Help required on Logitech Z-2300 toroidal transformer

[RishiGuru]

Hi, i am a newbie in this forum, and require help on my Logitech Z-2300 2.1 multimedia speaker system. My Z-2300 toroidal transformer have died and i need a replacement. But i do not know the VA rating of this transformer.

I opened my Z-2300 subwoofer and clicked some pictures, which i am posting below:

Toroidal Transformer
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Z-2300 slow blow fuse rating
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Input voltage from the wall
[IMGDEAD]http://www.freeimagehosting.net/uploads/e4bac254c9.jpg[/IMGDEAD]

I was also able to gather the following information from the net:

Transformer Details
Manufacturer: Ten Pao International Ltd.
Model No: TOG433028F0
Input: AC 230V/50Hz
Output: AC 20.1V x 2
Diameter: 9.5 cm;
Height: 4.5 cm.
Amperage: Unknown

Also i want to change my capacitors from CapXon which are know for bulging & exploding. Which company capacitor should i use? Will a even higher farad value give an even better result?

Capacitors
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[IMGDEAD]http://www.freeimagehosting.net/uploads/bdddf5d025.jpg[/IMGDEAD]

 

[John Audio]

A quite accurate way to work out the VA rating of a toroidal transformer is to weigh it and compare it with the specification of a manufacturers range.

Based on the size - I would guess that this one is about 120VA.

Does it weigh about 1.3kg?

 

[RishiGuru]

Thanks John, i will try to dismantle the toroid & weigh it. I cannot find any details of their toroids in Ten Pao website. I am providing the specification of Z-2300 below. I don't know but in some forums i found out that the output power of a system can provide some insight about the VA of its toroid used.

Z-2300 Specifications

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
Subwoofer Type: Long Throw with 6th order bass reflex
Satellites: 80 W (2 X 40 W) @ 8 ohms @ 10% THD @ 1kHz
Satellite Size (inch): 2.5
Satellite Type: Polished aluminum phase plug drivers
Frequency response: 35 Hz - 20 kHz
Signal to noise ratio(SNR): @ 1kHz > 100dB
Sound Pressure Level (SPL): 117db
Total weight : Near 18 Kg

 

[RishiGuru]

Another picture of the toroidal transformer

I have sent a request to the manufacturer Ten Pao in their en-query section asking for the VA rating, till now no answer.

However here is another picture of the toroid.

[IMGDEAD]http://www.freeimagehosting.net/uploads/75bfa118ec.jpg[/IMGDEAD]

Can anybody refer to a company that makes similar toroid, that i can fit into my Logitech Z-2300. Thanks in advance.

 

[quadtech]

There are many companies in India such as Delta, Miracle etc
which can supply you a 2x20V toroid. There are also a number
of smaller winding shops who do not have a web presence.
In a pinch, you could use a regular EI type transformer too.

-: MIRACLE :-

 

[RishiGuru]

There are many companies in India such as Delta, Miracle etc
which can supply you a 2x20V toroid. There are also a number
of smaller winding shops who do not have a web presence.
In a pinch, you could use a regular EI type transformer too.

-: MIRACLE :-

quadtech, though i know the toroid has 20.1V x 2 output, I do not know the amperage of the toroid. Do you think, considering the size that it is a 120VA?

 

[Minion]

I had a Logitech 5.1 system that had 6 TDA7293 chips and the torriod in it was a 2x24v 520Va ...... a simular 2.1 system with 4 chips would probably need about 300Va .....


Cheers

 

[RishiGuru]

Z-2300 power chip amps

I had a Logitech 5.1 system that had 6 TDA7293 chips and the torriod in it was a 2x24v 520Va ...... a simular 2.1 system with 4 chips would probably need about 300Va .....


Cheers

Well all I can find out is Z-2300 amplifier is

The amplifier uses:
i) Two STMicroelectronics Class-AB, 80W, TDA7295 amplifiers bridged together to provide a total of 2 X 80=160W for the subwoofer.[Assumed]

ii) Two STMicroelectronics Class-AB, 60W, TDA7296 amplifiers powering each of the satellites.

iii) A Japan Radio Corporation’s JRC-4565 operational amplifier required for the headphones in the control pod.

iv) Filtering of the audio signal is done by two beefy SamXon/ CapXon 10,000 uF, 35V capacitors.

v) The amplifier board have two voltage regulators/ stabilizers a 78M18 and a 79M18, making positive and negative 18 volts respectively.

So, do you think since it powers 4 TDA chips, it is 300VA rather than 120VA considering its size?

I personally believe 120VA is to less a value to provide power to the above 4 TDA chips and also when yo consider 200W RMS of power.

 

[Minion]

Well , if the Amp chips are Class AB and the Sub is supposed to put out 160w then you are going to need at least 300Va for that , and if the satalites are 60w each you are going to need about 200Va .....

After a Bit of Research I found that the Z-2300 Sub is 120w and the satilites are 40w each so a total of 200w or about 400Va , I"m sure logitech used a smaller one as it seems to be standard for companies to use undersized transformers to cut costs which also shortens the life of the transformer .....

 

[Cobra2]

Measure, and get as big as you can fit/afford...
Do the speaker terminals at the same time ;-)

Arne K

 

[RishiGuru]

Well , if the Amp chips are Class AB and the Sub is supposed to put out 160w then you are going to need at least 300Va for that , and if the satalites are 60w each you are going to need about 200Va .....

After a Bit of Research I found that the Z-2300 Sub is 120w and the satilites are 40w each so a total of 200w or about 400Va , I"m sure logitech used a smaller one as it seems to be standard for companies to use undersized transformers to cut costs which also shortens the life of the transformer .....

Total RMS Power = 80(TDA7295) + 80(TDA7295) + 60(TDA7296) + 60(TDA7296) = 280 W

I think any amplifier will produce a lot of distortion & noise at the peak. So, in order to produce distortion free sound at peak volume the amplifiers generally need to reduce its output peak power by 25% or more & also to comply with THX certification.

Reduced Total RMS Power = 60(TDA7295) + 60(TDA7295) + 40(TDA7296) + 40(TDA7296) = 200W

I think to comply with THX, Logitech have limited the power output. But i can be wrong.

I also believe in order to produce 200W, Z-2300 needs at least 400VA. But looking at the diameter of 95mm & height of 45mm it does not seems so. But since this toroids are manufacture specific can they deceive the normal size and produce more VA?

Also do you think my logic of reducing the peak amplifier output is correct?

Minion these are all my assumptions. Please correct me if i am wrong. I am anxiously waiting for your reply.

 

[RishiGuru]

Measure, and get as big as you can fit/afford...
Do the speaker terminals at the same time ;-)

Arne K

Man you have gone the whole hog!!! Cobra2 can you kindly tell the details of the modifications you made? It will be very kind of you.

Have you completely replaced the old toroid with a new one? What are their specs & which company? Man am I excited.

 

[Cobra2]

Sorry, no other mods than replacing the rca-speaker-connections
(Want to try some 3" tangbands when time allows...)

Arne K

 

[RishiGuru]

Am I right?

State whether I am right or wrong

From a local transformer manufacturer, I got the following choices of toroids to fit in my Z-2300 :

1) 120 VA --> 2 x 20 V, 3.00A
2) 120 VA --> 2 x 22 V, 2.72A

3) 160 VA --> 2 x 18 V, 4.44A
4) 160 VA --> 2 x 22 V, 3.63A

5) 225 VA --> 2 x 18 V, 6.25A
6) 225 VA --> 2 x 22 V, 5.11A

7) 300 VA --> 2 x 18 V, 8.33A
8) 300 VA --> 2 x 22 V, 6.82A

Z-2300 toroid stated secondary = 20.1V (AC)

TDA7296 max capacity = 35V (DC)

Power capacitor rating = 35V (DC), 10000uF

Transformer primary: 250V (AC)

Transformer actual secondary:
20.1V + 10% (mains tolerance) + perhaps 4% (transformer regulation) = 20.1 + 2.1 + 0.9 = 23V (AC)

Passing through rectifier : Output voltage = (23V (AC) X 1.414) – 2 = 32.5 – 2 = 30.5V (DC)

Voltage gap between TDA7296 max capacity & toroid = 35 V (DC) – 30.5 V (DC) = 4.5 V (DC)

Voltage gap in AC = {4.5 V (DC)} / 1.414 = 3.2 V (AC)

Max. Voltage of the toroid that can be used: 20.1V (AC) + 3.2 V (AC) = 23.4 V (AC)

-----------------------------------------------------------------------------

Also, in order to produce Z-2300 clamied 200W RMS one needs a transformer that is capable of to deliver a minimum of 1.27 times the claimed watt. Since Watt = Volts X Ampere = VA

200W requires = 200 X 1.27 = 254 watt or 254VA = ~ 255VA transformer as a minimum requirement.

Also considering Z-2300 have four TDA7296 capable of 60 X 4 = 240W

240W requires = 240 X 1.27 = 305VA = ~ 300VA as a minimum requirement.

My Choice : 300 VA --> 2 x 22 V, 6.82A.

 

[Minion]

For a 200w amp you are going to need about double that in Watts in your PSU .... Most Class A/b amps are 50% efficient at best , which means that at least 50% of your power consumption is lost in heat , so for 200W you are going to need to draw 400w through the PSU so you will need a Transformer that can source 400W ..... that is if you listen at full volume , a lower Power transformer might be able to deliver enough power for loud transients if you don"t push the amp too hard but if you plan to use it at full volume then you should get a 400W transformer .....


Cheers

 

[RishiGuru]

Ampere rating of transformer

I know this is a noob's question, but we always talk about output voltages but the not the ampere rating?

After all the difference between a 120VA & 300VA transformer with same output voltages is their ampere rating. Now, suppose my system used a 120VA transformer & i replace it with a 300VA of same output voltage.

Will the increase of ampere rating be destructive for my amplifier?

 

[John Audio]

One of the many compromises made in the design of a product - is the size of the mains transformer - this is one of the most costly components in the product after all.

The designer knows that it is not necessary to provide enough energy to enable ALL of the amplifiers to produce full sustained power into the load - which is why some of the calculations we have seen - indicating that a HUGE transformer is required - cannot be correct, or necessary.

Back to a question I posed earlier - what is the weight of the faulty transformer?

This will give quite an accurate estimation of the VA rating, as this is proportional to the iron and copper in the construction of it.

There is no problem increasing the VA rating a little - but a big increase will just be a waste of money - and it may not fit!

 

[RishiGuru]

One of the many compromises made in the design of a product - is the size of the mains transformer - this is one of the most costly components in the product after all.

The designer knows that it is not necessary to provide enough energy to enable ALL of the amplifiers to produce full sustained power into the load - which is why some of the calculations we have seen - indicating that a HUGE transformer is required - cannot be correct, or necessary.

Back to a question I posed earlier - what is the weight of the faulty transformer?

This will give quite an accurate estimation of the VA rating, as this is proportional to the iron and copper in the construction of it.

There is no problem increasing the VA rating a little - but a big increase will just be a waste of money - and it may not fit!

The problem is I gave the Z-2300's toroid to one of my friends who live in a nearby city. My friend knows a shop that repairs transformers & so I gave him to repair it. But their is no guaranty that the toroid will be repaired.

Since, the torid is not in my hands, I cannot weigh it.

 

[RishiGuru]

I downloaded the TDA7296 datasheet from STMicro website. As we know TDA7296 is capable of producing 60W of power. Since TDA7296 uses 4 of them we get 4 X 60 = 240W.

The picture of the data sheet is provided below:

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As, you said I found out it can handle a maximum input voltage of 35V, but in the power output section the chart is divided into two parts :

1) RMS Continuous Output Power --> 30W

2) Music Power (RMS) Δt = 1s (*) --> 60W

What are the differences between these two types of power and why one is half of the other? And also since RMS Continuous Output Power is regarded my many as real power does that mean this chips are only capable to deliver 30W of real power?

All, my speakers are rated at 8 ohms rather than 4 ohms which is the general norm. But TDA7296 are perfectly capable to handle 4 ohm loads.

So, is it because the power supply [transformer + capacitors] are incapable to supply the amount of watts required at 4 ohms that the impedance of the system is increased to 8 ohms so that power supply is relieved a bit.

But those 10,000uF, 35V capacitors in the power supply seems really monstrous and can handle a lot of load.

[IMGDEAD]http://www.freeimagehosting.net/uploads/f523b564e2.jpg[/IMGDEAD]

 

[cent88]

weird thingie is a rectifier bridge.