Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

PT-7 motorboating
#1

Just finished recapping the whole radio. Get a faint signal sometimes but a annoying motorboating sound comes and goes. Anything particular I should look for?

thanks
Chris
#2

The last one I restored had the same problem it turned out to be a way out of spec plate resistor. The best way to check your resistors is to use a decade box if you have one this way you wouldnt have to unsolder the suspected resistor, the box resistor will bypass the bad one if the resistance has drifted way to high.
Hope this helps,
Todd
#3

Yes, there is a large paper capacitor, like a .22 microfarad, that will be tied between B- and the chassis, probably in series with a choke coil. That capacitor will also be paralled with a 220,000 resistor somewhere in the circuit. If that capacitor is open circuit the set will motorboat. It's also possible that the set needs an IF allignment, for some reason this can cause motorboating on a Philco. Another cause could be that the leads of the primary and secondary of an IF transformer may be crossed.
Regards
Arran
#4

Thanks for the info. Will have to check out what you guys recommended.

thanks
Chris




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
PT-6 antenna connections
Hi Bridcarl +1 on the others.  Pin 6 of the 7C6 is the AVC Diode so it is appropriate that that pin 4 of the coil con...MrFixr55 — 07:30 AM
462ron
Joseph, this is beyond awesome. A lot of thought and engineering went into this and you hit a home run! Now I must save ...462ron — 07:27 AM
Cannot Adjust an IF Transformer’s cores
Outstanding work indeed. I wish I could come up with solutions like this.slford310 — 11:16 PM
Cannot Adjust an IF Transformer’s cores
The abilities of our 'Phorum Pholks" never ceases to amaze me! Fantastic fabrication, Joseph! I'm waiting now for...GarySP — 08:27 PM
PT-6 antenna connections
Thanks. I never realized that was a notch noted in the schematic as described. I’ll recheck my wiring.bridkarl — 08:13 PM
Cannot Adjust an IF Transformer’s cores
Thank you! I was quite new to the Phorum when I started this post, so I feel like it might be advantageous to publish a ...jrblasde — 08:07 PM
PT-6 antenna connections
Notice in the schematic the notch at the bottom of the antenna coil is between pins 3 & 4. Yes, pin 6 of the 7C6 is...RodB — 07:34 PM
bridkarl
I have two PT-6 chassis. On both there is a blue wire that runs from the above chassis transformer to pin 6 of 7C6. So t...bridkarl — 07:23 PM
Cannot Adjust an IF Transformer’s cores
Joseph, now you are an engineer!!RodB — 06:37 PM
PT-6 antenna connections
Hi, reading your explanation I can see the confusion. If you take it one connection at a time it should result in a desi...RodB — 06:34 PM

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

>