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Thread: Philco 46-1226 Radio

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    Default Philco 46-1226 Radio

    before and after shots of the Philco 46-1226 code 125

    recap and re-resistor and Re-can of filter cap sections and Re-work power transformer and Re-align the IF amps, and add a polarized power cord, add a fuse block, update the 7AF7 section, calibrate an old update error on resistor R102 which was undersized to allow for a PM speaker, troubleshoot and find and repair carbon flash on a Loktal, almost successful at repair of the primary on the audio output transformer but ended up having to use an equal alternative, color coded transformer leads to match the schematic with heat shrink tubing.

    I used old school brown drops to keep some degree of antiquity integrated into the outcome,, making the appearance of the renovation to appear as though it may have happened in the 70's.

    there are actually people out there taking the old caps out, melting the wax out, pulling out the guts, inserting a modern cap into the cardboard tube, then re-melting the wax back onto the old cap tube then re installing.... thats really respectable when you think about it. there are even people rebuilding dog bone resistors !!

    Radio going back into its cabinet after being down since 1981. I rigged it up to work "for a while in 97' but it soon broke again.

    all is well in the 9.3 to 15.5 MC land.

    six weeks of restoration,, didnt bother with looks or a whole lot of cleaning so to speak,, didnt want it to look too good ,, LOL.

    With my other improvements and adding a vent mod to the power transformer, I think its good for another half century or more.
    I used an old Navy trick to the job but went a step further. If you want an piece of electronics to "speak" to you later when it breaks, then add a dab of white paint on each part dead center. When the part fails the color of the paint will physically turn brown. this give you a visual inspection aid later.
    I went a few steps further and designated all the small & large parts with their schematic name. This will benefit me or perhaps my son's later on.

    now i am at 80ma of current draw & 290v on pin 3 of my two 6k6's and 250v on pin 4 of the 6k6's,, in line with code 125 which states the PM speaker power supply update will yield approx 20v more than code 122. All of this hard work to finally put to bed the old incorrect prints saying my R102 needed to be 300 ohms. 600 ohms at 50 watts is the right solution. this resistor is now on top with the tubes standing straight up with a heat sync i made up to wick heat to the chassis.

    Tom,
    that email you sent me in 03' with schematic actually turned out to be several runs prior to this code 125.
    In order to make a repair to a 46-1226 code 125, you must use code 122 + run 1 + run 2 + run 3 updates which then = code 125.
    there is *NO* known schematic available for this exact code 125.,, it never was printed.
    Chuck at the philco workbench was very helpful.
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    Last edited by jcassity; 05-12-2017 at 12:27 PM.

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    my first go at hand making a dial needle, didnt take long but since i wanted it fast, i had to make it in two parts.

    I was able to leverage about 20 more deg F off that big stand up resistor now getting it down to a reasonable 190deg. the pig tail copper thing is how i got the temp a tad lower.

    i have one tube that glows a tad blue from being gasy,, its not in the anode or cathode or screen so i guess its ok. it kinda wave around in sync with the music
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    made up a heat sync for my first three tubes, one that reaches 350degF and tow that reach about 280degF. Old patents i saw shows ideas about solving this issue so that gave me the go ahead to fab something up with scrap i have.

    the purpose of heat syncs was to lower the temp on one of my tubes that was gasing, causing a cobolt blueish neon look. apparently harmless in my case because the blue is not in the annode, cathode or screen, its on the glass. when tunes are playing this blue fog dances with the music,,,, kinda neat actually.

    now its back in service. Next to solve a random wire antenna to get outside the bubble of the home so i can gather those milivolt signals in the air more cleanly.
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    a couple more with heat sync and in the chassis.

    my aftermarket dial glass is perfect,,
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    i watched an old westinghouse training film for vacuum tubes because ,, well,,, the generation gap in that i never clearly understood what they did because they appear in so many different shematic forms.

    once i watched the film, it was amazing and simple to fast track a person inside 30 min on whats going on in there.
    They can do six things,, 5 are defined but the sixth one is somewhat infinate.

    fast forward to a recent IBM training film i think from 09',, from what the speaker was saying, apparently three is not a single electronic part availble today that can do all the jobs a tube can.
    size was the reason to make them not so useful anymore, other than that one minor infraction, they would still be in use today.

    this chassis draws 80mA at 120v.
    can be fed with DC as well with some tricky engineering since it spends a lot of energy initially converting to dc.

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    thre is a big tall resistor in the back with a suspect looking pigtail copper roll. That is one of my mods.
    this radio needed a 300ohm resistor placed on the secondary of the power transformer to allow for the newly invented PM speaker.

    this particular resistor gave philco many troubles because it was always burning out.

    now basic electricity can help us find the right wattage but this is where it gets to an area i have never ever had to deal with.......

    the one line looks like this.......
    800v secondary with center tap (400vAC / 400vAC).
    one 400Vac leg to: one side of the big green resistor.
    Other side of big green resistor goes to the two filter caps cans each being a dual 40uf/25uf 400v type.
    the above prepare the ac for the DC converstion.

    This resistor is smack dab in the middle of the rectification section.

    my voltage drop across this resistor measured readings on both the AC and the DC scales but everyone on the Philco forum said to check what the dc voltage drop was across this resistor to size it for wattage.

    i came up with 48vdc drop across the resistor and at 300 ohms needed per philco well you can see that E^/R = watts which is about 8watts.

    well this resistor was getting too ***HOT*** with the 10watt i installed and at 300 ohms.

    since all the old timers told me it was a common problem, and at 300 ohms it introduced too high of a voltage to the push pull 6k6's, i calibrated it.

    since the resistor is in the middel of the AC / DC converstion,, you have to do a complicated forumla blending the AC and DC effects this resistor suffers from.

    my big green resistor shown is a 25watt 611 ohm which worked best. It gets to about 125deg even with my pigtail copper heat sync thingy.

    my point here is that ohms law applies,, but ... in some cases it dends on where you are in the circuit as to how you size for heat disipation.


    i am still learning about this stuff but ,, again my point here is that the basic ohms law did not apply in this case.. very odd how something with 48vDC and 600ohms sized to 25watts is still "telling me" ,, "I'm too small,, please insert 50 or 100 watts here".

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    Yee Haww, great job Scott...

    I wouldn't have worried about the heat sink on tubes, these sets ran for years without them... I'd be more worried that unequal expansion of glass and metal sink would crack the glass... Tubes can be rebiased to drop their operating temp...

    As far as 6K6 lemme kno if you need some, probably have 12-15 good used ones around here...






    My other rides (that actually do run & drive)

    1969 Fairlane Cobra 428CJ 4-Speed << New 49th Birthday Picture

    1972 Comet GT - 306 C4

  10. #10
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    yes i considered that in the design,, and you cant see it from the picture so ,, here is a quick etch and sketch of what that strap is actually doing.
    its able to expand and contract.

    the only big question mark is the "rate" of expansion of glass as compared to steel.
    I would only "think" that glass is harder than steel and expand slower, meaning the steel is always ahead of the glass during heating and cooling???????
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