The PHILCO Phorum

These take a 1/4 " hex to adjust but all I have is a metal driver. How much will this affect the alignment? I'm guessing I will have to go to either side of the peak then pull out the driver to see if they are actually peaked.

Jim, the metal nut driver will cause problems. Here's a thread on making your own plastic driver. http://philcoradio.com/phorum/showthread.php?tid=1544

+1 on what Bob said.

Also some of the trimmers have B+ on them. A metal tool can short the B+ to the chassis and is also a shock hazard.

Steve

I have tried this trick in the past and everytime the pen body just melted into a jumbled mess. I was using a torch to heat up the bolt. This time I used a soldering gun and it appears to have worked just fine.

There is one compensating cap though that it won't adjust as the nut is just too tight. Thankfully its on the secondary side of the IF so B+ involved. Guess I'll have to use my metal driver and play it by ear.

Jim, perhaps you can use the metal nut driver to loosen it initially (while the radio is unplugged) and then the plastic to align.

Loosening with the metal driver does no good, still too toght to turn with the plastic tool. Don't want to add anykind of lube to it fo fear it will throw the alignment WAY off.

Just a heads up, this has been put on the back burner until I get the speaker reconed.

Got my speaker back and have been trying to align this with no luck. Once I start reaching a peak reading on my output meter the radio breaks into a loud squeal/motorboating. If I back off the one compensator so that the squeal is gone and try to adjust the next one it starts squealing again. This with and withouit using a signal generator.

If I just back off each compensator to eliminate the squealing the radio picks up AM stations just fine but the Sw motorboats like crazy. Have already installed the 70 ohm resistor between cap #14 and the osc. coil like the service bulletin states.

Another thing I noticed is that when adjusting the compensators, it not only varies the volume but also the tone, which I have never encountered before. All the wiring is original so there was no rerouting of any of it. Tried cleaning the compensators but that didn't change anything. I'm stumped.

Simple question, but...do all of the tubes that require tube shields have the shields in place?

It sounds like you have an oscillation issue. If the 78 and 75 tubes do not have the proper shields over them, the set will squeal like crazy.

Yep, all tube shields are in place and are making good contact with the chassis. Now, the only thing thats not "original" , or as close as possible, is the placement of the electrolytic #49. Its placed between the terminal board where resistor #47 and resistor #15 are tied to and the negative end is attached to the ground terminal thats rivoted to the socket of the 6A7 tube.

Possible gassy 78 tube? That can cause oscillation as well.

Make sure all grounds are good and do not have any rust or otherwise high resistance paths to ground.

I'll try a different 78 later today, if I have one. Already checked the grounds but couldn't hurt rechecking. Thanks.

Some of the IF adjusting nuts have B+ on them, that is if the 66 is much like the model 60. The metal in the nut driver won't affect the adjustment that much, no more then using a flat blade job on a typical 1940s IF transformer, the main reason Philco produced the fiber adjustment tools was because of the B+. The way I got around it was by wrapping the socket end or the nut driver with electrical tape.
Regards
Arran

Well, every 78 I tried either made matters worse or had little effect at all. Next will be to try different 75's or maybe a combination of the 75/78's. If that fails then I'll redo the grounds.

Arran, klondike98 was kind enough to pass along a tool he made for adjusting these 1/4" compensators. Works very well.

Looks like I got it working. Tube combinations did no good as did reworking the grounds by trying to clean and solder them. Noticed that there was microphonic sound through the speaker just after the radio was turned on if I tapped the chassis and especially around the # 22 compensator.

I removed the little metal tail that was rivoted to the chassis that served as the ground connection for 400 ohm/.05MFD cap of the 78 tube. I installed a small 2 terminal strip and bolted that to the mounting screw for the 2nd IF can, making sure that all the metal surfaces were clean.

Didn't change a thing. Then I noticed that if I played around with the tube shield for the 6A7 that I got intermittent static. OK, try cleaning the inside of the shield connection on the socket as well as the outside on the shield. Also reshape the sides of the socket to tighten up the shield connection. BINGO, now I can pickup stations all across the AM band with no squeals/motorboating and there is no motorboating on the SW band.