[tonto007]

Hello, i have 2 49-900 philcos. They are wired identically. The first that I refurbished plays beautifully. The second one has much static after repair. So, I replaced all the components that I hadn't as they tasted okay. Still a lot of static. I replaced the tubes with the ones from the playing one with no success. HELP!!!

[GarySP]

Hello. Start with the easy things to do. I would clean all tube contacts and tube pins with Deoxit. I use thin strips of the green scouring pad (scrunge?) with the Deoxit on the tube pins. For the tube sockets try Deoxit on a Proxy brush (dental brush) to clean the contacts. Let everything dry completely before plugging it back in. You can also take a wooden chopstick and tap components on the chassis and listen for any change in the static. Minimal investment required, and at least is a place to start. Good luck! Take care and BE HEALTHY! Gary

[mikethedruid]

Look carefully at the tuning condenser. Dust between the plates of the condenser can also cause this. Blow it out well with an air gun, and then run paper between the plates to clean them some more. If they are far enough apart, you can use a thin pipe cleaner. Be careful not to bend the plates.

[falcon123]

deoxit the tuning cap shaft wipers clean and lube.be aware that you need to use a non filming contact cleaner to clean the tuning cap. you dont want lube on the fins or anything else on them either.some floks lube the ball bearing and bushing with machine oil,some use grease in the bearing.i prefer machine oil as any petroleum grease will dry up faster than you might think. but the rest of the suggestions are equally valid. normally when i decide to rebuild a radio the FIRST thing i do is deoxit using D100 all switch contacts and tube pins and sockets as well as the tuning cap. i leave it on there and periodically renew it during the rebuild. i do this AS DEOXIT TAKES TIME TO EAT THROUGH THE SULPHIDES and other crap that accumulates. after the rebuild i then flush and remove it and use fader lube. DO NOT use d100 or d5 in volume controls or any similar type control EVER or any other solvent as it can eat the resistive coating in the control and destroy it. only use deoxit fader lube. additionally if you have used any contact cleaner or somesuch in these controls and have not yet destroyed it, you must re lube the the wiper and resistive element with fader lube or rapid wear can result

[MrFixr55]

Hi Tonto. The thread has very good suggestions. I am a big believer in "Divide and conquer" troubleshooting.

Before anything else:
Caution! This radio is a "Hot Chassis (even if isolated by a capacitor) with a very real shock hazard. Worse yet, the power switch switches the neutral instead of the hot connection. Either use an isolation transformer or use a meter to ensure that the chassis is at neutral (ground potential by checking voltage between the chassis and ground. If voltage reading is near 120V then reverse the orientation of the power plug. Check agin for a low voltage between chassis and ground. Do not turn the switch off or then the chassis becomes hot again due to the continuity of the tube filaments.

If U wanna get down and dirty, look at the schematic from Ryders and break the connection between the volume control and the detector stage. connect a source such as an MP3 Player. If the sound is good, this eliminates the power supply, volume control and amplifier section. If this is not the way you wanna go then:

First test- Turn down the volume control and smack the radio around (Tap individual components with non metallic object). Static? Then check volume control, Power Supply(Including filter and all 'bypass' caps and Audio Section If good, then:

Second test- Set the Tuning Cap (Capacitor) to full open (1700KHz). Vary volume control. Static? If good, leave volume control high. Smack radio around Static? If so, then check connections, tap individual tubes, components, etc. If no static, then:

Third test- Slowly tune down till the first station is heard. Static, if not, then continue tuning downward. If static starts as the tuning cap plates start to mesh, tune up again and then tune back down. If the static starts at the same place on the dial scale the the tuning cap has dirt or aluminum oxide between plates or the plates touch.
One method is to take a feeler gauge and run between the rotor and stator plates. then blast with canned air or leaf blower. Also check the piece of spring copper that connects the rotor to the cap frame.

If static occurs only when the radio is played loud, then the voice coil wires (the flexible ones that go from the cone to the frame) may be intermittent.

Static can also occur from internal arcing from any of the coupling or bypass capacitors. The IF transformers may have issues (Silver Mica Disease), but that is the last place to go.

Hope this helps.

Best Regards,

Mr Fixr

[OZ4]

What they said. Yes I don't like the neutral switched. I been known to rewire the power switch to the hot side. And use a polarized cord. they have real nice ones at the home depot here. For now.

[MrFixr55]

Right, Chris. I do the same, makes the radio much safer, though in some cases it increases hum. Worst case, don't run anything to the volume control mounted power switch, and use a line cord switch (properly installed in the Hot Side) I probably exceeded the usual word count of experts so I did not add that mod to my original reply to Tonto, so here it is.

Hi Tonto,

One very bad habit of these "AA5" style radios and other radios that do not use a power transformer is that the chassis is either directly connected to one side of the AC Line or connected through a capacitor and resistor arrangement to the Common (B-) Bus which is connected to the AC Line. To make matters worse, the power switch is placed between this point and the power cord. Furthermore, the power cord is usually not "polarized". This is a loose - loose safety wise. If the chassis is connected to Neutral lead by the way the plug is inserted then with the switch on, the chassis and common bus is at neutral (ground) potential, lessening the chance of shock- until the power switch is turned off. With the switch off, the filament string ,which is at very low resistance when cold, connects the Chassis to the Hot lead. The shock can be lethal, especially to a geezer my age and condition.

A common safety mod made by many collectors and referenced in several websites is as follows:

1. Obtain a schematic of your radio. Confirm by schematic and inspection that the power switch connects the common bus to the power cord. Remove the power cord from the radio. Remove the connections to the power switch.

2. Obtain a line cord with a "polarized" plug. A common recently purchased extension cord with the "outlet" end cut off will do.

3. Connect the conductor that leads to the wider of the 2 prongs (the neutral conductor) to the common bus.

4. Connect the other conductor to one leg of the power switch. Connect the remaining connection removed from the power cord (usually the plate of the rectifier and rectifier filament to the power switch. Dress the power cord as far away from audio and RF Signals as possible and as close to the Chassis as possible to minimize hum.

Unfortunately, a picture is worth 1000 words (or 10,000 of mine). Maybe an expert has written an article that can be published in an appropriate section of of this Phorum.

Best Regards,
John "MrFixr" Stroh

[tonto007]

Thank you all for your input . I am well acquainted with using the proper tools & have repaired quite a few radios but this is the first one that is like this. Before I started on it it received one station with static everywhere on the am band. I have replaced all the components, tried tube replacement, and cleaned it thoroughly. I aligned it & still have static & receive only one station bot very strong. The if cans are the type without silver mica sheets. I've gone over it with a fine tooth comb & cannot find anything wrong. I made sure that the tuning condensor plates were not rubbing. I tried a new volume control pot with the same results. There is nothing left to try that I can see.

[RodB]

Have you checked the AVC voltage? When a station is tuned in it should be -8 volts or more, around -3 between stations. Or maybe the oscillator is weak. I don't know how to determine if it's not running on all cylinders.

[Radioroslyn]

You might have a look at C-301C and D. They are internal in the ceramic section of the second IF transformer. To troubleshoot use a signal tracer in the diode mode connect to the plate of the 2nd 7B7. If the signal is clean of static It's a good bet it's those caps are leaky.

[tonto007]

Thank you Radioroslyn for your responding. You showed me that I should not assume that it can't be one of the if cans just because there is no silver mica sheet. I need to pay more attention to the schematic. My signal tracer only has trace, noise & wattmeter as the selections. However, I'll replace those caps & let you know the result. Thank you again for your valuable input.

[Arran]

In my opinion there is very little electrical hazard from working on a floating chassis AC/DC radio, unless you intend to power the set up, and touch the chassis whilst standing, bare foot, on a concrete floor. Adding a polarized plug is a waste of time, once the chassis is inside the cabinet, which is either made of wood or Bakelite, nobody will be making contact with the chassis if the set has a back on it. I worked on dozens of AC/DC sets over the years, my habit was to only plug the chassis in to test it, then leave it unplugged the rest of the time. Even whilst plugged in you could only feel a current with the chassis powered on, plugged in one way, but plug it in the opposite way and you could feel a current when the chassis was turned off. You could invest in an isolation transformer, or just exercise common sense.
  I don't think the IF cans are the problem, I think it's in the local oscilator. Is the loop antenna connected whilst you were testing the set?
Regards
Arran

[tonto007]

Yes the loop antenna was attached. How is the oscillator checked to see if it's working?

[David]

You can do a easy check using a transistor radio holding it near the set to test. Tune the transistor radio about mid point on the dial or some where with no stations. Then tune the non working radio slowly around the same area on the dial. Since you have a working radio of the same model try that one first to get the hang of things. You will pick up the oscillator sound. David