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
philco predicta
The model is the holiday without UHF It has no sound and I don't have an oscilloscope or signal generator.cgl18 — 08:51 PM
Philco model 38 code 121 not receiving signal.
I will definitely check my lead length and wire dressing. Thanks for the ideas.Stormlord5500 — 08:06 PM
Philco model 38 code 121 not receiving signal.
Do make sure that you twist the 3 wires from the chassis to the transformer, and dress away from tubes, especially audio...MrFixr55 — 07:38 PM
Philco model 38 code 121 not receiving signal.
The cone unfortunately got damaged when I removed it. The glue that held the cone to the basket was sloppily applied and...Stormlord5500 — 07:12 PM
Philco model 38 code 121 not receiving signal.
So what was wrong with the original speaker? Was the cone damaged? Unless it's totally hopeless I would put it aside as ...Arran — 05:31 PM
My collection presentation
There is an article on my site that introduces the first portable radios in my collection. I have only provided a link t...Vlad95 — 01:17 PM
Electrolytic restuffing/internals
Bridkarl This specific cap you have is the easiset type to restuff. I usually cut it at the upper border of the depr...morzh — 11:35 AM
philco predicta
Hi CGL18, First off, welcome to the Philco Phorum. I have not worked on a TV for a while but here are some givens: ...MrFixr55 — 08:22 AM
Another amp build - here I go again!
Sweet! I actually have a Dynaco Mark 4 that I had been running with 6L6s with no mods. Seemed to my 14-year-old head a...MrFixr55 — 12:57 AM
PT-6 finished!!
Hi Gang, Tube heaters are not "Ohmic" devices (that maintain specified resistance over wide temperature, c...MrFixr55 — 12:03 AM

[-]
Who's Online
There are currently 1093 online users. [Complete List]
» 1 Member(s) | 1092 Guest(s)
Avatar

>