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

RF Choke and Condenser -42-PT-7
#5

Hi Folks,

If you are talking about Part #7, this is the cap that capacitively grounds the physical chassis to B- and is important. It should be 0.2uF and the coil portion is likely not urgent, just good engineering on Philco's part.

The likely proper values should be 0.2UF, similar to other Transitones, like the 42PT94.

Some people call this the "Death Cap" because of the following:

For some reason (possibly to reduce hum), the power switch is in the B- and filament return leg of the power line. This is the point where the cap in question connects B- to the chassis for RF coupling of the tuning cap, shields, etc., making this a "warm chassis" set. This is as opposed to a hard wire connection between chassis and this point making this a "hot chassis" set. The problem is that if this leg is connected to the neutral pin of the power cord, the chassis is at ground potential with the power ON, making it "safe". However, with the power switch off, the low cold resistance of the tube filaments make the chassis "hot", even though the cap. The cap will limit current (warm chassis) unless it shorts, then there is no limiting, making the thing a death trap.

So, the issue is that with the way the set is built, that the chassis will be hot depending on the position of the power switch and the polarity of the plug. With the plug in one direction, the chassis will be at ground potential when the switch is on but hot with the switch off. With the polarity of the power cord reversed, the chassis will be at ground potential with the switch off, but hot with the switch on.

Several restoration sites recommend moving the switch to the "hot" side (Input to rectifier and rectifier end of filament string) and using a polarized cord to prevent this condition.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


Messages In This Thread
RF Choke and Condenser -42-PT-7 - by Masonparker - 11-11-2024, 10:03 AM
RE: RF Choke and Condenser -42-PT-7 - by morzh - 11-11-2024, 12:28 PM
RE: RF Choke and Condenser -42-PT-7 - by RodB - 11-11-2024, 02:21 PM
RE: RF Choke and Condenser -42-PT-7 - by morzh - 11-11-2024, 02:51 PM
RE: RF Choke and Condenser -42-PT-7 - by MrFixr55 - 11-12-2024, 06:04 PM
RE: RF Choke and Condenser -42-PT-7 - by Arran - 11-13-2024, 07:00 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
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
Philco 42-345 Restoration/Repair
Thank you MrFixr55 the issue with this radio is that the internal coil antenna is missing and there was a wire in its pl...osanders0311 — 11:34 AM
Philco 610B oscillator wiring
Regarding the oscillator circuit which is comprised of the 6A7's cathode, control grid, and screen grid. These elements ...Radioroslyn — 10:33 AM
Philco 42-345 Restoration/Repair
Hi OSanders, First off, welcome to the Philco Phorum where Phine Phamily-Phriendly Pholks Phull of Philco Phacts and P...MrFixr55 — 08:41 AM
Philco 42-345 Restoration/Repair
Today I've been reading through the site trying to learn more about this radio. I also soldered the lose power cord cabl...osanders0311 — 08:24 PM
Philco 610B oscillator wiring
Thanks David! I do have that same later prodution model 610 schematic. I've also studied the Philco service bulletins fo...Tubester — 08:12 PM
Philco 610B oscillator wiring
Some info from Beitmans says late production. David   David — 06:06 PM

[-]
Who's Online
There are currently 2499 online users. [Complete List]
» 2 Member(s) | 2497 Guest(s)
AvatarAvatar

>