100W peak 4Ohm

[zeus_threat]

Well i know that it have to resign to it being a 125VA transformer but still i would like to know about how andrew will work out the Va as i mentionned i have other transformers unmarked which will help me determine the approx VA plus in case i buy new ones it will help me avoid be chosing wrong types.

So andrew the size of the whole limination is 8.6 cm by 4.8 cm from top and height is 7cm

In case this is what you need please explain you derive the VA rating

Thanks

 

[AndrewT]

Hi,
the E of the EI has three legs. Two narrow legs pass outside the bobbin.
One wide middle leg passes through the bobbin.
The wide leg is approximately double the width of each of the narrow legs.
Measure the width of the wide leg that passes through the bobbin.
Measure the thickness of the stack that passes through the bobbin.

I had the EI transformer programme on my old HDD, but not on my current installation.
Can anyone provide a link to the programme?

 

[zeus_threat]

oK Width fo the leg is ~2.8cm and thickness is ~4.3cm

 

[Andy L. Francis]

For conventional EI transformers the rule of thumb is that bringing to a square the product of these two numbers gives the approximate power rating.
In this case it's (2.8×4.3)^2=145VA
Attention, it's not a proper calculation, it's only a rule of thumb for such cases when rapid help is needed!

 

[zeus_threat]

Thanks a looooooooooot Andy that's what i was looking for this eill be of immense help to me even though being only a quick and approsimate calculation.

Well just as an info i can get toroids here but the people selling them are unable to tell me the VA rating( they just buy and sell their concern is no more). Its made and imported from china without any brand or marking except the primary and secondary voltage. Is there a similar rule of thumb for the toroid core's?

Thanks

 

[Andy L. Francis]

A 250VA rated toroidal transformer's weight is ~2.8kg and measures ~11×5cm. The regulation is 5...10% - depends on quality.

 

[zeus_threat]

Thanks Andy but sorry just a little precision is 11cm the internal of external diameter of the ring?

They have 3 models here (hope still in stock) but i'll see if i can drop around and check the dimensions.

They had a huge one had to lift it with both hands approx dia was 15 cm external and 6 to 8 cm high. You think that could be a 1000VA(was coded PVA1000 but i don't trust that)?

 

[Andy L. Francis]

Thanks Andy but sorry just a little precision is 11cm the internal of external diameter of the ring?

I mean external diameter.

They had a huge one had to lift it with both hands approx dia was 15 cm external and 6 to 8 cm high. You think that could be a 1000VA(was coded PVA1000 but i don't trust that).

Yes, 15×6...8cm dimensions for an 1000VA rated toroidal is absolutely realistic!

 

[zeus_threat]

But before i jump into another problem, each woofer is rated 8ohm 150Wpeak (has vented pole piece) to be used in sealed enclosure with LR4 xover + Linkwitz transform + bridged amp per woofer. Suppose i do go for a 500VA transformer for all 4 amps and that i am able to get 200W per bridged pair won't that damage or simply blow up the woofers in the long run?

With one 125VA per amplifier pair a very rough calc gives me max 87.5W. I know its a very bad way of solving the situation but won't that be safer assuming the sub won't be pushed to distorting volumes?

Thanks

 

[zeus_threat]

Previous post was a bad idea another solution i could consider is to go back to step 1 when i initially started the thread i.e use a 30-0-30V 150VA transformer which i have lying around. I would then use one of these amps per woofer and purchase a second one. Still i'll check the toroidal price and keep posted

 

[zeus_threat]

Fake TIP 36C???????

Got the caps for the amp yesterday am planning on building one unit for testing. Got 4x 10,000uF 63V. Am still thinking of something. Has anyone encountered fake TIP35C/36C around or have any pictures of what the die size should be like. Had one of them as a look yesterday at one supply store the markings on it looked stranged could be relabelled TIPs i'll check at a second store today and keep posted. If need be i'll purchase a pair and crack it open and post the pics

 

[zeus_threat]

On line parts purchase

Does anyone have a link for a reliable supplier that sells genuine power transistors online shipping worldwide on low amount orders

thanks

 

[Nordic]

Hi there, one way to go about it is to visit the homepages of the manufacturers you are after. Most have lists of global distributors, you may even be lucky and find a contact for your country listed...

 

[zeus_threat]

Thanks Nordic, do you know of any in SA that are trustworthy and that might ship to mauritius since we are almost neighbours shipping could be cheaper

Have you ever came to mauritius by the way? Think its a bit known in Sa remember was a huge poster on the street while i was in joburg talking bout it. Well talking bout joburg always reminds me of the lounge in case you happend to know the place

 

[Andy L. Francis]

Re: On line parts purchase

Does anyone have a link for a reliable supplier that sells genuine power transistors online shipping worldwide on low amount orders

thanks

I'd try Farnell.
Farnell homepage
Search for TIP35C/36C by STM (ST Microelectronics).

 

[zeus_threat]

Changing output devices

Thanks for the link i'll check it . Well actually i'll try to go for MJ15003 and MJ15004 instead since it comes to almost the same cost. I don't mind modifying the pcb. I'll try to see if i can get my hands on a local MJ15004 by tomorrow or saturday and crack it open. I have two choices here either Mospec or motorola. Mospec is slightly cheaper. Are both likely to be as counterfeited as the other?

thanks

 

[Andy L. Francis]

Then in my opinion one pair of MJ15003/15004 would be enough!
(MJ150XX devices has ~200W DC-SOA at 70°C Tc.)

 

[Andy L. Francis]

Re: Changing output devices

If they are as cheap as TIP35C/36C (~1 EUR or ~1.5 USD) then they are fake devices.
A genuine MJ15003 costs ~3...4 EUR (4...6 USD).

 

[AndrewT]

Motorola are quite old now. OnSemi took over production years ago.

 

[zeus_threat]

Fake MJ15004?

HI guys thank for the replies i got my jands on an On smi MJ15004 sold locally cost is around $6 but that does not mean anything. But am intrigued. I cracked one open no double die inside the die pattern looks exactly like the one shown at ESP. Only thing is that i did an acetone test had to rub a lot original marking was

ON
MJ15004
MEXICO
BM0222

After rubbing a cotton bud with acetone this is whats left

MJ1500 (the last zero is quite pale)
MEXICO (the last o is quite pale)

No thick silicon on die but a thin gray paste below the die.

die size 6mmX5mm

Looks like a pnp but opened it then tried measure polarity.Should have done that first

Could this be a fake?

On going ahead to see if i can post a pic of it