Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: sawdust on September 19, 2010, 10:14:45 am
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I have a choke with these markings; 320319-2; 806537. It measures 127 ohms and weighs about 1 lb. Anyone recognize the manufacturer and any specs?
Thanks in advance,
Dave
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Can you measure the inductance?
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No, I have no way to do that, my DMM doesn't measure inductance. :sad:
Dave
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I could not find much except that 806 refers to Gordos in NJ.
I do not know what they built but they did remove their EIA code in 1975.
Could you post a pic or give us the dimensions?
We may be able to "guesstimate" values for you.
Where did you acquire the choke?
I'm making the assumption that you are simply looking for parameters where you could use this choke in an amp and it's history isn't all that important.
Ray
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I actaully have the same problem. I hunted around on the net for some method by which I could measure inductance. Here is what I found:
1) get a 2k 10W resistor, measure its resistance accurately
2) hook the resistor in series with the inductor
3) apply 120VAC to the resistor/choke
4) measure the voltage drop across the resistor (Vr) and the choke (Vi)
Calculate the current through the resistor (Ir = Vr / R)
Calculate the reactance through the choke (Z = Vi / Ir)
Calculate the inductance (H = Z / (120 * pi))
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I actaully have the same problem. I hunted around on the net for some method by which I could measure inductance. Here is what I found:
1) get a 2k 10W resistor, measure its resistance accurately
2) hook the resistor in series with the inductor
3) apply 120VAC to the resistor/choke
That is a fairly abusive test- it is liable to saturate the choke, which would give a false reading. You can do the same test at low voltages though.
(http://i81.photobucket.com/albums/j207/merlinblencowe/Choke_Test.jpg)
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WOW!
I've been hunting for this info for a while!
No more "Best Guesses" for me!
TYVM
Ray
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Thanks Merlin,
I measured 3 chokes, 2 were known, and one unkown. Both methods gave similar results (+/- 1/2H) but the first method was nasty to one of my chokes - just really vibrating, not to the point of smoking. For your method I used 25VAC - more suitable I expect?
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I was gonna say.... 120VAC!!??
6V (your nearest filament winding) ought to be ample, give good readings, not over-strain any tube-suitable chole, and be a lot less lethal to you.
Use a 1K resistor. 1/2W 20% is fine, this isn't watchmaking. A good choke will take "most" of the AC voltage, so read the voltage across the resistor. 3V-2V may be a good rough filter; Fender often used such iron. 1V or less across the resistor is a high inductance for filtering; VOX did a few this way.
None of these methods, no simple method, will determine the DC current handling. You may read the DC resistance, multiply by your expected current squared, and determine the internal heat caused by DC current. Ponder whether that much heat is reasonable in that size lump. (Or compare with Hammond's chokes.) But something made in NJ in 1973 may not even be a DC-rated choke.... AC-only chokes are used for several things, from telco filters to motor protection.