50watt partridge transformers. Help please =]

[Yrps]

I got these two Partridge transformers from a 50watt Sound city P.A system. This is my first build (DR504). I'm starting with the power supply. I'm having a bit of trouble though, identifying tap leads for the pt and op (which goes to power in/filaments/impedance outs). Didn't get any help from the Partridge data base either regarding serial numbers. If you have any knowledge with these transformers, please share.

[J M Fahey]

Start by measuring which wire is connected to which other, so as to identify windings, and post a simple drawing showing that, with colours and wire to wire resistance indicated.

Some windings will have very small resistance, in the area of 1 ohm or less, post what you measure anyway.

Armed with those values we may suggest some voltage measurements.

[Yrps]

Start by measuring which wire is connected to which other, so as to identify windings, and post a simple drawing showing that, with colours and wire to wire resistance indicated.

Some windings will have very small resistance, in the area of 1 ohm or less, post what you measure anyway.

Armed with those values we may suggest some voltage measurements.

Sorry I took so long to reply. I've been away. Anywho, I'm currently trying to do some measurements at the moment. Unfortunately I only have two digital meters. I'm finding it quite difficult reading any real values. On another note, each individual wire (for the output transformer) has got 1,2,X,Y on one side, and on the other has A,B,C,D,E on the A wire it has a tag which reads 100Volts. Not sure if this helps determine anything. First time for everything.

[Yrps]

And with the Power transformer the red and black leads (I'm going to assume these are the mains) are reading 15 ohms. the other side has a lead with the bias value of 34volts attached to it. Not getting values on the other side however.

[Jazz P Bass]

Sorry I took so long to reply. I've been away. Anywho, I'm currently trying to do some measurements at the moment. Unfortunately I only have two digital meters. I'm finding it quite difficult reading any real values. On another note, each individual wire (for the output transformer) has got 1,2,X,Y on one side, and on the other has A,B,C,D,E on the A wire it has a tag which reads 100Volts. Not sure if this helps determine anything. First time for everything.

Output Transformer:

Output Tranny
Primary Windings
Red -Plate
Black-Center Tap (HV)
Orange- Plate

Secondary
Red- 100v Line
Yellow-16 Ohm Tap
Brown- 8 Ohm Tap
Orange- 4 Ohm tap

[Jazz P Bass]

And with the Power transformer the red and black leads (I'm going to assume these are the mains) are reading 15 ohms. the other side has a lead with the bias value of 34volts attached to it. Not getting values on the other side however.

Power Transformer:

PT-Voltage Switch:
Orange-- 115V ( jumpered lugs on switch to 105V lug-- no seperate 105V tap on the amp here)
Yellow-- 225V
Red-- 245V

Power Tranny
Primary Windings
Grey- Tranny Shield
Black- Common
Orange- 105v
Brown- 115v
Yellow- 225v
Red- 245v

Secondary Windings
Red- Heaters
Violet- Bias Supply
Black- High Voltage (HT)

[Yrps]

Thanks for the help. Provided a bit more insight. Unfortunately the colour codes don't quite match up to my photo's. Based on my pictures, would you be able to make any comparisons?

[Yrps]

Please excuse my amateur posts. Okay, these are the following resistance values I got from all possible combinations.
Please observe the pictures I posted as a reference

Red+Black=14.9 Ohms
Yellow+Black=4.4Ohms
Yellow w/black tip+black=0 ohms
Opposite winding
Red+black=29.5 ohms
Green+green=0 to 300 milliohms

Second transformer
Yellow1+BrownX=29.5 Ohms
Brown2+BrownY=26.3 ohms
opposite winding
YellowC=YellowD=300 milliohms.

Hope this helps...again.

[The Dude]

If you have access to a variac, you could hook it to the PT primary, run it up slowly to whatever your line voltage is, and see what you get out. I'm going to guess that the primary (red, black, yellow,.....) is multiple taps for different line voltages. The green wires on the secondary are likely 6.3V filament windings. Monitor those windings while bringing up the voltage slowly feeding the primary. When you have chosen the correct input wire combination, the filament voltage will be right. I'd suspect black to be "common" as in Jazz P's photo and the other wires for different input voltages.

If you don't have a variac, use a tone generator or find a 60hz tone on the web and feed the primary. Measure the AC in compared to the AC output on the filament winding. Using the ratio, calculate what input would give you the correct output. When you have this part figured out, just measure the other output winding(s) to see what the voltage is.

This is all based on the assumption that the green wires are the filament winding and should be approximately 6.3V, which could certainly be wrong, but my bet is that it's not.

Edit: If you try this, BE CAREFUL. Since it's unknown what the wiring configuration is, the potential for high voltage exists. Be careful not to touch any wires while power is applied.

[Yrps]

Okay, here's what I've tried so far. I used my dc power supply (I would use my function generator to create an ac waveform, but the 7 segments are in need of replacing...yes its that old).
Anyway, I applied 40V DC to the red and black wires, and got roughly 400 mV DC on the green wires, and some of the others? I know something isn't right here but alas, I got a ratio of 0.01 and calculated that with my usual mains voltage of 240V.
There for I calculated an expected output voltage of 2.4 volts.

Go ahead and let me know what I'm doing wrong.
Thanks.

[MarkusBass]

Transformers do not work with DC voltage. You have to apply AC (alternating current) voltage. You can use any (known) transformer to get AC.

Mark

[Yrps]

Ha, what a noob. I've looked into renting a Variac. I'll be back with more questions when I get that sorted. Just quickly, I got a decent piece of scrap wood from a friend that I intend on using as a bread board, and some screws to link everything. What gauge wire should I use for the power supply section?

[The Dude]

Oh WOW! As MarkusBass pointed out, you cannot apply DC to a transformer. You are lucky you didn't fry your power supply. DC will see the transformer as pretty much a dead short. Just to reiterate, if you can't find a variac, a simple 60hz tone will work. Here's one (of many).

https://www.youtube.com/watch?v=E_Sf7rSOU78

Basically, what we are doing is looking for ratios.

[Yrps]

Got a 60hz sine wave. To black and red wires. following measurements
Green1=65mV
Green2=270mV
brown w/black end=270mV
black=265mV
Red=370mV
Brown (bias tag)=3oomV

[The Dude]

I'm not getting your readings? What we need is the voltage across black and red primary and with that voltage applied, what is the resulting voltage across the green wires- green to green- two voltage readings (primary and secondary). Also, whatever you are using for a source, crank it. The higher the voltage, the more accurate readings will be.