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

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
Philco model 38 code 121 not receiving signal.
So one last question before I finish this radio. Regarding the speaker and output transformer. I salvaged the original o...Stormlord5500 — 09:31 AM
462ron
It’s on the bottom of the homepage of our Philcoradio.com homepage! Ron462ron — 07:20 AM
Model 70 Cabinet Trim
Steve might have some trim left. Not sure he is making anything.morzh — 06:12 AM
Model 70 Cabinet Trim
Hello musar, First all welcome to the forum and yes that is true that steve stopped making trim . Sincerely Richar...radiorich — 12:13 AM
Model 70 Cabinet Trim
I have recently come into possession of a Model 70.  The trim around the base needs to be replaced.  If this were years ...musar — 12:07 AM
philcorepairbench.com - shadow-meter
Anyone know of a way to recover these files from the repair bench? Thanks. fenbach — 11:16 PM
Philco model 38 code 121 not receiving signal.
That's true. Of course If I were to get a vtvm I'd probably have to sink money in to it to get it working right. Probabl...Stormlord5500 — 08:44 PM
Philco model 38 code 121 not receiving signal.
A DMM is good enough. One rarely has to measure indictance, but if you do, short of getting a serious LCR meter (I hav...morzh — 07:35 PM
Testing a speaker and output transformer Trutone A2-G
You guy's are right on. I found a broken wire on the speaker plug that I replaced and all is well now. Have better volu...murf — 03:43 PM
Philco model 38 code 121 not receiving signal.
I need to get a vtvm. I think that little component tester is just more accurate. Plus it shows the inductance which is ...Stormlord5500 — 03:07 PM

[-]
Who's Online
There are currently 368 online users. [Complete List]
» 2 Member(s) | 366 Guest(s)
AvatarAvatar

>