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

Model 70 plate to ground question.
#1

Still working on this unit. I measure 7k ohms first detector (converter 2nd 24 tube) plate to ground - all tubes installed playable unit, the volume control does nothing to alter it.  Is the first IF coil leaking or normal?

https://www.philcoradio.com/images/phorum/schem/70a.jpg
#2

No it is right. Your wirewound #37 divider plus the #36 field coil and the F to G volume regulator do this.
Simple test, remove the speaker, then the curcuit should become open.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#3

Shouldn't the volume control vary the ohms? The volume intercepts the wireround, my field coil is just resistors.
#4

I removed the speaker, still obtained 7k ohms.
#5

7K sounds like a good number. You have the winding of the IF transformer, a field coil, the volume control and three resistors in the BC resistor all in series to ground, should come out pretty close to 7K.

Steve

M R Radios   C M Tubes
#6

You mean you UNPLUGGED the speaker altogether and still got 7K?

Oh...wait, you have permanently replace Field coil with the equal value resistor?
Then yes, unplugging the speaker will not affect anything and this will remain about 7K.

And no, the volume will not vary anything. Not just because it is low value compared to the rest of the divider, but the wiper is not part of the circuit.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#7

Thanks for info, whew for me, the volume control confused me, but I guess it's a path to nowhere until fired up. Thinking about it, what a wonderful upfront test to check for failure areas.




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
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
Restoring Philco 96
Oh wow! Just found this thread.  Brings me back to early days on this phorum.  I did a 96 back in 2017.  Thread here: ...rfeenstra — 06:05 PM
Philco 610B oscillator wiring
Thanks for the replies. It's not the really the hum that I am after. Just trying to understand why only the shortwave ba...Tubester — 04:01 PM
Restoring Philco 96
70 and 90 are Superhets, but at least the 2x45 model of 90 uses the Plate detector (and so does 70). Also the Atwaters,...morzh — 03:28 PM
Restoring Philco 96
Morzh, Prayers for your mom. I am sure that there was enough pain living through the Holocaust as a child. I pray dail...MrFixr55 — 02:19 PM
Philco 610B oscillator wiring
Hi Dan, Divide and conquer. First off trry to differentiate between 60Hz and 120 Hz hum. 120 Hz hum has a higher pit...MrFixr55 — 01:49 PM
Restoring Philco 96
Yes, other than takin a toll on your back, they are undeed way more repair friendly than many other Philcos. To me, som...morzh — 01:04 PM
Philco 610B oscillator wiring
If the wires look like they were this way from the factory (very neat and very dull soldering joints), I'd leave them be...morzh — 12:58 PM

[-]
Who's Online
There are currently 1548 online users. [Complete List]
» 1 Member(s) | 1547 Guest(s)
Avatar

>