Philips/B6X12A - Power transformer connection (Techniek Radio/TV)

door Matthias Meijer , Dordrecht, 26.02.2011, 22:41 (5019 dagen geleden) @ svetolik

Two taps ar somewhat placed in a hole (right side of photograph) Those are the connections of a non resettable thermofuse, resistance between zero ohms when ok

There is no beep when checked resistance between these taps, so where is that thermofuse?

Then that thermo-fuse is broken.
And in that case it is no wonder the radio does not work.
The thermo-fuse is a small brown plastic tab that is stuck between the windings of the transformer.

I have measured voltage and on the left side is the taps with 6V+ for heating.
On the right side I have measured >200V between black wire tap (Central tap on the secondary winding from the schematic?) and other taps.

You mess up primary and secondary I think.

What you measured on the primary side is the case when the fuse is blown. You measure the voltage you apply to the radio from the mains outlet, and since all eyelets on the primary side are in series, you measure the same voltage there when there is no connection to the tab on the other side of the broken fuse.

All fuses seems to be ok buth radio is dead.

From what I understand from your explanation, the fuse is broken. But there must be a reason why the fuse is blown, so please take care when you proceed.

I have rotated the image 180 degrees to avoid neck-problems when viewing

And added the part of the B6X12A schematic which shows the primary and secondary windings.

Please note that my annotations are based on the A3 136 56.2 type number. Which is probably only different from the way the eyelets for the fuse are mounted on the face plate. I guess you have a radio that was specifically designed for sale outside the Netherlands/Belgium.

But as Henk already suggests, you can figure it out by looking at the wires that arrive at the eyelets and by measuring.

It seems that your transformer has both filament windings connected in parallel, and that these are probably connected to ground elsewhere in the radio. The center tap of the high voltage winding and screen (the screen is not indicated in the schematics) are also probably connected to ground somewhere else in the radio. The 'normal' case with all radios that I have seen is that the four lower eyelets on the secondary side are all connected together and to the chassis (ground).

I have other traf with two input taps two output HV taps, one central/ ground tap and 4 taps for heating, so I need to know connections to make it work.

Is that the exact SAME transformer?

The old traf that is inside was hot and after vibrations there was no voltage and lights. I beliewe it is dead except section for heating voltage.
Also there is a bunch of cables that comes from input voltage switcher and that makes problem.

What you can do to see if the fuse is the problem, is the following: remove ALL tubes from the radio. Then connect an AC current meter across the fuse, and apply the mains voltage.

You should measure very little current. Best is to include a 1A fuse in series with your meter to avoid damaging the (expensive) fuse inside the meter.

There are other methods to try, but since you are already having problems finding out which connection on a transformer is which, I think it is best to ask for some help from someone near to you, to look at the radio together.
You might do more damage to the radio or other things than necessary.

Best regards,

Matthias