Philco 90 Oscillator question - Printable Version
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RE: Philco 90 Oscillator question - Steve Davis - 02-20-2017
We need a schematic or at least tell us which version your chassis is.
Steve
RE: Philco 90 Oscillator question - Radioroslyn - 02-21-2017
So Mark,
Yous got that thing working YET?????
Measure the resistance from the ungrounded side of #14 (I think ur set is the one w/the signal 47 toob) to pin 3 of the 27 det/rec toob. Should see a low resistance like a few hundred ohms.
Good to see you the other day. If you like I'll dump out all of the dirty ashtrays and throw out all the empty beer bottles clear out a spot to have a look at ur 90.
RE: Philco 90 Oscillator question - sam - 02-21-2017
terry
your having radio party`s
With out us 
RE: Philco 90 Oscillator question - Radioroslyn - 02-21-2017
Hey ya know that's my life one BIG PARTY!!!!!!! HaHa...[Image: http://philcoradio.com/phorum/images/smilies/icon_shh.gif]
RE: Philco 90 Oscillator question - bdi1976 - 02-21-2017
It's a single 47 philco 90... I was lucky enough to get one with an extremely clean chassis with no visible rust or corrosion.
RE: Philco 90 Oscillator question - bdi1976 - 02-24-2017
I found a new resistor which somehow drifted 50% out of tolerance in only 1 year..the 10kOhm on the antenna..was only reading 5 disconnected from the coil. Put in a new one, cleaned all tube prongs with 200 grit sand paper, and got additional sound and clarity. Still a lot of background noise though unless I screw around with that IF secondary trimmer which clears it up. Is it possible it's just alignment since I rewound the oscillator coil? I tried adjusting by hand and don't know for sure if I'm at the right KC. I have a signal generator but not familiar enough To Try to align using it
RE: Philco 90 Oscillator question - bdi1976 - 03-12-2017
I'm getting closer. I rechecked all coils again- all ok. After some calibrating I had a stronger signal but still no volume control. The replaced trimmer didnt help. Then I realized by accident that the signal I am picking up is exactly the same with or without an antenna attached. The antenna circuit is not functioning. If I put my finger on the top of the 24 RF tube the volume control returns and the signal is very strong and the voltage on the plate of the 47 tube shoots up from 1 to 25 volts. Any ideas on what's dead ?
Also the #1 resistor was reading 10 ohms originally while attached to the antenna coil but riders says 10K ohms. I replaced it with a 10K at the same time as rewinding the oscillator but never rechecked the original one to verify what value it actually had. Is 10K Ohms correct per the schematic?
RE: Philco 90 Oscillator question - Radioroslyn - 03-12-2017
Well yes and no. If you are looking at #1 it is a 10,000 ohm resistor. But it is wired in parallel with the primary of the ant coil which is a MUCH LOWER resistance so what you are measuring is the resistance of the coil not the resistor. To measure it unsolder one end and then measure it.
RE: Philco 90 Oscillator question - bdi1976 - 03-12-2017
Terry..is it that the antenna isn't working or is it an amplification Stage that is out? If coils are intact could this be strictly an alignment issue? Why would bringing my finger near the top of the RF tube cause a 20X boost in voltage going to the 47 amplifier?
RE: Philco 90 Oscillator question - Radioroslyn - 03-12-2017
Check the resistance of the ant coil primary and secondary. Both should show a low resistance like 20 ohms or less. Check the plate and screen voltage on the rf amp should see about 200v or so. Cathode should have a low voltage maybe 5-10vdc. Acts like your ant coil is open. If you want to bring it over just give me a heads up so I can clear off the space to work on it.