Pilot tv brightness issue - Videokarma.org TV - Video

timmy · #1 12-02-2018, 05:25 PM

Ok so I have this pilot tv with a 3kp1 of course and it works great however the brightness is just not there as I know it's got the green tube and are not usually bright but I feel it should be brighter and it's not, any quick ideas would be a great help. All the tubes are nos and tested again. I do have a filiment trans tied in for the crt and that's good .I had also put a diode under the IIRC 35w4 because the b+ was on the low side when I restored this set so I don't know if that would have anything to do with low brightness. Maybe someone here had the same issue and was able to cure it quickly without tearing into the whole chassis but if I have to well that's ok to. I plan on checking the cathode voltage at pin 3 of the crt which should be 185 Vdc from there I may check voltages at the brightness pot.

***Kamakiri*** · #2 12-03-2018, 06:42 AM

I have a Pilot with a 3KP1. Let's see a screen shot.

timmy · #3 12-03-2018, 08:21 AM

Well this iPad does not take a good pic of this pilot, so this is a dud. Not to mention it's upside down, lol.

timmy · #4 12-03-2018, 08:24 AM

In well lit room it's hard to see the pic it could also use more contrast to darken it a bit which would help. No matter what the screen shot is going to look good but it's not.

Electronic M · #5 12-03-2018, 09:16 AM

Most sets of the day were meant to be used in subdued room lightning. Curtains drawn, lamps placed to not place light on the screen, etc...if it looks dim under those conditions you have a problem, but don't expect it to compete with a SS era CRT.

timmy · #6 12-03-2018, 09:25 AM

How can I increase the dark level in the pic there's not enough. Alittle darker will help.

Electronic M · #7 12-03-2018, 09:29 AM

For an easy fix to weak contrast replace the video amp tubes and video IF tubes with the strongest ones you can get.

I don't think this set has AGC but if it does try adjusting that before tube swapping.

timmy · #8 12-03-2018, 10:14 AM

I guess you mean higher gain ? Well I can't seem to find a high gain tube list for substitute tubes like the 6ba6 and the 6au6.

mrjukebox160 · #9 12-03-2018, 08:17 PM

I think he means the strongest testing tubes you have.

jr_tech · #10 12-03-2018, 08:20 PM

For comparison, here are a couple shots of mine when I had the P1 jug in it:

Normal roomlight (room glare obscures information on right side)

Total darkness:

Both are iPad shots.

jr

timmy · #11 12-04-2018, 05:41 AM

Lots more contrast in this pic , if I had that much I would not really worry about the brightness.

Tom9589 · #12 12-04-2018, 08:44 AM

Tom C. is right. This set doesn't not have AGC per se. However, the contrast control varies the gain of the RF amp and the 1st, 2nd and 3rd IF amplifiers. You might also trouble shoot the DC restoration circuit as it applies DC bias directly to the CRT grid and could affect brightness directly. There is an electrolytic (C5 on the SAMS) that could affect this circuit.

timmy · #13 12-04-2018, 01:04 PM

Well all the electrolytics are new and for the tubes I only put the best in there, very good reading tubes . The first pic above shows a good pic with contrast so if I had that contrast I think I'll let the brightness go because maybe it's no so much the brightness but rather the contrast that's lacking because it does need more contrast. I'll try to post another pic this time clearer.

Dave A · #14 12-04-2018, 01:17 PM

Could the RF you are sending to the set be low to start with? That would max out the contrast control and it still wants more.

timmy · #15 12-04-2018, 01:36 PM

Quote:

Originally Posted by Dave A

Could the RF you are sending to the set be low to start with? That would max out the contrast control and it still wants more.

I'm using an RF amplifier already so I don't think it's that.