The PHILCO Phorum
Output Trans on 34 - Printable Version

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Output Trans on 34 - marty - 07-14-2013

Hi All;
On the Output Transformer on my Philco 34, the Output measure about .4 Ohms.. The Schematic looks like it says 89, but it could be .89 or 8.9.. Could this be a problem ??
Also on the primary side one side measures 304, the other side 345 or a total of 649.. The Schmatic shows 680, I am not worried about the total ohmage difference, but one side against the other.. Would a 40 ohm difference make or mean it is unbalanced to the tube ??
THANK YOU Marty

RE: Output Trans on 34 - morzh - 07-14-2013

1. The two halves will read differently because one is longer than the other being wound opn top of it. Resistance itself is not that important, the turns are. The fact that the two are close means they are likely OK.
2. Your secondary may be in parallel with your speaker voice coil, so you in fact may be reading the voice coil. Disconnect the speaker coil first, then measure.

RE: Output Trans on 34 - marty - 07-14-2013

Hi All;
Thank You, Morzh.. On the Secondary, I am only measuring the the Transformer Secondary coil.. Not with the Speaker attached to it.. The Speaker by itself, measures 1.4 Ohms..
THANK YOU Marty

RE: Output Trans on 34 - morzh - 07-14-2013

On the sch 89 (whatever it is - not too legible) denotes the speaker's voive coil, not the transformer's secondary from what I can see.

There was a thread where we discussed how to test a transformer.
One way of doing it is you could disconnect the primary and connect it to a Variac output, and bring the voltage up (10-20VAC) until you hear buzz from the speaker. It is a PM speaker so it should be easy.

RE: Output Trans on 34 - marty - 07-14-2013

Hi All;
Thanks Morzh, I just wanted to make sure before I did anything, that I wouldn't make anything worse than it already is..
So, yes, I can test the Transformer with my 4" PM Speaker attached to it, and see what comes out of it..
I am not going to use the Speaker that came with it, as it is in too bad a shape, the voice coil works, but the cone is torn and in very bad shape and is not attached to the Speaker frame at all..
I am going to use my Signal generator, which also has a 400 hertz Audio tone output on it and see if it is enough to make the Speaker Hum, then using the Output Transformer and then the number 19 Tube and then the Input Transformer and then the number 30 Tube driving it..
Working back ward from Speaker to antenna making sure that each section works before going any further..
Hopefully the Signal generator has enough oomph to work the Transformer to the Speaker, before wiring in the 19 Tube and so on..
THANK YOU for Your Help.. Marty

RE: Output Trans on 34 - morzh - 07-14-2013

The sig gen may not have enough: remember, the output transformer converts tens to a couple of hundred volts to a very few volts, like 3 to 10 maybe.
But...maybe. You don't stand to lose anything by doing it, and it just might work to the degree that you will be able to hear a very quiet tone. Which is all you need.

RE: Output Trans on 34 - marty - 07-14-2013

Hi All;
Thanks Morzh, exactly, and if not I can always revert back to the Variac for a 60 cycle hum..
THANK You Marty

RE: Output Trans on 34 - marty - 07-15-2013

Hi All;
I just got both transformers to pass the 400 Hertz Audio signal thru them.. With my 4" PM Speaker.. So I know that both of them are good, for at least passing a signal thru.. I can't say they have the correct resistance, but until I am proved wrong, I am assumming they are good..
THANK YOU Marty