Philco 48-1000

It's been a long time since I posted here, just no time for hobbies & such. But I put aside the Tele-Tone without getting too much into it because there's something else taking up most of my bench space and I'd rather it be elsewhere and in a more working condition.

I've had this Philco 48-1000 that I got at the now defunct Norton Flea Market for a little more than 20 years. It's always "sorta" worked, in that it would be OK for 15-20 minutes then the picture would gradually fade away. While it was working, the pictures were fairly decent.


But it's gotten progressively worse, meaning it's only OK for about 5 minutes now, so it's time for a recap. There's LOTS of caps, though.



All of those brown cylindrical parts are capacitors. In addition, if you look at the top of the chassis,there are also 5 other round objects (that aren't tubes) that are a different type of capacitor and will be replaced in a different manner.

First, a few tidbits of information about the set.

• Year of manufacture - 1948
• Number of tubes (including CRT) - 26
• Number of semiconductors - 1 (a Sylvania 1N34 to be exact)
• Power consumption - about 250 watts.
• Channel coverage - 8 VHF channels set up at time of purchase with specific coil sets loaded into the tuner - this set covers channels 2,3,4,5,7,9,11 and 13
• High Voltage Supply - about 8000 volts.
• Receiver IF type - Split sound - separate IF strips for video and audio

After counting up all the electrolytic and paper type capacitors a total of 72 capacitors were ordered. In addition, I figured most of the high value resistors (470K and over) were probably bad as well, so 20 resistors of various values were added to the order.


Fortunately, parts have gotten much smaller in the last 60 years.

In any event, I'm fairly well along in the part replacement process, I decided I should at least start the blog and catch up to where I'm at over the next days. There have been quite a few surprises along the way, most of them not too pleasant.

Preliminary steps

It had been at least 9 months since the set was last powered up, at that time there was no audio and I could have sworn I discovered an open primary on the audio output transformer. About 2 months ago I brought the set up slowly with a variac (about 5V every couple of minutes) and monitored the power supply voltage and power consumption. Since there are no longer any VHF analog signals around, I used a DTV converter box.

The first thing that surprised me when I got to around 90VAC was hearing very scratchy audio. Wasn't expecting that. By the time I reached the "nominal" supply voltage of 115, bad things were starting to happen. The picture which was out of focus and very dim with significant blooming as the brightness control was advanced to begin with was fading away to nothing, the power consumption was rising quickly (from 230 watts up through 250 watts), and the power supply voltage was falling (from a high of 350 to about 320).

After shutting down I started checking some of the tubes. The 1B3 high voltage rectifier tested very weak (even though I had replaced it only a couple of years ago and the set has very little use), so I had to liberate the 1B3 out of the TeleTone (oh well). A quick check showed the picture was much brighter now and there was no blooming, but it still faded away quickly. While inspecting the chassis I nearly burnt my hand on the capacitor between the power transformer and filter choke in the lower left hand corner of the chassis top picture. With my new multimeter with an infrared thermometer function, I measured the capacitor temperature at 150 degrees. Apart from feeling really stupid that I let it get to this point, I'm even more surprised that the cap didn't go boom. That explained the power consumption rising and the power supply voltage falling, which also caused the picture to fade out. This capacitor is the first filter off the low voltage rectifier.

In the next installment of the blog, we'll actually get to work.