The PHILCO Phorum

Hmmm...micas at Just Radios are half the price of Mouser, and they go all the way up to 10,000 pF. It means I likely won't have them until next year (a week or two), but that's okay. After all, I don't NEED to have this radio operational. It's just a fun thing to do.

Nathan, you posted as I was typing. Thanks! I'll look into that...

Edit: The eBay seller doesn't have the other values I need (3600, 3000, 400, 50) so I'll likely order from Just Radios instead. Thanks anyway for the suggestion.

On my RCA the large MMF values e.g. 6800 had been replaced by film caps. I don't believe they are frequency determining critical components, and you 4500 mmF might well be similar. I'll keep studying the schematic.

The oscillator coil is back in the radio, all wiring reattached save for the now-missing 4500 pF mica cap, 50 pF replaced with a new 50 pF silver mica (the only mica cap I had in stock which this radio needs).

Ed, I thought about that but the closest value I have is .0047 uF (4700 pF) in metalized film. I'd rather use a mica here.

Time to make an order with Just Radios.

Edit: Order made. That's all I can do with this one until the mica caps arrive.

Until then...on to other things.

Understood, Ron.

Especially if the original was mica. However, I was reminded last night that the factory-fitted 6800 MMF cap on my radio was a paper cap on pictures I found of an original chassis - you might experiment here, if you feel so inclined, but your way will certainly work, of course!

The one that is now bugging me is how the antenna trimmer should need such extreme adjustment? But then I rather like understanding this part of restorations.

Cheers, and Season's Greetings,

Ed

Mica caps have arrived! It only took a few days.

A word of praise for the folks at Just Radios. They go to the trouble of mailing orders from Buffalo, NY for their American customers, giving us a break on postage. Now that's customer service! I hope you will join me in supporting the Cantelons by ordering as many capacitors as you can from them. (And of course I forgot to order any 0.1 uF film caps while I was ordering the micas. )

So...sometime this weekend or New Year's Day, I shall replace the remaining mica caps in the 6T2.

So...have you ever seen $80 worth of mica capacitors?

If not, here's a picture.



Expensive little buggers...even from Just Radios whose mica caps are about 1/2 the price of Mouser.

Enough to take care of the 6T2 and an RCA C15-3, plus some left over.

This afternoon I replaced every mica cap in the 6T2 that had not yet been replaced. The results:





It still plays well. I'll realign it on New Year's Day (I have to work tomorrow ).

Incidentally, none of the other mica caps had any cracks although a couple were bulging slightly.

I order all of my caps and resistors from Just Radios, the Cantalons. The last order I got had an error. I ordered the orange dip 2000vt caps and was sent yellow film 1600vt caps. I sent an email stating the error and got a response almost immediately. Dave said he was really sorry and that he would get them out the next day and to keep the ones he sent in error. Awesome customer service and I had the new ones two days later. That's why I will continue to buy from them. Awesome Service!

The silver micas are probably viewed as a specialty item over at Mouser, lower demand hence a higher price, most electronics manufacturers have been switching over to NPO rated capacitors of various types, and have been doing so since the late 1930s. Those components that you run into in sometimes that look like dogbone resistors, but are hollow, those are early NPO rated capacitors. Most 1930s and 40s radios didn't use silver micas, they were just plain old mica capacitors, a sandwich of copper or brass and mica sheets, which is probably why they are so robust, even though they can still fail.
Regards
Arran

Ron, too bad you don't live closer to Gateway Electronics. 

Steve

I know. At least I don't have to buy high value micas (that is, in the thousands of pF or as Morzh Mike would say, above 1 nF) too often...

Set realigned. Tracking is still off at 15 mc (it comes in at 15.4 on the dial and still can't get it any lower) but I'm going to live with it.

Before the realignment, though, I remembered that I had a junk 53-960 chassis out in the garage. Its tone control is 5 megohms. From my previous experience with early 1940s Philcos, I remembered that they used a high value tone control (5 to 6 megohms) in a circuit which connects between the tone compensating tap of the volume control and the plate of the 1st audio tube (not the audio output).

With that in mind, I removed the 5 megohm tone control from the junk 53-960 chassis, cleaned the control, cut off its control shaft and tried to flatten it as best as I could. Then I installed it in the RCA, modifying its tone control as follows:



The original C28, .035 uF, was removed and replaced with a .01 uF cap, connected to the plate of the 6F5 (instead of the plate of the 6F6) as shown above.

The radio now has a very mellow, pleasing sound and the tone control is very smooth and effective from treble to bass.

I'm about to reinstall it in its freshly refinished cabinet and call it quits on this set.

Well, it still needs a new dial cover (the original is badly yellowed) but otherwise, this one is finished.

I revisited this 6T2 today because I had never cleaned and re-lubricated its dual speed tuning control assembly.

I disassembled as much of it as I could get to come loose and then soaked it for 4-1/2 hours in naptha (I put the cup outside because of the fumes). Afterward, I brought the assembly back to the basement and finished cleaning it up. This was followed by relubrication with white silicone grease, reassembly, and reinstallation on the chassis.

The tuning is much smoother now. This almost eliminated the backlash. Not completely, but it is much better now.

Afterwards, I realigned the radio. It turns out my original alignment was nearly spot on as I really didn't change much other than the 1st IF adjustments...and those, only a little bit.

It is now finished.