode is now -350V to ground
A1 is +30V above cathode
A2 is +150V above ground, that is +500V above cathode
I'm having some problems with Grid voltage, I'm guessing...
@gregebert
This is the pinout I'm using:
Pins 1-14 heater
Pin 2 Cathode
Pin 3 Grid G1
Pin 4 A1 (focus anode)
Pin 5 n/c
Pin 6 Grid G2
Pin 7 X1
Pin 8 X2
Pin 9 A2 (acceleration anode)
Pin 10 Y1
Pin 11 Y2
Pin 12 Grid G3
Pin 13 n/c
Pins 3-6-12 are all internally connected, other than on mine 3 is no
longer soldered on the grid.
Pin 3 or 6 or 12 (Grid) is connected to -525V (that's 40V above -485V
negative voltage doubler in Cathode Corner's schematic), still not
good (pic attached). I connected a few resistors in series 500k, then
1M to bring voltage down up to -250V, with not much difference. So
it's clear I don't understand how to connect the Grid pin!!
I did find a schematic here (suggests to reduce max negative voltage
rail to -300V):
https://www.catahoulatech.com/index.php?product=KIT-0001
https://www.catahoulatech.com/products/KIT-0001/OscilloscopeCrtDriverData.pdf
I also find something else that is exactly what I'm trying to do. It's
using different POTs and +350V vs -350V (whereas I'm using +250V and
-485V)... Schematic attached.
Il giorno sabato 25 novembre 2023 alle 10:07:25 UTC Grahame ha scritto:
Hi Max
https://threeneurons.files.wordpress.com/2015/05/3lo1i.pdf
gives the normal operation acceleration anode A2 voltage as 500V
(WRT cathode) and the focus anode A1 as 0 to 50V. Your voltages
are higher, especially the focus anode voltage. Hence the green
splat rather than a dot.
My experience with this tube and the 6LO1i which is the slightly
larger rectangular version is very poor. The phosphor literally
turned grey, then black and the light emission faded over a couple
of months in use. It wasn't that the phosphor burned with the
image but the phosphor greyed uniformly. Most odd. Might have it
been a bad batch of tubes? IIRC someone else has seen this effect.
If you want a small tube then look out for a 1CP1 or DH3-91 or
CV2302 would be my suggestion.
Grahame
On 24/11/2023 22:49, Max DN wrote:
Hello,
I managed to successfully build a scope clock almost entirely
based on Cathode Corner design using CRT 3RP1A.
I happen to have a 3LO1i (I know it only lasts for 1000 hours...)
and I tried to modify the voltage doublers to use my circuit with
this CRT but I'm not too sure about the correct voltages. At the
moment I have:
Grid: -480V; HTR2: -380V; HTR1: -384V; HTR1-HRT2: 6.3VDC; CATH:
-384V; A1: -248V; A2: +200V
However I cannot get a small green dot, only a wide green shade,
picture attached.
I'm sure I'm doing something wrong with the voltage divider. Any
suggestions please?
Thank you,
Max
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