[Guest]

All,

I am presently in the process of restoring a Model 640. Initial startup on a Variac yielded the all too familiar hum with no reception. Recapping the filters yielded weak reception. Replacing the non-bakelite block paper caps resulted in functional volume and tone controls with good reception on three of four bands (not much on the old police/utility band these days). Only wish I could get 1936 radio broadcasts.

At this point I have several questions. First, The filter caps I replaced were 2 Sprague "600" Line 16 MFD electrolytics that didn't function. The Philco schematic and parts list indicate an 8MFD (30-2025) and a 12 MFD (30-2117). I assume the Spragues would have been replacements by someone and not original equipment. I liked the old paper labels.

Second, the 640 has a shadow tuning meter which appears to function properly (moves with varying signal strength). However, I appear to be missing a part of the illumination system. Comparison to photos of the older style shadow meter appears to indicate that all parts are there except for some type of holder (slide on ?) that goes around the round base portion of the bulb and holds it to a mounting. Does this sound right? If so, is this part difficult to find, old or repro? Has anyone created something from scratch?

Third and final. Being a member of the "if it ain't broke, don't fix it club", based on members experience, other than the electrolytic and paper caps I replaced, are there any other components the would be candidates for outright replacement based on age/reputation? I appear to be getting good reception on the three bands I previously mentioned, but since I don't know what a properly functioning 640 should sound like, I have nothing to compare to.

Any help would be greatly appreciated.

Thanks,

Tad

[Chuck Schwark]

Re-build the bakelite block caps too. Also perform a full alignment per the instructions for best reception and shadow meter action.

See the easy steps from my site:

[Image: http://www.philcorepairbench.com/images/bblok-01.jpg]
• BAKELITE BLOCK RE-BUILDING •

Also see the Service Tips section for Shadow Meter info and Model 640 Dial Drive info.

Chuck

[Bill Hutchinson]

Tad,

Yes, the Sprague caps sound like replacements.

The shroud that goes around the bulb would probably look like the reflector from a small flashlight. Actually, that's not a bad idea - perhaps you could come up with one (preferably metal, not plastic) to use as a replacement. You could probably leave it in its silver color, or paint it a flat black. The material is fairly thin, so if you need to, cut it to shape as needed.

As far as other components go, resistors can often drift out of tolerance. Check them and replace any that are 20% or more off. When they do drift, they go up in value. Stay close to the correct wattage as best you can. The higher value resistors are the ones that are the worst (500K and up). Also, generally speaking, the smaller mica caps rarely go bad, so leave them be.

After getting it working, I'd recommend doing an RF alignment on the set. It should really sound great after that.

Looks like you have youself a winner!

Bill

[Guest]

Chuck and Bill,

Thanks for the replies and information.

Just out of curiosity, after the replies, I tested a couple of resistors that needed to be unsoldered on one end to replace a 2/2/1 MFD electrolytic cap. A 16K resistor tested at 29K and a 20 K resistor tested at 28K. Just to be sure the meter was accurate, I tested a couple of unused resistors of similar value on the meter and they were within 1K of value. Guess I'll be checking some others.

Bill, when you mentioned the reflector shape, were you refering to the bulb that backlights the frequency dial? The radio does have that one. However, there is a second bulb that illuminates the shadow tuning meter. This bulb has some kind of holder around the screw base that appears to hold it to the bracket. (A picture of this can be seen at Chuck's site: (http://www.philcorepairbench.com/images/smrepair01.jpg). I held the bulb bottom against the small metal L-shaped tab and jumped the screw base to the metal center of the fiber washer stack and it lit. It's the holder around the bulb as shown in the picture that's missing.

One comment. After preparing to attack the resistors, I wondered how to determine the wattage values of the existing ones. A few minutes of searching previous questions/replies on the Phorum yielded the text/photos regarding resistors with the information I needed. This is a very useful site.

Thanks again.

Tad

[AI2V]

If it's the 150-390 KC band that doesn't work, it's usually not worth the effort to make it work. There's really nothing to hear on that band these days. There's a chance it's working and you just don't realize it!

When working, the 640 is a super sounding, sensitive radio. I've got a 640 and 650 along with a spare recapped working 645 chassis (and a host of other Philco's).

If the audio develops intermittent static, jiggle the audio tubes (42's) to see if corrects (temporarily). These tubes run very hot and the tube sockets oxidize over time. The best solution for this is just to change the sockets - cleaners and deoxidizers just won't cut it.

[Bill Hutchinson]

Tad,

Yes, that was the one I referred to, the shadow meter bulb.

With the other one, it was a matter of completing the circuit to ground to get it to light. You can probably get a replacement socket with a mounting flange at a nearby electronics store (it's possible Radio Shack might have something that'll work), or Antique Electronics Supply for sure would have something.

Chuck has more detailed info on resistor wattages, but I can tell you the majority of resistors are 1/2 watt. A few in the power supply section will of course be higher. Avoid using 1/4 watt resistors on stuff this old.

Good luck!

Bill

[Guest]

Pete,

Actually it's the 2.2-2.6 mc "police band" that's the quiet one. I can hear background noise, but no stations. I'm not sure what, if anything, is on these frequencies today. I can receive a few NDBs located at nearby airports on the 145-390 kc longwave band.

No issues with the 42s yet, but thanks for the info.

Tad

[planigan]

Tad, that shroud around the bulb on the shadow meter is basically a tube with a slot down the length on one side. It is three quarters of an inch long, thirteen sixteenths in diameter, and caped at the end. The slit down the side is one sixteenth wide. Painted flat black on exterior (I use high temp. BBQ Grill paint). It slips over the bulb, no mechinical connection. You should be able to fabricate with brass tubing from hobby store. Cut tube to inch and an eighth, cut almost through tube about three eigths inch from one end (stop cut when you have about quarter inch of diameter left), cut slit down side opposite from remaining quarter inch diameter, flatten out shorter portion of tube and fold over open end and snip off excess. Actually it was made out of a flat piece of sheet metal and rolled together but you would need diagram. Its sole purpose is to direct light down the channel passing the vane. If you have any questions let me know. PL