03-13-2012, 10:43 PM
Ron,
You had replied back to me in the Wanted Ads thread about my missing 38-5 speaker:
RE: ATTN Ron Ramirez: WTB Philco 38-5 Speaker
Okay...I had forgotten to whom I had sold that radio!
I've since replaced it with another 38-5B, and wouldn't you know it, this one has a speaker, but it is not an original Philco speaker.
Anyway...
The original speaker used was a K-39. 660 ohm field, 1.25 ohm voice coil. Primary impedance of the push-pull output transformer: 14,000 ohms.
Now you need to replace it.
You need a speaker with a field coil in the range of 660 ohms (650 is OK). You can always mount a new "universal" push-pull output transformer onto a replacement speaker.
There are a few other Philco models that used speakers with 660 ohm fields, but not very many. Here's the list:
K-23: Used in Model 19 Code 128, and Model 144B. (Uses a single ended audio output transformer that will have to be replaced with a push-pull unit.)
K-34: Model 37-640B. (Original push-pull transformer will work in the 38-5.)
Your other option is to install a PM speaker and replace the field coil with a 660 ohm, 25 to 50 watt resistor. 25 is actually large enough but 50 gives you a greater margin of safety.
I think I would have a hard time finding the K-23 or K-34 speakers. I looked on eBay and found a couple but they are in full sets. I think my best option would be to purchase a modern permanent magnet speaker. However, I'm not sure how I would actually hook it up. According to the schematic it looks like there would be 3 wires going to the K-39 speaker but there are 4 wires that connect to the speaker plug. A modern PM speaker has 2 connection lugs. How would I actually connect the wires from the plug to the PM speaker? Where would I connect the 660 ohm resistor?
Thanks,
Geoff
You had replied back to me in the Wanted Ads thread about my missing 38-5 speaker:
RE: ATTN Ron Ramirez: WTB Philco 38-5 Speaker
Okay...I had forgotten to whom I had sold that radio!
I've since replaced it with another 38-5B, and wouldn't you know it, this one has a speaker, but it is not an original Philco speaker.
Anyway...
The original speaker used was a K-39. 660 ohm field, 1.25 ohm voice coil. Primary impedance of the push-pull output transformer: 14,000 ohms.
Now you need to replace it.
You need a speaker with a field coil in the range of 660 ohms (650 is OK). You can always mount a new "universal" push-pull output transformer onto a replacement speaker.
There are a few other Philco models that used speakers with 660 ohm fields, but not very many. Here's the list:
K-23: Used in Model 19 Code 128, and Model 144B. (Uses a single ended audio output transformer that will have to be replaced with a push-pull unit.)
K-34: Model 37-640B. (Original push-pull transformer will work in the 38-5.)
Your other option is to install a PM speaker and replace the field coil with a 660 ohm, 25 to 50 watt resistor. 25 is actually large enough but 50 gives you a greater margin of safety.
I think I would have a hard time finding the K-23 or K-34 speakers. I looked on eBay and found a couple but they are in full sets. I think my best option would be to purchase a modern permanent magnet speaker. However, I'm not sure how I would actually hook it up. According to the schematic it looks like there would be 3 wires going to the K-39 speaker but there are 4 wires that connect to the speaker plug. A modern PM speaker has 2 connection lugs. How would I actually connect the wires from the plug to the PM speaker? Where would I connect the 660 ohm resistor?
Thanks,
Geoff
