Philco 38-3

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Philco 38-3

Post by Wildcat445 on Fri Apr 18, 2014 7:27 pm

A friend of mine brought me this set to work on.  "It just quit" is the complaint.  Everything is original, including the filter caps!  Not good on a 1938 Philco.  Preliminary tests confirm that there is no continuity in the primary circuit of the PT.  NOT GOOD!!   Crying or Very sad  Thwe switch and the power cord check good. The electrical tape that holds the power cord to the innards of the set checks good, too.


Methinks he ran it one time too many.  I have been after him for 25 years to get the thing serviced.  But, oh no, old 'Cat doesn't know anything.  Who does he bring it to after he fries it?   Rolling Eyes 

Wish me luck, guys.  Just for grins, does anybody out there have a spare PT for this thing?  It is the kind with a 5V4 rectifier on top of the PT.  The schematic is in Riders 8-58 thru 60.  Thanks.

Regards

WC

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Re: Philco 38-3

Post by Dr. Radio on Fri Apr 18, 2014 9:01 pm

If you would have asked about a Philco PT about 2 years ago I coulda maybe helped ya out when my Elmer was getting rid of his stuff.

By the way WC, I hope you haven't been e-mailing me pictures lately. STUPID hotmail has me locked out of my account. The security provisions they provided don't work on the system they enforce! So if you have sent me pics to post, I haven't been ignoring you. Mad 
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Re: Philco 38-3

Post by Wildcat445 on Fri Apr 18, 2014 9:38 pm

No, Doc, I haven't. But I appreciate your thinking of me. I have some I could share, but I will hold off until you get back up and running. I thank you for bailing me out all the time. Next to finding my Concert Grand, the NEXT thing on my bucket list is to get more friendly with technology. They tell me that I MUST get a new cellphone. My old one will no longer be serviceable. I got it in 1998, and that is modern for me. I don't know how this will work, but I gotta get off my can. You guys are the absolute best. Seriously.

Regards

WC

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Re: Philco 38-3

Post by 75X11 on Fri Apr 18, 2014 11:02 pm

Could this be of any value?

http://www.ebay.com/itm/VINTAGE-TUBE-AMP-POWER-TRANSFORMER-129-/251504968138?pt=Vintage_Electronics_R2&hash=item3a8edd41ca
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Re: Philco 38-3

Post by Wildcat445 on Fri Apr 18, 2014 11:08 pm

Yes, 75, it could, and thank you. I would really like the Philco part number for that transformer. I have one for a six tube Philco, and need to test it to see if it is good. I also need to compare part numbers to see if it will work. I don't know how many different transformers Philco made with the rectifier in the transformer. Thank you for the link. I still need to do some numbers checking to be sure.

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WC

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Re: Philco 38-3

Post by 75X11 on Sat Apr 19, 2014 6:41 am

If you have the Riders and Beitmans libraries, their sections on Philco units are lifted from the Philco RMS year books and have good parts listings. After reading you needed the xfmr, I just went to Ebay. all categories, entered "philco power transformer" in the search box, and that unit linked was the first of about 60 different units that came up. It was the only one that matched your description. A lucky strike.
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Re: Philco 38-3

Post by Wildcat445 on Sun Apr 20, 2014 12:10 pm

The 38-3 I am working on has been thoroughly fried. The PT, rectifier, and at least the wiring to the field coil and input filter cap are all cooked. The 10 mfd input filter cap has salt running out of both ends. The glass on the 5V4 rectifier is black. The schematic lists a 5Y4 as the correct tube. I remember when this man got this old radio, back in the 1980's. He has used it a lot. He likes to listen to basketball games on it. It hasn't even been dusted inside in all this time. In addition to repairing this damage, there are about a dozen bakelite block caps to rebuild and whatever else needs done. This thing is in worse shape electronically than my 116-B was. Were this man not a close personal friend, he would be getting his radio back with my sincere condolensces.

Regards

WC

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Re: Philco 38-3

Post by 75X11 on Sun Apr 20, 2014 12:20 pm

How much of the season will he hear on it this year?  Very Happy 
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Re: Philco 38-3

Post by Wildcat445 on Sun Apr 20, 2014 6:58 pm

Basketball is almost over for this year, playoffs notwithstanding.

I kluged in the power transformer from the 37-630 parts set I have. The transformer is for a six tube set, and this one is a nine tuber. It looks to me like the input filter cap shorted, took out the rectifier and the power transformer. I still am not sure why the wires to the field coil were burned. The field coil continuity checks somewhere around 1500 ohms, give or take, so that should be good. There is nothing that appears burned, nor does anything smell burned around the field coil. The voice coil checks about 2 ohms, right on the money. The only thing I see amiss is that there is no continuity from one side of the secondary of the output transformer to the center tap. I don't usually get too excited about this, pending measuring the voltage on the plates of the output tubes. I have found that merely checking resistance on the secondary of an output transformer is not always a reliable indication of trouble. I am in the process of rewiring the plug on the speaker with the wires going to the output transformer and to the field coil. I have to drill out the rivet that holds the plug together, effect the repair, then figure out how to put the plug back together. All the rivets I have are too large. I may be on the hunt for some smaller rivets. Lowes or HD maybe?

Yet again, I am involved in a radio that has been hacked. Why I always seem to get ahold of these old dogs is beyond me. This radio, a Philco 38-3, has five knobs on the front panel. The upper one is for tuning the dial, the one under that with the handle is the band switch. The one directly under that is the magnetic tuning switch. The knob on the left of the panel is the tone control/power switch, and the one on the right side of the panel is the volume control. Usually. Not on this thing. Somebody, in their infinite wisdom, has (I think) removed some, most, or all of the magnetic tuning hardware. They have wired the magnetic tuning switch as a power switch. Now there are TWO. Yepper, to turn this radio on, both the original switch on the tone control, and the magnetic tuning switch need to be on. And, to make it better yet, the magnetic tuning switch works backwards from a normal switch. Turn it to the left to go on, to the right for off. Nice. There appears to have been four wires connected to this switch originally. I have thus far only found one wire that has been cut. I haven't investigated thoroughly, so am not sure how this magnetic tuning is supposed to work. Pending further investigation, or someone educating me, methinks that with the magnetic tuning "on" you could push on the different buttons in the teledial and select a pre-set station. Magnetic tuning off would allow manual tuning. This radio will probably end up with the magnetic tuning switch being a dummy, performing no function. Barring a miracle, of course.

I have tested the primary circuit of the temporary PT and have found that to be satisfactory. The tubes all light, the dial lamps work, and there is voltage to the rectifier. I am going to go ahead and change the filter caps, the by-pass cap, rebuild all the bakelite blocks and test the resistors before I try to apply B+ to the chassis. Then I will power up and see what I have. I can't believe that the owner of this set did not see smoke, smell something getting hot or hear some strange noise when he fried his Philco. He's lucky he didn't burn up more than his radio, judging by the damage that was done. This baby is going to get some fuses installed before it leaves the shop.

Regards

WC

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Re: Philco 38-3

Post by Bill Cahill on Mon Apr 21, 2014 2:34 am

That's the primary. Not secondary. It is half open.. Wires probably rotted. Philco also tended to use chassis resistors that shorted to chassis. This set is going to need a lot to save it... It's fried...

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Re: Philco 38-3

Post by Wildcat445 on Mon Apr 21, 2014 9:47 pm

You're right, Bill. I misspoke. I tested the secondary and it is okay. The primary is the problem. Maybe. I have a ways to go before I will be concerned with that. This set can't be any worse than that Hallicrafters S-38C that I did for my neighbor. This one is a piece of cake compared to that thing.

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WC

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Re: Philco 38-3

Post by Bill Cahill on Tue Apr 22, 2014 11:14 am

I don't know. you will have trouble with that power transformer, and, will likely have to cut a hole in the chassis for a separate rectifier socket. This sounds like an expensive repair to me. When will some people learn?? How many burned radios, and, TV's have I run into in my life?? I could tell you horror stories that would curl your hair.......

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Re: Philco 38-3

Post by Wildcat445 on Tue Apr 22, 2014 12:48 pm

Actually, Bill, the transformer I took out of the parts chassis is only temporary. And, it is the "Run 1" transformer, which has the rectifier on the transformer, ala the 38-3. I have the wires twisted together and kluged in, admittedly, but it gives me a basis in which to test the rest of the radio, without buying a PT without knowing the condition of the rest of the radio. I have a Philco 40-180 that the output transformer checked open on one side, like this one, yet it proved to work just fine. That is why I have little concern at this time about the OT. Its failure to pass muster may be operator error, if you get my drift. I have some yard work to do today, but hope to get some bench time with this thing yet today. I have been scrathcing my head trying to think of how to diagnose an output transformer with an open to one half. I would have B+ on one plate of the P-P output, but I MIGHT have a red-hot screen on the other, due to the lack of B+ on the plate. Is that thinking correct? It has been a spell since I actually ran into this. This being the case, I need to be set up to read B+ on both plates, simultaneously, to avoid further damage. The "test" transformer I am using now will in no way work permanently in this radio. It is smaller than the original and will fall thru the mounting hole. I will have to source and obtain the correct PT in order to affect a correct repair. Thanks.

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WC

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Re: Philco 38-3

Post by Bill Cahill on Tue Apr 22, 2014 3:24 pm

Not a good idea. Doesn't it use PP 41 tubes, or, something like that? If so, one plate is running red because it's getting no voltage.............

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Re: Philco 38-3

Post by Wildcat445 on Tue Apr 22, 2014 7:01 pm

It uses P-P 6F6's. I shouldn't have a red PLATE with no voltage on it, should I? How about a red SCREEN, since all the current that should be attracted by the normally positive plate will be flowing thru the screen, with no voltage on the plate?

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WC

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Re: Philco 38-3

Post by Bill Cahill on Wed Apr 23, 2014 12:21 pm

Yes you would because the screen still has voltage. You must replace the transformer.

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Re: Philco 38-3

Post by jerryhawthorne on Wed Apr 23, 2014 3:47 pm

W/C, as best as I can tell after working on one is the magnetic tuning is really only useful (if that) for using the teledial. Due to the construction of the teledial tuner stops you can only adjust it to reasonable precision approaching the station from one direction. Approaching it from the other it will be off slightly. The magnetic tuning will bring it in properly. Not really necessary if you don't mind a little fine tuning manually.
Best, Jerry

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Re: Philco 38-3

Post by Wildcat445 on Wed Apr 23, 2014 5:24 pm

Thanks, Jerry. That was my thinking as well. I'm not sure what the magnetic tuning mechanism should look like, but it appears that something is missing on the dial tuning mechanism. I have other problems to tackle before I tackle the magnetic tuning, or lack thereof. I appreciate your input, and I thank you.

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WC

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Re: Philco 38-3

Post by jerryhawthorne on Thu Apr 24, 2014 6:30 pm

W/C the one I worked on was missing the lever/knob assembly. I did source one. There was a lot going on with contacts and insulators inside. Have fun. I did ultimately get it working as it should.
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Re: Philco 38-3

Post by Wildcat445 on Thu Apr 24, 2014 10:08 pm

Thanks, Jerry. This one still has the lever/knob assembly. I don't know enough about how this thing should work to be sure, but something just LOOKS like it's missing. I know for sure there are wires cut. I may need your coaching on this thing before it is all said and done.

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WC

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Re: Philco 38-3

Post by Wildcat445 on Fri Apr 25, 2014 7:17 pm

This set is getting curiouser and curiouser. At Bill's insistance that the output transformer was bad, I decided to start my restoration/repair project on this set in the audio section. It has already been established that the power supply is as burnt up as it can get without taking the house with it. I needed to know what, if anything, was going on in the audio section that might have caused a problem with the output transformer. OT's don't normally just "go out." A defective component normally fails and takes the OT with it.

The schematic for this set is in Riders 8-58 thru 62. I decided to start with capacitor #75 a bakelite block, number 8318 SU, an .03 at 400 volt coupling capacitor. When I unbolted the bakelite block, I noticed that the tar had been running over the side of the bakelite. Further inspection revealed that this cap had been pretty hot at one time. More investigation, measuring resistors with my ohmmeter, found four resistors, #85, 3500 ohms, #76, 190K ohms, and #77, 490K ohms, and #78 330K ohms, all burned in two. I removed both 6F6 output tubes and checked them on my tube checker. One of them checked good, no gas, no shorts, but the other was totally dead. Open filament. I shook the tube and heard parts rolling around inside. This Philco branded 6F6 has a silver getter than prevents inspection thru the glass. So I broke the glass to further inspect the tube. The electrical elements in this tube appeared to have been white hot at one time. It looked like someone has taken a welder's torch to the insides of this tube. Capacitors #82 and #86 are the plate by-pass caps, rated at .003 at 1000 volts. Cap #82 checks to be dead shorted. Exactly why all this happened is still out to the jury, but I think it is safe to claim that a catastrophic failure has occurred in this radio. I feel confident that I do indeed need an output transformer. To get this radio working dependably again, EVERY capacitor will need changed, and I would bet that the resistors will need changed as well. Both the power transformer, and the output transformer will need replaced. At least two tubes, so far are bad. This will be an interesting project by the time I am done.

Regards

WC

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Re: Philco 38-3

Post by Bill Cahill on Fri Apr 25, 2014 7:37 pm

I beg to differ with you.. In my day I've replaced not only open transformers, but, also shorted ones. And, I finally gave up the ghost on a basket case Philco 49-1201 because the primary of the audio output transformer shoted to chassis, and, nearly burned the place down.
My favorite Admiral tv had an open primary on output transformer.
I've seen them where half of the primary opened, and, other half shorted. I've seen it all.

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Re: Philco 38-3

Post by Bill Cahill on Fri Apr 25, 2014 7:39 pm

Oh, yes. And, remember this, dampness, overheating, and, circuit stress often damages the transformer, and, the speaker.

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Re: Philco 38-3

Post by Wildcat445 on Fri Apr 25, 2014 8:26 pm

So, if I understand you correctly, your theory is that all this was caused BY the output transformer. The transformer was not the victim, but the perpetrator? So, in one event, BOTH the output transformer AND the power transformer just decided to take a dump? Interesting. And a lot of work to fix.

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WC

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Re: Philco 38-3

Post by Bill Cahill on Fri Apr 25, 2014 8:41 pm

Wrong theory. That is exactly NOT hwat I was saying. I was saying the transformer is needed for full power, and, in PP without it, will damage one of the tubes.
The filter probably killed the power transformer. And, It is not theory. It's a coomon fact on output transformers.

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Re: Philco 38-3

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