The PHILCO Phorum
53-1750 Alignment question - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: 53-1750 Alignment question (/showthread.php?tid=17055)


53-1750 Alignment question - ODPILOT - 07-24-2017

This is my 3rd Philco 53-1750 I am aligning but having a problem with this  recent one so I have some questions. 
The way I had been doing it successfully was to attach a 6" wide loop wire  wound 5X   attached to the signal generator and hang it near the antenna of the radio.  I then place the radio on 1620 Khz and the radio picks of the signal generator, which I can hear in the radio speaker, at 455 Khz, after which I adjust all the tuning capacitors.   Has worked great in the past. 

This current radio, was picking up only one station very weak at 1000 KHz.  This radio will not pick up the 455 KHz signal using my former method.   I tried aligning the radio using the one station at 1000 Khz  I could get by  turning the tuning capacitors until it came in louder, and then was able to received several more stations -but still  all coming in weak.   I then went back to 1620 Khz to see if I could get the radio to give a signal at 455 Khz, and still nothing.   All tubes test as good and I do not have an oscillascope.

Alignment procedures for this model recommend hooking up the signal generator to one of the pins of the output tube (I think it's the 7A8 tube), with a .01 mf capacitor.      I wonder if this would work better to receive the 455 Khz signal rather than just the loop wire method.  Photo I attached is the same radio I have but it not mine - mine is CLEAN !   Thanks....

RE: 53-1750 Alignment question - Radioroslyn - 07-24-2017

You should be able to receive the 455kc signal by using your loop but if that isn't working for you you can connect the output of the generator thru the cap to the connection on the loop ant that is connected to the tuning capacitor. Be sure to use an isolation transformer connected to the power cord and outlet.
Your not really connecting the sg to the output tube but to the mixer tube (7A8) and by adjusting the tuning capacitor shouldn't change the 455kc signal (doesn't matter where the dial is set) .

RE: 53-1750 Alignment question - ODPILOT - 07-24-2017

I will try it with the isolation transformer, I need to go out and buy one. Is there a particular brand of isolation transformer you like? Other than preventing a shock while working on the radio, is there any advantage to running it all the time with an isolation transformer? Thnks

RE: 53-1750 Alignment question - morzh - 07-24-2017

You don't need it all the time, but while working on it, it's a must. And when aligning - double must.

RE: 53-1750 Alignment question - Radioroslyn - 07-24-2017

The one I've been using is an old Heathkit job that has a variac and meter built in. Kinda handy.
http://www.w6ze.org/Heathkit/Heathkit_018_IT1.pdf

RE: 53-1750 Alignment question - klondike98 - 07-24-2017

I use one of these, a VIZ Isotap.  There are a number of different models including several on ebay at the moment.  One similar to the one I have is seen in this ebay posting:
http://www.ebay.com/itm/Vintage-VIZ-Isotap-II-120V-150V-Variac-Variable-Transformer-WP-27A-/201987609135?hash=item2f0766522f:g:iYwAAOSwrf1ZZi4H

RE: 53-1750 Alignment question - ODPILOT - 07-27-2017

The alignment instructions on this 53-1750 call for the hot (center) side of the RF out cable from the signal generator to be connected to pin 6 of the 7A8 tube and the grounded part of the cable (shield lead) to be connected to B- in the radio. Is B- just the same as the metal radio chassis? Also, in addition to plugging the radio into an isolation transformer, should I plug the signal generator into the isolation transformer as well? Thnx.

RE: 53-1750 Alignment question - Radioroslyn - 07-27-2017

>Is B- just the same as the metal radio chassis?
Generally no. To do voltage measurements from the chassis ground to any point on the chassis will not give you an accurate reading. Always measure voltage from B-. If you look at the schematic most sets will have a large paper cap from B- to the chassis, it does 2 things. It isolates any dc voltage from the chassis and provides a rf ground from the chassis back to one side of the ac line. This is why sometimes by plugging the set in the other way around it will have less hum.
> should I plug the signal generator into the isolation transformer as well?
NO! This defeats the purpose of using it. Most just have one receptical for the output. That Viz unit has some outlets that are isolated and other that aren't. The object here is to have the radios ac source coming thru the transformer and the test equipment plugged in to the ac line.

RE: 53-1750 Alignment question - morzh - 07-27-2017

I always plug my radio in the isolation xfmr and my generator in the wall outlet. This way they are de-coupled and should you touch two with two hands (I still try to avoid that) nothing bad will happen. If they are both plugged in the transformer, it is the same as if they both plugged in the wall outlet with the sole difference of you now not being able to complete the circuit to Earth but still able to complete it between the radio and the generator should the radio polarity be such that you touch it's hot and the generator's chassis.
Worse yet, if in the case of the wall outlet, if it were GFI, the GFI would save you, when both plugged after the transformer, the GFI will not act.

RE: 53-1750 Alignment question - ODPILOT - 07-27-2017

Wow, OK got it.. Thanks

RE: 53-1750 Alignment question - Radioroslyn - 07-27-2017

If you are in doubt use an ac voltmeter and measure the ac voltage between the two chassis. If there is 120vac you'll either get a nasty shock or pop ur breaker w/a big spark. Don't ask me how I know[Image: http://philcoradio.com/phorum/images/smilies/icon_rolleyes.gif] Or you can ask the birthday boy.