Philco 48-2500 Restoration Blog - Page 3 - Videokarma.org TV - Video

***Eric H*** · #31 09-23-2010, 04:45 PM

Success, after a couple false starts.

I took all the tubes with me today and tried firing the chassis up during my lunch hour, all I got was a glowing red plate on the 6BG6.

I messed around with it a little, pulling the cap off and seeing how much current it was drawing, anyway I fooled around a bit too much and cooked the 6BG6, it shorted and caused a little 50v cap on the Damper tube to explode.

fixed the cap and did a little troubleshooting around the Horiz Oscillator tube, I had zero B+, a little troubleshooting found a solder glob that had shorted a 120k resistor (R115 on the Sams) to an adjacent terminal on the strip, cleared that out and the voltages on the Osc tube fell in line.

Now that I knew it was probably working I went and borrowed a 6BG6 from a friend who lives near my work, put it in and fired it up.

The first indication that I had HV was the inch long spark that jumped from one of the doorknob caps to the second anode lead, the lead has a bad spot where I melted it with the heat gun.

Moved the lead, grounded the CRT more securely to the metal bench and tried again, this time I got a raster!

The raster fills the screen, I put in a set of tuner strips and it appears I'm getting something through the i.f strip, if I had a DVD player I think I could get a picture.

I used the CRT that came with the set, it was the most burnt so I figured I had the least to lose if something went wrong.

It works OK, decent brightness after it warms up a little but the area where the phosphors are burned are noticeably dimmer, there's also a barely noticeable vertical line burned in the screen, I think this is due to the way the set warms up, there's a brighter vertical line first then it expands and fills the screen, it could have had a horiz sweep failure at some time too I suppose.

There's also a faint image of Uncle Milty burned in the screen (just kidding but that would be cool)

Next I want to try my supposedly NOS TP400 and see if it actually works.

mbates14 · #32 09-23-2010, 07:52 PM

***Eric H*** · #33 09-23-2010, 08:17 PM

At your command!

Here's a couple shots of it running, this is with the NOS tube.
It doesn't seem to get all that bright, except when you adjust the controls it'll get brighter for a moment then settle back down, I think perhaps it needs a signal to work it's best.

All I know for sure is you have to be really careful where your wires are laying when you turn this thing on, anything that gets in range of the HV area will get zapped! I don't have the cage on it yet though, wonder how much X-rays it makes if any?

BTW, when it's installed and adjusted properly the screen won't be filled like it is now, it's supposed to be a bit smaller than the tube and keystoned slightly to compensate for the angle of projection, this can be seen on the face of the old tubes in the brown Phosphor.

A pair of magnets attached to the sides of the CRT do the keystoning.

***Eric H*** · #34 09-23-2010, 08:25 PM

Oh yeah, earlier I said I used the old CRT in case something went wrong, it did.
I was taking everything apart to bring it home and I pulled the base cap off while trying to disconnect it!
It came off clean with the wires intact so I can put it back on, if it's even worth bothering with.

mbates14 · #35 09-23-2010, 08:45 PM

nice. comming along very nicely. wow that tube is bright..... even for a worn tube.

***Eric H*** · #36 09-23-2010, 08:48 PM

Quote:

Originally Posted by mbates14

nice. comming along very nicely. wow that tube is bright..... even for a worn tube.

That's actually the new tube, the camera makes it look brighter than it is.

mbates14 · #37 09-23-2010, 08:55 PM

Quote:

Originally Posted by Eric H

That's actually the new tube, the camera makes it look brighter than it is.

ooohhh ok... i was wondering why it was so bright.

John Folsom · #38 09-23-2010, 09:06 PM

Eric, you won't get a super bright raster with no signal. Once you give it video, you should get very bright highlights in the video. The CRT does emit soft X-rays, as it is operating at 20KV. A little exposure wont' hurt, but you don't want to spend hours and hours with the CRT facing you in the barrel. Point the barrel away from you on the bench, and observe it through a mirror. That will minimize your exposure.

Tom Albrecht · #39 09-24-2010, 09:10 PM

NTE523 tripler: Found one on eBay for $16.00, shipping included, so decided to go for it and try it out on mine. Still one more left at that price for Eric if he wants to try one later.

I figure at this price, shipping included, it beats getting one for free with a 1980's TV attached.

***Eric H*** · #40 09-25-2010, 12:59 AM

Thanks Tom, I went ahead and bought the other one just in case I want to try it.

***Eric H*** · #41 09-28-2010, 03:23 AM

Brought the chassis in the house tonight to see if it would make a picture.

First I tried the CRT from my first 2500, the one that I junked, I thought it might be good but it turned out to be nearly dead! It wouldn't even make a visible raster in a normally lit room.

I reattached the base to tube number 2, the one that came with this set, hooked it up and turned on the TV and the DVD player, got a raster with lots of static and lines but no picture.

I wasn't sure if I had a matched pair of channel 4 tuner strips since the numbers were pretty messed up so I robbed a pair out of my spare chassis, this time when I turned it on I could see it had a picture but the horiz was flopped over and wouldn't lock in with the hold control.

Apparently the control is the only method of adjusting the Horiz, there is no frequency coil that I can find so something must be out of tolerance in the circuit. I grabbed a jumper and a resistor and hooked it across the resistor that's in series with the Horiz control and the picture popped in!

I also discovered the Kine Bias control, turning this up along with having a signal and this old CRT has a tremendous amount of brightness, despite the dark phosphors, it should be perfectly usable so I can save the new tube for later.

Here are some pictures, it's really hard to take a good picture of the screen because of the sharp contrast ratio, also the brown band is a camera artifact and not visible with the eye.

Obviously it still needs a little work to fix the horiz and get the picture looking it's best, there are probably some resistors out of spec here and there but I'm pretty happy with these early results.

mbates14 · #42 09-28-2010, 08:39 PM

yup. certainly turning out to be a good performing set.

kvflyer · #43 09-28-2010, 09:41 PM

Yes, I would agree. Very nice early results. This gives you a benchmark to work from. A dead set is a lot of hit and miss until you get that raster! It can only get better. Good for you.

bandersen · #44 09-28-2010, 10:02 PM

Cool. I knew you could get it running

***Eric H*** · #45 09-28-2010, 10:07 PM

I've been working on it for a few hours this evening, checking resistors and trying to get the Horiz to lock in without any help.

I must have replaced a dozen resistors, nothing really far out but it seems like every resistor in the set is on the borderline of 20-25% high%.

I replaced a few in the Horiz Osc circuit and now it'll fall into range with the control, though it'll only flop one direction, I wish it had a fine Horiz adjustment.

I finally hooked up a speaker and found out I had no sound at all, a little poking around turned up a resistor I had broken while recapping, replacing that got me some static, tweaking the fine tuning and the coils in the sound circuit got it working well but only with the picture tuned off peak a little bit so it needs more work there.