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Old 9th March 2004, 11:02 PM   #21
mwh-eng is offline mwh-eng  United States
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Quote:
Originally posted by sdoom
If the only problem was the transformer core #2 could I use the old one and rewire it? There is a "big" edge missing but this core is still complete.
Is this core a toroid? What are the measurements of the core? For a toroid, what is the inside and outside diameter, and the height or thickness? You can get a new core to replace the bad one, I think. What is the name and model number of the amp? Maybe the core part number can be found online. If not we can design this from scratch and choose a core that should work. Probably the Mag Inc. P or F core material or the other core manufacturer that makes the 3C8 or 3C85 will work. Also, the primary inductance measurement on the good transformer will help. What are the values of the R and C on the TL494 for setting the oscillator frequency?

Also measure the depth and length of the "big" edge missing from your existing core. Having a chunk of ferrite core missing will make the core act like a step gapped core. In some applications it would be desirable.
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Old 9th March 2004, 11:33 PM   #22
sdoom is offline sdoom  Germany
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@ mwh-eng

Hi again Well Iīm still sitting here and drawing the schematics. I was in school today what actually was a complete waste of time today! I would have finished the schematics already , but well.

I will make pictures of everything and post them together with the schematics. The broken core had the following measurements.

outside diameter: 36mm

inside diameter : 22mm

height : 19mm

The spare core I used has the same basic measurements and the same windings and wire thickness as the broken one. Would it really effect the TL494 that much? I mean I havenīt put a load on that thing yet. Like I said, I was realy surprised that with only 4 Fets it was running, maybe I should try that again to see if that is still so or if I really have a broken part somewhere.

The regulator is a Motorola TL494CN . CT is 0.001 and RT is 27kOhm . That should be an oscillator frequency from around 40kHz if I am right (taken from a spec-sheet from Texas Instruments)

Well I īll continue drawing )
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Old 10th March 2004, 12:08 AM   #23
sdoom is offline sdoom  Germany
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the Amp is called "ALTAI B005Q (MA8000)". On the curcuit board there is also a number: PAM03001.
As far as I know it is the same as "Caliber CA500"
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Old 10th March 2004, 10:53 AM   #24
sdoom is offline sdoom  Germany
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ok I have some schemtics done. Only one part missing.
I will update the missing drawing as soon as possible and some pics, too.



Schematics
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Old 11th March 2004, 06:13 PM   #25
sdoom is offline sdoom  Germany
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Here is a picture of the transformer cores.
As you can see there are just a few windings on each core.
Click the image to open in full size.
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Old 11th March 2004, 08:57 PM   #26
mwh-eng is offline mwh-eng  United States
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Based on what I can see, I would have expected a little more copper for a dual 450 Watt amp.

Even though you said it worked fine without all the Mosfets in the circuit, maybe you should check all the output capacitors for proper value and possible leakage (resistive).

Did you make measurements on the PWM without the Mosfets or transformer in the circuit? You are probably still waiting on an Oscope to use.
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Old 11th March 2004, 09:22 PM   #27
sdoom is offline sdoom  Germany
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I tested the caps on the output side of the transformer with a good capacity tester and they are fine. Also the caps on the input side had been good. I assume the use of the IRZF48N caused too much ripple current and I somehow donīt belive the guy that sold the new caps to me that they really can be used for switching purposes. A friend of mine told me to re-install the IRFZ48N again as their values are better than the IRFZ44N. Also he said I should replace the 100 Ohm resistors to 47 Ohms to make sure the FET are switching fast enough and I should use "orange" low ESR caps with 63V . What Iīm afraid off is that if I make too many changes at once the whole thing wonīt turn on or instantly burn or something. As "eva" mentioned I probably have already a huge difference with the cores.


the 450W are considered max musik power Tonight I found a guy that actually has schematics for this amp. No kiddin, now as I am almost finished drawing this guy comes up and says " hey, I have the schematics"...

He also has a spec sheet for the amp that says 2x220W RMS @ 4 Ohms or 1x 500 W RMS @ 4Ohms and I think those values should be realistic.

On the picture above you can see the upper transformer (lightly brighter core and darker wire) is transformer No. 2 , the transformer I have replaced. This core comes from a 240W RMS amplifier and has exactly the same windings as the broken original.

I will finish the schematics soon and upload them.

Thx again

Steph
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Old 11th March 2004, 11:20 PM   #28
sdoom is offline sdoom  Germany
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Hi

I dont know why but if I send an email it always returns undelivered.

I have a better quality pic of the transformer section now

trafo_picture
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