The PHILCO Phorum

Troubleshooting mode so I started a new post. Philco 37-650 is done but when I turn it on I get nothing but loud humming with no volume and tone control at all. Sounds like filter caps right? I don't know. When I was putting the set back together I noticed discrepencies between the parts list page Riders 7-68 and the schematic. There's a parts layout diagram at the top of the page.

1st Discrepancy: Parts page shows part #52 3.5K resistor connected to the part #53 490K resistor at one end of a terminal strip just to the right of the two 6F6 audio tubes. On the schematic the two resistors never directly connect to each other. The 3.5K goes between pins 4 of both 6F6's and one end of it is connected to the + side of the 8ufd filter cap. The other end of the 3.5K connects to a .01ufd cap and that cap connects to one end of the 490K resistor and pin 5 of one of the 6F6's. Other side of the 490K connects to a 99K and ends up at the CT of the power transformer. I DO NOT have my set wired like this.

2nd Discrepancy: In my radio there is no direct connection between the part #44 99K resistor and part #46 330K resistor nor the part #53 490K resistor.

I told you this set was chopped up when I got it. My inclination is to tear this set apart and make it per the schematic but I'd love to have some input on this. The discrepancy on the polarity of the 10ufd 50V filter cap that filters the bias resistor has me questioning the integrity of the whole schematic.

Can you give me your ideas on this?

Thanks,
John

There are discrepancies also between the parts diagrams and schematics on the 47-1230. So far, what I observed physically with my radio and the schematics did match, while the parts diagram didn't. I would tend to believe the schematics over the parts diagrams.

I'm just gonna tear it apart and wire it per the schematic. Don't ya just hate it when someone has chopped a set like this up. Hopefully that's all it is. We already know the schematic is wrong on the polarity of that 10ufd filter. Positive should go to chassis ground not negative as the schema shows.

John

EDIT: I revamped the audio circuit to match the schematic and it worked but the volume was low and it would motorboat if I turned it up. Disconnected the after market tone control from the circuit and the set works great. I need a tone control!!!

John