FOUND! ARVIN 9219-cm-uhf television.

[dtvmcdonald]

I've got a good test of the USPS running. Two large and heavy boxes of 78 RPM
records won (at minimum bid prices) at the usual record auction. Shipped by
USPS media mail last Friday. Supposed to arrive by 9 PM tomorrow, Tuesday.
Currently "in transit".

This would be some sort of record for Media Mail.

This is almost on topic: they are played on a period-correct record player also
used as the audio of a pre-war TV, albeit with a replacement 7 gram pickup and
a counterweight.

[Yamamaya42]

it DID arrive safely, in spite of FedEx's attempts to destroy it in shipment
https://i.imgur.com/JtGnIXL.jpg

it DOES need an ion trap
https://i.imgur.com/yy8qIUO.jpg


prepped to install
https://i.imgur.com/7KDNdaT.jpg

https://i.imgur.com/tef59wr.jpg
installed... still have to remove safety glass to clean it

[Yamamaya42]

I'm, almost ready to stick the chassis in this thing and see what happens with this tube now.

I may have found a way to deal with the weak tuner, not sure if it will last

https://i.imgur.com/fus0tzQ.jpg

i noticed that it is clearer in " distant" and if i use an RF amp between the modulator and the input.

then I decided to change R60 from 47k to 120k, this made a major improvement, much more contrast, no more snow in picture, GAIN BOOST,
I have no doubt that R25 is WAY out of tol, but I can't get to it cause it's part of the tuner, the others were replaced ( in the AGC area ) so I will just have to run with this tweak.

[Yamamaya42]

now how to figure out how to add a 6th connection to a CRT socket that only has 5 in it right now, and hook it to focus voltage, most likely 75v.

[Yamamaya42]

adding the missing line will be easier than I though!
https://i.imgur.com/t4DIo5M.jpg

the 21aup4a wants to be tied to the boost voltage 400+ to focus,
I wont know what the 21fp4c wants until I try it.

[Yamamaya42]

https://i.imgur.com/qS8Ih4Z.jpg

i do have to wonder, since the 21aup4a wants 400+ ( tied to pin 4 , boost ) in the SC, will the 21fp4c be the same? or will it need 95v like on pin 5 on the SC, and so on?

[dieseljeep]

Originally Posted by Yamamaya42

https://i.imgur.com/qS8Ih4Z.jpg

i do have to wonder, since the 21aup4a wants 400+ ( tied to pin 4 , boost ) in the SC, will the 21fp4c be the same? or will it need 95v like on pin 5 on the SC, and so on?

One most sets, they specify connecting pin 6 to chassis ground or to boost source though a 100K resistor. GE specs a 135 VDC source.
They all specify, which ever provides best overall focus.

[bandersen]

Another common technique is to tie pin #6 to either pins #2 or #10.

Those happen to be equal distance apart and I've seen sets that came with a metal strip with holes in the ends that you would flip one way or the other.

Bottom line, that voltage is not at all critical. You can go from 0 to 400 volts and probably not see much difference.

[dieseljeep]

Originally Posted by bandersen

Another common technique is to tie pin #6 to either pins #2 or #10.

Those happen to be equal distance apart and I've seen sets that came with a metal strip with holes in the ends that you would flip one way or the other.

Bottom line, that voltage is not at all critical. You can go from 0 to 400 volts and probably not see much difference.

Motorola usually furnished that metal strip. When replacing the CRT, I usually reinstalled the strip in the same location as the old tube. Focus was good.

[Electronic M]

I've seen some sets where the focus wire from the socket goes to a spade connector that plugs into an above chassis terminal strip with chassis ground, various B+ voltages and Boost all available on the strip, and instructions to plug the spade connector on to whichever terminal provides the best focus...It's really a check and go with whatever seems to work best scenario.

[Yamamaya42]

I just know that the 21aup4a in the stromberg carlson x-21 needs the 400+ boost st stay focused through the brightness range, anything else, it blurs.
Until last night, while using the CRT as a test subject for the Arvin chassis, the focus pin was unhooked and floating, but when I did, as mentioned, it took 400v to make the tube happy as before.

I will just have to wait and see till I drag the Arvin chassis dowstairs to where the 21fp4c is waiting to see if it will be happy with the same voltage or not.

[Yamamaya42]

first test of the 21FP4C
https://www.youtube.com/watch?v=cSrWCYWmja8


its blue! :O
https://i.imgur.com/0ykFyqZ.jpg


edit

how its set up for now
https://i.imgur.com/wAK5ZJd.jpg

[Yamamaya42]

I really don't know why it is glowing like that, but I guess it's not a problem, I DO KNOW that it is related to the focus grid, pin 6, because when it's not connected to anything just floating, no blue glow..
But if grounded, or hooked to any voltage, blue glow, even if I grab it with my hands, blue glow.
. Weird.

I still have it in a temporary setup at the moment, none of the perm hardware is on it yet, and when it all is, yoke mounting, pincushion assy, all that jazz, once all that is on, and the fine adjustment of the ion trap and focus done, we shall see, but I guess the blue glow is normal for this, and will stay.

[bandersen]

Stray electrons hitting glass likely. If it was air leaked in it would be purple.
Make doubly sure the ion trap is position correctly. If the beam hits metal it can vaporize and cause a burn on the screen.

[Yamamaya42]

Originally Posted by bandersen

Stray electrons hitting glass likely. If it was air leaked in it would be purple.
Make doubly sure the ion trap is position correctly. If the beam hits metal it can vaporize and cause a burn on the screen.

I have no reference on this CRT for the trap, other than the standard, brightness all the way down, and position for best display.