Discharging High Voltage on RCA CTC-5

[TVBeeGee]

Any advice on how to SAFELY discharge the ultor on a RCA CTC-5 with the metal 21AXP22 CRT? I have not done this type before. Looks like the connection to the tube is buried behind the insulator surrounding the entire tube and the other end of the lead connects directly to a chassis connector at the high voltage cage. Unplugging the charged cable from the chassis seems like a really bad idea (shocking!), so can this be done by a method that avoids electrocution?

[Electronic M]

Originally Posted by TVBeeGee

Any advice on how to SAFELY discharge the ultor on a RCA CTC-5 with the metal 21AXP22 CRT? I have not done this type before. Looks like the connection to the tube is buried behind the insulator surrounding the entire tube and the other end of the lead connects directly to a chassis connector at the high voltage cage. Unplugging the charged cable from the chassis seems like a really bad idea (shocking!), so can this be done by a method that avoids electrocution?

On mine I would unplug the HV lead from outside the box (there's a factory cardboard handle on the wire of mine for that) and direct the tip to touch the chassis to short out the HV (not a bad idea to leave it touching the metal CRT mounts to avoid HV bounce back).

HV especially when the set is off shouldn't kill you (unless you have a heart condition).... You'll screw up and and body discharge a CRT eventually Lord knows I've done that MANY times.... After you come up with new combinations of cuss words you'll get used to it and find it more of an annoyance than anything.

[old_tv_nut]

Just as an irrelevant item of curiosity, I wonder how much HV bounceback there is with the metal cone CRT and the dielectric being the plastic shroud instead of CRT glass (not going to do a touch test to find out, though).

[old_coot88]

Originally Posted by old_tv_nut

Just as an irrelevant item of curiosity, I wonder how much HV bounceback there is with the metal cone CRT and the dielectric being the plastic shroud instead of CRT glass.

Edit, delete. I was thinkin' in terms of a B&W CRT.

[JohnCT]

Originally Posted by TVBeeGee

Any advice on how to SAFELY discharge the ultor on a RCA CTC-5 with the metal 21AXP22 CRT? I have not done this type before. Looks like the connection to the tube is buried behind the insulator surrounding the entire tube and the other end of the lead connects directly to a chassis connector at the high voltage cage. Unplugging the charged cable from the chassis seems like a really bad idea (shocking!), so can this be done by a method that avoids electrocution?

I don't know if the 5 is like the 9 or 11, but the first second anode shock I got was at the hands of one of these beasties.

My dad handed me a HV rectifier and asked me to change it in a 9 or 11. I rocked the tube but it wouldn't budge out of the socket. I figured it had the two alligator teeth spring locks so I slide my hand down around the 3A3 to release the springs and got whacked. I pulled my hand out of the cage opening and scalloped the back of my wrist and hand but good. Turns out the 3A3 socket was mounted on a metal base (corona ring?) directly connected to the second anode.

The point (other than rooting around for sympathy) is that if the CTC5 is like the later versions, simply sliding a screwdriver down the side of the rectifier while keeping contact with the cage will discharge it right at the rectifier socket base.

Take a flashlight and see if the rectifier socket is a metal base.

John

[TVBeeGee]

Thanks for all the terrific answers. I haven't actually taken possession of the CTC-5 just yet. The seller is storing it for me for a few weeks. I'll post what I find as soon as I get to the TV and start to dig into removing the chassis.

Meanwhile, you might enjoy this little story: The first CRT shock I ever got was way back when I was just 14. I built an EICO 460 oscilloscope kit. While calibrating it during the first power up, I went to turn the chassis around to get better access to a control. With one hand quite firmly on the chassis and my eyes fixed on the adjustment I was trying to reach, I reached around the top of the naked scope and stupidly brushed my other hand across the top of the Intensity or Focus pot. It just happened to have the second anode 1,600 Volts on it.

Yeoww! It went up one arm, across my shoulders and down the other arm...and lit my eyeballs up REAL good! Fortunately, I jerked away before anything serious happened, but I was gasping for air for a few minutes afterward.

Ever since then, I've been EXTREMELY careful with high voltage supplies...and I've never gotten bitten again. I hope that luck continues! And that's why I wanted to check with you folks first. Nice to have the benefit of your experience. Thanks!

[bgadow]

I was tinkering with my CTC-5 tonight (it has some minor but annoying intermittents that I've been trying to trace). Believe me, I've had that chassis out more times than I can count. Never any drama with that HV connection. I've never noticed even the slightest spark, even when it was just powered off prior to be pulling it. I will usually try to touch the lead to something inside the cage before yanking it all the way out.

I've never been bitten by really HV voltage; I think the most was 2kv from a 3" Pilot TV. That was plenty enough!

[DavGoodlin]

Replacing a regulator tube 6EH4 compactron version in the case of a '68 GE, (or 6BK4 in RCA/Mag) cap after a power up to rule out regulator as cause of intermittent blink-off of HV, whilst leaning over the cast-aluminum escutcheon of the GE with a 25UP22 fluoride tube, sent me across my room backwards. Problem was an intermittent 6BH11 hor osc tube