Starting a Restoration on a 1951 RCA 7T111B

[Aperna1985]

I think the set does cut the tube off in phono mode. I have the chassis back in the cabinet and I have everything plugged in like it should be, I even replaced the dial light bulbs.

When the chassis was out I sprayed all the controls with contact cleaner a few times to get the gunk and dirt out then control cleaner and worked them back and forth. I think they're good.

I tested all the vacuum tubes and replaced the tired ones. My tube tester does have a plate cap, so I tested the horizontal output tube, and the high voltage rectifyer tubes.

I do have a set of test sockets that let me plug a tube in to the Tv chassis and give me tabs where I can check voltages. I don't have a scope, but I do have a DVOM that goes up to 600v.

The thing I find interesting is if I switch modes quickly I'll get a couple lines on the screen for a split second. I'm wondering if I'm not getting a negative voltage somewhere and flipping the switch is similating it?

I'm not sure if I'm looking at things the right way, but to get any kind of picture even a bad one, I need to get the horizontal running so I can get the line in the middle of the screen, then the vertical to fill the screen right?

But to get the horizontal working I need to look at the horizontal oscillator then the horizontal output? I'm trying to piece it all together from reading online and watching YouTube, and trying to find an order I should work in.

[Notimetolooz]

There is another test you can do on the horizontal that doesn't use any typical test equipment.
It requires that you have a fluorescent bulb however and they might be on their way out. Replaced with LED bulbs. The bulb does not have to work in a socket.

Hold the bulb near the flyback or horizontal output tube and it should glow.
It doesn't tell you the frequency is right and it doesn't tell you that the DC HV for the CRT is there. It is just another test.


Are you sure about the voltages on the CRT base? They could momentarily change when you change that switch.

[Kevin Kuehn]

After spraying controls don't overlook that the brightness control needs to be turned up in order to see a raster. Next step is to see if all DC voltages look reasonable at the CRT socket pins.