Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Philco Model 80C - tuning question
#1

I have a Philco 80C that I've rebuilt.  It was in bad shape when I got it, so it never was pre-tested.  I've gone through replacing caps and resistors, coils are good and so on, keeping it the same as what it was without changes.  It doesn't exactly match the schematics, and already had the "gimmicks" done.   Reception "seems" ok, but I expected better, maybe my expectations are a bit too high.  Anyhow, as I go through the alignment all goes well till the last step adjusting the sensitivity.  It seems odd that I can't adjust to a point where the squealing starts.  Don't get me wrong, I don't want the set to be a "squealer", but for tuning purposes, according to the doc's, it should be adjusted to the point just before the squealing starts. 
So for now, I'm just looking to see if anyone has any suggestions before I dig into it again.  Are the instructions for tuning correct that it should squeal, and then adjust it back to stop?  Any thought are appreciated.  Thanks
#2

WElcome to the Phorum!
Icon_wave

The 80 I restored did squeal when the sensitivity hex head nut was turned.
#3

Hi and welcome,
Just a few thoughts. Does your sensitivity adjustment have a fiber nut or a brass one? Should have a fiber one. Check the grid leak resistor for the det circuit, may be high in value. I've found it easier the drill the three rivets out and remove the coil shields as a unit rather than unsoldering the coil and dropping it out the bottom to change it out. You can measure it by checking the resistance from the grid cap to the chassis, the sm caps and coil look like a short by comparison to the 4M resistor.
Double check your resistors around the det to be sure you have the right ones in the right places.
Are you using a signal generator to align the IF stage? If you are trying to do it by ear it's difficult to get it right and it's fairly critical.
You can try making the sensitivity adjustment w/o the ant or signal generator connected. A very strong signal may overload the det.

GL

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#4

Thanks for the ideas.
Well question 1 answered, it should squeal when adjusted, so I'll have to go back and check things out again.

The adjustment has a bakelite nut.  At the moment, that is still functional, but it has a crack and I have to be gentle with it till I find a replacement. 

I ended up replacing almost every resistor and cap including a bad mica which was the first one I ever found bad.  Early on I did find resistor (old) that measured acceptable when cold and then once it warmed up opened up.  Probably should have just replaced the two or three I kept.  That will probably be my first stop.


I had pulled all three coils, which one had the bad mica, resistors replaced.  All checked, all good and then soldered them back in.  That's wasn't a hard job to do.  However, I wonder if when they were soldered back in that created a problem.  I've read somewhere here on the web that sometimes the connections get broken when they are resoldered.

I am using a signal generator to align, and by ear, and connected in all but the last step.  But your probably right that the generator outputs too strong a signal. 

I'll go back and recheck the coils, see what I find there, and re-check and probably replace that last two or so resistors and go from there. 

Thanks
#5

It took a while to get back to this radio, but what I found was what I read somewhere.  In the beginning, I pulled all three coils and checked them out replacing resistors and a bad mica.  Everything was good, they were put back in, and wires re-soldered.  The problem ended up being on one coil where the coil wire came off the solder tab, apparently when I soldered the wires back on.  So that's what it was, all is good now.  Attached a long wire to it, and picked up some stations from half way across the country.
#6

Icon_thumbup Icon_thumbup Icon_thumbup




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 39-116 radio and remote
The transformer I located is from a Philco TV chassis, circa 1948. The part number is 32-8391 I do have the replace...Brad Winder — 08:59 PM
Philco 41-221 Restored
Hello Rod, Wow that radio looks great nice job ! Sincerely Richardradiorich — 07:39 PM
Philco 269 - 444 FIVE VALVE VERSION?
From what I can remember the model 444 "People's Radio" used a special tube/valve called a PenDD61, it was the...Arran — 06:54 PM
Philco 41-221 Restored
Nice Radioslford310 — 06:24 PM
Philco 269 - 444 FIVE VALVE VERSION?
Hi Chaz,  You may want to post the tubes used in your radio.   From Radio Museum, it seems that the set uses some ...MrFixr55 — 05:14 PM
Philco 41-221 Restored
Today my grandson and I finished the restoration of this Philco 41-221. It has had all the rubber coated wiring replaced...RodB — 03:19 PM
Philco 39-116 radio and remote
Hi Brad, I had no idea that the overheating was problematic in this radio.  Do you know the part number of the transfor...RichG — 03:01 PM
Philco 269 - 444 FIVE VALVE VERSION?
From the photo it looks the sockets are screwed and the front one does not even match the hole.morzh — 02:54 PM
Philco 269 - 444 FIVE VALVE VERSION?
Hi Chas a welcome, Perhaps we'll have to reverse engineer this to sort it. So let's start w/what tubes does it use? And...Radioroslyn — 12:28 PM
Philco 39-116 radio and remote
Hi Rich, From my experience, unfortunately it is not uncommon to find the power transformer in the 39-116 to be overhea...Brad Winder — 09:25 AM

[-]
Who's Online
There are currently 1707 online users. [Complete List]
» 1 Member(s) | 1706 Guest(s)
Avatar

>