The PHILCO Phorum
Newbie Model 71 questions - Printable Version

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Newbie Model 71 questions - gmg - 03-13-2017

For my first restoration attempt, I have a Model 71-121 but I’m not a radio guy. It looks like this has been partially recapped in the past (anyone recognize those colorful speaker wires?) with components wired point-to-point and sometimes to the Bakelite blocks, which were not unstuffed but several caps are just handing with unattached connections. Pics, schematic and parts list are all here http://chronology.weebly.com/philco-71.html

My plan is to empty all the Bakelite boxes (done) and replace the necessary caps onto lugs, and add insulation and a line fuse. Then move on to tubes before powering up for the first time with dim bulb tester.

My questions are these: 

Are there any critical wire lengths that I shouldn’t alter as I clean up and rewire?

Part  (21) Filter Condenser Bank ( 2x0.05u, 1x0.25u)  04731 appears to be missing. Three caps numbered (21) appear on the schematic but I don’t know which of them is the 0.25u.

Part (7) 0.5u Number 3583 not present on the chassis. 

Part (38) 3903AA  and line filter caps (49) are also missing also missing but I can work around those.

The tone control (39) appears to have an integrated cap but the schematic shows no value. Any suggestions? 

Anything else you spot? Any other warnings, hints, suggestions? Thanks very much.

RE: Newbie Model 71 questions - TV MAN - 03-13-2017

Welcome! Lots to experience and helpful people here!

Looks like an older recap to me, possible from the 1980's. You can put an add on the wanted section and maybe someone here would have something you could put back in there. Looks like on one of the blocks a terminal has been torn off. On the tone control, it uses a standard cap which you can remove and should be able to read the value. Also check your resistors. They tend to drift, esp the ones in the power supply.

Also, as others may mention, there are high voltages in this set, can be around 400-600 volts. I recommend reading some other threads and maybe a book like "Practical Radio Servicing" by Marcus and Levy. There are a lot of You Tube videos to check out also. Don't go into this without some research. Do you have and know how to use an ohmmeter?

RE: Newbie Model 71 questions - Radioroslyn - 03-13-2017

Hi and Welcome to the Phorum,

>Are there any critical wire lengths that I shouldn’t alter as I clean up and rewire?

Generally speaking wiring should be neat, close to the chassis when possible and not excessively long. Wiring that can create problems are if heater wiring is near control grid wiring (can induce 60cy hum) and if control grid wiring is near plate wiring (can induce unwanted feedback).

>Part  (21) Filter Condenser Bank ( 2x0.05u, 1x0.25u)  04731 appears to be missing. Three caps numbered (21) appear on the schematic but I don’t know which of them is the 0.25u.

On #21 the .25mf should be connected to the center tap of the power transformer's hv winding. The .25 may have been replaced by a small electrolytic like 10 or 20mf @35v + side to the chassis and - to the ct.

>Part (38) 3903AA  and line filter caps (49) are also missing also missing but I can work around those.

OK

>The tone control (39) appears to have an integrated cap but the schematic shows no value. Any suggestions?

Value is not very critical it just determines how much high frequency response it cuts off. Larger the cap the less highs you will hear. Typically a .01 or .02mf  at a 630v or higher voltage.