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

Philco 38-690 Oscillator Not Working?
#1

I have strong audio signals and strong IF signals. I am receiving no stations at all.

The local oscillator does not seem to be working. Oscillator voltages are as follows:
Pin 3 - 191.8 VDC
Pin 4 - 93.0 VDC
Pin 5 - 1.58 VDC
Pin 6 - 195.5 VDC
Pin 8 - 2.53 VDC
Grid Cap - 0 VDC

The mixer voltages are as follows:
Pin 3 - 238.1 VDC
Pin 4 - 99.7 VDC
Pin 5 - 1.58 VDC
Pin 6 - 99.7 VDC
Pin 8 2.53 VDC
Grid Cap - 0 VDC

Shouldn't the pin 5 of the oscillator grid measure a large negative voltage? Does the OSC CONT tube
have control over the oscillator?

Thanks for any suggestions and help.
nv3g
Oscar
#2

>Shouldn't the pin 5 of the oscillator grid measure a large negative voltage?

I wound think so also the control grid of the mixer too as they wired together.

If you are not seeing any -voltage there you may want to check the normal suspects. These being a dirty band switch, weak 6A8, or bent plate on the osc section on the tuning cap. Did you replace ALL of the foil paper caps in the sub chassis? A missed one could kill the osc. If you removed the sub chassis is it wired in properly?

>Does the OSC CONT tube have control over the oscillator?

Yes it does via the magnet tuning circuit. Don't think that it would stop the osc from working.

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




Users browsing this thread: 2 Guest(s)
[-]
Recent Posts
91H Code 126 Restore
Just to make it more confusing here is another model 91 schematic that doesn't show parts with dotted lines in that spot...Arran — 10:37 PM
Atwater-Kent 84, restoration.
The wires were desoldered from the can, and the capacitors checked. All checked at 0.102 uF, which is correct. So the c...morzh — 09:41 PM
An attempt to remove the Field Coil from a G speaker
Arran Yours probably then the H speaker, same as mine.morzh — 08:39 PM
An attempt to remove the Field Coil from a G speaker
Mike; I would like to have a look at the speaker in my model 96, but the set is packed into a corner in the basement. ...Arran — 08:04 PM
91H Code 126 Restore
Thanks Arran, I'm convinced the power cord is good but have a nice repro plug for it. Would it be prudent to add a fus...RealRider — 07:28 PM
91H Code 126 Restore
As I was studying this schematic I was wondering what does this dotted line means?  I haven't traced it out yet. An o...RealRider — 07:22 PM
91H Code 126 Restore
When it comes to the cloth covered power cords, if they are not frayed, and are flexible, and if I can bend one without ...Arran — 06:21 PM
An attempt to remove the Field Coil from a G speaker
Could be. The central cylinder is OK, but the sides are...well. What's done is done. I wonder if some standard bobbine w...morzh — 06:02 PM
An attempt to remove the Field Coil from a G speaker
Mike; As I was saying it doesn't look like they used much of a bobbin for the field coil, not like a Magnavox one wou...Arran — 05:49 PM
Atwater-Kent 84, restoration.
This AK84 was bought, I think, last fall. For a whopping $100. It has been, according to the seller, restored. As I go ...morzh — 05:48 PM

[-]
Who's Online
There are currently no members online.

>