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

Model 50A rebuild
#21

The model 50 is a tuned RF receiver, two tubes progressively amplify the radio signal. To do that effectively each stage with one tube has one section of the tuning condenser connected mechanically with a common shaft called the rotor. The rotor is at "ground" potential, the fixed set of plates are called the stator, these are insulated and each section is connected to its respective tube. The third section is for tuning the detector. It was difficult to make a precise tuning condenser with multiple sections, so attached to the stator is a trimmer capacitor consisting of a blade of metal, a wafer of mica for an insulator an insulated washer and a nut or screw to compress the package to change the capacity.

What may have happened is that one or more of the trimmers was mal-adjusted or damaged during the cleaning process.  By disconnecting the wire to the stator to each section of the tuning condenser an ohmmeter can determine if the trimmer has shorted. If the mica has been damaged it must be replaced. Mica can come from a salvaged tuning condenser, but if no mica can be found. A poor but workable substitute is a piece of PEET plastic taken from a water bottle, the thinnest and flattest as possible.

Plastic changes with temperature and moisture so it is not ideal but the radio will work at least until correct mica can be found.

With the tuning condenser now out of adjustment, if a station can be found around 1000khz, adjust the three trimmers to bring that station in the loudest. Any more precise adjust is possible, helpful is using an RF generator or a pocket transistor radio using its oscillator as a signal by local coupling. Follow any alignment instruction published by Philco. If a trimmer is tight and still not peaked (loudest signal the plastic is too thick...

Above assumes problem began with tuning condenser cleaning, but a short created during re-installation of the tuning condenser may have occurred too. Trace the schematic to the radio and do the measurements.

Chas

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


Messages In This Thread
Model 50A rebuild - by Mtmattking - 04-08-2024, 07:19 PM
RE: Model 50A rebuild - by GarySP - 04-08-2024, 08:43 PM
RE: Model 50A rebuild - by morzh - 04-08-2024, 09:30 PM
RE: Model 50A rebuild - by Mtmattking - 04-08-2024, 09:35 PM
RE: Model 50A rebuild - by Mtmattking - 04-08-2024, 09:37 PM
RE: Model 50A rebuild - by klondike98 - 04-08-2024, 09:51 PM
RE: Model 50A rebuild - by Mtmattking - 04-08-2024, 09:57 PM
RE: Model 50A rebuild - by klondike98 - 04-09-2024, 03:20 AM
RE: Model 50A rebuild - by Mtmattking - 04-09-2024, 10:56 PM
RE: Model 50A rebuild - by morzh - 04-11-2024, 08:01 AM
RE: Model 50A rebuild - by Mtmattking - 06-29-2024, 09:58 PM
RE: Model 50A rebuild - by morzh - 06-30-2024, 11:07 AM
RE: Model 50A rebuild - by Mtmattking - 06-30-2024, 12:41 PM
RE: Model 50A rebuild - by morzh - 06-30-2024, 01:16 PM
RE: Model 50A rebuild - by GarySP - 06-30-2024, 04:25 PM
RE: Model 50A rebuild - by Mtmattking - 07-06-2024, 08:26 PM
RE: Model 50A rebuild - by morzh - 07-06-2024, 10:20 PM
RE: Model 50A rebuild - by Mtmattking - 07-07-2024, 01:00 AM
RE: Model 50A rebuild - by RodB - 07-07-2024, 09:24 AM
RE: Model 50A rebuild - by Chas - 07-07-2024, 09:50 AM
RE: Model 50A rebuild - by Paul Philco322 - 07-07-2024, 01:19 PM
RE: Model 50A rebuild - by GarySP - 07-07-2024, 03:19 PM
RE: Model 50A rebuild - by morzh - 07-07-2024, 07:33 PM
RE: Model 50A rebuild - by Mtmattking - 07-15-2024, 01:02 PM
RE: Model 50A rebuild - by Mtmattking - 07-20-2024, 10:28 PM
RE: Model 50A rebuild - by Radioroslyn - 07-22-2024, 09:29 AM
RE: Model 50A rebuild - by Mtmattking - 07-22-2024, 07:10 PM
RE: Model 50A rebuild - by Radioroslyn - 07-23-2024, 07:58 AM
RE: Model 50 Capacitor values - by Mtmattking - 04-08-2024, 10:39 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
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
The list of my radio & TV collection!
Magical chords of forgotten melodies, old nostalgic music on an old radio... Saturday night blues on the Mid-Waves on an...RadioSvit — 12:20 PM

[-]
Who's Online
There are currently 1525 online users. [Complete List]
» 2 Member(s) | 1523 Guest(s)
AvatarAvatar

>