I am currently restoring a Philco Model 16 (chassis 122). I have it partially recapped and will spend a few days restuffing backelite blocks. At the low end of the tuning dial on all bands the set is quiet between stations and has loud sharp static noises. When tuning a station one has to be very precise to get "right on" the station. Oftentimes the only way to tune a station such as 590 on the broadcast band is to get close and lightly tap the tuning condensor at which time the colume goes from weak to loud depending on how high the volume is set. This phenomenon seems to be present on all bands. I replaced the front rubber washers on the tuning condensor and I have installed an additional ground strap from the cahssis to the body of the tuning condensor. The plates look undamaged and spacing looks even when fully meshed which is the end of the band at which the problem occurs. I have also tried adjusting the wavetrap withe no luck. The radio tunes fine from about 650 on up on the am broadcst band and equivalently so on the shortwave bands all of which function well on the rest of the band. On all bands the in between station static is different on the low end (fully meshed).
Thank you for any insights.
JT in Albany
Posts: 893
Threads: 9
Joined: Mar 2008
City: Vieques, PR USA
State, Province, Country: PR
JT Wrote:The plates look undamaged and spacing looks even when fully meshed which is the end of the band at which the problem occurs.
Sure sounds like plates touching to me. The way to go about checking this would be to disconnect the tuning cap sections from whatever they are connected to (one at a time) and use an ohmmeter to watch for intermittent shorts. The only other thing would be the wiper on the shaft of the tuning cap making intermittent contact at that end of the range. I can't think of anything 'electronic' that would make it behave that way.
-Bill
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
I agree with Xray.
Now to find out which leaf is shorting, slide a piece of paper bwtween the leaves. When the short opens up, you know which one needs to be straightened. Could be more than one, and it's usually the first couple or last couple on the rotor that need attention. Could also be some crud or steel wool caught in there too.
Good Luck!
Thank you Exray and Codefox you hit the nail on the head. According to the schematic the first two gangs should have continutity on the non grounded side and they do. They also had a short to ground starting at about 80 percent fully meshed. Visually, the spacing looked OK on the plates but a bit of sideways pressure on the fourth gang, the one with the least plates and also (right next to the rectifier tube), caused the short to cease. With careful but deliberate sideways presure on the gang I was able to keep the short from coming back when I released the pressure.
My suspicion is that the lack of mass made the fourth gang more susceptible to alignment issues and this may have been excaberated by the heat from the rectifier tube. The boradcast band works well from end to end when I bypass the wavetrap which appears to have issues and the reception on the other bands is nothing short of spectacular with a few feet of wire for an antenna. I was dubious of a radio with two IF sections and no RF section but the reception speaks for itself and is much better than a contemporary model 118 I restored that has the traditional RF and single IF sections.
Thanks again.
JT
