Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: g-man on April 29, 2013, 12:43:09 pm
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PT wires with resistances measured:
2 x Black (0.9 Ohms) = AC input at primary ?
2 x Green (0.2 Ohms) = heater ; 6.3 Vac
2 x Yellow (0.2 Ohms) = tube rectifier heater
2 x Red (0.2 Ohms) = B+ high voltage Power supply
1 x Red-Yellow = B + center tap ( to ground )
2 x Brown? (117.3 Ohms) = heater or bias ?
1 x Yellow-Brown? (57.6 and 60.3 measured to each Brown) = heater or bias center tap ?
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839830
830 =Triad transformer
8 = 1978 , 1968 . 1958 ?
30th week ?
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I write "standard" wiring code I see very often on amp.
About your tests , I can't tell more , not enough information. It is not like if I test myself
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The red/red/red-yel is a low voltage winding. 12-0-12 (24VCT) is a common enough winding voltage. It may be for bias, but I bet it's for relay control, or 12v filaments, or just a low voltage supply for some solid state circuitry. Cloth covered wire may be too early for SS though.
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the OT measurements seem inconsistent.
red & brown & blue should be the primary with red being the center tap. black and green the secondary.
seems like you connected ac to primary AND secondary.
measure resistance between red to brown & red to [what you think is blue].
bet the green and black are the secondary?
some winders use different gauge wire for pri/sec. look for leads with same gauge wire - usually the primary is 22-24awg and the secondaries are 18awg.
--pete
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839830
830 =Triad transformer
But the first three digits are 839, so it's not Triad.
Unfortunately, 839 isn't listed in the charts of EIA codes I looked at (not necessarily exhaustive). I know it's a transformer (or organ) manufacturer, as someone else here also has a PT with "839" as it's EIA code.
I have a couple sets of power/output transformers that were removed from old amps a few years ago. I think they came out of old organs but am not sure.
Your voltage measurements with ac applied to the 2 black wires (almost certainly the primary) will tell the tale.
The big lesson for everyone is: Don't remove a transformer from a chassis without documenting how everything was connected, and preferably keep a schematic of the original amp with the transformer. Better yet, don't remove the transformer.
We all learn this the hard way... Some lump of iron in a box and no idea of how to use it. Most of the time, the transformer was ideally suited for the exact output stage it powered and often not much else. So it makes the most sense to use the transformer exactly the way it was used in the piece of gear it was taken from.
This is not intended to be mean... I learned the exact same lesson the hard way a few times over. Our mistake is thinking "it's a tube power transformer, so I can make a ______ with it, right?" A lot of times it's cheaper and faster to simply modify the original item into being a guitar amp, if such a change is even possible (and it may not depending on how exotic the item is you started with; I've got a bunch of tube o'scopes that won't be guitar amps without a stupid amount of work :laugh:).
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The big lesson for everyone is: Don't remove a transformer from a chassis without documenting how everything was connected, and preferably keep a schematic of the original amp with the transformer. Better yet, don't remove the transformer.
+1
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However I do agree that, with two black leads, it is reasonable to apply 12V (better 6V(*), though it means more math) to the black leads and see what comes out the other end.
(*)Note that HIGH voltage secondaries may still be lethal at 1/10th the nominal voltage. (See the 80V found in the first post.)
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839830
830 =Triad transformer
But the first three digits are 839, so it's not Triad.
Unfortunately, 839 isn't listed in the charts of EIA codes I looked at (not necessarily exhaustive). I know it's a transformer (or organ) manufacturer, as someone else here also has a PT with "839" as it's EIA code.
I see that before but I though digit was reverse when print on transformer .
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Found reference to the 839 EIA code. in the following link http://www.davelevasseur.com/1994%20EIA%20Source%20and%20Date%20Code%20Book.pdf (http://www.davelevasseur.com/1994%20EIA%20Source%20and%20Date%20Code%20Book.pdf)
Mel Rain Controls out of MI. A quick check on the company indicates the company is still operating, and providing electronic equipment.
Great information , thank's .
Where is 839 , I see 837 and next is 844 Mel ray control is 639
How do you call that .....? Dyslexia ;)
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http://home.comcast.net/~seluckey/pink.mp3 (http://home.comcast.net/~seluckey/pink.mp3)
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:laugh: