Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on December 20, 2010, 02:10:19 pm
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I have an old 1936-37 Philco radio. Furniture size. There are two cap cans but they only have a part numbers on them. Any old timers recogize these or there possable value? Both cans have the same number on them with a single high voltage terminal
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Hey Plexi,
I've restored a few components for a couple of radio collectors. For the cap can restoration I ran into a similar situation.
First, can you identify where this is in the circuit? most cap cans I've seen are in the B+ rail.
Next can we know the operating voltage?
If it is in the B+ rail we can guess it to be in the 20 to 50 uf range. maybe as low as 8 or 16.
As a ripple filter going bigger (to a point of reason) will not hurt performance.
Multiply your supply voltage by 1.5 and you have the WVDC for the cap.
A dremel tool opens the unseen bottom end of those cap cans nicely, (messy) leave the wire that is attached to the can to solder a new cap in its place. A good glob of epoxy / JB Weld holds the cap secure for the next 50+ yrs.
I'm looking at doing the same thing to the big Mallory cap in my 1946 Zenith Transoceanic.
Ray
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Sound good to me. I have to put a power cord on it and then plug it into my variac and bring it up slowly. None of the cap cans or other electrolytic PS caps which are 16uf/450 show any indication of buldging or damage. The dang thing just may work with a power cord. I have one bad tube though so i will have to get that first. I may have what i need
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Note that the chassis-mount can is INSULATED from clamp. This rig is probably back-bias: the first B- node runs through the power stage cathode resistor and then to ground.
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I repaired those old radios in the 60's. Those are old fluid-filled caps with an anodized aluminum foil inside. No doubt the fluid (mostly water) has dried up long ago. Most were rated 450V, 8uF or so. You should be able to replace them with 22uF 500V.
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Interesting. I will use some 22uf/500 caps here. Just hope when i turn it on i dont tune into Rod Sterling or War of the Worlds
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Sound good to me. I have to put a power cord on it and then plug it into my variac and bring it up slowly. None of the cap cans or other electrolytic PS caps which are 16uf/450 show any indication of buldging or damage. The dang thing just may work with a power cord. I have one bad tube though so i will have to get that first. I may have what i need
What tube do you need?
I've got a bout 1000 TV and Radio tubes rattling around my place.
Hopefully I might have what you need, It would help me justify keeping these otherwise useless tubes LOL
Ray
Heck for that matter give me your whole tube chart.. if you have equipment that uses them, spares may be nice.
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Hey Plexi!
Like you don't have enough on your bench to do, but when your finished with that Philco you need one of these unless you're good with talk radio on AM.
I haven't built this one personally, but everyone I know who restores radio's has one with a mp3 player attached.
Most put them inside old cathedral radio's that are beyond repair, but heck it would look slick covered in a tolex box too!
OH! the L1 coil is an AES part P-C70-RF
Back to back wall warts can be used for the PT, just use a LED instead of a 12V bulb to minimize current loss. and 4 foot of antenna is over kill for in house use, if you have a ancient set of rabbit ears or even a 20ga dipole you're good.
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I have 4 more tubes to test that i forgot about. There in those square sheild cans. One did not want to come out and the glass came out with all the wires that were attached to the tube base. It came out so clean it looks like you could just get all the wires back in the base socket position and resolder at the pins. But no way. I have enough to do.
I will make a complete inventory in the next day or two. I used to have an underground radio station. 12 watts FM can go pretty far believe it or not. Farther on AM.