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Philco P-4735 voltage questions. - Printable Version

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Anyone ever restore a Philco p4735 - 37silverstreak - 10-09-2015

Hey everyone,
 I'm planning on tackling the Philco P4735 radio for my 1949 Packard project sometime this winter. I've never really worked on a car radio before and was wondering if anyone here has any tips? Overall the radio itself is in good shape and looks like it has never been worked on. It still retains its original warranty card, lots of "bumble bee" caps inside. Should be fun! Thanks!
Kevin

RE: Anyone ever restore a Philco p4735 - Ron Ramirez - 10-10-2015

I haven't...only thing I've worked on close to a car radio was a Philco A-801 chairside which contains a Philco/Mopar chassis intended for Chrysler cars but converted for 115 volt AC use.

The process should be fairly straightforward, same as working on a home radio for the most part.

There may be one or two paper capacitors in the vibrator circuit that have a high working voltage on the order of 1000 or 1500 WVDC. Be sure you replace those with the same high working voltage as the originals (whatever the service manual calls for), not the typical 600/630 WVDC caps as they will fail if used in this circuit.

RE: Anyone ever restore a Philco p4735 - Radioroslyn - 10-10-2015

One of the basic differences is their cramped inside which can make them a bit of a pita to service. One thing I've done is connect the set to the bench p/s that provides the hv/htr volts so I don't have to fool with the 6v battery till I get to the vibrator supply.

Terry

RE: Anyone ever restore a Philco p4735 - codefox1 - 10-19-2015

Agree with all. Do fuse battery/bench supply, I reckon 5 amps, maybe 10, will keep you out of trouble. My dad had a '49 Packard, then a 56 Clipper. They were very nice cars indeed.

Philco P-4735 voltage questions. - 37silverstreak - 12-05-2015

Hey everyone, Maybe someone here can answer this. Just got done restoring the radio on my '49 Packard. I replaced all the caps and most of the resistors as they had drifted in value. I hooked up the 6 volt car battery and powered the set up for the first time. All I got was a hum at the speaker which changed with the volume control. I did a voltage check and my B+ voltages were low, so I checked the voltage on the battery which sure enough was low as well. So, now I hooked up my 6 volt battery charger to the radio and powered it on again. This time I could hear the vibrator ( a brand new solid state one)kick in and voila, the radio came to life! However, when I went to do some voltage checks, the B+ voltages on my meter show about 1/2 of what the schematic says they should be, i.e. pin 3 on one of the 7C5 output tubes reads 120vdc where the schematic says it should be 240vdc? I haven't aligned the set yet but I'm getting local stations with plenty of volume. I'm using the same digital multimeter I've used on other sets and it's always read voltages correctly. This is my first car radio resto so I'm not sure if I'm missing something. Anyone have any thoughts? Thanks!
Kevin

RE: Philco P-4735 voltage questions. - klondike98 - 12-05-2015

I merged your voltage question with the original P4735 thread.

RE: Philco P-4735 voltage questions. - Radioroslyn - 12-06-2015

What does your A voltage volt look like? Are you 6v or better? Why did you replace the chopper?? Old one missing or bad?? You may what to check the B current to see that it is like, would expect maybe 45-50 ma with a single end output stage or 70-80ma with P/P. If you have the old chopper I'd cut it open  and clean/file the contacts to see if the S/S one is doing something goofy.

Terry
ps Welcome back Bob!

RE: Philco P-4735 voltage questions. - David - 12-23-2015

This may be a real stupid question, did you check ground + or - . Some of the old cars were positive ground. David 

RE: Philco P-4735 voltage questions. - 37silverstreak - 12-24-2015

(12-23-2015, 09:17 PM)David Wrote:  This may be a real stupid question, did you check ground + or - . Some of the old cars were positive ground. David 

Yes, it is a positive ground system and it is set up correctly. Actually the radio plays beautifully so I'm not concerned. Mostly just curious. I have it back together again and all I have left to do is to make some kind of replacement speaker gasket. The original has deteriorated into a sticky goo!
Kevin