[Guest]

Hello Philco Fans,

Just a little background on me. I've got an associates degree in electronics, but it has taken only a short time to realized that only gets me started in restoring vintage radios. I am quickly learning how much I don't know.

I've restored 3 vintage radios so I had an intoduction into the world of tubes, and alignment, and plates, and heaters, etc. But this is my first Philco.

When I first fired it up it had an obvious filter cap hum, so the first thing I did was replace the two 20uf C15 I believe, and that cured that problem. Then I replaced all the capacitors, except I had to order the 40uf/10uf combination as 2 capacitors. There not here yet. The ones in the set were toast, only 1 had any capacitance at all.

I blew a 50x6 by connecting my signal generator negative probe in the wrong place. Today my replacement tubes came in so I put the bad 40/10 back in to see if would still give me enough sound to align the IF frequency. Nothing...

I have removed a .2uf cap with a wire wrapped around and around it. I have been told that I don't need this. Is that true? I have it out now, and it had more leads on the bottom than I expected and as a result I have lost track of where it hooks up. I have a good schematic and voltage chart so my question is should I put it back in or will it work without it.

Like I said, before I started it was making lots of noise but now it's making no sound...Neal

[Chuck Schwark]

See here about that coil/cap combo:

From Service Tips section of my site:
Typical B-minus I-F wave traps

Theory also here: http://www.philcorepairbench.com/tips/svctip37.htm

[Guest]

Chuck...thanks for the respone,

I skimmed the reading material but my dense brain didn't come up with an answer to the question, "can I leave it out".

Best I can tell, I better not leave it out and it may well be that it is the source of my latest trouble. It has a loud hummm, LOUD humm when it powers up.

Thanks for the info, I'll read it more in depth later....Neal

Any ideas on the hummm?

[Chuck Schwark]

You read too fast.

(From first link above.)
"....When this wax-paper cap is replaced during restoration, the coil most likely will be of
little or no effect if left out. Purists will want to preserve this wave-trap capacitor look which is alright too....."

:Just change the cap.

[Guest]

I do read too fast...I did read that and I missed the "just change the cap" part of it.

Do you have any suggestions for my speaker Loud humm problem. I've triple checked the tubes and wiring. It sounds like wiring doesn't it? I've checked the output transformer for shorts and opens and resistance values. It checks good.

Could it be the candohm looking choke? I have replaced that with 500 ohm 50W resistor. I heard a pop that sounded like it came from that, but it looks good and still measures 500 ohms. Can chokes be just resistance or do they have to have inductive quality's?. Nevermind, I just SLOWLY read where if you replace a choke with a resistor it can cause an output humm....Neal

[Texasrocker]

You can feel free to: "cut loose" those old coils of wire wrapped around all those vintage wax caps! In some cases, those wraps add as a "resistance",(one end to chassis gnd),.. but that small amt resistance isnt anything to worry bout either. If your chassis has the old "crusty" rubber coated wiring now deteriorated, look closely for direct-shorts among the mess of orig point-to-point connections. Better yet, replace all those old wires 1 by 1,( point-to-point) carefully, and you may find any residual "hums" gone after doing so. Old "leaky wires" can cause probs sometimes indeed! Make sure your AC plug on your test bench is isolated from modern AC type noise generated from overhead florescent lighting fixtures, TVs, computers, etc.
Vintage tube type radios pick-up inteference from many modern day devices/ home appliances that cause "hum" probs. Just tryin to help!!

[Guest]

Hi Texas Rocker,

Thanks for your response and all the ideas you gave me. That fact of the matter is I shot myself in the foot on this one.

When I was replacing caps, I cut out the .2uf cap with the wire wrapped around it. I thought when I was cutting it out, "boy this sure has alot of leads coming out of it?" Well two of the leads were a filament wire embedded and through the wax at the bottom of the cap. So, I cut the filament wire going from 7c6 to 7b7 without knowing it. After days of studying the schematic, I noticed there was no filament connection between those two tubes. I don't know how many tubes were affected, but as soon as I hooked it back up I had it made in the shade. I just retuned the IF frequency that I had all messed up and It was ready to go back in the console for finalizing alignment.

It seems so simple now that it's over but it had me stumped for days and days.

Just looking for a needle cartridge for the phono and that set is officially restored