08-30-2018, 09:18 PM
Back in July's Phinds I noted that I'd picked up an Emerson 25A, schematic LINK.
[Image: https://www.dropbox.com/s/v0ioedp4u8x80m....jpg?raw=1]
At the time I just posted a quick picture and it came up that it might have a resistive "curtain burner" power cord. From the schematic it appears that R7 305ohms would be the power drop resistor and it would be in the chassis. But after taking a look at the chassis more closely I can see remnants of the resistive element in the power cord (a bit of asbestos insulation still showing) so that R7 is simply the schematic representation of the resistive power cord element.
[Image: https://www.dropbox.com/s/7tvcs04pgx5659....jpg?raw=1]
I've not replaced one of these before so am reading about capacitors as voltage dropping components. There are a number of articles out there...more later.
The on/off/volume control was very dirty and I thought might have failed completely but after taking it apart and cleaning it up it seems to be work OK now. I did find that the volume pot is only a 25K ohm pot rather than the 200k noted in the schematic. It remains to be seen whether the schematic is in error or the pot is a replacement. I do have a 250k on/off pot that I can substitute if needed.
[Image: https://www.dropbox.com/s/vphk5xynx07guc....jpg?raw=1]
[Image: https://www.dropbox.com/s/v0ioedp4u8x80m....jpg?raw=1]
At the time I just posted a quick picture and it came up that it might have a resistive "curtain burner" power cord. From the schematic it appears that R7 305ohms would be the power drop resistor and it would be in the chassis. But after taking a look at the chassis more closely I can see remnants of the resistive element in the power cord (a bit of asbestos insulation still showing) so that R7 is simply the schematic representation of the resistive power cord element.
[Image: https://www.dropbox.com/s/7tvcs04pgx5659....jpg?raw=1]
I've not replaced one of these before so am reading about capacitors as voltage dropping components. There are a number of articles out there...more later.
The on/off/volume control was very dirty and I thought might have failed completely but after taking it apart and cleaning it up it seems to be work OK now. I did find that the volume pot is only a 25K ohm pot rather than the 200k noted in the schematic. It remains to be seen whether the schematic is in error or the pot is a replacement. I do have a 250k on/off pot that I can substitute if needed.
[Image: https://www.dropbox.com/s/vphk5xynx07guc....jpg?raw=1]
