Hk395 transformer output voltage - Dell HK395 Computer Speakers

If you have the skill to determine the transformer input is open, I would expect you have the skill to replace a transformer. Based on this assumption: determine the input voltage (120 vac?), determine the output voltage (14 vac?), determine the power requirements (output voltage times the charging current), find a transformer at www.digikey.com or www.mouser.com or www.newark.com.

Hi Hashim.
EHT (Extra High Tension) usually reefers to the 24kv to 30kv, focus and first anode (A1) voltages required to operate the crt (picture tube). These voltages are supplied by the line output stage, primarily the line output transformer (often refered to as the flyback transformer). This transformer steps the voltage up to 8kv and an embedded rectifier trippler circuit tripples this to 24kv dc to supply the final anode voltage to the tube (Hence the big rubber cap and thick cable.
The line output transformer is driven by a smaller transformer (line driver transformer) via the line output transistor.
The driver stage is fed by the hoizontal oscillator circuit.
So we can see that a failure in any part of this circuitry will most often result in no picture. The line output transformer is the heart of the system, it not only supplies the EHT voltage it also has to
supply an LT voltage for the vertical output stage but also the sound output stage.
A Fault in the A1 circuitry would result in a very dark picture but sound ok. Or the picture badly out of focus.
The line output transistor going short circuit results in no picture and no sound with the set shutting down to the standby mode or
hic upping (making a ticking noise. This problem would be amongst the most common and is easily confirmed with an Ohm meter. The line output transformer itself can develope an internal short with the same results (less common). Failure of the line oscillator and driver stages are most easily confirmed with an
oscilloscope. A fault in the power supply will also give these symptoms. To confirm line output stage is functional look to see if the tube heaters are glowing, this supply also comes from the line output transformer. Can you feel the static if you run the back of your hand across the front of the screen (often feels like running your hand through cobwebs. this would indicate that the EHT is present and the fault is elsewhere. Understanding how something
works enables you to find out why it doesn't. If you have occasion to replace a short circuit transistor, be sure to reslder all pin connections to the line driver transformer. I've found dry joints here
to be a cause for random inttermittent failure of this transistor,
Best regards from Vintie.

Try to download the service manual to sony ICF 212, from internet. It will have all the details.

Doing a resistance test on a transformer will not give the information you require as you will read very little, if any resistance. What you need to do is an impedance check and that gets involved. If it is a normally wound transformer, not an auto transformer, you can isolate which is the primary and the secondary windings. Unless the transformer is a multi voltage input unit, the primary side will have continuity through only two terminals. The secondary could be more than two if it is a multi output voltage one. If the transformer is a step down, the primary windings will be the thinner wired windings and vice-versa. To actually test the transformer, get hold of a transformer with about a 20 vac output and try it across the two terminals you have identified as the primary windings, you should ge a proportional voltage of the actual output. eg. with 20 vac input and a 2 vac reading at the secondary, the actual output would be 11 vac if your mains voltage is 110 volts. Take care that you are using the transformer at the voltage it is designed for, otherwise it will overheat and burn out.

Firstly - DANGER.Power can kill so be very careful.
These can be made of a couple of parts but are sold as one peice.Check your manufacter for more info.

How Magnetic Iron Core Transformers work........
the transformer has a pair laminated wires normally copper or iron core wrapped around in a tight coil called windings.they are independant circuits not electrically connected together(x2 wires = 2 Circuits)
this creates a magnetic effect when power is applied to one end and mutual inductance creates a power output at the other end.Like a magnet really.

There are some transformers that have a multi voltage outputs called TAPS which will have different voltages to the input voltages.

ie
Input in New Zealand can be 230volts
Output can be 12 volts or 5 volts or 230volts
depending on the applications required,
for example

Street Transfomers can be 11,000 volts INPUT stepping down to 230volts.OUTPUT for your household power
or
Garden lighting transformers output can be 12volts but still be 230volts input
or
computers power packs can be multi voltage outputs of 12 volts,9 volts,5volts but still 230volts input.

There are also Electronic Transformers available too.
Commonly used for dichrioc Halogen downlights in homes or the office,

I think I remember it being in the 12-24VAC range. If you are still interested I will open mine up and measure it.

CVB

if your speakers have a warranty can you return that to the store with the receipt because the store will replace a new for defective product..or you can go to the web site of the brand of your speaker if you intent to buy the main board you can order trough the online shopping.