Help required on Logitech Z-2300 toroidal transformer

[RishiGuru]

Number of Capacitors

I found no matter what the make or model of any amplifier in these computer audio systems, there are always two capacitors to help the transformers out instead of one.

I mean my Z-2300 uses two 10,000uF, 35V capacitors. Why not one big 20,000uF, 35V? I mean it will save cost for sure.

Among the cheap chinese speaker systems there is a norm of using STMicro TDA2030A power amps in multiples. And always there are two capacitors in the power supply part using 4700uF, 25V capacitors, irrespective of make or model.

Why two caps? why not one?

Is the number of caps is in any way related to the number of power amps in use? Would it have been even better to use 10,000uf caps for each of the four power chips used in Z-2300?

 

[mvs sarma]

The transformer could well be repaired, i suppose, and might not cost a moon. Please reach out a local transformer re-winder. Delta transformers of Delhi make these toroids but may not be off-shelf.
regarding other query, ESR(Equivalent Series Resistor) value becomes less if two are used in place of one. Cost reduces
you may reach MIRACLE here
Miracle Electronics Devices Pvt. Ltd.
No 65/2,1st Floor,
Kamakshipalaya Industrial Estate
Magadi Road,
Bangalore - 560079 (INDIA)

Tel: +91-80-23485149, 23489971
Fax: +91-80-23480882

E-mail: miracle@vsnl.com

Directors:-

Mr. Nilesh S. Vadhar
Mr. Jitendra K. Davda

 

[RishiGuru]

The transformer could well be repaired, i suppose, and might not cost a moon. Please reach out a local transformer re-winder. Delta transformers of Delhi make these toroids but may not be off-shelf.
regarding other query, ESR(Equivalent Series Resistor) value becomes less if two are used in place of one. Cost reduces
you may reach MIRACLE here
Miracle Electronics Devices Pvt. Ltd.
No 65/2,1st Floor,
Kamakshipalaya Industrial Estate
Magadi Road,
Bangalore - 560079 (INDIA)

Tel: +91-80-23485149, 23489971
Fax: +91-80-23480882

E-mail: miracle@vsnl.com

Directors:-

Mr. Nilesh S. Vadhar
Mr. Jitendra K. Davda

Do, Miracle Electronics Devices Pvt. Ltd. have any dealer/ outlet in Kolkata?

 

[mvs sarma]

They don't have a branch in your place, they said
but the cost of a new transformer with 0-20 and 0-20 at a total of 300 VA , could approximately cost 3Kin Indian currency. I fear whether the whole amplifier is not at Rs3K, LoL
another person known to me from Hyderabad **broken link removed** is willing to make a new one from R-core material and this is used for audio systems, as per them
you may contact them. perhaps courier within India may be cheaper than international.

 

[Diver300]

I found no matter what the make or model of any amplifier in these computer audio systems, there are always two capacitors to help the transformers out instead of one.

I mean my Z-2300 uses two 10,000uF, 35V capacitors. Why not one big 20,000uF, 35V? I mean it will save cost for sure.

Among the cheap chinese speaker systems there is a norm of using STMicro TDA2030A power amps in multiples. And always there are two capacitors in the power supply part using 4700uF, 25V capacitors, irrespective of make or model.

Why two caps? why not one?

The power amplifiers need a +ve and a -ve supply. There is one capacitor for the +ve supply and one for the -ve supply. The transformers always have two windings connected as a centre-tapped winding and the centre-tap is the ground for both the +ve and -ve supplies.

 

[mvs sarma]

As per the code used, i feel it should be 200VA with two windings, means each winding say 100VA.

The specifications as seen from their site indicate that they have over temperature protection. I suspect that some thermal fuse failed. from the enlarged photograph, it appears one wire on the outer has turned black. perhaps it would be easy for you to get the secondary rewound, provided primary is OK. You might connect a 60w bulb in series to primary and connect to mains. the bulb should glow DIM, to indicate the primary good health. the fans windings etc are checked this way by a local electrician.

@diver300,
thanks
that is the correct information,. Sorry for misjudging it.

 

[RishiGuru]

They don't have a branch in your place, they said
but the cost of a new transformer with 0-20 and 0-20 at a total of 300 VA , could approximately cost 3Kin Indian currency. I fear whether the whole amplifier is not at Rs3K, LoL
another person known to me from Hyderabad **broken link removed** is willing to make a new one from R-core material and this is used for audio systems, as per them
you may contact them. perhaps courier within India may be cheaper than international.

Thanks again, mvs sarma. Nah, My Z-2300 costs Rs. 7000 INR. I think to spend 3K on the toroid alone is a waste of money. I think it would be better to go for a 200VA , 2 X 20V toroid. What will be assumed cost of a 200VA? At around Rs.2000 INR?

 

[RishiGuru]

The power amplifiers need a +ve and a -ve supply. There is one capacitor for the +ve supply and one for the -ve supply. The transformers always have two windings connected as a centre-tapped winding and the centre-tap is the ground for both the +ve and -ve supplies.

Diver300, I can find three wires on my Z-2300 toroid --> YELLOW-BLACK-ORANGE.
Manufacturer: Ten Pao International Ltd.
Model No: TOG433028F0
Input: AC 230V/50Hz
Output: AC 20.1V x 2
Diameter: 95 mm
Height: 45 mm

Do you mean that:
YELLOW --> -20.1V
BLACK --> 0V
ORANGE --> +20.1V

Am I right?

 

[mvs sarma]

i would ask you to better perform some checks and reply?
after all a small multimeter costs Rs200.
whether the primary is really open circuited?
If not, please get the secondary voltages measured with 230V on primary, and let us see
whether the transformer is getting heated?with out secondaries connected to rectifier?
did you search underneath the cloth binding for any thermal fuse like thing? Little self help methods might result rewards at times?
any local TV/audio techie could help you .

PS: the Hyd firm estimated a new one below 2K
you may reach him from the " contact us" of their site i indicated.

 

[Diver300]

Diver300, I can find three wires on my Z-2300 toroid --> YELLOW-BLACK-ORANGE.

Do you mean that:
YELLOW --> -20.1V
BLACK --> 0V
ORANGE --> +20.1V

Am I right?

That is probably correct.

However, you can't say that a transformer connection is +ve or -ve. To check, you need an AC voltmeter. It should read about 20 V from black to either of the other wires, and about 40 V from yellow to orange.

 

[mvs sarma]

Rishi guru,
in transformer secondary, it is called 20V- 0(centre tap) - 20V this followed the order Yellow, Black and Orange.
if, primary is OK and connected to 230V AC mains, you measure 20V AC between yellow and black and approx., 40V AC between Yellow and Orange. while the load is not connected, the transformer could be nominally warm but not HOT.

While with 6amps load on both secondaries, 6 amps on black to yellow and another 6 amps between black and orange, the transformer might still show at winding, say17 to 18V each wing, and would become reasonably hot at 60to 70°C

 

[MrAl]

Hi again,


Sorry i could not get back here until now as i picked up the flu just before Christmas and have been in bed pretty much ever since then. Im starting to recover now so i thought i would add a few things here again.

There are quite a few questions coming up in this thread about the suitability of a given transformer based on various criteria of the amplifier and heatsinks and everything else...a number of factors that are a little hard to pin down without a number of tests to confirm. This leads me to the following conclusion. If we have to pick a single transformer for a given application and we dont have a chance to test the application first or know what the original designers had in mind when they first designed it, then it might not be a bad idea to go for the best transformer we can find and if later we find out that the circuit can not keep up with it we can always find ways to degrade the better transformer or at least put a limit on how high we crank up the volume if the amp doesnt look like it can handle the new transformer entirely.

This would mean buying the 300va 20v transformer and installing it and then doing a short heat study on the resulting circuit probably with a dummy load. This would mean measuring the temperature of the IC chip as close to the chip as possible and going from there. Does it get too hot? If so, then dont crank the volume up too high.
I also have to wonder who needs to have the amp turned up that loud anyway

 

[mvs sarma]

wish you Mr Al, speedy recovery!!
i was of the opinion that the transformer would still be OK with a minor fault, might be a diode blown in the molded bridge.
Anyway he took out the transformer, i expect him to do some minor tests. By Load, i mean could be two auto lamps of 12V in series. on each winding, or any other, locally readily accessible.
most datasheets indicate that such transformers from Ten-pao, have thermal safety . Thus i presume that the thermal fuse embedded in the transformer might have fused !!! Any repairer would otherwise exploit, and a new shopper tempts him pour money for a replacement
.

 

[MrAl]

Hi there,

Oh yes, that's a very good idea for sure. Check the transformer itself first for any simple problems before buying another one, might get lucky there

I also forgot to mention that if a new transformer is purchased and the new transformer is bigger it may not fit exactly into the same case so the case might have to be extended a little.

A couple other notes:
With a better transformer the amp will still only be able to put out a certain amount of power because the voltage wont be any higher. This should mean that the circuit should run ok with the new transformer. The main thing to check (using a new or old transformer) is for over heating of the main IC chips. They do have built in current limit though so maybe they have thermal limiting too.
The continuous rating of the chips is 30 watts each, 60 watts in bridge configuration. The max power output into 4 ohms load will be 50 watts rms with a plus and minus 20v buss, or in bridge config 100 watts rms into 8 ohms load. I am now wondering if they specified a minimum load of 8 ohms for this amp.

 

[RishiGuru]

I wish speedy recovery MrAl, and you are absolutely right, Z-2300 amp is specified a minimum load of 8 ohms.

Here is the specification of Z-2300:

Total Continuous Power(RMS): 200W
System THD: Better than 0.05% before clipping
Total Peak Power(RMS): 400W
Power distribution: 120 W (Subwoofer) + 2 X 40 W (Satellites)
Subwoofer: 120 W @ 8 ohms @ 10% THD @ 100Hz
Subwoofer Size (inch): 8
Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz
Satellite Size (inch): 2.5

I may be getting a little offline but does "System THD: Better than 0.05% before clipping" means? And also why the speakers are at 10% THD.

I have given Z-2300 toroid to a local repair shop. I have also told them to check the thermal fuse. If they can repair ok, or else i have to buy one.

 

[RishiGuru]

One thing I have realized, that I have much to learn for sure. Though I am an engineer in IT, I want to learn more about how audio amplifiers work and what is the role of the individual components of an audio amplifier.

For example, looking at the picture below I still do not no know what "close up cap" portion of the amplifier with many 25V small capacitors doing in there. Six small caps are surrounding the JRC4565 and another four in square formation below them.
**broken link removed**

Can anybody specify some websites where I can learn about them & how they work? I will be glad if anybody can help me out.

Thanks for being with me.

 

[mvs sarma]

please try to have a fresh reading of an old book, principles of electronics by
AP Malvino, published those days by TMH.

The caps across the bridge rectifier help reducing the abrupt noise generated while ac sine wave crosses the 0.6V(approx)
the caps shown across the opamp JRC4565 are for cleaning up the noise g and supply pure DC to the audio preamp etc.

 

[mvs sarma]

Hope to hear from RishiGuru. probably he is still busy with Newyear celebrations!!

 

[MrAl]

Hello,

Yes i'd like to hear back too. He took some nice pics too so we could see what everything looked like.

 

[maharajan18]

One thing I have realized, that I have much to learn for sure. Though I am an engineer in IT, I want to learn more about how audio amplifiers work and what is the role of the individual components of an audio amplifier.

For example, looking at the picture below I still do not no know what "close up cap" portion of the amplifier with many 25V small capacitors doing in there. Six small caps are surrounding the JRC4565 and another four in square formation below them.
**broken link removed**

Can anybody specify some websites where I can learn about them & how they work? I will be glad if anybody can help me out.

Thanks for being with me.

That weird thingie is probably a bridge rectifier.

Did you try contacting the Logitech service center? They might be having a transformer with the correct specs.
If you are not able to find a torroid you can go for a normal 20-0-20V EI transformer. Enclose it in a separate case and connect to the rectifier inside the speaker box.

Maxine makes a 20-0-20V 5A EI transformer. this should be able to give you 200 VA. **broken link removed**