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:
[-]
Recent Posts
Philco 91 code 221
Chassis grounds thru rivets is another good place to look. Oh and the stator screws on the tuning cap where the leads at...Radioroslyn — 08:11 AM
Philco 91 code 221
Dirty tube pins and socket, cold solder joint, stray tiny strand of wire, clean the entire area around the oscillator tu...RodB — 08:43 PM
Philco 91 code 221
I have been restoring one of these sets and switched it on yesterday. It didn't exactly spring into life, but after a co...Philconut — 08:26 PM
Philco 50-925 antenna connections
That's super. Glad to hear you figured it out. Paul.Paul Philco322 — 11:11 AM
Philco 50-925 antenna connections
Hello Keith, great news !! Sincerely Richardradiorich — 02:14 AM
Philco 50-925 antenna connections
Finally, got the antenna fixed (repaired some broken wires) and have the radio playing. I've got four different schemat...keith49vj3 — 09:38 PM
1949 Motorola 5A9M
Bob, Nice radio.  I’ve not seen one before.  Keep us updated!Joe Rossi — 07:56 PM
Phioco 90 Power Transformer Wire Colors
Thanks for adding that information.klondike98 — 06:09 PM
Phioco 90 Power Transformer Wire Colors
Although I have used this site as a resource for a number of years this is my first post.   I am restoring a Model 90 si...vincer — 05:02 PM
My collection presentation
There is a complete instruction how to solve your problem. One piece of advice - be careful with the low-voltage capacit...Vlad95 — 09:32 AM

[-]
Who's Online
There are currently 861 online users. [Complete List]
» 1 Member(s) | 860 Guest(s)
Avatar

>