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Fender PT wiring?


 
7/18/2004 2:35 AM
marrstians
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Fender PT wiring?
i got an old fender PT for a project i'm doing but it has a few extra wires i'm not sure what they do... the primary has 4 wires, black, green-black, red-black, and yellow-black... the first two were soldered together and the second two were soldered to each other as well... is this for hooking up 120v and 220v? which way do i need to hook it up for 120v? also there's an extra wire in the secondary that's orange, i believe it's for a bias circuit... i'm building a champ clone so do i just leave it disconnected?
 
7/18/2004 4:08 PM
Wild Bill
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The green/black is probably a centretap for the 6.3 vac filament winding. It is normally grounded.  
 
The red/black is almost certainly the centretap for the HV winding. You really should study up on typical power supplies. The centretapped fullwave circuit is the usual style for tube amp supplies. If you don't use it you'll get twice the voltage you need to work with. With the centretap grounded and a diode/tube rectifier in each of the other lines you get the normal voltage.  
 
The yellow black may be for a centretap on the 5volt winding for the rectifier. You should decide on your circuit before you use it. You ground it if you have an indirectly heated cathode with your tube rectifier.  
 
The orange may indeed be for a bias supply - measure it and see if the voltage makes sense. You can of course ignore it for a cathode biased Champ circuit.  
 
Hammond Transformers shows the typical circuits and the voltages/currents involved in their electronic transformer catalogue and also I believe on their website  
 
http://www.hammondmfg.com  
 
You absolutely should measure the HV voltage - it may be way too high for a Champ.  
 
Have fun!  
 
---Wild Bill
 
 
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7/18/2004 5:08 PM
Bruce /Mission Amps
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Are there numbers on the tranny anywhere?  
I'm sure it can be cross referenced.  
My guess is this... you have a mass produced American/Euro transformer.  
But wired for 120v or 220v? I don't know. Did it come from an amp distrubuted in North America?  
Red/black and yellow/black are usually multitaps on the primary for running 220v or 240v.  
Black is almost always 120v or 220v... the green/black one is a little odd but possibly quite common for all mass produced amps from some manufacturer who sells all over the world.  
The organge wire typically is a frame ground but I also have seen them used in the high voltage secondary windings as a tap for bias voltage.  
If using an ohm meter finds that the orange is connected to the high voltage secondaries, then it's a bias tap. If not, I'd suspect it's the transformer's frame ground. In any event, see if it is connected to any other winding.  
I guess after you post numbers on the bell cover here, you could start by unsoldering the primary leads pairs and find out which pair of the primary leads are common... those would be 120v, as it probably is two 120 volt primary windings on one core, used in parallel for 120v or series for 220v.  
In other words, when the two 120v primaries are wired in series and in phase, then the tranny can be run at 220 or 240v.  
When they are wired in parallel and in phase, the primary is no 120v.  
Bruce
 
7/18/2004 11:40 PM
Enzo
Yeah, sounds like a split primary to me too. Parallel for 120v and series for 220v.  
 
If you apply power to the soldered pairs and the tranny makes expected voltages on the secondaries, then it is OK - the wiring is right.  
 
HV secondary is usually red, and the CT is red-yellow, not red-black. Yellow stripe usually means a CT. Red-yel for HV, blue-yel for the 5v, green-yel for 6v.  
 
Is it yellow-black or black-yellow? Stripe color is second. Black wire with yellow stripe is blk-yel. Black wires are generally primary, stripe or no.
 
7/19/2004 2:12 AM
Wild Bill
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Geez, I shouldn't assume the whole world runs on the same line voltage as Canada!  
 
Hell, there might actually be folks who don't put maple syrup on their back bacon...  
 
I should've noticed the primaries - that's what happens when your beer is not as weak as American... :)  
 
---Wild Bill
 
7/19/2004 3:16 AM
marrstians
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ok... here's what i've got... i was told it was pulled from a fender princeton amp... the numbers on it are l010020 csa 827 eia606-848... there's two places on the transformer where the wires enter the core... one side has the black and green-black soldered together, the other side has 2 greens, 2 yellow, 2 red, one orange, and one yellow-red...
 
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