The PHILCO Phorum

New guy.....although the names that I see here are familiar. So, after some voltage checks on the power transformer w/o the 80, I variaced this thing up and was happy to hear something! One odd thing, the wires to the volume control were unsoldered and it was loosely mounted, as if someone had an issue with it. I sprayed contact cleaner into it and my DVOM seemed to show 0 to 10K ohms, so I jumpered it in for the power up. The operation of it seemed backwards, but I'm not too concerned right now. The radio tuned normally, but the audio was weak and had a tinty ringing sounded to it. Since there was an oily residue around the base of the cap tar box, I guess that I'm doing a de-tar rebuild. That's OK. But my question is: where's a wiring diagram that identifies all of the numbered parts on the schematic? (I searched all of the Philco 87 threads and gleaned all that I could from them.) THANKS-DENNIS

Welcome. Please look here:

Duh!....I had printed that out but the lighter shade of printing eluded me. Sorry and thanks.

Hi Dennis and Welcome!
Just finished up a model 87 a few months back. Good playing set for 1929. When rebuilding the filter bank be sure to follow the values of the caps pretty closely when selecting the replacements. Open primaries on the rf coils is common but easy to rewind and leaky bypass caps too.
Terry

Three more questions. The resistor on the detector tube on mine is marked as a 3/4 meg. It measures almost 1 meg. And the schematic calls for 2 meg. Is this critical? Is the resistor on the cap block #34? It measures 98K (#34 is 70K). What's the resistor on the other end of the chassis mounted on a transformer and tied to a 45 tube? Also, on an old post, Ron says that after removing the cap can from the chassis, the bottom plate easily removes and the wires are cut; with melting out the tar as the next step. I take it that this plate can't be separated from the tar can and be left hanging on the chassis (with all of the wiring still in place)? In other words, is carefully un-soldering all of the wires from the cap can the only way to drop the can from the chassis?

If you are very careful, you can separate the metal piece at the bottom which frames the bakelite panel with all of the terminals, from the main part of the metal can without removing any wires from the bottom. I suggested removing the can completely before opening it up as it is easier to do that way.

(34) is the resistor on the underneath side of the multi-section capacitor can, and should be 70K. I don't see a resistor connected to one of the 45 tubes in Philco's under-chassis photo.

Click this thumbnail to view a larger photo:

Here's a photo of the left side. The resistor in question is black and sits on a transformer.

Looks like it is connected across the primary of the second audio interstage transformer (25). You should remove one leg of that resistor, then measure to see if there is any continuity across the primary.

I'm not aware of any production changes adding a resistor across the primary.

I did that and there is not continuity. The resistor measures 11K.

That's a problem. You will need the replace it with a single plate to p/p grid transformer. 3:1 ratio should work fine. Not hard to find and may be able to mount the replacement inside original housing.
Terry

Quote:Not hard to find

LOL....elaborate, please

Both Antique Electronic Supply and Radio Daze carry 1:3 interstage transformers with center-tapped secondaries.

Great....thanks.....I did notice a rusty, tubeless Philco 87 chassis on eBay for $24.99, 100 miles from me. I suppose that if that transformer was good and I wanted an original look, I could think about that one.

Is this the one?

http://www.radiosupply.com/category/256.aspx