Another local Hoffman! COLOR!

[Yamamaya42]

https://www.youtube.com/watch?v=pHtgBbdJNqo

LED upgrade complete!

[Yamamaya42]

It's getting close to the point to where I'm gonna need to fix the cataract on the CRT.

There is pretty much little left to do on the chassis now. :O

The greyscale setup in the SAMS is a bit odd, of diff from what I have seen before, this may be cause it's a set with a POT for bias and not a switch.
but that last step of turning it up till it blooms, then backing off, seems a bit odd to me. :O


http://suzaku.live-evil.org/greyscale.jpg

[Yamamaya42]

Speaking of the cataract repair, since I have never done this type before, I was thinking of using,
Nichrome-28-Gauge-Resistance-Wire, and heating via a filament transformer on variac and pulling it through.

I have seen a video or 2 of people using this method, and it worked rather well, does 28 gauge sound about right?

[old_tv_nut]

Originally Posted by Yamamaya42

https://www.youtube.com/watch?v=pHtgBbdJNqo

LED upgrade complete!

[Yamamaya42]

https://www.youtube.com/watch?v=J1Iu4QmVs9w
getting closer to done.

[Yamamaya42]

I have also noticed that I can't bring the picture into full focus, I'm at the max I cant adjust the focus coil and it's the best it can get, the 66m seems OK at about 70m and the 2w 4.7m load resistor to the focus grid seems fine as well, so I'm pretty sure the selenium focus diode is tired, but I don't wanna put another one like it in there.

I have 10 cheapy 20KV 5mA HV High Voltage Rectifier Diodes I'm pretty sure that 2 in parallel should be more than enough to handle it.

[Yamamaya42]

original focus diode specs

ECG503(NTE503)/RCA # SK3068
PRV: 14,400 Volts (No Load)
Forward Current IF: 0.5mA
Forward Voltage Drop VF: 260V @ 2.5.mA


i have 10 of these
Rectifier 2CL77

https://digchip.com/datasheets/parts.../2CL77-pdf.php

it SHOULD work IMOH,

[Yamamaya42]

I can already tell that convergence is going to be a pain in the ass on this set, even though I'm going to have to pull all things off the CRT for safety's sake when I attempt the cataract repair, I have already tried convergence a few times to see how it's going to behave.

First off, I DO NOT like the convergence clover on this set, it sits way too loose on the neck, held in place by spring clamps, way too easy to shift it's position when you try to turn the static adjustment magnets,(discs) which are in an awkward position and hard to turn, I might try to lube them up a bit to make them glide a bit better.

The dynamic convergence is showing signs of trouble, this is not unexpected as I have not gone over the convergence PCB yet, I fully expect the diode array to be tired and out of spec, have already ordered a replacement NTE120, would not be surprised to find worn resistors, just know I'm seeing the same type of non linearity that can't quite be adjusted out that I have seen before when there are parts worn on the convergence PCB.

The old focus rectifier was replaced this weekend by 4 of the cheepy 20kv diodes, 2 in series , in parallel, seems to be holding up OK, and made a slight improvement in focus range.

[Yamamaya42]

X-ray hazard or hyped up scare?

I have run this set a few times now w/o any problems, but have noticed the FBT gets slightly warm, not TOO hot, but warm to the touch after it's off. (slight smell of warm corona dope. :P )
Right now the cover to the HV box is removed, I'm thinking of keeping it of like I have in my GE set, because I have found that if I place a fan right in front (120mm), then it has a drastic improvement on cooling, I felt NO warmth at all after running it for quite some time.

So I have to wonder, is the unshielded X-ray risk from the 3A3C/6BK4C really that big a deal?
Were they just being overly cautious? By leaving it off one is not going to end up like Zaphod Beeblebrox or something 2 heads & 3 arms?

Inquiring minds want to know!

[old_tv_nut]

The high voltage rectifier should not be a significant source of x-rays as far as I can figure - The voltage across it is low when it's conducting and high when it's not conducting.

The high voltage regulator, however, has high voltage on it while conducting. If all the elements are aligned well, the internal elements provide quite a bit of shielding; the scare started with tubes that were improperly constructed. If no one is going to be below the bottom of the regulator, and you keep some distance, it's probably OK. The caution I would add is that I don't know how to differentiate between a proper and improper tube by eye.

[old_tv_nut]

Remember that the danger is cumulative increase in the risk of cancer. There is no particular threshold of safe/not safe. That's why the dental technician steps out of the room to press the X-ray button, not because of immediate effects. In the same way, TV X-ray limits were set so that no consumer could get a significant increase in radiation dosage from them in a lifetime. But techs were expected to heed warning labels when they opened a set.

[Yamamaya42]

http://www.nj7p.org/Tubes/PDFs/Frank...ania/6BK4C.pdf

It has a warning about "close range" ,not sure how to define that.

The set has a 6bk4c vs a 6bk4b as it was built for, which is an improvement.
And it's pointed backwards horizontally in it's own section at the top of the HV box.
Much like the CTC-16(XL), which has it mounted vertically behind the HV box also walled in it's own section with no top, oddly enough.

So the way I sort of see it, using the improved tubes over what was originally designed, 3A3A->3A3C & 6Bk4B → 6Bk4C, any risk should be minimal, for instance what is the difference in this situation with the shunt top open facing backwards ( back on set ), and the CTC-16 line with it pointing up?

Perhaps... don't sit on top of a CTC-16, or you will glow in the dark!

[Tom9589]

I remember an urban legend that surfaced when they were having problems with these shunt regulator tubes. The story goes that a woman had a cat which liked to nap under the new console color TV because it was warm. After a while, the cat started losing its fur. The vet diagnosed radiation exposure. The woman complained to the TV dealer who escalated the problem higher up until the radiation was measured underneath the console and found to be excessive.

Moral of the story: Don't let your cat nap under your console color TV.

[old_tv_nut]

The X-rays don't come out the top of the tube, they come out the bottom. The limits for complete sets with shielding in place were tested at the outer surface of the cabinet. If you look at the regulations for TV sets, and compare the intensity in a complete set to the value from the tube itself you will get some idea, but note that the tests are done with the set deliberately run to maximize X-rays.

https://www.fda.gov/radiation-emitti...2015%2C%201970.

"A Federal standard limiting x-ray emissions from TV receivers to 0.5 milliroentgen per hour (mR/hr) was issued on December 25, 1969. The standard is applicable to all TV sets manufactured after January 15, 1970. The overall effect of the standard is to require that TV receivers must not emit x-radiation above the 0.5 mR/hr level when tested under adverse operating conditions. Test conditions do not represent normal use and ensure that when used under normal conditions, TV sets do not pose a radiation hazard."

[old_tv_nut]

I believe the big cup at the bottom of the 6BK4B is the added shielding.