[Guest]

hello im trying to wire the electrolytics on this philco 37-10 i wired most except for #31 before i mess up it seems this cap the positive is going to ground is this correct? also right now the radio plays with a hum and the 5y4 rectifier tube is working very hot thank you for info

[NV3G]

The electrolytic capacitor that has the positive lead going to ground is connected to the center tap of the power transformer that feeds the plates of the rectifier. I can not read the number of the capacitor because it is blurry on the download from Nostalgiaair.com. This is correct for this capacitor's positive lead to go to ground.

The connection generates a negative bias voltage for the control grids of the audio output tubes.

Number 31 looks like it negative lead goes to ground.

Best Wishes
Oscar
nv3g

[Guest]

thank you for reply,i was reading the cap symbol backward, i thought the side with smaller line (upside down t ) was the ground. also should i recap all bakelite blocks? thanks for info

[exray]

Hi manny,
I always remember it on the Philco diagrams as the 'u' shaped part of the symbol as resembling the can. The can is always the negative side of the cap but that doesn't necessarily mean ground or chassis connection. In fact, none of the three caps showing in the power supply section have their negative side (can) connected to the chassis.

By all means, replace the innards of the Bakelite blocks.

Good luck,
Bill

[codefox1]

I have an little box on my workshop bench which inserts a common light dimmer into the circuit. I sometimes use this to control the heat for a throwaway soldering pencil (like from the 99 cents store) to just hot enough to melt the tar in those bakelite capacitors. That way it's a little easier to get all the crap and what ever is left of the original capacitor out without a lot of fumes and smoke. Sometimes, it's just a matter of digging all the stuff out with a scalpel or box cutter, other times the tar is real hard. There is always at leasts one crack, which has let moisture in and ruined the component inside. In any case, for authenticity, and ease of assembly, you will want to get the old material out without destroying the bakelite case, put new caps inside (there will always be enough room, use 600 or 630 volt modern orange drops or equivalent.) There is cross reference available on this forum to double check values. Of course some of these bakelite blocks have nothing connected internally, and are only used as tie points. That's why it is probably better to retain them, so you do not have to resort to adding new terminal strips, or tacking things together without any physical support. As suggested many times before by persons with more experience than me, it is unnecessary to attempt to fill the bakelite "tombs" with wax or anything else, as the modern components have good enough enteric coatings to survive for several decades, and will probably be readily identifiable after that, should the set again need service.

BTW. the light dimmer trick can also be used to stupid check just about anything, or slow down a drill to a crawl. The worst that can happen is that the dimmer craps out. Then you put in another one. Not a replacement for a variac by any means, and will not be friendly to any solid state devices, but just another little old school bench stunt.

[Guest]

thank you for kind replies, i had some of the caps wired backwards, which did not show on my light in series tester, when tried radio out it cooked the 5y4 tube, this is my first attempt at this sort of radio, and yes i know that the negative terminals does not go to ground. i will keep working on radio i dont think i damaged any thing else
regards Manuel