What could Account for This? RCA 9TC-240 Power Issue

[Chris K]

No I removed it

[Chris K]

I'd like to devise a way to 3D print a cylinder, about 2" long with an OD that fits in the yoke tunnel and an ID that will accommodate the 5AXP4 neck. The issue is the ID has to be big enough to slide over the base. If it does, then the neck won't be held in the center because there will be some play. Maybe making the ID big enough to get past the base and line the ID with adhesive foam will do the job. It wouldn't be designed to mount the CRT, just to center it. I'd still use the clamp.

[bandersen]

It shouldn't really make that much difference though. I'm literally working on one right now with the same setup.

Can you grab the CRT base while the set is running and move it around a little? Can you center the image?

[Yamamaya42]

The 5AXP4 and 10BP4 have the same neck diameter from what I see, so the only issue is how the yoke meets to the 5AXP4 and it having no support, this all should be minor stuff in the debug stage, as Bob suggested, just shift it till it is centered.
No where near as tricky as with the 8YP4 I have, :p, for that I did have to use a cardboard spacer, as it has a thin neck.

[bandersen]

I use a large clip-on clamp on the neck. Fully supported and snug against the yoke. Works just as well with the 8XP4.

[Chris K]

Originally Posted by bandersen

It shouldn't really make that much difference though. I'm literally working on one right now with the same setup.

Can you grab the CRT base while the set is running and move it around a little? Can you center the image?

I managed to get the image centered but not low enough. I did expect it to move more when I wiggled it but...it's not great but it's better than it was. I can tilt the image if I roll the yoke left or right. I do have a signal passing through that's horizontally stable but rolls and wont vertically lock and the crosshatch is mostly bunched at the bottom of the image...but I still have several caps to replace in the vertical circuit so, I'll get that done and we'll see where we are.

[Chris K]

So, I don't know if there was a consensus regarding the TV/Phono switch. Since grounding the 3rd tab on the brightness control got light on the screen, does that indicate the selection switch is bad and should be repaired/replaced or removed from the circuit? I have no intention of using the phono RCA jack for mono audio amplification so if disabling it is the easier route, I'll do that. Any long term performance or safety issue with soldering in a wire from the brightness control to ground for a permanent solution?

Thanks Guys

[bandersen]

No, none at all. The switch is supposed to connect the 3rd tab to ground. That's why I suggested you bypass it.

[Chris K]

Better. The vertical hold is quite touchy though. I don't have all the NOS tubes I ordered yet.



I have no audio. The speaker pops when I move tubes around so I think the output transformer is OK. Other than that it's completely silent.

Could the switch be causing this? If the switch was killing the brightness, could it be diverting the phono input to the volume control and disabling the TV audio? Only issue with this theory is the speaker is still silent if I touch and probe the phono RCA jack on the back with a metal screwdriver.

[bandersen]

Yes it absolutely could be

[Chris K]

Seems like the best thing would be a fabric belt like the original because these bands slip and have backlash as the stretch from winding relaxes and moves the fine tuning wheel a slight amount. But it's the best thing I can find at this time. I used two 2 1/2" X 1/3" bands held together with a little super glue.

[Chris K]

How in the world do you clean this tuner? It’s in a bank vault!

[bandersen]

You have to disconnect the wires and unmount it. I wouldn't bother unless you are having problems.

[Chris K]

Yeah…not gonna do that. It’s just stiff and feels like it has a lot of gunk in there. Maybe I’ll spray a bit of contact cleaner in through one of the holes and be done with it.

[Chris K]

I'd like some advice regarding removal of the TV/Phono switch from the circuit. It's not exactly part of the title of this thread but I don't want to start another thread on the same TV...if I understand SOP here. If I should move this to the start of a separate thread, then please let me know.

Yesterday, the Riders service manual I purchased, Volume 4, arrived at my house. In it is the wiring diagram and schematic for the 9TC-240 with the KCS28B1 chassis. The switch on the wiring diagram and schematic is pictured below.





So if I understand what has been described earlier in the thread, if the switch is moved to the phono position, the TV brightness control ground is interrupted and the screen goes dark. There's still HV however. The sound circuit then comes out of pin 5 of the 6AL5 discriminator as coaxial to the switch where it picks up audio input from the RCA jack and is brought back into the sound circuit as a grounded coax line. Around there I get lost! To me it seems the signal goes to terminal 3 of the volume control and out of terminal 2 as coax to pin 1 of the 6AV6 bias clamp???

Below is the WD at the volume control.



The yellow and green coax are from the switch.

I need to understand how this all works with the goal being removal of all the switch wiring and circuitry interruptions. I'd like to just cut it all out and wire the sound like any TV would be without this feature.