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

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

Restoring a Philco 71 Code 121-No sound
#17

Try using another meter, a VOM is recommended. The readings, now, are not really out of line. Re-solder the terminals of the observed offending coil.

Check the capacitors in the circuit. Schematic seems to indicate four variable condensers. At least two are the main tuning condenser and its (mounted) compression trimmer. Any leakage from damage, corrosion or dust can kill the oscillator.

NOT associated with any particular radio is that the insulators for the stator of tuning variable condensers have been known to leak. Poor electro-mechanical connections to the rotor can also be troublesome.

I see no copper corrosion but, the decaying celluloid can be a source of low resistance by shorting turns of the tickler, unseen on the inside of the winding.

The tickler is at cathode potential, any leakage to the other windings which reference ground, will carry some of the total plate current.

GL

Chas

Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”


Messages In This Thread
RE: Restoring a Philco 71 Code 121-No sound - by Chas - 07-07-2024, 12:22 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
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
Zenith H725
Ed; One material that I have seen, but never tried for this was material for making exhaust gaskets, it's similar to ...Arran — 11:42 PM
Zenith H725
I just remembered, I have some hi temp silicone rubber material which could do the trick. Or a piece of FR4 laminate. Th...EdHolland — 08:39 PM
Zenith H725
The PSU filter cap arrived today (thank you USPS!) so I will work on that later. Meanwhile, I have the dial, speaker...EdHolland — 06:42 PM
Philco 610B oscillator wiring
Thanks Terry. After checking my notes I think I recorded about -10v at the 6A7 G4/control grid. The screen grid (G3 &...Tubester — 05:59 PM

[-]
Who's Online
There are currently 2634 online users. [Complete List]
» 2 Member(s) | 2632 Guest(s)
AvatarAvatar

>