[Guest]

Hi, my name is Tom, and I am new to the phorum. I'm located in the Denver, CO area. I inherited a 1940 Philco 40-180 about 10 years ago when my father-in-law passed away. The radio had been unused since the 1950s and stored away in a basement. It was in working order when it was set aside. Since then, I have had it in storage as well, but now would like to restore it. It has all the original parts. The cabinet is in good condition - just a few scratches and a ton of dust. The cabinet fabric is in good shape, just really dusty. The dial needs cleaning. The bakelite pushbuttons are cracked and basically toast. The chassis looks pretty good, but all of the rubber insulated wiring looks dried out and cracked, as does the power cord. The speaker and tuning antenna look ok as well. I have not powered it up. It looks like a shock hazard, and it looks like applying power would just ruin what is there. I've been lurking around the phorum for a while, and I have followed all the repair links. It looks like my first step is to replace all of the capacitors, and get a variac or build a dim bulb tester. It also looks like I need to rewire the thing completely. I'm an electrical engineer, and I'm good with a soldering iron, but I have never attempted a project like this. I have no real knowledge of vacuum tubes. I just never learned the technology in school. But it looks like this is an achievable project, as long as I take my time, do the research, and just be careful. So, I will be checking in from time to time to gain some knowledge from the experts here at the phorum. I do have a couple of quick questions. Electrolytic capacitors scare the H**l out of me with the charge they can hold. Now since this radio has not been powered up for years, I will assume they have discharged themselves over time. But after I do finally power it up, what is a good technique and tool to discharge them? Also, what type of wiring should I use to replace the old rubber coated wires and power cord? Thanks in advance for your help, and I look forward to chatting with you all.

[Uffda]

Welcome Tom. To expand your question; How long do caps hold the charge? When is it safe to not bother to discharge?

[codefox1]

A fully tube functional radio will pretty much discharge most of the charge because current continues to flow after the set is off. Not so when there is no load. A capacitor is capable of storing a charge for hours, if not days. I use a 10K 2 watt resistor and test leads to discharge anything I'm working on. Leave this attached for at least 10 seconds to drain all the juice out.

And I usually install a "bleeder" resistor of about 100-or 200 K across the main resovoir as a further safety measure when I rebuild something. Two resistors in series, if the voltage is over 400 volts.

You should replace all the electrolytics and paper capacitors in the set before you apply any voltage to it. The cost is very little compared with the likelyhood of burning up an expensive tube or transformer. If you have to replace the wiring as well, I would probably go ahead and replace all the carbon resistors as well (you will find that in most cases they have increased in ohmage,) and this can make a big difference in performance once you are finally done with the set.

Good Luck

[Ron Ramirez]

Hi Tom, and welcome!

For the wiring, I replace the old rubber insulation with heat shrink tubing, which is available in various colors. When replaced in this manner, the wires look like they have new rubber insulation. Others replace the wires with new insulated wire. Do whatever works best for you, but just be sure and replace all of that rotten insulation!

Pushbuttons are available from Old-Time Replications and Renovated Radios, as well as Radio Daze. Links are on my site's Resources page.