The PHILCO Phorum

Hello Everyone,

I'm new to the forum and also new to the wonderful world of vintage radio repair. I'm actually more of a collector and hobbyist of vintage Phonographs and Gramophones but I've recently purchased an old Philco console with a great phonograph hiding inside it. My plan is to completely
restore both the radio and the phonograph so I can enjoy my small collection of 78's without damaging them any further by using one of my gramophones.

Here's where the problems begin and the questions start...

I have no idea what the model number is for this radio except that the chassis number is 715A. When I search the internets for that model, the only thing I find is this great image http://www.radioatticarchives.com/radio.htm?radio=9172 which looks exactly like my radio (minus a different phonograph) and a few sites with 715P.

Either way, I've contacted a site which seems to carry many Canadian made radio schematics and they've told me they can only find a schematic for a 715. I have no idea if a 715 is a close match or what the radio even looked like as google has less information about this one than it did for mine.

I'm hoping someone could point me in the right direction, or perhaps knows of a substitute for this model number so I can start the restoration.
I'd try removing and replacing the capacitors one at a time without the schematics but there appears to be two wires underneath that are not attached to anything and I'd like to know what belongs here. Perhaps this is why the phono isn't working?? (that and a bad motor)

Which brings me to my next question....

What have I got myself into? As if restoring old gramophones didn't consume enough of my time!!

Thanks Kindly,

Looking forward to posting more in the future....

Vince

Welcome aboard! Don't be afraid of being a newbie. To ask questions is to learn.

According to Ron's info at PhilcoRadio.com, there is a 715AP and a 715P, both of which correspond to the 41-608P.

Sweet lookin' beast, too.

Thanks very much! It looks like a perfect match.

Looking at the schematics and the radio, some of the wires don't seem to be going
where I'd expect them to, I thought I'd be able to comprehend them a little better than i am.

I may have more questions than I thought....

There is a code 121 and a code 122 chassis. Look on the back of the chassis and it should be stamped there in black ink.

Unless you have a copy of the 1941 Philco RMS manual, recommend you ctc Chuck's site philcorepairbench.com to get the appropriate schematic/info for this radio. The 41-608/609 online schematics in N.A. are not accurate.

Also be aware that you must have the BOL player plugged in to the radio chassis in order to get any volume out of the set.

It's a code 122, I just received the schematics I purchased and they make a lot more sense. The one I got online for free was missing a lot of missing keys to this puzzle and it confused me.

I was wondering if someone would be kind enough to educate me on what the purpose of a specific component is? The pictures show what i would think is an isolator? It's held in place by the metal of the chassis and formed of some type of thin black material. It has several pins protruding from it that have various resistors and wires soldered to them.

In the photo you can see that some of it is burnt out and when I plug in the radio this area shorts out (I can see tiny sparks and sizzles but I only plug in the radio for a quick second - please don't yell at me)

My question is, what is it for? Are each of the pins carrying power and this material is keeping them from contacting the chassis ground? Is that why I'm getting sparks? It just seems odd because some of the resistors and other leads that are soldered to it end there. There's nothing else soldered to it so It makes me think that it's supposed to be grounded there?

As you can probably tell by my question, I'm VERY new to this and probably not qualified but you've got to start somewhere I suppose.

Enough chit-chat, here's the pictures and hopefully someone with answers?

Vince, I'm very new to this as well so there will be other more experienced folks who will provide information but that looks like what is called a candohm resistor. I only had the model 121 schematic to look at but looks like item #77 to me. Candohms are a resistor string mounted to the chassis for heat removal with taps at various resistance values. Replacing them is often done by removing the candohm and putting wire wound power resistors of the appropriate resistance and wattage on a terminal strip. Looks like its a pretty crowed spot on the chassis so perhaps some advice from someone who's worked on this model will help.
Cheers
Bob

Klondike is right on. It is component #77 on the schematic.

These resistors are known to fail. In the case of the 41-608/609, it will be a pain in the thing one sits on to replace, as you have noticed, because it runs down the middle of the chassis and serves as a tie down for several other components.

Have you measured the respective sections to see if it is serviceable or not?

Here's a picture of a replacement by morzh from another thread in this phorum http://philcoradio.com/phorum/attachment.php?aid=959. You may need to be creative in those tight quarters.
Bob

Wow, thanks very much! A Candohm resistor eh? learn something new ever day I suppose!

Below is an image of it removed from the chassis and the resistance values across the terminals. I put question marks after the 590 because it was constantly fluctuating up and down and never really stabilized.
I should also mention that I have a very CHEAP multi-tester I purchased years ago for automotive use.

Could i just buy a terminal strip and then solder new resistors across the terminals (in series)?

Quick question - I've never purchased resistors before, how do you know what wattage you should be buying? does it indicate somewhere on the schematic?

Thanks again.

Mr Grumpy Wrote:Could i just buy a terminal strip and then solder new resistors across the terminals (in series)?

Absolutely! This is what I did in my 41-616.



The extra long terminal strip was pulled from a junk Philco chassis, so it looks sort of period "correct."

You can read the details here:
http://philcoradio.com/phorum/showthread...8#pid27888

Unfortunately, the service info does not give the wattage info for the Candohm resistors. To get an accurate wattage, you need to know two of the following:

1. The voltage drop across each section
2. The current flowing through each section
3. The resistance of each section

You are given the resistance. If you can find the voltage drop, you can determine the current with Ohm's law.

And then you can determine the power in watts using one of the two formulas:

P = (I*I)R or P = I*E

where P = power in watts, I = current in amps, R = resistance in ohms, E = voltage in volts

Unfortunately, Philco does not give the voltage drop or the current. So we have to guess at it.

Since the 268, 28 and 26 ohm resistances are used as a B- voltage divider, and the 780 ohm section provides cathode bias to the first and second IF tubes, the voltages are small. You should be safe using 5 watt resistors to replace each section. In fact 5 watt resistors may be a bit overkill, but better safe than sorry.

I used 5 watt resistors to replace the B- voltage divider Candohm sections in my 41-616, along with one 7 watt unit to replace one section with a high resistance. It worked out fine.

Cool. 8)

I actually was just about to order new power resistors for this same purpose.

I always like to see what others who have been there and done that have put together. It saves me from self-inflicted misery.

Do add a fuse, 1 1/2 or 2 amp would be OK. And of course, replace each and every electrolytic and wax capacitor before carefully powering up slowly with a variac or dim bulb tester. Candohms do fail on thier own, but when they are burned up it's usually not "thieir fault."

Keep a meter hooked up to the B+ when you do so to see what is going on. I use an analog ammeter (at least 1 amp to start) in the B+ line as well. Belt and suspenders, I expect, but it's better than burning up some unobtanium.

Many thanks to everyone for the help, I learned so much but I'm sure there's a lot more to come.
I'm off to buy the resistors and give this a try today, Please keep your fingers crossed for me.

Okay, I went out and bought all the resistors (ceramic) and installed them on a new terminal strip then fastened the strip to the chassis. I'm fairly confident I did this all properly but the same resistor (270 Ohm) started smoking and burnt up again.

Originally I was hoping to just recap this radio since it was working for over an hour when I first brought it home. Should I just stick to that plan and re-cap the whole thing and then try plugging it in again? I wanted to fix this problem and get it working again so I could replace a few caps at a time and then test it each time (as confirmation that my work was done correctly)

If I post this bit of schematics would anyone be able to tell me if there's something I could check or where the problem might lie? I hope this isn't asking too much because i also wanted to ask why on my schematic some of the tubes have a lead with the letter 'B' next to it. One of the tubes has a letter 'A'

I'd also like to thank you all for your patience with me, as I indicated I'm really new to all of this and trying to learn as much as I can.

The "A" and "B" are filament windings on the secondary of your power transformer. You will see them marked in the same manner.

This was done to reduce the number of lines on the schematic and make it less confusing.