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A/V Philco model 369: A 1930s tube radio

Discussion in 'Hardware' started by woof82, 12 May 2014.

  1. woof82

    woof82 New Member

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    Hi all

    I recently acquired a Philco 269 medium / long wave radio receiver and amplifier.

    [​IMG]

    The plug had been cut off. On the inside it said it was rated for 200-250V AC, so I wired on a plug with a 3A fuse and plugged it into the mains (220-240V AC). Unsurprisingly nothing happened.

    The switches seem to have a tactile response that suggests nothing mechanically wrong with them. I can see the variable capacitor rotating when I move the tuning dial. Other than that I have no idea about amplifiers, tubes, RF etc. especially not those manufactured in the 1930s!

    I managed to find a service manual here with a lot of technical information but haven't been able to deduce much from it.

    Is there anything that might we worth looking at / trying first? It would be nice to give it a new lease of life as it really is a thing of beauty.

    Before I forget - photos!

    [​IMG]

    [​IMG]

    [​IMG]
     
  2. Unicorn

    Unicorn Uniform November India

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    That thing looks spectacular! It'll be such a gem if you can get it working! Sadly you broke the golden rule of old electronics, don't plug it in and turn it on when you first get it! You can do more harm than good, and getting your hands on spare parts for something that age is near impossible. But anyway, it's too late for that now.

    The first thing I would look at is the power input circuitry. Being of 1930s vintage it's older than anything I've ever worked on and I can't see the images on my current connection, but there has to be some sort of AC/DC voltage transformer in there, so the AC input side is where I'd start and work by a process of elimination from there. It may be something as simple as a blown internal fuse.

    [edit]

    Sorry, I missed the link to the service manual! That's amazing... I can't get service manuals for things manufactured in the past 5 years and you found one for a 1930's radio :D Yes, there's a whacking great transformer (T2) in there, so you need to check that first. If you don't know how, just google "how to test a transformer for an open/short circuit" and you'll need a DMM. If T2 turns out to be in working order, the next thing to look at would probably be capacitors which will be fairly crusty given their age. C14 and C15 are electrolytic, so check those and let me know what the pre set caps are. They're probably fine, but throw up a pic because they could be something ancient like Mica ones. I'm amazed that there isn't an internal fuse to be seen. It must rely entirely on the fuse in the plug!
     
    Last edited: 12 May 2014
  3. woof82

    woof82 New Member

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    Hey Unicorn thanks for the response!

    Yeah I guess I should have done more research before trying to plug it in. I have a DMM and it looks very easy to remove the electronics from the case, so I might have a look at the transformer this evening. Thankfully electronics from the era seem to be fairly self servicable.

    Is there anything in particular that is a likely point of failiure? I guess capacitors are subject to chemical degredation, and the tubes could have lost vacuum over time?
     
  4. Unicorn

    Unicorn Uniform November India

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    The two electrolytic smoothing caps I mentioned above will be 100% dead, I can guarantee that. You'll need to find suitable modern replacements and solder them in. Having seen some restoration work on old hifis in the past, what people like to do is keep the old electronics in place on top of the chassis but disconnected from the PCB underneath, then solder in the replacement components which are covered by the chassis. This makes it look all-original when the unit is opened up and should help keep some of the value. I'm not sure about the tubes, they should hold their charge for a lifetime, but then again this thing is over 70 years old and anything is possible. I have no idea how to test a vacuum tube though, I'll have to look that one up!
     
  5. KidMod-Southpaw

    KidMod-Southpaw Super Spamming Saiyan

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    If I were you, I'd be testing all of the caps. Even if they're not a point of failure, there will still most likely be some that will affect the sound or cause noise/ popping or the like. Of course, the largest caps in there can be bloody dangerous! They're huge things!

    Most tubes definitely do have a lifetime, and I've no doubt at least a couple of them will need replacing. Honestly, I'm not sure if a cheap tube tester would do the trick, but I suppose it would be worth a try. Replacing those ought to be the easiest part anyway, as the model of each tube will be displayed either on the tube, or it'll definitely be in the service manual. Just find out each one that needs replacing and look up an equivalent as best you can to buy. :)

    If everything is mechanically in order as you say, you should be good to go after that; following Uni's steps first, of course. :D
     
  6. woof82

    woof82 New Member

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    Finally got around to having a poke aroud inside this thing. Thankfully I'm a huge moron and forgot to put the fuse back in the plug when I re-wired it, so I never succesfully connected it to the mains.

    [​IMG]

    Speaker cone looks like it is still in good condition, was worried it might have become damp and mouldy at some point.

    [​IMG]

    First look at the insides of this thing. All the electronics are contained in a metal frame that just slides out of the wooden case. Flipping it upside down reveals in inner workings. It looks like it has been maintained, lots of notes scratched into the frame inside reveal tidbits of information left by previous electricians.

    Capacitors seem visually fine, no bubbling or discolouration. There are lots of what look like modern components, bright orange. They simply read "47K250" along the top, no other information.

    Following Unicorn's advice I tried to check the transformer.

    [​IMG]

    I probed between valve V4 and transformer T2, checking every combination of the blue and red lines marked on the diagram. No connection between any of them, so there doesn't appear to be any leak across the transformer. Whether there's a short across some of the coils on either side is a bit harder to test.

    When poking around I did notice that I was unable to find a connection across the switch S9 when the switch was closed. There is a red circle on the photo illustrating where I think the S9 terminals are. It's possible this pot is not working, even though the tactile response is good (makes a click when turned).

    In other news this thing looks pretty dangerous, there's no earth lead, no fuse, and the mains goes straight through the power switch / volume knob (S9). o_o

    Anyway here's a side by side of my photo and the photo in the manual:

    [​IMG]
    [​IMG]
     
    Last edited: 21 May 2014
  7. KayinBlack

    KayinBlack Currently Rebuilding

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    Sounds par for the course. Some people actually hide the caps inside the package of the old paper caps, as they're almost always a good bit larger.

    A good rule of thumb is if it's an electrolytic, replace it. Mica caps hold up, but oil/paper and wax sealed electrolytic caps do not.

    It's also often true that all the tubes are OK. Assume they are, but make sure some moron didn't put them in the wrong spots.

    http://antiqueradio.org/restoration.htm. This should help quite a bit.
     
  8. Nexxo

    Nexxo Queue Jumper

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    Man, that's a thing of beauty. Should restore nicely.
     
  9. trintragular

    trintragular New Member

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    Agreed. Hope the OP keeps up posted with any progress.

    Out of curiosity, if this can be fully restored, are there many (or any) MW or LW stations to listen to in your area? (Even just for testing purposes.)
     
    Last edited: 24 May 2014
  10. KidMod-Southpaw

    KidMod-Southpaw Super Spamming Saiyan

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    There should always be a decent amount at nighttime when things are easy to pick up. Although my units mostly pick up French and Irish stuff.
     

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