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Old 28th April 2013, 09:50 PM   #51
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Quote:
Originally Posted by ceteras View Post
No luck with the C1237HA, it was money sent down the drain.
In my application, the Vcc is 20V, and all four pins no. 4,6,7,8 are at the same voltage: 20V.
It's just like I didn't solder the chip on the board, and I've triple checked everything.
I will try an original uPC1237 from an Akai amplifier just to verify if the circuit is allright. If it works, I'm going to start designing the replacement board for this chip.
On the NEC PC1237 datasheet it states that the chip works with a supply voltage from 25-60Volts. As you are using it at 20v I suspect that has more to do with problems your are encountering than counterfeit chips. I am bemused as to why anyone would bother to fake a 1 chip.
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Old 29th April 2013, 05:51 AM   #52
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Originally Posted by Rickshaw View Post
......I am bemused as to why anyone would bother to fake a 1 chip.
Indeed, but they even fake T092 transistors for how much profit? Member Ilimzn has given us an idea of the reasons behind the proliferation and the different types of fakes from the many Chinese fabs now also churning out our genuine popular semis too.

Let's just say it's can be a "creative" way to dispose of and get some return on substandard products that would formerly have been destroyed. Why do we shop at their known outlets for unobtanium products, begging for fakes and then complain about getting them? To me, that is the real bemusement.
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Old 16th June 2014, 02:46 PM   #53
jarkaa is online now jarkaa  Finland
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Originally Posted by zeonrider View Post
3

Regards zeoN_Rider
This is very old thread, but referring to Zeons schematic. I do not know how to calculate R10 to ground. Can someone help me?

J
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Old 16th June 2014, 02:56 PM   #54
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Quote:
Originally Posted by ceteras View Post
No luck with the C1237HA, it was money sent down the drain.
In my application, the Vcc is 20V, and all four pins no. 4,6,7,8 are at the same voltage: 20V.
It's just like I didn't solder the chip on the board, and I've triple checked everything.
I will try an original uPC1237 from an Akai amplifier just to verify if the circuit is allright. If it works, I'm going to start designing the replacement board for this chip.
The chip works with the stated voltage through a series resistor to the supply pin, as it has an internal shunt reg. Did you take that into account?

Jan
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Old 16th June 2014, 02:56 PM   #55
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Originally Posted by jarkaa View Post
This is very old thread, but referring to Zeons schematic. I do not know how to calculate R10 to ground. Can someone help me?

J
Where is that schematic?
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Old 16th June 2014, 04:08 PM   #56
ceteras is offline ceteras  Romania
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Originally Posted by jan.didden View Post
The chip works with the stated voltage through a series resistor to the supply pin, as it has an internal shunt reg. Did you take that into account?

Jan
I did.
As I've updated in my post #46 and #50, I've replaced the new faulty 1237 with an old original from an Akai amplifier. The board then worked as it should, without any other changes.
So the counterfeits were the only problem there.

As for the equivalent circuit, I gave up on that, I'll simply avoid uPC1237 in the future.
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Old 16th June 2014, 04:24 PM   #57
ceteras is offline ceteras  Romania
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Originally Posted by jarkaa View Post
This is very old thread, but referring to Zeons schematic. I do not know how to calculate R10 to ground. Can someone help me?

J
Perhaps you refer to the schematic in post #12.

R10 is series with the relay. So you need to now the ratings of the relay's coil.
For instance you can get the voltage (V) and power (W) from the datasheet.
Example:
Let's say your power supply is Vdd=30Vcc.
Also let's say your relay is V= 12V and P= 0.4w. This means the current through the coil when it's on, is:P/V =0.4/12 A, or 33mA .
You will have to have this current through R10 as well.
Also the voltage across R10 has to be Vdd - 12V, that is 18V in this case.
R = U/I , so you need 18/0.033 ohms, or 545 ohms. I think you can use a 570ohm here.
The dissipated power in R10 is U*I, that is 18V * 33mA = 0.6W . Use a 1W or bigger resistor.

Of course you can do this by trial and error, pretty much. Start with a high value resistor, like 1K, and lower it experimentally until you have the correct voltage on your relay. Use 2W resistors and you're done.
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Old 17th June 2014, 06:28 PM   #58
jarkaa is online now jarkaa  Finland
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Quote:
Originally Posted by ceteras View Post
Perhaps you refer to the schematic in post #12.

R10 is series with the relay. So you need to now the ratings of the relay's coil.
For instance you can get the voltage (V) and power (W) from the datasheet.
Example:
Let's say your power supply is Vdd=30Vcc.
Also let's say your relay is V= 12V and P= 0.4w. This means the current through the coil when it's on, is:P/V =0.4/12 A, or 33mA .
You will have to have this current through R10 as well.
Also the voltage across R10 has to be Vdd - 12V, that is 18V in this case.
R = U/I , so you need 18/0.033 ohms, or 545 ohms. I think you can use a 570ohm here.
The dissipated power in R10 is U*I, that is 18V * 33mA = 0.6W . Use a 1W or bigger resistor.

Of course you can do this by trial and error, pretty much. Start with a high value resistor, like 1K, and lower it experimentally until you have the correct voltage on your relay. Use 2W resistors and you're done.
Right on spot! Thanks ceteras.

I just ordered these chips few weeks from ges electronic.

J
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