The PHILCO Phorum
Philco Model 91 - Printable Version

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RE: Philco Model 91 - texan george - 06-27-2022

Terry,
Your right, I measured right but called it wrong. The O/P transformer p/n 2585 is open on both sides. Ordered some more caps to replace the condenser block caps. Will a PT-125 series transformer work for a replacement? Also, the RF and Det coils each has a wire cut off, don't know what the previous person in here did or why. One problem at a time.
George

RE: Philco Model 91 - Radioroslyn - 06-28-2022

Looks like the 125E is going to be the replacement as the maximum plate current on the 42's (6F6's) is 82ma. Hope your rich [Image: https://philcoradio.com/phorum/images/smilies/icon_lol.gif]. As for the under the hood wiring I think I have a 91 chassis around which I can snap some pics of if that will help out. But have to find the darn thing...

RE: Philco Model 91 - texan george - 06-28-2022

Thanks Terry,
No, I aint rich, retired like most of folks my age, but I'll look into it price wise. If you get a chance to look at yours, I would appreciate it. I did send Mark Oppat a email asking if he had the transformer or on/off switch. Been looking online for parts but no go so far.
George

RE: Philco Model 91 - texan george - 06-29-2022

Terry,
I see now why you put the emoji in your thread. AES has it for $55.37 plus shipping. I guess I will have to order one if nothing else comes up soon.
Q. Why would Philco rivet the trans onto the speaker frame, going to be a delicate move to remove and replace it.
George

RE: Philco Model 91 - Chas - 06-29-2022

A (large) makeshift collar of electrical tape around the drill bit will reduce the chance of the bit punching through the cone. Start with a very small bit to keep the hole through the rivet body on center. The large bit is to remove the flange of the rivet. Use a "slip-stone" (by hand) on the cutting edge of the bit to reduce the cutting angle so it is less likely to grab the thin metal. if this is a PM speaker beware of chips in the voice coil. Still, some dynamic speakers will have residual magnetism that will grab drilling chips.

RE: Philco Model 91 - texan george - 06-29-2022

Thanks Chas,
I have drilled out rivets before but will take extra care on this.
George

RE: Philco Model 91 - Radioroslyn - 06-30-2022

To answer your question of recent date. In an assembly line it's much quicker to slam in a couple of rivets rather than screwing in screws, lock washers, and nuts. The cone isn't in place yet there's free access to the inside under the transformer.

You may have to fabricate a mounting plate as I think the bottom of the 125E is wider than the Philco transformer. And figure out how stabilize the wiring as there are no terminals for the primary on the 125E, just for the secondary taps. It's not a big deal.

RE: Philco Model 91 - texan george - 07-01-2022

Thanks Terry,
I haven't gotten the 125E yet but will see about a mounting plate shouldn't be to much of a problem. Been going thru it and think I may have an open RF coil for some reason I'm having problems reading stuff, so I have been highlighting everything on the schematic, (enlarged to 11X17). 
George

RE: Philco Model 91 - texan george - 07-12-2022

Finally got the 125E and mounted to speaker frame. I thought I had it figured out on how to hook up, but now I just don't know, do not want to burn up or short anything. Sure could use some help.
Thanks,
George

RE: Philco Model 91 - Radioroslyn - 07-12-2022

Voice coil connects to 3 and 4 on the transformer. Blue and Brown wires connect to pin 2 of the 42 tubes, one per tube. Red wire connects to one of the field coil wires. That in turn goes to the + side of the 2nd filter capacitor. The other end of the field coil goes over to the B+ side of the drive transformer or terminal 1 of #46 volt divider resistor.

http://www.nostalgiaair.org/PagesByModel/657/M0029657.pdf
your set is the code 121.

RE: Philco Model 91 - texan george - 07-12-2022

Thanks Terry,
I will hook it up and get back to you. The label on the chassis says it's a code 126 but should be the same. Thanks again, I rely on yall's knowledge and willingness to help.
George

RE: Philco Model 91 - texan george - 07-12-2022

I see what you mean by the code 121

RE: Philco Model 91 - Radioroslyn - 07-12-2022

I could be wrong about the code but that was the schematic I found with a single speaker.

RE: Philco Model 91 - texan george - 07-13-2022

Terry,
Hooked up the trans like you said, turned it on and got some background type noise out of the speaker that changed in loudness with the vol control. Noise is not a hum or anything like that, more like in between stations. Did not get any reception, so need to look into that. Will try some more checks.
George

RE: Philco Model 91 - texan george - 07-14-2022

I pulled the RF coil out and found a problem. Going clockwise from the mount/ground terminal number 1 which connects to the ant connection and 10k resistor has a broken wire hanging on the inside about 1/2 inch but doesn't connect to anything. According to the schematic is should also go thru a 25-ohm coil to ground. Also, the small coil at the top of the RF coil has broken wires and has only one wire coming up thru the main coil to cap item 6 which I believe goes to ground. The cut wire I mentioned early on is on terminal 3. My guess is that someone took out the on-off-freq switch and that would be part of that, because there is also a cut wire on terminal 4 of the detector coil.
So how do I fix this? Where does the broken wire off terminal 1 go?
Thanks,
George