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Old 14th March 2008, 08:42 AM   #21
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Quote:
Originally posted by jaycee


Small-signal transistors suitable for the job will always be available

So, let me get this straight then. Because you fear that 10 years from now there is a chance you can't get a uPC1237, you think it is *better* to built a circuit from discretes today?

That's Ok, but I just thought you really meant *better* in terms of performance.

Jan Didden
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Old 16th March 2008, 12:36 PM   #22
d3imlay is offline d3imlay  United States
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Default UPC1237/NTE7100

OK, so I worked out the design and got boards made. In the mean time it seems as though the chips have disappeared. Does anybody know who has them in stock at reasonable prices? I'm looking for 100pcs.
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Old 16th March 2008, 09:48 PM   #23
jaycee is offline jaycee  United Kingdom
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Quote:
Originally posted by janneman

So, let me get this straight then. Because you fear that 10 years from now there is a chance you can't get a uPC1237, you think it is *better* to built a circuit from discretes today?

That's Ok, but I just thought you really meant *better* in terms of performance.

Jan Didden
Yep, that's it exactly. The only real reason to use the IC is to save board space as you can make a good DC protect circuit with only a few resistors, a capacitor, 4 diodes and 2 transistors

Actually I'm looking at doing it with a resistor (per channel), capacitor, 4 diodes and an optocoupler. I don't know if thats much of an improvement, but I have a load of suitable optos from dead PC PSU's i could use
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Old 17th March 2008, 08:29 AM   #24
d3imlay is offline d3imlay  United States
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Quote:
Originally posted by jaycee


Actually I'm looking at doing it with a resistor (per channel), capacitor, 4 diodes and an optocoupler. I don't know if thats much of an improvement, but I have a load of suitable optos from dead PC PSU's i could use
The opto is a good idea I hadn't thought of. If you're only using the opto to drive the relay make sure the transistor can handle the voltage it will see when turned off. Seems to me you'd want at least another transistor and a cap for turn on delay.

Does the opto constitute an IC?
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Old 17th March 2008, 10:21 AM   #25
jaycee is offline jaycee  United Kingdom
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I was actually going to use the opto because I wanted to send the DC fault signal to a microcontroller, which would be in control of the speaker relays anyway.

The opto solves the interfacing between amp rail voltages and 5V, and also provides some isolation from digital noise.

Opto's are pretty common again and 4-terminal opto's are probably going to be widely available for some years yet - especially as theyre so commonly used in SMPS.
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Old 17th March 2008, 01:57 PM   #26
alex mm is offline alex mm  Romania
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Default uPC 1237HA and soft start

Hi,
my pcb with DC prot.and soft start Click the image to open in full size. thank u zeonrider
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Old 17th March 2008, 04:46 PM   #27
d3imlay is offline d3imlay  United States
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Default Re: uPC 1237HA and soft start

Quote:
Originally posted by alex mm
Hi,
my pcb with DC prot.and soft start Click the image to open in full size. thank u zeonrider

Board looks nice. What was the corner frequency of the filter circuit and total delay time to drop out the relay?
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Old 10th May 2008, 05:33 PM   #28
paulb is offline paulb  Canada
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Default Re: UPC1237/NTE7100

Quote:
Originally posted by d3imlay
OK, so I worked out the design and got boards made. In the mean time it seems as though the chips have disappeared. Does anybody know who has them in stock at reasonable prices? I'm looking for 100pcs.
Are you referring to the NTE7100? Mouser has stock; 100 pc @ $1.44.
I've built one on a perf board, with external relay. Nice and compact. Seems to work fine at 65V. I was thinking of doing a PCB but if yours is based on the 1237/7100 maybe I could 'lift it' from you.
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Old 10th May 2008, 05:49 PM   #29
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This is my 1237-based offset protection, switch-on delay as well as amplifier Safe Operation Area protection. This is the unit published by Elektor Electronics in their May issue.
Details at my website.

BTW, I can get 1237's here in Holland for about $1.50 + VAT at 19% if you need help.

Jan Didden
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Old 10th May 2008, 06:06 PM   #30
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Default Hi!

@janneman, Put schematic if you have!?

Regards zeoN_Rider
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