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Old 12th September 2010, 07:40 PM   #31
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Quote:
Originally Posted by pra3718 View Post
I think Indian market is full of fake chips.
It's about the same here. I bought a TDA7294 a couple years ago, that had the same behaviour as your 7265. At first i forgot to connect the negative supply, the chip worked but sounded awful (reason is obvious). Then when i connected negative supply correctly the chip would not go out of standby mode, no sound output. Exactly like yours did.

It turned out to be fake. I bought another one and installed it on the very same PCB and it's still working today.
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Old 22nd September 2010, 01:51 PM   #32
pra3718 is offline pra3718  India
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As per Post # 8 Picture I am building bridge where 5.6nf is not available at my regular suppliers. Is it 5.6nf = .56 uf ?
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Old 22nd September 2010, 02:53 PM   #33
sangram is offline sangram  India
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1F = 1000mF
1mF = 1000uF
1uF = 1000nF
1nF = 1000pF

5.6nF = .0056uF
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Old 22nd September 2010, 03:37 PM   #34
pra3718 is offline pra3718  India
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Thank you sangram, Now I understood conversion. I will ask for 5.6nf to my supplier. Is 5.6nf available in local mkt ? Or any substitute is possible ?

Another question is

1) For Input cap, Can I use 0.47uf 63v Polypropylene (.47K63) instead of 1uf 25v electrolytic for Satellite-Amp.

2) Till today, for 0.1uf I was using ceramic cap. But today I purchased 0.1uf 63v Polypropylene (.1K63) box type cap. It is yellow color. Is it better for Supply Voltage Bypass ?
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Old 22nd September 2010, 03:57 PM   #35
sangram is offline sangram  India
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5.6nF can be made by parallel combo of 4.7nF and 1nF - it's close enough, if you can't find the exact value.

Input capacitor value will form high-pass filter with Rin, you can use value larger than required - if reducing, then check what the new roll-off frequency is.

Ceramics work well enough for supply bypass. MKP caps can be used as well, there will be some reduction in microphonic behaviour of disc ceramics but I'm not sure about output noise. They would be similar.

Small yellow box types may be MKT (Polyester) or MKP (Polypropelene).
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Old 22nd September 2010, 04:07 PM   #36
pra3718 is offline pra3718  India
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Thank you, will go ahead with this info.
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Old 25th September 2010, 04:35 PM   #37
pra3718 is offline pra3718  India
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Default Success Story But problem with power supply.

I purchased genuine chips. I always used general dotted pcb. Chips pin alignment was not match with general pcb. I visited to professional pcb fabricator and fabricated my design. But he asked for quantities. I ordered 10 nos. which was minimum qty. I build my design such way that four chips (5.1) mounted on single pcb including pre-amp (ne5532) for sub. (Bridge). Yesterday, everything was ready & tested with gain=33, transformer = 12-0-12 (Regulated Split Supply)

One thing which I was looking from couple of months is ( BUILD AMP LIKE PROFESSIONAL ) I think I achieved today. Now I have PCB like professional with masking & tinning.

Observations :

After all connections I power switch ON, as general practice I did not find any activity in the amp. The amp was like dead, I touched speaker no hum it was like dead. After 2-3 seconds, suddenly music/sound started and I found poor loudness with 4ohm speaker. ( I should try with 18-0-18 trafo ) After 5 minutes listening I power switch OFF. I think my amp is working correctly. There is no POP on switch ON/OFF.

My fault : I design pcb such way that ne5532 + tda7265 both power supply with single track. Maximum voltage for 5532 is 22v per rail. 7565 is 25 per rail. 15-0-15 trafo is not available to my supplier.

As I am using regulated supply, the amp's loudness poor ? I think some voltage is eaten by regulated chips.

I am looking for SINGLE POWER SUPPLY which will supply below the 22v rails to ne5532 and perfect 25v per rail to tda7265.
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Old 26th September 2010, 10:30 AM   #38
pra3718 is offline pra3718  India
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With the same configuration (post # 37) test again. I found if I touch mute capacitor 47uf 25v loudness increase but there is no weak/dry solder.
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Old 26th September 2010, 10:37 AM   #39
pra3718 is offline pra3718  India
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Pictures of my amp.
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File Type: jpg Photo1.jpg (279.2 KB, 206 views)
File Type: jpg Photo2.jpg (264.3 KB, 197 views)
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Old 26th September 2010, 05:09 PM   #40
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Measure the voltage from pin 3 to 5. There should be more than 6 or better more than 7 V to switch the amplifiers completely on.
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