Philco 48-2500 Restoration Blog

[Eric H]

I posted a video on YouTube showing the set working.

[TV Engineer]

Originally Posted by Eric H

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.

Please note...

These sets did NOT have AFC for the horizontal oscillator. It is a straight blocking oscillator circuit. As a result, the horizontal hold control will be VERY critical in adjustment.

This is normal.

[Tom Albrecht]

That's looking really good. Time to give the projection optics a test run. Picture won't seem quite so bright once it's been projected to full screen size.

The screens on these are really cool. They have a pretty good viewing angle left and right, but in the vertical direction, you only get a bright picture at head height sitting on a chair (sit up straight, young man!). That's how they conserve light and get a reasonably bright picture over such a large screen from that small tube.

[Tom Albrecht]

Ok, so my solid state voltage tripler has arrived. It has a few more terminals than I anticipated, so if anyone is familiar with this unit (TCG523 or NTE523), how is it connected?

Terminals are:

IN - HV AC in?
G - ground?
F - what's this?
CTL - what's this?

One lead is fairly straightforward to identify -- the big red wire with a CRT anode connector on it. Think I know what to do with that one.

Tom

[Findm-Keepm]

Originally Posted by Tom Albrecht

Ok, so my solid state voltage tripler has arrived. It has a few more terminals than I anticipated, so if anyone is familiar with this unit (TCG523 or NTE523), how is it connected?

Terminals are:

IN - HV AC in?
G - ground?
F - what's this?
CTL - what's this?

One lead is fairly straightforward to identify -- the big red wire with a CRT anode connector on it. Think I know what to do with that one.

Tom

IN - HV AC in? Yes, from the flyback
G - ground? Yes
F - what's this? Focus Tap from the internal voltage divider.
CTL - what's this? Focus or Screen Control Tap from the internal Voltage Divider.

Datasheet archive has the datasheet fro the ECG triplers, IIRC - so you can see the divider network resistance values.

Cheers,

[Eric H]

I'm waiting on parts for the Westinghouse so I decided to play with this set again.

I put the CRT in the barrel and projected it against the Vertical Blinds behind my workbench. (got to get that second anode lead replaced, it leaks the 20kv like a 60 year old garden hose!)

Not too bad considering the geometry is all wrong, the brightness is really good using one of the old CRT's. (the picture is also upside down and backwards because it's being projected directly, I flipped it in Photoshop)

I can't wait until I can get it back in the cabinet and see what it looks like when it's set up correctly.

[bandersen]

Looking good, I can't wait either

[Eric H]

I started on the cabinet today, I removed all the hardware and the grille for cleaning and/or painting.

The grille cloth is in fair shape, there's one 1/4" hole in it, I could touch it up and it wouldn't be very noticeable but if someone makes a correct repro I may go with that.

Once it was removed I sprayed the grille with some strong cleaner, I wish I had a camera because what ran off that grille was really disgusting, it looked like strong black coffee going down the drain, I'm guessing it was Tobacco gunk.

It lightened up by several shades too, not quite as clean as the parts that were hidden under the trim but close enough.

[Tom Albrecht]

Well, after a few years, I got back to my 48-2500. As you can see above, I picked up a solid state TCG523 voltage tripler (equivalent to ECG523), and I finally tried it out.

It's important to ground both the "G" and the "CTL" terminal; otherwise the CTL terminal floats up to the HV and arcs over to the G terminal. The CTL terminal is meant to be connected to a focus control, which raises and lowers the "bottom" of the focus voltage divider. I'm not using the focus terminal for anything, so simply grounding the CTL terminal makes everything happy.

With the 1X2 voltage tripler, the HV varies between just short of 22 kV down to a little over 18 kV with the brightness high. With the solid state module, it seems to hover in the 22-23 kV range. As was reported above by TV Engineer, the focus drift problem with scene brightness almost goes away with the solid state module. Looks like the solid state module is going to get built into this set.

I also tried the trick of pulling out the DC restoration tube. That helps quite a lot naturally, although I certainly miss the nice DC restoration the set had before. But priorities being priorities, I'll take a more stable focus over DC restoration, so the DC restoration tube will also stay out.

Will give this thing a full going over, since I restored the chassis quite a few years ago, and I've learned quite a bit about alignment, etc., since then.

I have a resilvered mirror for this guy that I installed quite some time ago. Needs a little cleaning up, as does most of the optics after sitting in my dirty shop for a few years.

I also tested the three different TP400 CRTs I have. One is much better than the other two. Just in case you're paying attention, the nice bright one is the one I bought from you -- Craig R -- many years ago! Of the other two I have, one has huge spot size bloom at high brightness (sign of a dying tube; would be interesting to try a brightener on it), and the other has some kind of poor connection, which might be recoverable with some work on the socket pins. Anyway, the good one does not show obvious spot size bloom, even when it is very bright. So that's the one I'll be putting back into the set when I've gone over the chassis again and cleaned up the optics.

I think I have a buyer for this set, so I'm trying to get it into great shape before saying goodbye to it. No real place to display it in the house, and it takes up too much room in my shop.

Will post some pics sometime in the next few days.

Tom

[cwmoser]

Hey Tom, its nice to read your observations about these 48-2500 projection TVs.
I still have mine playing and have it in my shop where I occassionally play it.
Currently I have the TP400 I got from you in the set - remember I thought there
was an intermittent with my TP400? Turns out even with your TP400 I still
get an intermittent -- so I'm thinking there is something amiss with the wiring
harness from the chassis to the CRT connector.

Thanks everyone who helped me getting my 48-2500 working. Still find it
interesting when others post about these sets. Still looking to learn
all I can.

Carl

[dtvmcdonald]

About X-rays: its unlikely that these come out in a directional manner
from these tubes. The glass is probably more of less uniform all around,
and for sure they are actually generated uniformly in all directions.

[cwmoser]

Originally Posted by dtvmcdonald

About X-rays: its unlikely that these come out in a directional manner
from these tubes. The glass is probably more of less uniform all around,
and for sure they are actually generated uniformly in all directions.

We need an inexpensive way to detect X-rays.

Carl

[Tom Albrecht]

While I'm working on mine on the bench, I've left the CRT in the metal barrel with the spherical mirror removed. I'm viewing it indirectly using a mirror. This allows me to point the CRT away from me, and hopefully keep the x-rays down to a safe level.

[Tom Albrecht]

Everything looks good on the bench right now, except for a touch of horizontal foldover at the left edge of the picture. Looks like a possible horizontal phase problem, so I'll see if I can figure out how this particular horizontal sync system works.

Further updates on my set here: http://www.antiqueradios.com/forums/...=unread#unread .