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  • #13180
    garykuster
    CVRS Member

    I’m finding I like the build quality and the space to move around in the 30’s consoles, only they take up a lot of real estate. My next adventure is tackling my newly acquired basket case
    Philco model 38-4. 8 Tubes and some were in the wrong sockets and one tube didn’t belong!, Many are shot, one has shorted, will pick up the new tubes this afternoon. The bizarre one year only tuner is a mess with a broken pivot and other issues. The tuner is definitely a Macgyver challenge! The cabinet will test my veneer repairing skills! Basically , this is a parts radio, but I can’t not fix it.
    Here’s the long awaited question: I have done all the caps save 2 which are .003 MFD and .002 MFD, BUT it says ‘Working Voltage 1000 on each cap. I have both of the Caps in 630 V.
    Do I need to source the 1000 V. versions? or will my 630 volt ones work? This thing has a bloody big transformer in it with a tube perched on top. I have heard the adage, “you can go up in voltage, but not down” Is that the case here?

    After some reading, I have to stick to the 1000v. or better. Thanks anyways.

    Gary K.

    • This topic was modified 3 months ago by garykuster.
    #13185
    Alistair Thomson
    CVRS Member

    Looking at the schematic, the 18µF capacitor, component no. 66, will be the one with the highest required working voltage since it’s smoothing the power transformer output. That capacitor has 350V on it according to Fig 1 in the service bulletin. So your 630V replacement for any capacitor in the radio will be good.

    The manufacturers probably just put in the high V component because that’s what they had at the time. As you said, you can go up in V with capacitors.

    #13186
    garykuster
    CVRS Member

    That’s great Alistair ! I’m working from an enlarged schematic and parts list on my PC. The printer has been down for a week. Thanks a bunch for the intel. Because of the age of the thing I want to do the resistors as well to practice soldering. I will take my time. Much more fun than a AA5 !

    #13198
    garykuster
    CVRS Member

    Caps are done, but not much point to continue until I have addressed the crazy 1 year only, automatic presets tuner mechanism. One of the crucial parts has snapped in half and in order to get to it, I have to remove a very small rectangular headed threaded bolt. Does anyone have a tool like that? I was thinking of crushing a 3 mm socket in the vice or something along those lines. If I can’t fabricate a tool to remove the bolt (visible in the last pic behind the gear) I am dead in the water as I don’t think I can find a new “selector arm assembly” anywhere. I can probably repair the broken one IF I can get to it.

    #13212
    Alistair Thomson
    CVRS Member

    It’s difficult to see, but is there not another one of these “bolts” on the right? If that is the same thing, it seems to me that, in that other fixing that we can see edge-on, there might be a spring behind it, and that the “bolt” head might actually be a small rectangular plate. That would tie in with what looks like a nail head in the centre of the plate. It might be that the actual dis-assembly can be done on the other side of the shaft from the plate. Or maybe you simply press these plates against their springs, or pull them, and the cog can be popped off.

    I have no idea if any of that is correct, and if it is, I have no idea why they did it like that! 🙂

    #13213
    garykuster
    CVRS Member

    After considerable fiddling with penetrating oil and a stout pair of needlenose, I managed to get the tuning dial apart by removing the “bolt” on the outside behind the dial pointer. At a glance, one can see why this was a one year only design! Asinine comes to mind. The selector arm assembly is now removed and now it’s time for the macgyver part . The strange part is that I’m unable to decipher how this whole thing stays together and operates as a tuner. Hopefully, once the broken parts are mended, it will become clear. I also had a chance to completely clean the chassis from years of nicotine and schmutz. Looks much better!

    #13220
    garykuster
    CVRS Member

    After much fiddling, I managed to come up with a way to wrap the broken aluminum arm with metal as epoxy alone doesn’t have a chance to hold this together.. I secured a metal splint with 1 screw and a drift pin from a 1957 Mercedes door lock cylinder. I will coat the whole thing in JB weld to finish the repair. Even after having the tuner drive completely apart, it will still be a surprise to see how it works all back together. Haven’t a clue how this system works. I have removed the station preset cones as with the splinted arm, I don’t want to stress my repair. All the stations at the cones locations are long gone anyways. More pics of this cockamaimie system.

    #13238
    Sterling Spurrell
    CVRS Member

    Looks like you have it all under control.

    #13251
    garykuster
    CVRS Member

    I have completed the tuner repair and reassembled the radio. All the bad tubes are replaced, every resistor has been hunted down and tested and any out more that 20 % replaced. Almost all were o.k. as you would expect. I replaced all the caps including the ones in the cans. Dan warned me about the capacitor blocks, boy were those fun to do. What a mess of sticky tar. The radio shows signs of frequent repairs in the past with 4 different tube manufacturers all present. Radio powers up the tubes normally and has a slight hum. The volume control works as does the 3 position tone switch. I can barely hear a station or 2, but that’s it. This radio has an Audio kill switch built into the tuner to eliminate static or hum while between stations. It does so by opening a ground circuit from the plunger switch on the tuner. When locked on a station, the tuner supplies ground somewhere in the circuit !
    This wire was cut off and I can’t find where it would have gone by looking at the schematic. Anyone have any ideas or run into this problem? I know this is a one year set -up.

    https://www.tubesandmore.com/schematics/philco-radio-television-corp/38-4

    #13315
    garykuster
    CVRS Member

    Wiring conundrum solved. The Audio kill switch wires up tp the volume switch. Proof positive if you stare at a schematic diagram long enough, the answer is always there.

    #13323
    Dan Walker
    CVRS Member

    It looks like you got it all figured out, and working.
    Maybe now you know why I don’t like working on those Philcos, with the caps in blocks,and the different systems they used for most everything.
    That particular radio you just did probably took a lot of figuring but you did it .. I am glad it worked out for you
    Now you are ready for another one of the same model.
    Good job.
    Dan in Calgary.

    #13324
    garykuster
    CVRS Member

    Thanks, Dan. The first one may have to be parted out as I need the on/off 3 position tone switch. Imagine that, the on off switch only lasted around 80 years! I could also put a toggle at the back
    until I find a switch. The working one in the first radio is also very worn out. These radios were a challenge, but they taught me a great deal including the value of patience.
    The veneer is also in tough shape on the first radio and the second one I just got still needs refinishing, but the wood is all good.
    I can’t strip or refinish the wood until summer anyways. Here’s some pics. The second radio has great original looking speaker cloth and has a super clean chassis. Just waiting for parts to arrive.

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