Question about testing flyback

[Aperna1985]

I have a 1951 RCA television that I can't get to produce more than 5kv of high voltage. The other day I was testing for voltages and the 6BG6 was reading low voltage or no voltage on a lot of terminals. Then I accidentally knocked the wire off the focus knob as soon as I did that I got all my voltages back. And they were close to what was specified in the Sam's. The focus wire I knocked off comes from the flyback Transformer, and connects to the focus control and then to the picture tube. I tried metering the fly back and the resistance ratings were within two or three ohms of what Sams said. Is that a reliable enough test? Or should I buy a flyback tester of some kind

[bandersen]

What model TV or chassis # ?

[jr_tech]

Perhaps the focus pot/coil is leaking/shorted to ground and drawing excessive current from the focus supply.

jr

[bandersen]

Saw on Facebook he has an RCA KCS-47GF chassis. That uses an air core flyback and should have a PM focus mechanism with a 16GP4 CRT.

Rather confused at this point
https://www.earlytelevision.org/pdf/...edata-1951.pdf

[Aperna1985]

No disrespect to anyone. I feel I've created a great deal of confusion. It's an RCA 7T111B, using a the KCSGF-2 chassis it does have a focus. It's apparently an odd set because it's throwing a lot of talented people for a loop. I'm having a hell of a time uploading the schematic so I'm sharing it on my Google Drive. The link is below


https://drive.google.com/file/d/1Wse...w?usp=drivesdk

[bandersen]

Got it. They modified that chassis to use a metal cone rectangular CRT with high voltage electrostatic focus.

Here's a photo he shared with me. High voltage focus pot and back beauty filter cap tacked onto side of HV box.

[jr_tech]

Yikes! an early rectangular metal jug with hv electrostatic focus.

https://frank.pocnet.net/sheets/127/1/17GP4.pdf

jr.

ps: that black beauty cap would be my prime suspect.

[Yamamaya42]

If C124 is the fault, then the 15 meg resistor R135 may also be a bit toasted.

Hopefully, the 1V2 did not self destruct due to overload!

[Aperna1985]

With the help of a seasoned TV restorer I was able to get an image on the screen. I'm getting ringing from the damper on the screen and still have low voltage. I'm waiting for the cap to come in the mail from Digikey, I'll report back after. Thank you to all who helped.

[Aperna1985]

Okay I went through the set again, I installed the new cap on the focus control, found one defective new cap in the damper circuit. I also found someone had replaced the socket on the 1V2 and they did a terrible job of it, the wires were making intermittent in contact. So I redid that whole section. I now have almost 15,000 volts the picture is plenty bright. But I have it changed the main filter caps yet. It's actually the only old capacitors left in the set at this point other than discs. The tuner isn't getting high voltage at the moment. So I tried to inject a signal in on the video amp. This TV has a video input which is pretty cool it connects right to the grid of the video amp. As I reach down to connect my pattern generator it actually Drew an ark. So I went to go test the voltage on that tube. What was interesting is I had no voltage on pin one pin 2 or pin 3 I had 272 on pin 6 and 50 volts on pin 7 and no voltage on Pin 8. Also will the image not lock if you don't have a video signal? I'm getting patterns on the screen but I can't seem to get it to lock and just become like a blank picture.