Calcell CWB 102 isn't brigdeable anymore... - diyAudio
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Old 3rd September 2007, 12:56 PM   #1
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Default Calcell CWB 102 isn't brigdeable anymore...

Hello at all first...

I've got a problem with a Calcell CWB 102.
Bought it with noise on both channels, because there were some defective drivers.
I changed all the drivers in both channels and now it's working fine in stereo.
But when I bridge it, you don't hear anything until you turn up the gain to maximum.
Then you can hear a distorted, very quiet version of the inputsignal and after a few seconds the amp goes into protection mode.

What I've done so far:
- I've measured all transistors, none of them seems to be defetive.
- Changed all Op-Amps in the signalpath
- Changed the PWM IC and an Op-Amp in the SMPS circuit (don't even know what this one does... Protection circuit?)

Does anyone have an idea what's wrong with this amp?

Thanks in advance!

gisewhcs
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Old 3rd September 2007, 03:00 PM   #2
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With two speakers connected (one to each channel), what happens if you feed signal into only one RCA jack at a time?

With signal being fed into both RCA jacks, do the speakers produce good bass?

Is the bass better with only one speaker connected?

Make sure the speakers are properly connected (+/- connections on the correct terminals).

Is the switch on the amp for the crossover or something else?

Have you tried it in all positions?
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Old 3rd September 2007, 04:43 PM   #3
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The switch inside is for the crossover (flat, 80Hz lp, 200Hz lp)

After some more testing i noticed, that the right channel is still distorted and the N-channel FETs (IRF530) in the left channel are becoming hot quiet fast.
Another strange thing is, that there are IRF530 for the negative halfwave and and SFP9540 (same as IRF9540) for the positive halfwave... Those are non-complimentary types, right?
The guy where i bought the amp said that he had changed the outputs, and this were the parts used in it...

Another thing I've noticed, is that the power LED stays on, after power is removed and dims very slow, it takes ~1/2min. until the LED is really
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Old 3rd September 2007, 06:44 PM   #4
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I worked on a mark antony amp which is a clone of this amp. It had IRF530s and IRF9540s in it and I believe they were the originals.

The LED remains lit until the filter caps are discharged.
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Old 21st May 2008, 05:11 PM   #5
JoergST is offline JoergST  Germany
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Hello, I have also a calcell CWB-102and some problems with it. The red LED is shining and I remove the big diodes from the power amplifier to separate the power supply from the power amplifier.
But the power supply doesn´t work. The red LED is shining.

My question: When I remove the big diodes from the power supply, is it possible, that the power supply can start?
Or is it a problem for the amplifier?

Regards Jörg
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Old 21st May 2008, 05:25 PM   #6
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If the power supply transistors have not failed, post a list of the voltages on the TLx94 and the 8 pin SIP op-amp near the TLx94. If pin 16 on the TLx94 is high, you only need to post the voltages on the 8 pin sip op-amp.
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Old 21st May 2008, 06:40 PM   #7
JoergST is offline JoergST  Germany
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Hello, I give you the value from the two ICs

NJM4558LD from JRC

Pin
1: 1,27
2: 9,65V
3: 3,14V
4: 0V
5: 11.58V
6: 4,94V
7: 11,96V
8: 13,24V

TL494CN

1: 11V
2: 2,3V
3: 4,73V
4: 52mV
5: 1,44V
6: 3,62V
7: 0V
8: 13,93V
9: 0V
10:0V
11: 13,93V
12: 13,93V
13: 4,95V
14: 4,95V
15: 4,74V
16: 80mV

Is it possible to check the IRFP 044 when they are soldered on the circuit board? There are 8 transistors in the power supply.

Mfg jörg
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Old 21st May 2008, 08:00 PM   #8
JoergST is offline JoergST  Germany
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Quote:
Originally posted by JoergST
Hello, I give you the value from the two ICs

NJM4558LD from JRC

Pin
1: 1,27
2: 9,65V
3: 3,14V
4: 0V
5: 11.58V
6: 4,94V
7: 11,96V
8: 13,24V

TL494CN

1: 11V
2: 2,3V
3: 4,73V
4: 52mV
5: 1,44V
6: 3,62V
7: 0V
8: 13,93V
9: 0V
10:0V
11: 13,93V
12: 13,93V
13: 4,95V
14: 4,95V
15: 4,74V
16: 80mV

Is it possible to check the IRFP 044 when they are soldered on the circuit board? There are 8 transistors in the power supply.

I use my Osziloscope and on pin 9 and 10 I got a square wave signal. So I think the mistake must be after the power supply. There is something anomalous.
When I turn the amplifier on in the first 15 sek. the green LED is on. After the 15 sek, the red LED goes on. When you turn than the amplifier off and again on, the red LED is on again.
Then I turn off the amplifier and wait for 5 minutes. After 5 minutes the green led is on for 15 sek and than the red led goes on.

Mfg jörg
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Old 21st May 2008, 09:09 PM   #9
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The problem appears to be the input to pins 1 and 2. I'm not sure what they're used for. Follow the circuit back to see if you can determine their function.

If you have pulses on pins 9 and 10 and you have a square wave on the primary side of the transformer that swings from ground to 2*B+, the FETs are OK.

You won't have pulses on 9/10 if you have 11v on pin 1 and 2.3v on pin 2.

Check the emitter/source resistors to make sure that none are broken. If a leg is broken on one of them, it can make the amp go into protect.
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