Philco model 18 (code 121) - HELP! - Printable Version
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+--- Thread: Philco model 18 (code 121) - HELP! (/showthread.php?tid=5934)
RE: Philco model 18 (code 121) - HELP! - jerryhawthorne - 02-26-2013
Yes Plith, some radios (early) don't go above 1500. Hard to tell from your video but you have to have the signal from your sig gen hooked up right. The high side to the antenna and the ground on the radio chassis. Modulator turned on. Just set the sig generator somewhere on the middle of the AM dial and scan your radio to see if you can find that sweet and annoying tone. If no joy, you may not have the oscillator on your radio working. Glad to see you passed the first test.
Jerry
RE: Philco model 18 (code 121) - HELP! - Pithicus999 - 02-27-2013
Silly question, are there one or two leads coming off the signal generator? This thing didn't come with any leads when i bought it and from what I saw on Youtube there should only be one lead?? When I adjusted the first three tuners (#24,#25,#28) I only used one lead. Sorry about that video, I'll try to get a closer view of the signal generator tonight after work, I want to make sure that I'm using the signal generator properly.
Jerry, when you say that I may not have the oscillator working properly, do you mean the:
- Oscillator Transformer (#16)
OR
- Detector Oscillator (#5) also called the Tuning Condenser Assembly
Also, I just remembered something, when I first started restoring this radio, there was no antenna wire...I added a wire per the schematics and connected one end to the ANT clip on the top/rear of the chassis and the other end I soldered to the Antenna Transformer (#3) from the underside of the chassis. I'll have to go back and double check that I used the correct tab on the Antenna Transformer, who knows, maybe that’s the problem right there? I'll let you know.
Thanks again for your help Jerry.
RE: Philco model 18 (code 121) - HELP! - Pithicus999 - 02-27-2013
Jerry, I just read up on the signal generator. I see it says the AF-In goes to the ground of Chassis (like you said) and the RF - goes to the Antenna wire.
As far as modulation turned 'ON' (as you say) my options are either 'EXT.' (on the left side of the switch) or turning the switch to the right for 'INT'. Which way would be the same as 'ON'....I'm leaning towards 'INT'???
RE: Philco model 18 (code 121) - HELP! - jerryhawthorne - 02-27-2013
We might need a picture of your sig gen. Mine, a simple one, has a coaxial cable attached to the front. This cable ends with a couple alligator clips. The center of the coax is the RF signal, the shield goes to ground on the chassis. As for your modulation control, yes, set on the Internal position. In this position the internal (inside the generator) tone oscillator is used to modulate your RF selected. I suspect the ground is not necessary unless you are using just the tone (AF) output of the generator to troubleshoot the amplifier (audio) part of the radio. It appears that you have pretty much tested everything out from the 6A7 to the speaker! That would be the IF section, second detector and audio. The first dectector 78 is also known as the mixer involves the oscillator as part of it. Too early to tell, check your antenna hook up.
Jerry
RE: Philco model 18 (code 121) - HELP! - DKinYORKpa - 02-27-2013
Quote:Also, I just remembered something, when I first started restoring this radio, there was no antenna wire..
What do you mean by this? Are you saying that under the chassis, there was no wire going to the antenna terminal?
RE: Philco model 18 (code 121) - HELP! - Pithicus999 - 02-27-2013
Hi DKin, yes there was no wire going to antenna clip on top of chassis on one side or going to the antenna transformer tab under the chassis.
I had to add a wire and connect both ends. I see 4 tabs onantenna transformer and one had nothing attached, so that's where I soldered it.
RE: Philco model 18 (code 121) - HELP! - jerryhawthorne - 02-27-2013
Yes Pith, that clip for the antenna should go to the antenna coil. I found the schematic for the code 124 attached. I could not locate one for code 121. It is attached. Looks to me there should be a resistor going from the antenna lug as well as the antenna. Appears to be going to ground, possibly attached to another lug (ground) on another antenna transformer tab that is attached to ground. According to the attached schematic there should be two leads on that vacant coil. Time perhaps to do a little measuring. Does the tab you hooked the antenna line to measure to ground (chassis) with a low resistance. Like really low?
Jerry
http://www.nostalgiaair.org/PagesByModel/149/M0013149.pdf
RE: Philco model 18 (code 121) - HELP! - DKinYORKpa - 02-28-2013
Quote:I had to add a wire and connect both ends.
Yeah, that's a red flag. A bad RF coil on a Philco that I'll be working on again soon had several wiring changes made by the last guy to deal with the bad coil.
RE: Philco model 18 (code 121) - HELP! - Pithicus999 - 02-28-2013
Jerry, I see a little difference in the schematics of the 124 and 121. How can I attach a picture? Or a PDF file to show you? Worst case is I’ll take another video of the 121 PDF and the underside of the Antenna Transformer and load that tonight.
The other thing is, I still have not checked all the voltages. I’m hoping it’s just a bad tube.
Jerry, what does it mean when they say “F” to “F” when measuring the tube voltages? Does that mean the two BIG pins on the tube? Say the 78 tube for example, I see where the “P”, “K”, “SG”, “SUP” and then I see “H” and “H” for the BIG pins…are those the “F” to “F”?? On the #80 tube it shows the BIG pins are the “F” to “F” so I’m just taking a stab in the dark here.
DKin – It may have been my dad who removed it for all I know. I don’t know if anyone has ever WORKED on this thing, it’s been in a spider cocoon in my parent’s basement for at least 35 years, before that who knows…
RE: Philco model 18 (code 121) - HELP! - morzh - 02-28-2013
1. Attaching a pic;
Instead of "quick reply" press "new reply" button, it will give you full interface.
Press "New attachment" button.
Browse to the pic, choose it, then press "Add attachment" button.
Once it is added below, press "place in text" (or something like it) button.
Press "post reply".
2. F-F means "filament to filament" that is a heater voltage.
3. Big pins (fat ones) are usually the Filaments. Those also serve as the key when inserting the tube, as fatter pins won't go into smaller pin sockets.
RE: Philco model 18 (code 121) - HELP! - Ron Ramirez - 02-28-2013
Adding pictures as attachments is easy, but it isn't really the right way to do it.
The right way is explained in detail here:
http://www.philcoradio.com/phorum/showthread.php?tid=29
http://www.philcoradio.com/phorum/showthread.php?tid=4371
But if you must use the attachments method, this too is explained in detail here:
http://www.philcoradio.com/phorum/showthread.php?tid=4407
Just keep in mind that if we ever have another server crash - and hopefully we won't - your attached photos could disappear like they did the last time.
RE: Philco model 18 (code 121) - HELP! - jerryhawthorne - 02-28-2013
Pith, please respond to your resistance measurements as posted on post 52. Do that first. Then worry about voltages. One step at a time. Measuring filament voltages are not your problem. Other voltages possibly. Let's look at the antenna situation first.
Jerry
RE: Philco model 18 (code 121) - HELP! - Pithicus999 - 03-01-2013
Thanks Ron.
Jerry, as for the resistor, here is a video of the 121 schematics and my set. Although I must have been tired when I made it because I called the transformers condensers! Clearly I need more sleep.
I do see the 70K resistor in the schematic and it appears to be hooked up correctly on the set with #6 cap (0.05) as well.
http://www.youtube.com/watch?v=TsSknzFmfks
RE: Philco model 18 (code 121) - HELP! - Pithicus999 - 03-07-2013
Jerry,
I measured the resistance of the antenna wire, it was 0. Like there was no current flowing at all.
But now I have a bigger problem ( or hopefully the same problem) one of my resistors completely fried, as in started smoking...not good. It was a 33K resistor #61 on schematic, says it should be 32K but couldn't find that type, only could find the 33K I hope using the wrong resistor isn't the problem? It said the tolerance was 5% so I figured it would work.
I was trying to see which way current flowed, so I could measure voltage and resistance step by step to isolate the problem but its hard to tell from the schematic.
I think I'm kind of lost at this point.
RE: Philco model 18 (code 121) - HELP! - codefox1 - 03-07-2013
The negative bias capacitor gets all of us once in a while. Remember there is nothng sacred about "ground." it may well be positive with respect to B-. Fix it, and let us know. You probably did not harm the part.