The PHILCO Phorum
Line in for 41-285 - Printable Version

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+--- Thread: Line in for 41-285 (/showthread.php?tid=8776)


Line in for 41-285 - Diverted - 02-14-2014

Hello all,

I have posted a bunch of questions here in recent days about my Philco 41-285. Thanks for all your help; this is the first Philco I've seen and apart from the rubber wiring Icon_thumbdownIcon_thumbdown it's been a pretty fun rebuild.
I am having a problem, however. I need help in correctly wiring in a line in.

I wired one in the other day the same way I have done in other radios: Tapping into the high side of the volume pot and ground.
This worked; I was able to play an auxiliary source in this manner. However, it caused a problem I have not seen in other radios. When I disconnected the auxiliary source (BUT left the auxiliary wiring in place) and attempted to listen to the radio, the signal was a lot quieter than it should have been. Once I completely emoved the line in from the volume/pot ground, the radio volume returned to normal. Here is the adapter that I plugged into the volume pot:
http://www.antiqueradio.org/iPodAdaptor.htm

Any idea why this problem occurred? Some sort of impedance mismatch? As I said I've run this adapter into other radios and never had this radio signal attenuation problem. Any ideas on fixing it would be much appreciated!

Thanks,

Ted

RE: Line in for 41-285 - morzh - 02-14-2014

Before I look in teh sch I think the problem is due to the adapter being a transformer and as such presenting a low resistance that shunts the volume pot.

Yep, your volume pot is 2Meg. Your apteer is, Gow willing, in hundreds of Ohms if not less.
You could make a switch, so only to hook up the adapter when needed.

RE: Line in for 41-285 - Diverted - 02-14-2014

Thanks.
Instead of wiring in a 1-2 switch, could I do something along the lines of adding some large resistance to the adapter? It uses 10 ohm resistors as built; Would I be better off putting larger ones in and if so, what size? 5K? 10K?

Thank you!

RE: Line in for 41-285 - morzh - 02-14-2014

No, not there.
You could try to add a large, on the order of 100K-1M to the output in series (does not matter which pin).....but the problem is the iPod is a low signal source.
Still, you could try.

RE: Line in for 41-285 - Diverted - 02-16-2014

Added a SPDT toggle switch. Works like a charm, using the adapter I mentioned. Thanks for the help!

RE: Line in for 41-285 - morzh - 02-16-2014

Good.