Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

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

Model 39-70 stations there, but dial off
#1

https://www.tubesandmore.com/sites/defau...pg10-1.png

Haven't gotten to the power supply yet on this. Have been battling a stubborn chassis. Icon_crazy

As mentioned in the thread about adding an A supply to a B power supply, I found the primary of the OSC coil was open. I replaced it with one of the P-70-OSC coils from the Antique Radio Supply but I could not pull in stations. I then found a winding open on the ANT coil as well, so I replaced that with the P-70-A coil from AES. It receives stations now but the bandwidth is quite a bit off. I get 620 AM with the rotor about half way out of the stator on the tuning capacitor, when it should only be out about an 1/4 at most. I tried aligning it but was only able to move the station back a short way before I ran out of screw (the adjusting screw on the tuning cap is backed out all the way). I can get our other strong local station at 1470 and that seems pretty close to where it should be.

Is it just that that replacement OSC coil may not be close enough to the resistance values / number of windings on the original coil to be compatible? Does anyone have any ideas on what I can try doing to move the lower end of the dial back to where it should be?

Greg V.
West Bend, WI
Member WARCI.org
#2

In the center of your osc coil there is a hex shaped hole use a plastic alignment tool or the proper allen key to turn this adjusting slug. If you use a metal allen key it will change the adjustment a little as the metal will increase the inductance of the coil when inserted.
Use this adjustment to set the low end of the band (550kc or so) and use the trimmer (the screw thingie) to set the high end (1500kc or so).

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
#3

That did it! I never even noticed that allen head set screw inside there. Thanks!

Greg V.
West Bend, WI
Member WARCI.org
#4

It's easy when you know how!!
General rule. Adjust inductors (coils) for the lower frequency and the trimmer caps for the high end of the dial. This goes for the osc and mixer/rf coils.

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




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Need to purchase some accessories for restoration of my Old Philco Radio
Hi Paulo, Welcome to the Philco Phorum. I can see why you want to find good reproduction parts. That is a bea...MrFixr55 — 11:10 PM
HiFi (Chifi) tube amp build - but my own design.
Tim, I have some bakelite sockets in my work shop that I can dig up. I believe quite a few are NOS. I will take photo...RodB — 10:03 PM
Philco 610B oscillator wiring
> The cathode as noted is wired directly to the ground side of the heater filament for that tube, not to the #17 and ...Radioroslyn — 08:12 PM
HiFi (Chifi) tube amp build - but my own design.
Tim; I noticed your post a little late, but I would take one of the junk sockets and try to break a chunk out of it wi...Arran — 08:07 PM
Need to purchase some accessories for restoration of my Old Philco Radio
Here is a list of resources found in our online library that you might find useful. Mike's Gobs of Knobs email addres...klondike98 — 01:46 PM
First Radio restoration
Hi Tubeman, Welcome to the Philco Phorum.  Phamily Phriendly Pfun with Phine Pholks Phull of Philco Phacts. (See a p...MrFixr55 — 12:33 PM
First Radio restoration
You could post in the WANTED ADs section here on the Phorum and see if anyone has an RF generator that they want to sell...klondike98 — 11:55 AM
Zenith H725
Good ideas, thank you Arrange and Rich. I have the adhesive aluminum foil already and can try that immediately. More ...EdHolland — 10:18 AM
Graphics for majestic 1050 dial glass.
Murf; I found this thread on the ARF, the first photo has a pretty good view of the dial glass. Regards ArranArran — 01:12 AM
Zenith H725
hello Ed, how about that speacial tape used for ducting it's like foil or how about thin piece of aluminum roof flash...radiorich — 12:19 AM

[-]
Who's Online
There are currently 1404 online users. [Complete List]
» 1 Member(s) | 1403 Guest(s)
Avatar

>