Hello, this is my 1st post in this phorum. I bought a Philco model 70 from Ebay that was in good condition and mostly original. The problem is they didnt remove and pack the speaker (which I had requested), and it came loose and busted the grill. I had the cabinet repaired, and it looks really nice. I havent powered up the radio yet to check things - the seller said it had a low hum and static. The speaker voice coil rubs the magnet when I press the cone. It has the screw in the middle. Before I send this off for a repair, is there some kind of adjustment to center the coil? I havent had any success in searches here on this, and havent found anything on youtube (although there are some interesting videos on rebuilding some of these radios).
A little about myself: I am a 'retired' electronics technician from a large company from about 12 years ago. I had studied (from reading a bunch of my uncles McGraw Hill books), have knowledge and worked with tube electronics from a very young age, which is, and always has been a love of mine. I graduated from a technical college and worked as an in home/shop electronics technician with about 17years in the profession. I gave it up right after 911, and the introduction of plazma and LCD tv's. I caught the very tail end of tube sets that came in for repair in the mid 1980's. I am not retired from the company, but no longer work on electronics for them.
I have the electronics knowledge, but lack experiance on early equipment, such as this Philco 70. Any help or links would be appreciated as I work to restore this radio. Also, I am trying to find the post/thread about products that remove rust from metal. I read it a month or so ago, and now cant find it.
Thanks,
Tim
You can loosen up that screw and slide the voice coil around slightly. If it is not broken or warped, that is often all it takes.
Philco 70 is as simple as it gets with superherts.
It is one of those "milestone" radios with Philco, this is why I got it, together with 20 and 90.
When done with it don't expect a stellar performance, but it will sound OK.
Thanks for the advice. I loosened the screw and it seemed that it helped a little. I dont know if this type speaker is pretty 'tight', or if there should be pretty free movement of the cone. It may have some crud around voice coil. This is a little different than what I have seen in the past, no spyder or cover over the voice coil. This speaker is tight. Ill know for sure when I power it up and test things. Field and output trans checks ok with the ohmmeter. I had been concerned that the ship damage might have tweaked things.
I did find the post on rust/chassis cleaning by Bob Anderson. Evapo-rust was what I was looking for. It's in the Electronic section, which may be where I should be posting this.
Thanks,
Tim
In fact what you see in the center, the rigid piece of paper through which the screw goes, is actually the spider. Does not add to quality sound, but that is how it is.
I guess you could try to unsolder the voice coil, remove the screws holding the cone and then this central screw, remove the cone (never done it myself but I think this is how it should work looking at the speaker) and try to clean whatever crud or some other cr.... which is in there, and then replace the cone and center it.
My model 118 speaker rubbed lust like that. when I removed the spider center screw the whole cone came loose as the cone surround to basket glue had dried out and didn't support the cone in position. So I lifted the cone out being careful not to damage the cone wires and blew our the coil gap with compressed air. Then I re-glued the cone surround and carefully set the cone back into position tightening the spider screw before the glue dried. No more rubbing!
Steve D
Now that I have the 70 rebuilt and working decent, I decided to tackle this speaker. It sounded pretty bad with a lot of rasping and popping. I unsoldered the voice coil leads, removed the screws and lifted the cone out of the speaker. A word of caution - part of my speaker cone was stuck to the metal frame and started to tear. I used a knife to gently remove it. I didnt have any speaker cement, so I used fabric glue to repair. Also, make sure you guide the screwdriver with your thumb so it doesnt slip off the screw and puncture the cone.
Here are a few pics.
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attachment=3855]
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Here was the problem. The air gap is full of a lot of metal shavings. I cleaned out with a small screwdriver, then blew out with compressed air.
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attachment=3857]
I put things back together. Remember the order of the washers in the screw on the spider. I put this screw in first. This centered things. Next I put the outer screws, loose, then gently tightened, pushed the cone to check, then tightened up. A mistake I made was cementing the cone where I ripped it after I reassembled. I had a noise from the tear between the metal frame cone ring. I had to remove, glue the part under the cardboard ring, let the glue dry, then put back together. (I didnt unsolder the VC leads for this) This time, it sounded good.
Very good.
I have a 70 speaker which has:
1. Bad transformer.
2. Bad field coilo.
3. Cone missing 1/3 and brittle at that. The spider and voice are OK.
I think of shipping it to someone to restore provided they do field coils (the transformer I will tackle).
I also have a 20 speaker that I do need to restore (bad field) as I will soon start on that 20 (Delux I recently bought).
I know there is a shop in Jersey. But from what I read on the website the communication is not great. the Speaker shop ismuch further but I could call them and speak to them.
Wow Mike, that almost sounds like a direct hit by lighting! Sounds like yours needs a little more help than average. They arent too bad to get apart with a little patience (that comes and goes for me
). I didnt figure I had much to lose - it wasnt right anyway, so I gave it a try. Here is a shot of the finished product.
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Except it wasn't - there is no visible fire destruction
But while 20 speaker can be easily disassembled, just have to remember to take your cone off first and unscrew the pole after, the 70 will require pressing it out which I am not equipped to do.