[Guest]

I've rewired, recapped and basically re-everythinged my 42-355. The radio sounds great and pulls in lots of stations on BC and even on the SW band, however, the field coil gets almost hot after about 30 min. The power transformer gets pretty warm too, although, I understand this may be normal considering the AC line is at 120v. Is it normal for the field coil to get very warm? thanks, -Karen

[Texasrocker]

Hello Karen,... sounds like you did a superb-job restoring your vintage chassis! It "is-normal" for the spkr field-coils And power trans to get pretty-hot to "touch", once these old vintage sets play a hour or so on modern type AC current!
I always use a 1-amp fast-blo fuse on one side of the AC line feeding the AC trans for backup "safety", however, that is not original if your concern is keeping the set "all-orig"? It just adds a "safety factor", just in case something goes wrong in the future, and can "save" the AC trans windings from high-current draw that can permanantly damage them.
Since your vintage set has been operating already over 1 hr increments, and everything is OK, ... your most-probably in the "safe-zone" already!! If your concerned, just add the 1-amp fuse on one-side of your lead-in AC line under-chassis. A properly working vintage tube radio shouldnt pull much more than 1/2 to 3/4 of "1-ampere" total. Enjoy your vintage Philco!!

[Guest]

Thanks very much. I originally purchased a new power transformer from Radio Daze(They were very helpful), but decided not to put it in because I had subsequently found a good used one(from same model-42-355) on e-bay which I installed. So, if need be, I'll install the brand-new trans(I'll have to make a bracket because it hangs off the side of the chassis). I have an in-line fuse under the chassis with a 2A fuse, so, I'll definitely get a 1A slow-blow in there. Thanks again for the advice! -Karen

[etech]

Hi Karen,

There is most likely, no need to install a new transformer. However, the transformers on most old radios, even Philcos, have a tendency to run very hot at todays high line voltages. A quick way to resolve the issue is to install a 15 ohm 20 watt resistor in series with one side of the transformer primary. That should drop the line voltage enough to cause the transformer to run much cooler and operate in a much safer range. I make this mod to all my radios.

Note: It is also possible to install a 6 to 12 volt buck\boost transformer in series with the primary to accomplish the same goal. It is your choice.

Regards,

Ed

[Guest]

Ok! I installed a 15 ohm, 25w resistor(and replaced the 2A with a 1A slo-blo fuse). The transformer and field coil run significantly cooler now. At 121vac, I'm getting around 114v at the transformer primary, past the resistor. Thanks so much for your help. -Karen

[Texasrocker]

Very good advise etech! Applying "ohms law" is something many forget in restoring these old radio chassis indeed! Most of those old AC trans are "built like a tank", but it is always better to be safe than sorry!! Wish it was as easy to "dispense" 6 volts DC from a 12v DC battery when restoring vintage 6 volt DC auto/truck radios! Whew, Ive wound several turns of "nichrome wires" in the past, on old porcelain type power resistor bodies to acheive the same results when dispensing incoming DC current on vintage auto electrical systems. Those homebrew ( 12 volt DC stepdown to 6 volt DC) homebrew resistors get "hot" in a hurry!,... but do the job!! Sure beats folks buying the new high$ DC power-invertors for vintage auto collectors that have "up-dated" their vintage orig 6 volt DC vehicles to 12 volt systems over the yrs.
I also remember back in the old-days, of converting old orig 6 volt auto/truck radios wiring that used a "positive ground system", by reversing all wires on the vintage engine generators, and underdash to the dashboard guages.
Those old automotive type DC generators "reverse polarity" automatically when wiring is setup accordingly. Ah,... the momories!!

[justlrnin]

Sorry hijacking this thread, but...
Texasrocker--An inexpensive solution for a 6v battery eliminator is to buy on ebay a Heathkit BE-4 or BE-5 battery eliminator. You can get one for as little as $10. All of these will not work because the selinium rectifiers are shot. Go to radio shack and buy a 4-pack of 50v 6 amp diodes for $3.00 and you can build a new rectifier bridge. I can email the manual and schematic if you need it. The end result is a nice vintage piece of equipment for $13.00 plus shipping that will have a 0-18vdc range on the low setting with much more amperage capacity than you'll ever need. I restore the old 6v radios as well and this works beautifully. At 6 amps it's hardly working! The high range (which I never use) will be 0-36vdc (instead of 0- 18 ) with only half the amperage (just like it originally did because of the voltage doubler circuit). It sure beats $200-$300 for a modern battery eliminator that works in that amperage range and looks great on your bench!

[Ron Ramirez]

Welcome, Pilkco! Glad to have you aboard.

Just thought I would mention that while some Philco field coils may run warm (especially those made after 1938), they should never run HOT! If they do, a problem is indicated.

And as others have mentioned here, today's line voltages are higher than they were during radio's Golden Age; so transformers will run warmer (sometimes hotter). It is always good to reduce the line voltage through use of a buck/boost transformer set-up or dropping resistor, if you plan to run your radio a lot.

The voltage here varies between 125 and 128...the power transformers of various radios I have had here vary from barely lukewarm to very hot at full line voltage. My friend Ed Locker sent me a bucking transformer setup, mounted in a metal enclosure, which reduces the line voltage to 110, and makes those power transformers run cooler.

Finally, whenever I have to have a power transformer rewound, I ask for a primary of 130 volts in order to eliminate the hot transformer problem.

[etech]

Karen,

I'm glad to see the dropping resistor worked out OK for you. It does generate some heat, but usually does not cause a problem as long as you mount it away from any nearby components. My line voltage here is typically 127-128 volts, similar to Ron's. I can not operate any of my antique radios without a dropping resistor or buck/boost transformer, without significant heating (overheating) of the transformers.

BTW, welcome to the forum.

Ed

[Guest]

Many thanks to everyone for your hospitality, and Ron, it's great to be aboard.
That resistor does get pretty hot, but, it is clear of other components. It's mounted between the on/off switch on the push-button switch chassis, and a new (generic) line filter. I may modify that later because the switch chassis flexes by design, though, not as much with the new ( http://www.renovatedradios.com/ ) rubber mounts. But, the transformer runs fine now. The field coil still gets a little hot after about 2 hours of radio listening pleasure. I'm wonder if I couldn't rewind that coil myself (assuming that's the cause). But for now, the radio sounds great!
I think the best thing I've done is join this forum and I am most grateful for everyone's invaluable advice.

Regards and a Happy 4th of July everyone, -Karen

[etech]

Randal,

Yes, sometimes its the simple things we forget to apply, like ohms law. Recently, I was restoring a Stewart Warner 950 radio and the ballast was open. After opening the ballast, I determined that it was nothing more than a power resistor wound using nichrome wire on a ceramic form. But where to get nichrome wire these days? One of the guys on another forum mentioned that a number of sizes of nichrome wire with their ohm/ft rating was available from AES. I bought the nichrome and rewound the ballast and it worked well. As you say though, it does throw a lot of heat. These forums are really great because they are so filled with knowlegeable and friendly people who are willing to help. Now, if I could only get spell checker on these pages, lol! Maybe I should compose my reply in Microsoft Word and then paste them into these pages.

Regards,

Ed

[Ron Ramirez]

Now, if I could only get spell checker on these pages, lol! Maybe I should compose my reply in Microsoft Word and then paste them into these pages.

It is my understanding that a lot of the guys over on that quirky little alternative forum do just that when they compose their messages.

For me, it isn't an issue because I use Firefox, which catches misspelled words by underlining them in red.

[BDM]

Or, if you use IE, you could use this:
http://www.iespell.com/

I've used it for several years now and love it

[etech]

Wow! You learn something new everyday, lol! I didn't realize that iespell existed. Also, I just loaded Firefox on this machine last week, but I did not realize it had a spell checker built-in. It's not that I am that bad of a speller, it's mostly typos. Thanks guys.

Ed

[Texasrocker]

Yes Justlrnin, I certainly appreciate your offer to help me "rid" 6 volts DC! In my previous post, I was referring to "ridding 6v DC", once the orig 6v radios are installed back into vehicles that have been upgraded to a 12 v vehicle battery system since vehicles were originally wired for 6v electrical systems. Some of those vintage car/truck owners want the orig 6 volt radios installed, but work via a 6v dc stepdown power resistor, to attain originality of the dashboard orig 6v radios installations. About the only way I know how to acheive this conversion in the vehicles ( dropping 12v dc to 6v dc, is to hand-wind nichrome wire around a large ceramic power resistor core). They work like a champ, but run "red hot" in dispensing the extra 6v dc once installed in the 12v converted vehicles using the 12v dc vehicles upgraded voltage regulator. I have a vintage Knight model KG-660 6-12 v dc battery-eliminator to use on my workbench when restoring these vintage car/truck radios. I replaced the orig selenium-rectifier in it using diodes many yrs ago as you suggested. Works like a champ indeed! Thank You for offering your help! You bet, your conversion applied to the vintage Heathkit BE-4 , BE5 , models battery eliminators, is a superb idea to restore those vintage pcs of great looking bench test gear, back to very reliable operation indeed for "bench testing"!! Thanks again for offering to help me with the schematics!!
etech and justlrlin, if any you guys need some nichrome-wire to handwind your own power resistors when needed, I purchased 2 almost full spools vintage nichrome wire from a vintage radio repair shop several yrs ago that had been closed back in the 50s, and remaining inventory auctioned in 1990! I need to check the "ohms per ft", as I have 2 different (diameter) sizes on 2 different rolls.(both very small diameter nichrome wire). But these 2 sizes fit most vintage radio applications indeed, and each roll has enough nichrome wire to wrap around the Earth several times! This vintage nichrome wire was mfd back in the 1950s. It is good (nos) quality!As you know, nichrome wire cannot be soldered,period! About the only way to use this wire, is by cutting to length,close as possible to proper ohms needed, then "hand wind" the nichrome wire around a old defective "open" type ceramic vintage power resistor body, then carefully twist the wire around the old end solder connections points.If needed, I will share this nichrome wire for actual cost of postage if you guys need any of it in the future! I will never be able to use all of it in my lifetime!!, so if anyone needs any, I have plenty here to share for free, if you can use it! It works well for rewinding AK ballast resistors indeed! I rebuilt a AK mod 42 power pack using it, and it works great on AC current! This nichrome wire is too small for DC use however, it takes much larger diameter wire for DC use! I rob that size diameter nichrome wire ( for DC use),... from old vintage electric room heaters! You can find mucho spare nichrome wire o-plenty at garage sales,etc., in those old elec heaters elements for cheap,cheap prices these days!!! The elec heater turn "red hot" also when you plug-em in! Having some spare Nichrome wire in your shop, is also fun to experiment with on AC and DC. You CAN, build your own power resistors by hand, and experimenting is half the fun!!