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

Chassis 26 Heater string
#1

    Okay, so I've completed the electrical (cap and resistor) restoration of this chassis #26 radio I mentioned in my first thread, but I'm having a real Ohm's Law brain freeze with the series heater string. Unlike most models like this, the series dropper consists of 175 ohm and 103 ohm (pilot tap)  instead of the more common 175 ohm and 53 ohm. Either way, I figure with 120 volt line and tube drop of 89 volts, the drop across the resistors together is 31 volts. Assuming 150 mA current, the resistors should total 207 ohms, instead of my 278 ohms or the seemingly more common 228 ohms.
This all came about because after I complete the re-cap and power up, I like to check voltages. I found two things: the voltage across the pilot (#47) was about 3.75 volts, and more curious, the heater voltage on the 35A5 was 30 volts. All other heaters were normal. Any suggestions?
One other thing is the coil-capacitor combo, part #4 was missing (probably from a previous butcher job). Is this item necessary, and if so, how would I build one?
#2

In reference to item 4, it can just be replaced with a cap, coil winding not necessary.
Where did you find the schematic?

Carl
Northern Panhandle, WV
#3

You missed the fact that #31 and 32 don't really equal 278 ohm as the lamp is a much lower resistance than the resistor it's in parallel with.  The 103 ohm section is lower than 103 ohms, if you remove the bulb it is.

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

(01-23-2017, 05:26 PM)Carl Travis Wrote:  In reference to item 4, it can just be replaced with a cap, coil winding not necessary.
Where did you find the schematic?

Thanks, I'll do that. This is a Canadian radio and I have a full set of RCC manuals, hence the schematic
#5

(01-23-2017, 06:30 PM)Radioroslyn Wrote:  You missed the fact that #31 and 32 don't really equal 278 ohm as the lamp is a much lower resistance than the resistor it's in parallel with.  The 103 ohm section is lower than 103 ohms, if you remove the bulb it is.

Hmm. Okay thanks I'll check that. Just wondering why most schematics show the parallel resistor to be 53 ohms. Perhaps the pilot lamp is of a different rating other than the 47 I'm using? I haven't been able to find anything about the lamp in any parts lists.




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
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
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

[-]
Who's Online
There are currently 2365 online users. [Complete List]
» 1 Member(s) | 2364 Guest(s)
Avatar

>