[Oldresistor47]

Currently repairing a model 70 , pre B220000, ( determined this, thanks to Ron's explanation on Philco's numbering system). Problem: can only receive one very strong station.
Originally I did not get any signal but located an open primary winding of 1st Detector coil (6). Re- wound the coil. Now I only receive the strongest local station on the correct dial frequency. Checked voltages at the RF, a 24 tube. Found screen voltage high (120v), schematic called for around 90v. Checked resistance at the long tubular resistor and fond it had changed values. Corrected the voltage to the screen voltage (now 90) with another resistor. Still no change. Checked RF coil windings and they are correct.
I ordered a new 24 just to eliminate it, although I think the current one is good but can't verify it.
Question 1. While checking the long tubular resistances I compared the current ohms readings to the Resistor data sheet and I find them way off. Has anyone found the schematic to be wrong?
Question 2. Has anyone encountered the same problem and found the solution to only receiving one strong station and nothing else?
Question 3. Can anyone offer any suggestions as to a repair

I am still new to this forum and very grateful for all of the wonderful posting on this forum. I look forward to your comments. A special thanks to Ron for all of his input and expertise.

[Nathan Slingerland]

I've split this into its own thread.

[Oldresistor47]

Thank you

[Radioroslyn]

Still sounds like your local oscillator it's running. Verify by using a counter connected to the grid cap of the 24A mixer tube or have a listen for it in a working receiver @ dial frequency + IF frequency. Place the working set's ant lead near the 27 oscillator tube.
As for the wire wound resistor you may have to disconnect it from the circuit to get an accurate reading. Generally they are pretty reliable.

Saw something wrong on the schematic, the 47 tube has the internal connection from the screen grid to the filament tap. Should be the suspresser grid not the screen.

[Oldresistor47]

Before receiving "Radiorososlyn's" reply, I replaced dogbone resistor 16. It had changed value, down to 4K from the called for 51K but there wasn't a change in condition. I also received the 24 tube and replaced the 1st RF. The radio came to life. Now it time to restore the cabinet. Not looking forward to it.
Can anyone tell me the wattage on the dogbone resistors? I have a 5 Watt temporarily installed.

[Nathan Slingerland]

Do you mean resistor #14? According to the schematic resistor #14 is 5K. Resistor #16 is 13K.
http://www.nostalgiaair.org/PagesByModel...013834.pdf

In any case part 14 is Philco part #3526.
Part 16 is Philco part #3766.

Those are both 1 watt:
http://www.philcorepairbench.com/carbonres.htm

(Note: it looks like Chuck's site may be down - I had to look at the cached version)

[Oldresistor47]

The colors are, body green, tip is brown and an orange dot. I see on another schematic, "16" is 13K. It used to load the plate of the OSC. Colors seem correct for a 51K. Maybe it was previously replaced. I will try a 13k and see if it affects the performance.
PS, When I bought this radio, someone had installed a smaller all American five radio chassis on top of the original chassis. The controls were inserted on the side of the cabinet. This indicates to me it has had previous repairs.
Bought it thinking I could use it to learn the 1930's Philco circuitry. I'm very impressed by the early circuitry of Philco and the amount of room under the chassis. I am considering removing the tuner to clean it thoroughly but a little hesitant to cause myself additional problems. Any suggestions?

[Nathan Slingerland]

That does sound like a 51K resistor.

The Nostalgia Air schematics leave something to be desired, so you may find the service bulletin a bit easier to work with: Philco Service Bulletin No. 057A.pdf

You can remove the tuner to clean it - not a problem but I wouldn't mess with the alignment trimmers on it without carefully noting their position or capacitance value so that the set won't be too far out of original alignment when you put it back together.

How are you planning to clean it? I've taken tuners off of Philco 70 and 90 models to derust in Evaporust. That works pretty well.

It any case I'd also wait to do that until everything else on the radio is working well so that by the time you mess with the tuning condenser you don't inadvertently also trip over some other marginal issue at the same time and make any problem hard to diagnose.

[Oldresistor47]

Thanks for the advice. Did clean chassis with evaporust and found a few gold coins under the dirt (only kidding). Tuner was a breeze compared to the 38-650. Just cleaned it a bit. Not sure what type of metal was used so was reluctant to use anything acidic, etc. I re- attached the 51K dogbone and it worked fine. Will load some pics once I put the number under back on.

[Oldresistor47]

The dial is in one piece but it has some type of haze. Can that be removed? I tried warm water on the back side but the haze is still evident.

[morzh]

Try mineral spirits but first try on a corner. See that it does not remove graphics.