10BP4 without Ion Trap?

Originally posted by jshorva65
10BP4A used the same gun as 10BP4. The only difference was a faceplate of gray filter glass instead of clear. The 10BP4C and 10BP4D (clear and gray filter respectively) versions were the ones with aluminized screens. Aluminized-screen tubes are easily identifiable by the aluminum coating being visible particularly near the front of the "funnel" at the junction of the faceplate just ahead of the front border of the outer "dag" coating and near the anode connector where the tube was masked to keep the outer "dag" away from the HV terminal. If you see a silvery coating through the glass in these areas, the tube is probably equipped with an aluminized screen (example, 10FP4).

1. The 10BP4 and 10BP4-A require a double field ion trap.

2. The 10BP4-C and 10BP4-D require a SINGLE FIELD ion trap, even though they are aluminized.

3. There is no telling what a rebuilder might have done, but if straight guns were used for rebuilding, they most likely would have been used on the C and D versions, since these already had aluminized screens. Rebuilders usually do not replace the phosphor screen, so the A and B versions should have been rebuilt with bent guns requiring an ion trap (unless the screen was replaced, but this would make it a C or D version).

[Tubejunke]

Wow! More great information on this lost subject. I am so glad I set this project to the side instead of believing my tube needed no trap at all. No telling what damage I would have done trying to operate this set with a single field trap or no trap at all. Yes my set produces a non linear raster with no trap. I take it that the rule of thumb about no ion trap no raster does not apply to the less common double field requirement. I hope my trap gets here soon. Any thoughts on getting a double d screen border anyone?

RCA 8T-243

Tubejunke,

Were you able to see the "flags" on the gun in your tube?

[Tubejunke]

If by "flags" you mean the small metal rods that stick out of the cylinder (2 on each side) that mount it to the glass electron gun support than yes I see them. There is nothing else connected to the second cylinder. With the gun supports paralell to the chassis my HV connection will not be 12:00 but more lile 2:30. I have not got a trap yet so I am still at a standstill and working on that God awfull 58 Zenith Space Command that I have posted plenty about. Just dropped another $10 in that catastrophe. I wanted the correct 5au4 instead of 5u4. Still the same set I carried through the door. I kind of got stuck into basically a complete rebuild of this set chasing problem components with an ohm meter. By now I would have come out cheaper sending the thing to a shop and having the original problems tracked down and then brought it home and replaced things. Something on this set is above my knowledge base I guess. Maybe some transformer or disc cap. Who knows?

Here's a little sumpthin sumpthin that y'all may find interesting: D'OH!

Anthony

[Tubejunke]

Anthony, are you sure you are on the right topic? That is cool if you have NOS crts. Do you sell them? We have been talking about the lost art of the double field ion trap magnets and 10BP4 tubes and variations of the type. Is that a 10BP4 in the box. You mentioned Christmas early. You can send it to me if you want. As long as its not newer than 1966. Tell us what it is......

Nah, I don't have that bottle.....click on the "D'OH!" link above and you'll see what I'm talking about.....plus you'll smack yourself in the forehead and exclaim loudly D'OH!!!

Anthony

[jshorva65]

Looks like Tony D is the current high bidder on that 10BP4. I bought the 721TS that's currently in my display room from him and I'm extremely pleased with it. I thought I was hallucinating when I won that auction for a fully-recapped set with an excellent 10BP4 with a bid of only $200. The only peculiarity with that set is that the vertical hold takes longer to stabilize at warm-up than I expected, but after warm-up it's rock solid. Considering that the winning bid for the recapped 721TS I sold on eBay in '02 was over $1,000 I almost felt like I'd stolen that 721 at $200. The CRT in the one I sold 2 years ago was "pretty good for its age" but not "like new" although it produced an amazing picture. I had some serious bench hours in optimizing the alignment on that one.

Once I find time for a "break" to work on my own stuff, I'll check out why the picture rolls for about 2 minutes after it first appears on that set and probably take the time to optimize the IF response.

At the moment, I've just uncrated a Motorola 19CT1 with the factory 21" upgrade that was shipped here for a full recap. That one will keep me busy until the Dumont RA-104 gets here for its turn on the bench, then there's an RCA CTC5 scheduled after that.

[Tubejunke]

Yep! Your right. Smack... D'oh... Brain fart...