The PHILCO Phorum
Zenith Model K725 - Printable Version

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RE: Zenith Model K725 - Elijah - 01-22-2013

I got the kit today with the proper tool. Unfortunately, I can't get the FM aligned as there's no response in trying to do so. I hooked up the generator to the points indicated in the instructions on the 12AU6 tube(grid), put the VTVM on the proper point and hooked the ground to chassis and tried tweaking one of the first IF's and turned it several turns back and fourth but the VTVM didn't respond. The needle didn't move. I had it set on the -DC scale since the tubes grid is negative but nothing. I then tried setting the VTVM to what's called the "zero center indication" buy setting the needle right on the 0 in the +0- setting. Still no response. Any ideas what's wrong? Sort of aggravating when you've waited for the right tool to get here and then no response for FM tuning.

RE: Zenith Model K725 - Elijah - 01-23-2013

I found out what was wrong. I disconnected all test equipment and tried to get some stations and from low to high end it was totally silent. I had gotten several stations some days before albeit, low volume. Now, there was nothing perceived. I finally decided just to tweak by ear several of the IF's and several stations started coming in and as I tweaked the cans the volume got louder. This FM section must have been way out of alignment so, it's back to the bench and try the alignment again, hopefully this time with some success.

RE: Zenith Model K725 - Elijah - 02-02-2013

I'm having one heck of a time trying to get the FM stage aligned. I hook up the VTVM to the proper points according to the instructions, set the signal generator or 10.7mHz, tweak the point(s) indicated first and it just doesn't respond. There' very little if any needle movement.

I've tried with and without a 1 meg resistor in series with the VTVM probe to no avail. I know the VTVM is working as it will measure DC as well as AC voltage and ohms so, it has to be something else. All capacitors have been replaced as have most resistors and I've checked the tubes out with an EICO 625 and replaced a couple that were weak or questionable. I don't' know anything else to do. Any suggestions? These are the instructions I followed...

[Image: http://i180.photobucket.com/albums/x220/ColColt/Misc%20Stuff/Old%20Radios/ScreenHunter_01Jan161835.jpg]