21fbp22 red gun advice - Videokarma.org TV - Video

timmy · #1 06-26-2013, 08:46 AM

hey all i have this silvertone roundie with a weak red gun and the brightness is limited to the red gun to match the other colors. so what would be the best route to go to try to get more from this weak red gun, run the red gun on the crt tester for a few hours and see if it comes up but using the set didnt get results from that, or should i try to rejev the gun , or i have a single gun brightener for the red, which way would anyone think is best to go at this point. and with a weak gun and the other drives low to match up with the bad gun would this effect the contrast in a way that one way its soft and the other way things seem to take on black and get really dark, and the pic gets really lousy. i do remember the cutoff on the red gun was not good.

Charlie · #2 06-26-2013, 10:21 AM

I don't think you can use a brightener for just one gun. The heaters are all connected in parallel.

Have you already tried increasing the heater voltage on the tube? What were the results? How much do you have to increase the voltage before your red gun shows good on the meter?

If increasing the heater voltage brings the red gun up pretty quickly, then you have a good chance at correcting your problem just by letting it sit there for a while with the increased voltage.

Do you have a "clean" or "balance" feature on your crt tester? I would try that first. The rejuv function should always be your last choice since you can possibly do more harm than good with it.

timmy · #3 06-26-2013, 11:21 AM

well i have 2 boosters and its wired for only one gun and the 2 i have is for the red and one for green as it only has the red wired thats boosted. on the crt tester 300 is good but the rde is only 260 which is low but raising the heater voltage to 7 volts brings it up nice.

Zenith26kc20 · #4 06-26-2013, 12:03 PM

If you have to clean or rejuv the tube, use a Beltron. Some of the others are "kill or cure" machines.
I have had very successful results from a Beltron on roundies.

timmy · #5 06-26-2013, 12:07 PM

yes i know some of them kill crts like the bk 440 that i have, it can be harsh im told on crts.

timmy · #6 06-26-2013, 12:31 PM

the single gun brightener i think takes out the red gun and leaves the others alone and increase the red to whatever it does because it is for a single gun marked for the red gun and the other i have is for the green gun. so its how its wired and i think it may be isolated incase of shorts as well.

rca2000 · #7 06-26-2013, 12:40 PM

My sencore CR-70 is pretty good too, and a lot safer than the older units.

marty59 · #8 06-26-2013, 01:22 PM

Quote:

Originally Posted by timmy

the single gun brightener i think takes out the red gun and leaves the others alone and increase the red to whatever it does because it is for a single gun marked for the red gun and the other i have is for the green gun. so its how its wired and i think it may be isolated incase of shorts as well.

???????????
Timmy, as mentioned all of the filaments are in parallel so all a "CRT Booster" will do is increase (and isolate) the filament voltage and thus increase emission on all three guns. There's only one point of connection at the socket. What are you referring to?

OTOH is great to see the emissions jump up with the increase of filament voltage. Do you have a life test? I'd be curious how the other guns do just for observation initially, but you need to concentrate on that red one for sure.

timmy · #9 06-26-2013, 02:01 PM

Quote:

Originally Posted by marty59

???????????
Timmy, as mentioned all of the filaments are in parallel so all a "CRT Booster" will do is increase (and isolate) the filament voltage and thus increase emission on all three guns. There's only one point of connection at the socket. What are you referring to?

OTOH is great to see the emissions jump up with the increase of filament voltage. Do you have a life test? I'd be curious how the other guns do just for observation initially, but you need to concentrate on that red one for sure.

im not sure how itworks but i do understand that the heater voltage is one wire or one point of connection but it looks just like any other booster but one red wire no green or blue so i dont know how it works but it s in the wiring some how.

Charlie · #10 06-26-2013, 06:25 PM

Timmy, just for shits & grins, could you please post a photo of the device you are speaking of? I'm kinda curious about this.

Ya know, if ya crank that heater voltage to about 8 volts for an hour, and then let it cool, and then check that red gun again at 6 volts, you should have a good idea if it will hold up for a while.

But then, if the booster you speak of does indeed correct only one gun, then perhaps that's the way to go. Of course, the rest of us want to acquire one of those as well!!

Electronic M · #11 06-26-2013, 07:56 PM

Timmy, a booster or isolation type booster only act on the filament wires of a CRT by inserting a transformer in between the heater supply of the set and the heater of the CRT. All other wires of the socket are merely jumpered from the male to the female connector of the booster. A regular booster just steps up the voltage to the heater which increases cathode emissions due to the increased heat boiling off more electrons from the cathode. An isolation transformer is used to eliminate the DC path between the heater supply of the TV and the CRT heater to cure the symptoms caused by a heater to cathode short inside the tube. An isolation booster merely combines the functions the booster with that of the isolation transformer.
All roundy color tubes(and all color and monochrome CRTs that I know of) have only two filament pins.
Given this and the fact that there is only one filament circuit loop through the socket(meaning that the filaments for all three guns have to be wired together in series or parallel for all of them to light) there is no way for a booster, isolation type or not, to act on only one gun in a color tube.

What you describe is impossible unless it operates on vastly different principles from the vast majority of, if not all other boosters made.

You are either remembering wrong or you posses an extreme rarity that many folks here(myself included) would very much like to know the operational principles of.

I'd like to see a picture of this device as well.

rca2000 · #12 06-26-2013, 10:37 PM

Well, I DO remember. My recent hospital stint did NOT in ANY way damage my memory.

NOt sure if I have seen one myself, but I* THINK I have. I KNOW I have read about them. They seem to be a small, rectangular device, that connects to the CRT in some way to boost the emissions and NOT just raising the filamant voltage. i know They were advertised in radio--electronics. Jack Darr reviewed one, and talked about how good one did for a tube with a weak red gun. The device had a control on it that would adjust to how much "boost" was needed for the bad gun.

rca2000 · #13 06-26-2013, 10:39 PM

Seems that I remember reading they were made by someone like "Oneidea", or something like that.

mstaton · #14 06-26-2013, 11:02 PM

Quote:

Originally Posted by Electronic M

An isolation transformer is used to eliminate the DC path between the heater supply of the TV and the CRT heater to cure the symptoms caused by a heater to cathode short inside the tube.

I'd like to see a picture of this device as well.

I think you mean AC path. there are no DC filament voltages

old_coot88 · #15 06-27-2013, 10:23 AM

Quote:

Originally Posted by mstaton

I think you mean AC path. there are no DC filament voltages

By "DC path", he means the fault condition that occurs when there's a heater-cathode short. When this happens, it kills all luma (B&W signal) displayed by the CRT, while leaving the chroma display unaffected. Rapping on the neck of the CRT will usually reveal the condition, causing the luma to flash in intermittently.

An isolation booster will eliminate the "DC path" but introduces a new problem: the parasitic capacitance between the secondary and primary windings of the isolation xfmr. causes smearing-out of fine detail in the pic.