I have a Philco 551, 51, 51A I'm trying to restore and I've run into an issue with the #16 (Schematic) 2nd IF coil part # 03886.
There are 4 tabs and I'm looking for resistance values and which tab's they go with, someone has been in this and rewound part of it, is turning into a bear to sort out.
An IF transformer is difficult thing to rewind and make it work properly. The type of wire, the distance between the coils, how it's wound, and the amount of Q of the coils are all factors that determine the IF transformer's performance.
If the rewind looks like it's hand wound or spun on a drill I would look for a replacement 175kc transformer. They were popular from the '30s-50's so they're not hens teeth.
The resistance readings don't really mean anything in this case. It would just tell you if the coil is open or not. Your probably looking for about 20-30 ohms.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Yes it has been partially rewound and I get about 7 on one coil and 3.5 on the other. I will look around for a 175 kc can.
I put the tape on to keep the end coil from unraveling.
Thanks,
Hold on - that is not an IF transformer. It looks like an antenna coil.
Please study the under-chassis drawing (taken from Service Bulletin 114, for model 51) carefully.
Notice that the 2nd IF transformer, part (16), is in a cylindrical container mounted above the 2nd det. tube socket (when looking underneath the chassis). The 1st IF transformer, part (12), is in an identical cylindrical metal container, mounted above the 1st det.-osc. tube socket. The antenna coil, part (2) and probably the coil you have photographed, is mounted inside the chassis as shown in the drawing below.
Please confirm where that coil came from in the chassis.
You are spot on!
I now see the IF's 12, 16 (I would have never spotted them) in the chassis and the coil I pictured is in the can marked by #2.
I paid $10 for this as you can imagine it is in pretty rough shape and the 35 was not there and a 24 was in its place, The original speaker is gone and a PM was put in.
I have recapped except for the #23 Capacitor Block as I have no info on that.
It powers up and I can get some static as I touch components so I think the Audio part is ok, here are the Socket Voltage readings that I took the one that looks really out of line is the control grid on the 24 2nd detector I get nothing.
I now have it working somewhat and it was way off the 175kc Now I'm going to do an alignment probably tomorrow as time allows but I think I have an issue with the Vol pot. What is the correct value for this pot I cannot find it anywhere in the paper work I have? It shows a max of 40k but very erratic.
The original volume control was 5000 ohms. It should not be hard to source a replacement. If you decide to replace it, be sure and get a linear taper potentiometer, not an audio taper.
Try some FaderLube (DeoxIT Fader F5) in it first. Don't use red label DeoxIT - that is for switch contacts only. Use the green label DeoxIT Fader F5. And for goodness' sakes, don't use WD-40!
A word about the antenna coil, part (2). As the winding that was rewound appears to have been done rather sloppily, this is in the antenna input of the radio and, therefore, is somewhat forgiving. If it had been one of the other coils, it is more important that they be rewound properly if they were to need it.
Thanks, I took out the pot it is a Centlab and the mounting was cobbled up so they just threw in what ever they had on hand. Across the two out side tabs I get 125K to 150k and the center to one side well is 125k-45k and the other is 108k- 2.2k I believe it is trash I have pots and will see what I have.
If you don't have a 5000 ohm control, a 10,000 (10K) or 20,000 (20K) ohm control will probably work just as well. All this control does is to shunt a selected portion of the incoming signal to ground, depending upon the setting of the control.
Just be sure any replacement is linear taper. An audio taper control will work, but will have a very large change in value over the first third or so of its travel. Linear taper pots change gradually, in a linear fashion, from "low" to "high". For audio circuits, an audio taper pot is ideally suited. However, in this application, a linear taper pot is better.
Ron,
I have a 10k pot and I believe it is Linear any way it acts but I'm not getting a lot of volume I have about 20-25 feet of antenna (enough?) and it plays a bit better with the ground attached (I have a separate ground stake). I did not get into the Capacitor Block 23 is this worth getting into? I have a Schematic that does give me the values for the 5 caps inside. They all seem to be located between the 2nd detector 24 and the output 47, 23A thru C.
Yes, be sure you replace all of the paper capacitors including those in box (23), for best performance.
Also, a good alignment will also be beneficial, once all paper caps have been replaced. You will likely also need to replace all the resistors.
That said, 25 feet is not really enough for a vintage radio. The longer and higher the antenna, the better your radio will like it. Just be sure to keep it as far from power lines as possible, and use a suitable lightning arrestor.
Ron
I will work on replacing the rest of the caps and resistors, Also working on the cabinet it was in terrible shape and am in the process in making some of the wooden parts that belong on the top and speaker grill.
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