Picture Tube Swap - Videokarma.org TV - Video

refill233 · #1 01-30-2007, 05:39 AM

I have a set that has a metal picture tube (16GP4) that is about gone.I have found a (16WP4A) that looks like it may work.Any help on this swap will be
alot of help to me.Thanks.

jpdylon · #2 01-30-2007, 10:47 AM

The problem you are going to run into is in two places. 1. mounting, 2. HV supply.

The 16WP4a is an all glass tube, and cannot be used in the original mounting configuration. Depending on how the tube is held in (is it chassis mounted or cabinet mounted?) you can make a strap and hardware that will hold the tube in place, but its not easy, and pressure points on the tube will cause it to tail and send glass flying into you!

The other concern is the HV lead. You will need to steal one out of a newer set or a computer monitor to replace the one that clips onto the metal shell. This in itself is not difficult unless the HV rectifier socket is hard to get to.

is there any way you can get a shot of how the 16GP4 is mounted?

refill233 · #3 01-30-2007, 11:56 AM

Thanks for the fast reply.The tube is chassis mounted with a strap around the
picture tube.It is an HALLICRAFTER MODEL 818.The anode will not be any
problem to replace.I think the 16WP4A takes a double ion trap and the 16GP4
uses a single?Got a super deal on this 16WP4A if i can get it to work.I might
have some trouble finding the double ion trap, but i think you may have saved my set.

jpdylon · #4 01-30-2007, 12:57 PM

yes the GP4 uses only the single field ion trap, so you'll need to find a dual field. I would also consider buying some thin foam tape to put along the inside of the strap so it will not bite into the tube when you strap it in. i would also hold the tube in place on the chassis to make sure the CRT will clear chassis parts. You wouldn't want it to hit anything like a filter or tube.

good luck!

refill233 · #5 01-30-2007, 02:55 PM

Looks like i found a good site.You sure helped alot!I have been reading the forums here and looks like alot of knowledge can be had by only asking.Again many thanks for all your help.

Tubejunke · #6 01-30-2007, 09:33 PM

I would think that there may be a little more to this than shoving another crt in the space the old one came from. Besides physical charictaristics I would think that there would be some electrical differences. I know focusing methods can vary and cause swap trouble.

Are all of the old electron guns the same except for ion trap type? I know most of the filament voltages are the same but are the pin configuration and electrical charictaristics the same?

At least some things to consider.....

jpdylon · #7 01-30-2007, 10:18 PM

The tubes have very similar characteristics. Same focusing method. The only differences are physical characteristics (all wp4 is all glass, and 18-1/2" long instead of metal shell and 17-11/16" long), and higher anode voltage (16k vs 14k for the GP4), and of course the dual field ion trap (instead of the single bent-gun type for the GP4) If he can physically fit it in his application, he has nothing to worry about. Grid voltages and the like are identical.

refill233 · #8 01-31-2007, 05:20 AM

I may have some hv problems now (14k=GP4).I checked the hv with my probe
and max is 11k.Sams (set-124,folder-6)says about 13k on it.Well the 2k
difference may be hurting me some but the screen is so dim you have to turn out the light to see it.Adjusted the trap and it did help but not very much.So
what do you suggest i do ? Maybe a leaky cap? Where? This set has been a bear to get this far with it.I have replaced all output tubes and the hv rect with new ones.Forgot to tell you i replaced some capacitors but mostly in the vert. and horiz.circuits.A couple resistors that was way off value.To top it off the tuner is being rebuilt at Quality Tuner (nice guy).Tried a Beltron Restorer
on it and no go.So i don't know if the tube has been restored before or not.A
brightener sure helps alot so i came to the conclusion that i had a bad tube.
Open for any suggestions on how to proceed with this.I was about to give up
until i found this site and all the great help.So, with the help here, the OLD SETS have a good chance of living again.They are a very important part
of our past.Thanks Again-Don.

jpdylon · #9 01-31-2007, 10:41 AM

hey Don,

Have you put the tube on a tester yet to see what its emission is?

as far as high voltage goes you should be just fine with 13k B&w does not need to have exact high voltage to maintain luminance. 11k you should still see a good pic. Does it bloom when you crank the brightness? if so, then it is an HV problem, if not then it is a CRT problem

Look at your service data and see what the voltages are supposed to be at the CRT socket. if any are off by more than 10-15% good chances are you have some chassis work to do.

Steve McVoy · #10 01-31-2007, 01:05 PM

Or it may be a problem in the circuits driving the grid and cathode. The grid voltage should be only slightly negative relative to the cathode with the brighness control all the way up.

refill233 · #11 02-01-2007, 03:57 AM

I checked the tube and it goes about 3/4 the way over but it drops fast on the life test.The brightness contol works great with good control.There is no
blooming of the screen at all.I'll check my voltages to the tube to make sure
they are right.Looks like some of them has to be on the money.I'll let you know if they are off, because if they are, i'm lost.I should get my tuner back
by next week and i bet i have more problems to deal with.So hang in there
with me on this i'm sure going to need your help.I already see some vert fold
over at the bottom at the screen now.Thanks Again,Don

jpdylon · #12 02-01-2007, 10:44 AM

You can try re-activating the tube. This is different than rejuvenation.

Just bump the filament voltage up to about 8 volts, and let it sit for an hour or two. Then put it back down to 6.3 See if you woke up the cathode at all. If your tester does not have filament voltage selection, just put a brightner inline with the tester.

Tubejunke · #13 02-01-2007, 08:29 PM

Can I "re-activate" my crt that already uses a brightner? Obviously I would have to try a higher voltage than mentioned in this thread but what would be safe? I wonder how much voltage the filament can take before POP....

jpdylon · #14 02-01-2007, 09:05 PM

If you're tube already has a brightner on it, there is not much more you can do other than to try rejuvenation. Usually a weak CRT will benefit from adding a brightner after rejuvenation.

CRT filaments are about 100% over-rated so they can safely run at 12v. however this does shrten their life, and if you go beyond 12, they open in a rapid fashion.

refill233 · #15 02-03-2007, 06:30 AM

Okay i tried the brightner on the tube for about 2 hours.Took it off and fired
up the set and it looked good.Turned power off for awhile, and tube is about
the same as it was.Looks like the brightner has to stay to be watchable.I don't want to watch it all the time just short term plays at the time.So how
long do you think its got with the brightner? Nice set and its a keeper.Thanks!